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How to Write a Conclusion for Research Papers (with Examples)

The conclusion of a research paper is a crucial section that plays a significant role in the overall impact and effectiveness of your research paper. However, this is also the section that typically receives less attention compared to the introduction and the body of the paper. The conclusion serves to provide a concise summary of the key findings, their significance, their implications, and a sense of closure to the study. Discussing how can the findings be applied in real-world scenarios or inform policy, practice, or decision-making is especially valuable to practitioners and policymakers. The research paper conclusion also provides researchers with clear insights and valuable information for their own work, which they can then build on and contribute to the advancement of knowledge in the field.

The research paper conclusion should explain the significance of your findings within the broader context of your field. It restates how your results contribute to the existing body of knowledge and whether they confirm or challenge existing theories or hypotheses. Also, by identifying unanswered questions or areas requiring further investigation, your awareness of the broader research landscape can be demonstrated.

Remember to tailor the research paper conclusion to the specific needs and interests of your intended audience, which may include researchers, practitioners, policymakers, or a combination of these.

Table of Contents

What is a conclusion in a research paper, summarizing conclusion, editorial conclusion, externalizing conclusion, importance of a good research paper conclusion, how to write a conclusion for your research paper, research paper conclusion examples.

• How to write a research paper conclusion with Paperpal? 

Frequently Asked Questions

A conclusion in a research paper is the final section where you summarize and wrap up your research, presenting the key findings and insights derived from your study. The research paper conclusion is not the place to introduce new information or data that was not discussed in the main body of the paper. When working on how to conclude a research paper, remember to stick to summarizing and interpreting existing content. The research paper conclusion serves the following purposes: 1

• Warn readers of the possible consequences of not attending to the problem.
• Recommend specific course(s) of action.
• Restate key ideas to drive home the ultimate point of your research paper.
• Provide a “take-home” message that you want the readers to remember about your study.

Types of conclusions for research papers

In research papers, the conclusion provides closure to the reader. The type of research paper conclusion you choose depends on the nature of your study, your goals, and your target audience. I provide you with three common types of conclusions:

A summarizing conclusion is the most common type of conclusion in research papers. It involves summarizing the main points, reiterating the research question, and restating the significance of the findings. This common type of research paper conclusion is used across different disciplines.

An editorial conclusion is less common but can be used in research papers that are focused on proposing or advocating for a particular viewpoint or policy. It involves presenting a strong editorial or opinion based on the research findings and offering recommendations or calls to action.

An externalizing conclusion is a type of conclusion that extends the research beyond the scope of the paper by suggesting potential future research directions or discussing the broader implications of the findings. This type of conclusion is often used in more theoretical or exploratory research papers.

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The conclusion in a research paper serves several important purposes:

• Offers Implications and Recommendations : Your research paper conclusion is an excellent place to discuss the broader implications of your research and suggest potential areas for further study. It’s also an opportunity to offer practical recommendations based on your findings.
• Provides Closure : A good research paper conclusion provides a sense of closure to your paper. It should leave the reader with a feeling that they have reached the end of a well-structured and thought-provoking research project.
• Leaves a Lasting Impression : Writing a well-crafted research paper conclusion leaves a lasting impression on your readers. It’s your final opportunity to leave them with a new idea, a call to action, or a memorable quote.

Writing a strong conclusion for your research paper is essential to leave a lasting impression on your readers. Here’s a step-by-step process to help you create and know what to put in the conclusion of a research paper: 2

• Research Statement : Begin your research paper conclusion by restating your research statement. This reminds the reader of the main point you’ve been trying to prove throughout your paper. Keep it concise and clear.
• Key Points : Summarize the main arguments and key points you’ve made in your paper. Avoid introducing new information in the research paper conclusion. Instead, provide a concise overview of what you’ve discussed in the body of your paper.
• Address the Research Questions : If your research paper is based on specific research questions or hypotheses, briefly address whether you’ve answered them or achieved your research goals. Discuss the significance of your findings in this context.
• Significance : Highlight the importance of your research and its relevance in the broader context. Explain why your findings matter and how they contribute to the existing knowledge in your field.
• Implications : Explore the practical or theoretical implications of your research. How might your findings impact future research, policy, or real-world applications? Consider the “so what?” question.
• Future Research : Offer suggestions for future research in your area. What questions or aspects remain unanswered or warrant further investigation? This shows that your work opens the door for future exploration.
• Closing Thought : Conclude your research paper conclusion with a thought-provoking or memorable statement. This can leave a lasting impression on your readers and wrap up your paper effectively. Avoid introducing new information or arguments here.
• Proofread and Revise : Carefully proofread your conclusion for grammar, spelling, and clarity. Ensure that your ideas flow smoothly and that your conclusion is coherent and well-structured.

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Remember that a well-crafted research paper conclusion is a reflection of the strength of your research and your ability to communicate its significance effectively. It should leave a lasting impression on your readers and tie together all the threads of your paper. Now you know how to start the conclusion of a research paper and what elements to include to make it impactful, let’s look at a research paper conclusion sample.

How to write a research paper conclusion with Paperpal?

A research paper conclusion is not just a summary of your study, but a synthesis of the key findings that ties the research together and places it in a broader context. A research paper conclusion should be concise, typically around one paragraph in length. However, some complex topics may require a longer conclusion to ensure the reader is left with a clear understanding of the study’s significance. Paperpal, an AI writing assistant trusted by over 800,000 academics globally, can help you write a well-structured conclusion for your research paper. 

• Sign Up or Log In: Create a new Paperpal account or login with your details.  
• Navigate to Features : Once logged in, head over to the features’ side navigation pane. Click on Templates and you’ll find a suite of generative AI features to help you write better, faster.  
• Generate an outline: Under Templates, select ‘Outlines’. Choose ‘Research article’ as your document type.  
• Select your section: Since you’re focusing on the conclusion, select this section when prompted.  
• Choose your field of study: Identifying your field of study allows Paperpal to provide more targeted suggestions, ensuring the relevance of your conclusion to your specific area of research. 
• Provide a brief description of your study: Enter details about your research topic and findings. This information helps Paperpal generate a tailored outline that aligns with your paper’s content. 
• Generate the conclusion outline: After entering all necessary details, click on ‘generate’. Paperpal will then create a structured outline for your conclusion, to help you start writing and build upon the outline.  
• Write your conclusion: Use the generated outline to build your conclusion. The outline serves as a guide, ensuring you cover all critical aspects of a strong conclusion, from summarizing key findings to highlighting the research’s implications. 
• Refine and enhance: Paperpal’s ‘Make Academic’ feature can be particularly useful in the final stages. Select any paragraph of your conclusion and use this feature to elevate the academic tone, ensuring your writing is aligned to the academic journal standards. 

By following these steps, Paperpal not only simplifies the process of writing a research paper conclusion but also ensures it is impactful, concise, and aligned with academic standards. Sign up with Paperpal today and write your research paper conclusion 2x faster .  

The research paper conclusion is a crucial part of your paper as it provides the final opportunity to leave a strong impression on your readers. In the research paper conclusion, summarize the main points of your research paper by restating your research statement, highlighting the most important findings, addressing the research questions or objectives, explaining the broader context of the study, discussing the significance of your findings, providing recommendations if applicable, and emphasizing the takeaway message. The main purpose of the conclusion is to remind the reader of the main point or argument of your paper and to provide a clear and concise summary of the key findings and their implications. All these elements should feature on your list of what to put in the conclusion of a research paper to create a strong final statement for your work.

A strong conclusion is a critical component of a research paper, as it provides an opportunity to wrap up your arguments, reiterate your main points, and leave a lasting impression on your readers. Here are the key elements of a strong research paper conclusion: 1. Conciseness : A research paper conclusion should be concise and to the point. It should not introduce new information or ideas that were not discussed in the body of the paper. 2. Summarization : The research paper conclusion should be comprehensive enough to give the reader a clear understanding of the research’s main contributions. 3 . Relevance : Ensure that the information included in the research paper conclusion is directly relevant to the research paper’s main topic and objectives; avoid unnecessary details. 4 . Connection to the Introduction : A well-structured research paper conclusion often revisits the key points made in the introduction and shows how the research has addressed the initial questions or objectives. 5. Emphasis : Highlight the significance and implications of your research. Why is your study important? What are the broader implications or applications of your findings? 6 . Call to Action : Include a call to action or a recommendation for future research or action based on your findings.

The length of a research paper conclusion can vary depending on several factors, including the overall length of the paper, the complexity of the research, and the specific journal requirements. While there is no strict rule for the length of a conclusion, but it’s generally advisable to keep it relatively short. A typical research paper conclusion might be around 5-10% of the paper’s total length. For example, if your paper is 10 pages long, the conclusion might be roughly half a page to one page in length.

In general, you do not need to include citations in the research paper conclusion. Citations are typically reserved for the body of the paper to support your arguments and provide evidence for your claims. However, there may be some exceptions to this rule: 1. If you are drawing a direct quote or paraphrasing a specific source in your research paper conclusion, you should include a citation to give proper credit to the original author. 2. If your conclusion refers to or discusses specific research, data, or sources that are crucial to the overall argument, citations can be included to reinforce your conclusion’s validity.

The conclusion of a research paper serves several important purposes: 1. Summarize the Key Points 2. Reinforce the Main Argument 3. Provide Closure 4. Offer Insights or Implications 5. Engage the Reader. 6. Reflect on Limitations

Remember that the primary purpose of the research paper conclusion is to leave a lasting impression on the reader, reinforcing the key points and providing closure to your research. It’s often the last part of the paper that the reader will see, so it should be strong and well-crafted.

• Makar, G., Foltz, C., Lendner, M., & Vaccaro, A. R. (2018). How to write effective discussion and conclusion sections. Clinical spine surgery, 31(8), 345-346.
• Bunton, D. (2005). The structure of PhD conclusion chapters.  Journal of English for academic purposes ,  4 (3), 207-224.

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Research Recommendations – Guiding policy-makers for evidence-based decision making

Research recommendations play a crucial role in guiding scholars and researchers toward fruitful avenues of exploration. In an era marked by rapid technological advancements and an ever-expanding knowledge base, refining the process of generating research recommendations becomes imperative.

But, what is a research recommendation?

Research recommendations are suggestions or advice provided to researchers to guide their study on a specific topic . They are typically given by experts in the field. Research recommendations are more action-oriented and provide specific guidance for decision-makers, unlike implications that are broader and focus on the broader significance and consequences of the research findings. However, both are crucial components of a research study.

Difference Between Research Recommendations and Implication

Although research recommendations and implications are distinct components of a research study, they are closely related. The differences between them are as follows:

Types of Research Recommendations

Recommendations in research can take various forms, which are as follows:

These recommendations aim to assist researchers in navigating the vast landscape of academic knowledge.

Let us dive deeper to know about its key components and the steps to write an impactful research recommendation.

Key Components of Research Recommendations

The key components of research recommendations include defining the research question or objective, specifying research methods, outlining data collection and analysis processes, presenting results and conclusions, addressing limitations, and suggesting areas for future research. Here are some characteristics of research recommendations:

Research recommendations offer various advantages and play a crucial role in ensuring that research findings contribute to positive outcomes in various fields. However, they also have few limitations which highlights the significance of a well-crafted research recommendation in offering the promised advantages.

The importance of research recommendations ranges in various fields, influencing policy-making, program development, product development, marketing strategies, medical practice, and scientific research. Their purpose is to transfer knowledge from researchers to practitioners, policymakers, or stakeholders, facilitating informed decision-making and improving outcomes in different domains.

How to Write Research Recommendations?

Research recommendations can be generated through various means, including algorithmic approaches, expert opinions, or collaborative filtering techniques. Here is a step-wise guide to build your understanding on the development of research recommendations.

1. Understand the Research Question:

Understand the research question and objectives before writing recommendations. Also, ensure that your recommendations are relevant and directly address the goals of the study.

2. Review Existing Literature:

Familiarize yourself with relevant existing literature to help you identify gaps , and offer informed recommendations that contribute to the existing body of research.

3. Consider Research Methods:

Evaluate the appropriateness of different research methods in addressing the research question. Also, consider the nature of the data, the study design, and the specific objectives.

4. Identify Data Collection Techniques:

Gather dataset from diverse authentic sources. Include information such as keywords, abstracts, authors, publication dates, and citation metrics to provide a rich foundation for analysis.

5. Propose Data Analysis Methods:

Suggest appropriate data analysis methods based on the type of data collected. Consider whether statistical analysis, qualitative analysis, or a mixed-methods approach is most suitable.

6. Consider Limitations and Ethical Considerations:

Acknowledge any limitations and potential ethical considerations of the study. Furthermore, address these limitations or mitigate ethical concerns to ensure responsible research.

7. Justify Recommendations:

Explain how your recommendation contributes to addressing the research question or objective. Provide a strong rationale to help researchers understand the importance of following your suggestions.

8. Summarize Recommendations:

Provide a concise summary at the end of the report to emphasize how following these recommendations will contribute to the overall success of the research project.

By following these steps, you can create research recommendations that are actionable and contribute meaningfully to the success of the research project.

Download now to unlock some tips to improve your journey of writing research recommendations.

Example of a Research Recommendation

Here is an example of a research recommendation based on a hypothetical research to improve your understanding.

Research Recommendation: Enhancing Student Learning through Integrated Learning Platforms

Background:

The research study investigated the impact of an integrated learning platform on student learning outcomes in high school mathematics classes. The findings revealed a statistically significant improvement in student performance and engagement when compared to traditional teaching methods.

Recommendation:

In light of the research findings, it is recommended that educational institutions consider adopting and integrating the identified learning platform into their mathematics curriculum. The following specific recommendations are provided:

• Implementation of the Integrated Learning Platform:

Schools are encouraged to adopt the integrated learning platform in mathematics classrooms, ensuring proper training for teachers on its effective utilization.

• Professional Development for Educators:

Develop and implement professional programs to train educators in the effective use of the integrated learning platform to address any challenges teachers may face during the transition.

• Monitoring and Evaluation:

Establish a monitoring and evaluation system to track the impact of the integrated learning platform on student performance over time.

• Resource Allocation:

Allocate sufficient resources, both financial and technical, to support the widespread implementation of the integrated learning platform.

By implementing these recommendations, educational institutions can harness the potential of the integrated learning platform and enhance student learning experiences and academic achievements in mathematics.

This example covers the components of a research recommendation, providing specific actions based on the research findings, identifying the target audience, and outlining practical steps for implementation.

Using AI in Research Recommendation Writing

Enhancing research recommendations is an ongoing endeavor that requires the integration of cutting-edge technologies, collaborative efforts, and ethical considerations. By embracing data-driven approaches and leveraging advanced technologies, the research community can create more effective and personalized recommendation systems. However, it is accompanied by several limitations. Therefore, it is essential to approach the use of AI in research with a critical mindset, and complement its capabilities with human expertise and judgment.

Here are some limitations of integrating AI in writing research recommendation and some ways on how to counter them.

1. Data Bias

AI systems rely heavily on data for training. If the training data is biased or incomplete, the AI model may produce biased results or recommendations.

How to tackle: Audit regularly the model’s performance to identify any discrepancies and adjust the training data and algorithms accordingly.

2. Lack of Understanding of Context:

AI models may struggle to understand the nuanced context of a particular research problem. They may misinterpret information, leading to inaccurate recommendations.

How to tackle: Use AI to characterize research articles and topics. Employ them to extract features like keywords, authorship patterns and content-based details.

3. Ethical Considerations:

AI models might stereotype certain concepts or generate recommendations that could have negative consequences for certain individuals or groups.

How to tackle: Incorporate user feedback mechanisms to reduce redundancies. Establish an ethics review process for AI models in research recommendation writing.

4. Lack of Creativity and Intuition:

AI may struggle with tasks that require a deep understanding of the underlying principles or the ability to think outside the box.

How to tackle: Hybrid approaches can be employed by integrating AI in data analysis and identifying patterns for accelerating the data interpretation process.

5. Interpretability:

Many AI models, especially complex deep learning models, lack transparency on how the model arrived at a particular recommendation.

How to tackle: Implement models like decision trees or linear models. Provide clear explanation of the model architecture, training process, and decision-making criteria.

6. Dynamic Nature of Research:

Research fields are dynamic, and new information is constantly emerging. AI models may struggle to keep up with the rapidly changing landscape and may not be able to adapt to new developments.

How to tackle: Establish a feedback loop for continuous improvement. Regularly update the recommendation system based on user feedback and emerging research trends.

The integration of AI in research recommendation writing holds great promise for advancing knowledge and streamlining the research process. However, navigating these concerns is pivotal in ensuring the responsible deployment of these technologies. Researchers need to understand the use of responsible use of AI in research and must be aware of the ethical considerations.

Exploring research recommendations plays a critical role in shaping the trajectory of scientific inquiry. It serves as a compass, guiding researchers toward more robust methodologies, collaborative endeavors, and innovative approaches. Embracing these suggestions not only enhances the quality of individual studies but also contributes to the collective advancement of human understanding.

Frequently Asked Questions

The purpose of recommendations in research is to provide practical and actionable suggestions based on the study's findings, guiding future actions, policies, or interventions in a specific field or context. Recommendations bridges the gap between research outcomes and their real-world application.

To make a research recommendation, analyze your findings, identify key insights, and propose specific, evidence-based actions. Include the relevance of the recommendations to the study's objectives and provide practical steps for implementation.

Begin a recommendation by succinctly summarizing the key findings of the research. Clearly state the purpose of the recommendation and its intended impact. Use a direct and actionable language to convey the suggested course of action.

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The conclusion is intended to help the reader understand why your research should matter to them after they have finished reading the paper. A conclusion is not merely a summary of the main topics covered or a re-statement of your research problem, but a synthesis of key points derived from the findings of your study and, if applicable, where you recommend new areas for future research. For most college-level research papers, two or three well-developed paragraphs is sufficient for a conclusion, although in some cases, more paragraphs may be required in describing the key findings and their significance.

Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University.

Importance of a Good Conclusion

A well-written conclusion provides you with important opportunities to demonstrate to the reader your understanding of the research problem. These include:

• Presenting the last word on the issues you raised in your paper . Just as the introduction gives a first impression to your reader, the conclusion offers a chance to leave a lasting impression. Do this, for example, by highlighting key findings in your analysis that advance new understanding about the research problem, that are unusual or unexpected, or that have important implications applied to practice.
• Summarizing your thoughts and conveying the larger significance of your study . The conclusion is an opportunity to succinctly re-emphasize  your answer to the "So What?" question by placing the study within the context of how your research advances past research about the topic.
• Identifying how a gap in the literature has been addressed . The conclusion can be where you describe how a previously identified gap in the literature [first identified in your literature review section] has been addressed by your research and why this contribution is significant.
• Demonstrating the importance of your ideas . Don't be shy. The conclusion offers an opportunity to elaborate on the impact and significance of your findings. This is particularly important if your study approached examining the research problem from an unusual or innovative perspective.
• Introducing possible new or expanded ways of thinking about the research problem . This does not refer to introducing new information [which should be avoided], but to offer new insight and creative approaches for framing or contextualizing the research problem based on the results of your study.

Bunton, David. “The Structure of PhD Conclusion Chapters.” Journal of English for Academic Purposes 4 (July 2005): 207–224; Conclusions. The Writing Center. University of North Carolina; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Conclusions. The Writing Lab and The OWL. Purdue University; Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Structure and Writing Style

I.  General Rules

The general function of your paper's conclusion is to restate the main argument . It reminds the reader of the strengths of your main argument(s) and reiterates the most important evidence supporting those argument(s). Do this by clearly summarizing the context, background, and necessity of pursuing the research problem you investigated in relation to an issue, controversy, or a gap found in the literature. However, make sure that your conclusion is not simply a repetitive summary of the findings. This reduces the impact of the argument(s) you have developed in your paper.

When writing the conclusion to your paper, follow these general rules:

• Present your conclusions in clear, concise language. Re-state the purpose of your study, then describe how your findings differ or support those of other studies and why [i.e., what were the unique, new, or crucial contributions your study made to the overall research about your topic?].
• Do not simply reiterate your findings or the discussion of your results. Provide a synthesis of arguments presented in the paper to show how these converge to address the research problem and the overall objectives of your study.
• Indicate opportunities for future research if you haven't already done so in the discussion section of your paper. Highlighting the need for further research provides the reader with evidence that you have an in-depth awareness of the research problem but that further investigations should take place beyond the scope of your investigation.

Consider the following points to help ensure your conclusion is presented well:

• If the argument or purpose of your paper is complex, you may need to summarize the argument for your reader.
• If, prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the end of your paper to describe your main points and explain their significance.
• Move from a detailed to a general level of consideration that returns the topic to the context provided by the introduction or within a new context that emerges from the data [this is opposite of the introduction, which begins with general discussion of the context and ends with a detailed description of the research problem]. 

The conclusion also provides a place for you to persuasively and succinctly restate the research problem, given that the reader has now been presented with all the information about the topic . Depending on the discipline you are writing in, the concluding paragraph may contain your reflections on the evidence presented. However, the nature of being introspective about the research you have conducted will depend on the topic and whether your professor wants you to express your observations in this way. If asked to think introspectively about the topics, do not delve into idle speculation. Being introspective means looking within yourself as an author to try and understand an issue more deeply, not to guess at possible outcomes or make up scenarios not supported by the evidence.

II.  Developing a Compelling Conclusion

Although an effective conclusion needs to be clear and succinct, it does not need to be written passively or lack a compelling narrative. Strategies to help you move beyond merely summarizing the key points of your research paper may include any of the following:

• If your essay deals with a critical, contemporary problem, warn readers of the possible consequences of not attending to the problem proactively.
• Recommend a specific course or courses of action that, if adopted, could address a specific problem in practice or in the development of new knowledge leading to positive change.
• Cite a relevant quotation or expert opinion already noted in your paper in order to lend authority and support to the conclusion(s) you have reached [a good source would be from your literature review].
• Explain the consequences of your research in a way that elicits action or demonstrates urgency in seeking change.
• Restate a key statistic, fact, or visual image to emphasize the most important finding of your paper.
• If your discipline encourages personal reflection, illustrate your concluding point by drawing from your own life experiences.
• Return to an anecdote, an example, or a quotation that you presented in your introduction, but add further insight derived from the findings of your study; use your interpretation of results from your study to recast it in new or important ways.
• Provide a "take-home" message in the form of a succinct, declarative statement that you want the reader to remember about your study.

III. Problems to Avoid

Failure to be concise Your conclusion section should be concise and to the point. Conclusions that are too lengthy often have unnecessary information in them. The conclusion is not the place for details about your methodology or results. Although you should give a summary of what was learned from your research, this summary should be relatively brief, since the emphasis in the conclusion is on the implications, evaluations, insights, and other forms of analysis that you make. Strategies for writing concisely can be found here .

Failure to comment on larger, more significant issues In the introduction, your task was to move from the general [the field of study] to the specific [the research problem]. However, in the conclusion, your task is to move from a specific discussion [your research problem] back to a general discussion framed around the implications and significance of your findings [i.e., how your research contributes new understanding or fills an important gap in the literature]. In short, the conclusion is where you should place your research within a larger context [visualize your paper as an hourglass--start with a broad introduction and review of the literature, move to the specific analysis and discussion, conclude with a broad summary of the study's implications and significance].

Failure to reveal problems and negative results Negative aspects of the research process should never be ignored. These are problems, deficiencies, or challenges encountered during your study. They should be summarized as a way of qualifying your overall conclusions. If you encountered negative or unintended results [i.e., findings that are validated outside the research context in which they were generated], you must report them in the results section and discuss their implications in the discussion section of your paper. In the conclusion, use negative results as an opportunity to explain their possible significance and/or how they may form the basis for future research.

Failure to provide a clear summary of what was learned In order to be able to discuss how your research fits within your field of study [and possibly the world at large], you need to summarize briefly and succinctly how it contributes to new knowledge or a new understanding about the research problem. This element of your conclusion may be only a few sentences long.

Failure to match the objectives of your research Often research objectives in the social and behavioral sciences change while the research is being carried out. This is not a problem unless you forget to go back and refine the original objectives in your introduction. As these changes emerge they must be documented so that they accurately reflect what you were trying to accomplish in your research [not what you thought you might accomplish when you began].

Resist the urge to apologize If you've immersed yourself in studying the research problem, you presumably should know a good deal about it [perhaps even more than your professor!]. Nevertheless, by the time you have finished writing, you may be having some doubts about what you have produced. Repress those doubts! Don't undermine your authority as a researcher by saying something like, "This is just one approach to examining this problem; there may be other, much better approaches that...." The overall tone of your conclusion should convey confidence to the reader about the study's validity and realiability.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Concluding Paragraphs. College Writing Center at Meramec. St. Louis Community College; Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University; Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions. The Lab Report. University College Writing Centre. University of Toronto; Leibensperger, Summer. Draft Your Conclusion. Academic Center, the University of Houston-Victoria, 2003; Make Your Last Words Count. The Writer’s Handbook. Writing Center. University of Wisconsin Madison; Miquel, Fuster-Marquez and Carmen Gregori-Signes. “Chapter Six: ‘Last but Not Least:’ Writing the Conclusion of Your Paper.” In Writing an Applied Linguistics Thesis or Dissertation: A Guide to Presenting Empirical Research . John Bitchener, editor. (Basingstoke,UK: Palgrave Macmillan, 2010), pp. 93-105; Tips for Writing a Good Conclusion. Writing@CSU. Colorado State University; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Writing Conclusions. Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University; Writing: Considering Structure and Organization. Institute for Writing Rhetoric. Dartmouth College.

Writing Tip

Don't Belabor the Obvious!

Avoid phrases like "in conclusion...," "in summary...," or "in closing...." These phrases can be useful, even welcome, in oral presentations. But readers can see by the tell-tale section heading and number of pages remaining that they are reaching the end of your paper. You'll irritate your readers if you belabor the obvious.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Another Writing Tip

New Insight, Not New Information!

Don't surprise the reader with new information in your conclusion that was never referenced anywhere else in the paper. This why the conclusion rarely has citations to sources. If you have new information to present, add it to the discussion or other appropriate section of the paper. Note that, although no new information is introduced, the conclusion, along with the discussion section, is where you offer your most "original" contributions in the paper; the conclusion is where you describe the value of your research, demonstrate that you understand the material that you’ve presented, and position your findings within the larger context of scholarship on the topic, including describing how your research contributes new insights to that scholarship.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Conclusions. The Writing Center. University of North Carolina.

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Research Paper Conclusion – Writing Guide and Examples

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Research Paper Conclusion

Definition:

A research paper conclusion is the final section of a research paper that summarizes the key findings, significance, and implications of the research. It is the writer’s opportunity to synthesize the information presented in the paper, draw conclusions, and make recommendations for future research or actions.

The conclusion should provide a clear and concise summary of the research paper, reiterating the research question or problem, the main results, and the significance of the findings. It should also discuss the limitations of the study and suggest areas for further research.

Parts of Research Paper Conclusion

The parts of a research paper conclusion typically include:

Restatement of the Thesis

The conclusion should begin by restating the thesis statement from the introduction in a different way. This helps to remind the reader of the main argument or purpose of the research.

Summary of Key Findings

The conclusion should summarize the main findings of the research, highlighting the most important results and conclusions. This section should be brief and to the point.

Implications and Significance

In this section, the researcher should explain the implications and significance of the research findings. This may include discussing the potential impact on the field or industry, highlighting new insights or knowledge gained, or pointing out areas for future research.

Limitations and Recommendations

It is important to acknowledge any limitations or weaknesses of the research and to make recommendations for how these could be addressed in future studies. This shows that the researcher is aware of the potential limitations of their work and is committed to improving the quality of research in their field.

Concluding Statement

The conclusion should end with a strong concluding statement that leaves a lasting impression on the reader. This could be a call to action, a recommendation for further research, or a final thought on the topic.

How to Write Research Paper Conclusion

Here are some steps you can follow to write an effective research paper conclusion:

• Restate the research problem or question: Begin by restating the research problem or question that you aimed to answer in your research. This will remind the reader of the purpose of your study.
• Summarize the main points: Summarize the key findings and results of your research. This can be done by highlighting the most important aspects of your research and the evidence that supports them.
• Discuss the implications: Discuss the implications of your findings for the research area and any potential applications of your research. You should also mention any limitations of your research that may affect the interpretation of your findings.
• Provide a conclusion : Provide a concise conclusion that summarizes the main points of your paper and emphasizes the significance of your research. This should be a strong and clear statement that leaves a lasting impression on the reader.
• Offer suggestions for future research: Lastly, offer suggestions for future research that could build on your findings and contribute to further advancements in the field.

Remember that the conclusion should be brief and to the point, while still effectively summarizing the key findings and implications of your research.

Example of Research Paper Conclusion

Here’s an example of a research paper conclusion:

Conclusion :

In conclusion, our study aimed to investigate the relationship between social media use and mental health among college students. Our findings suggest that there is a significant association between social media use and increased levels of anxiety and depression among college students. This highlights the need for increased awareness and education about the potential negative effects of social media use on mental health, particularly among college students.

Despite the limitations of our study, such as the small sample size and self-reported data, our findings have important implications for future research and practice. Future studies should aim to replicate our findings in larger, more diverse samples, and investigate the potential mechanisms underlying the association between social media use and mental health. In addition, interventions should be developed to promote healthy social media use among college students, such as mindfulness-based approaches and social media detox programs.

Overall, our study contributes to the growing body of research on the impact of social media on mental health, and highlights the importance of addressing this issue in the context of higher education. By raising awareness and promoting healthy social media use among college students, we can help to reduce the negative impact of social media on mental health and improve the well-being of young adults.

Purpose of Research Paper Conclusion

The purpose of a research paper conclusion is to provide a summary and synthesis of the key findings, significance, and implications of the research presented in the paper. The conclusion serves as the final opportunity for the writer to convey their message and leave a lasting impression on the reader.

The conclusion should restate the research problem or question, summarize the main results of the research, and explain their significance. It should also acknowledge the limitations of the study and suggest areas for future research or action.

Overall, the purpose of the conclusion is to provide a sense of closure to the research paper and to emphasize the importance of the research and its potential impact. It should leave the reader with a clear understanding of the main findings and why they matter. The conclusion serves as the writer’s opportunity to showcase their contribution to the field and to inspire further research and action.

When to Write Research Paper Conclusion

The conclusion of a research paper should be written after the body of the paper has been completed. It should not be written until the writer has thoroughly analyzed and interpreted their findings and has written a complete and cohesive discussion of the research.

Before writing the conclusion, the writer should review their research paper and consider the key points that they want to convey to the reader. They should also review the research question, hypotheses, and methodology to ensure that they have addressed all of the necessary components of the research.

Once the writer has a clear understanding of the main findings and their significance, they can begin writing the conclusion. The conclusion should be written in a clear and concise manner, and should reiterate the main points of the research while also providing insights and recommendations for future research or action.

Characteristics of Research Paper Conclusion

The characteristics of a research paper conclusion include:

• Clear and concise: The conclusion should be written in a clear and concise manner, summarizing the key findings and their significance.
• Comprehensive: The conclusion should address all of the main points of the research paper, including the research question or problem, the methodology, the main results, and their implications.
• Future-oriented : The conclusion should provide insights and recommendations for future research or action, based on the findings of the research.
• Impressive : The conclusion should leave a lasting impression on the reader, emphasizing the importance of the research and its potential impact.
• Objective : The conclusion should be based on the evidence presented in the research paper, and should avoid personal biases or opinions.
• Unique : The conclusion should be unique to the research paper and should not simply repeat information from the introduction or body of the paper.

Advantages of Research Paper Conclusion

The advantages of a research paper conclusion include:

• Summarizing the key findings : The conclusion provides a summary of the main findings of the research, making it easier for the reader to understand the key points of the study.
• Emphasizing the significance of the research: The conclusion emphasizes the importance of the research and its potential impact, making it more likely that readers will take the research seriously and consider its implications.
• Providing recommendations for future research or action : The conclusion suggests practical recommendations for future research or action, based on the findings of the study.
• Providing closure to the research paper : The conclusion provides a sense of closure to the research paper, tying together the different sections of the paper and leaving a lasting impression on the reader.
• Demonstrating the writer’s contribution to the field : The conclusion provides the writer with an opportunity to showcase their contribution to the field and to inspire further research and action.

Limitations of Research Paper Conclusion

While the conclusion of a research paper has many advantages, it also has some limitations that should be considered, including:

• I nability to address all aspects of the research: Due to the limited space available in the conclusion, it may not be possible to address all aspects of the research in detail.
• Subjectivity : While the conclusion should be objective, it may be influenced by the writer’s personal biases or opinions.
• Lack of new information: The conclusion should not introduce new information that has not been discussed in the body of the research paper.
• Lack of generalizability: The conclusions drawn from the research may not be applicable to other contexts or populations, limiting the generalizability of the study.
• Misinterpretation by the reader: The reader may misinterpret the conclusions drawn from the research, leading to a misunderstanding of the findings.

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Writing the parts of scientific reports

22 Writing the conclusion & recommendations

There are probably some overlaps between the Conclusion and the Discussion section. Nevertheless, this section gives you the opportunity to highlight the most important points in your report, and is sometimes the only section read. Think about what your research/ study has achieved, and the most important findings and ideas you want the reader to know. As all studies have limitations also think about what you were not able to cover (this shows that you are able to evaluate your own work objectively).

Possible structure of this section:

Use present perfect to sum up/ evaluate:

This study has explored/ has attempted …

Use past tense to state what your aim was and to refer to actions you carried out:

• This study was intended to analyse …
• The aim of this study was to …

Use present tense to evaluate your study and to state the generalizations and implications that you draw from your findings.

• The results add to the knowledge of …
• These findings s uggest that …

You can either use present tense or past tense to summarize your results.

• The findings reveal …
• It was found that …

Achievements of this study (positive)

• This study provides evidence that …
• This work has contributed to a number of key issues in the field such as …

Limitations of the study (negative)

• Several limitations should be noted. First …

Combine positive and negative remarks to give a balanced assessment:

• Although this research is somewhat limited in scope, its findings can provide a basis for future studies.
• Despite the limitations, findings from the present study can help us understand …

Use more cautious language (modal verbs may, can, could)

• There are a number of possible extensions of this research …
• The findings suggest the possibility for future research on …
• These results may be important for future studies on …
• Examining a wider context could/ would lead …

Or indicate that future research is needed

• There is still a need for future research to determine …
• Further studies should be undertaken to discover…
• It would be worthwhile to investigate …

Academic Writing in a Swiss University Context Copyright © 2018 by Irene Dietrichs. All Rights Reserved.

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• How to Write Discussions and Conclusions

The discussion section contains the results and outcomes of a study. An effective discussion informs readers what can be learned from your experiment and provides context for the results.

What makes an effective discussion?

When you’re ready to write your discussion, you’ve already introduced the purpose of your study and provided an in-depth description of the methodology. The discussion informs readers about the larger implications of your study based on the results. Highlighting these implications while not overstating the findings can be challenging, especially when you’re submitting to a journal that selects articles based on novelty or potential impact. Regardless of what journal you are submitting to, the discussion section always serves the same purpose: concluding what your study results actually mean.

A successful discussion section puts your findings in context. It should include:

• the results of your research,
• a discussion of related research, and
• a comparison between your results and initial hypothesis.

Tip: Not all journals share the same naming conventions.

You can apply the advice in this article to the conclusion, results or discussion sections of your manuscript.

Our Early Career Researcher community tells us that the conclusion is often considered the most difficult aspect of a manuscript to write. To help, this guide provides questions to ask yourself, a basic structure to model your discussion off of and examples from published manuscripts. 

Questions to ask yourself:

• Was my hypothesis correct?
• If my hypothesis is partially correct or entirely different, what can be learned from the results? 
• How do the conclusions reshape or add onto the existing knowledge in the field? What does previous research say about the topic? 
• Why are the results important or relevant to your audience? Do they add further evidence to a scientific consensus or disprove prior studies? 
• How can future research build on these observations? What are the key experiments that must be done? 
• What is the “take-home” message you want your reader to leave with?

How to structure a discussion

Trying to fit a complete discussion into a single paragraph can add unnecessary stress to the writing process. If possible, you’ll want to give yourself two or three paragraphs to give the reader a comprehensive understanding of your study as a whole. Here’s one way to structure an effective discussion:

Writing Tips

While the above sections can help you brainstorm and structure your discussion, there are many common mistakes that writers revert to when having difficulties with their paper. Writing a discussion can be a delicate balance between summarizing your results, providing proper context for your research and avoiding introducing new information. Remember that your paper should be both confident and honest about the results! 

• Read the journal’s guidelines on the discussion and conclusion sections. If possible, learn about the guidelines before writing the discussion to ensure you’re writing to meet their expectations. 
• Begin with a clear statement of the principal findings. This will reinforce the main take-away for the reader and set up the rest of the discussion. 
• Explain why the outcomes of your study are important to the reader. Discuss the implications of your findings realistically based on previous literature, highlighting both the strengths and limitations of the research. 
• State whether the results prove or disprove your hypothesis. If your hypothesis was disproved, what might be the reasons? 
• Introduce new or expanded ways to think about the research question. Indicate what next steps can be taken to further pursue any unresolved questions. 
• If dealing with a contemporary or ongoing problem, such as climate change, discuss possible consequences if the problem is avoided. 
• Be concise. Adding unnecessary detail can distract from the main findings. 

Don’t

• Rewrite your abstract. Statements with “we investigated” or “we studied” generally do not belong in the discussion. 
• Include new arguments or evidence not previously discussed. Necessary information and evidence should be introduced in the main body of the paper. 
• Apologize. Even if your research contains significant limitations, don’t undermine your authority by including statements that doubt your methodology or execution. 
• Shy away from speaking on limitations or negative results. Including limitations and negative results will give readers a complete understanding of the presented research. Potential limitations include sources of potential bias, threats to internal or external validity, barriers to implementing an intervention and other issues inherent to the study design. 
• Overstate the importance of your findings. Making grand statements about how a study will fully resolve large questions can lead readers to doubt the success of the research. 

Snippets of Effective Discussions:

Consumer-based actions to reduce plastic pollution in rivers: A multi-criteria decision analysis approach

Identifying reliable indicators of fitness in polar bears

• How to Write a Great Title
• How to Write an Abstract
• How to Write Your Methods
• How to Report Statistics
• How to Edit Your Work

The contents of the Peer Review Center are also available as a live, interactive training session, complete with slides, talking points, and activities. …

The contents of the Writing Center are also available as a live, interactive training session, complete with slides, talking points, and activities. …

There’s a lot to consider when deciding where to submit your work. Learn how to choose a journal that will help your study reach its audience, while reflecting your values as a researcher…

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6.6: Formal Report—Conclusion, Recommendations, References, and Appendices

Learning objectives.

• Examine the remaining report sections: conclusion, recommendation, reference list, appendices

What Are the Remaining Report Sections?

Conclusions and recommendations.

The conclusions and recommendations section conveys the key results from the analysis in the discussion section. Up to this point, readers have carefully reviewed the data in the report; they are now logically prepared to read the report’s conclusions and recommendations.

According to OACETT (2021), “Conclusions are reasoned judgment and fact, not opinion. Conclusions consider all of the variables and relate cause and effect. Conclusions analyze, evaluate, and make comparisons and contrasts” (p. 7) and “Recommendation(s) (if applicable) suggest a course of action and are provided when there are additional areas for study, or if the reason for the Technology Report was to determine the best action going forward” (p. 7).

You may present the conclusions and recommendations in a numbered or bulleted list to enhance readability.

Reference Page

All formal reports should include a reference page; this page documents the sources cited within the report. The recipient(s) of the report can also refer to this page to locate sources for further research.

Documenting your information sources is all about establishing, maintaining, and protecting your credibility in the profession. You must cite (“document”) borrowed information regardless of the shape or form in which you present it. Whether you directly quote it, paraphrase it, or summarize it—it’s still borrowed information. Whether it comes from a book, article, a diagram, a table, a web page, a product brochure, an expert whom you interview in person—it’s still borrowed information.

Documentation systems vary according to professionals and fields. In ENGL 250, we follow  APA. Refer to a credible APA guide for support.

Appendices are those extra sections in a report that follow the conclusion. According to OACETT (2021), “Appendices can include detailed calculations, tables, drawings, specifications, and technical literature” (p. 7).

Anything that does not comfortably fit in the main part of the report but cannot be left out of the report altogether should go into the appendices. They are commonly used for large tables of data, big chunks of sample code, background that is too basic or too advanced for the body of the report, or large illustrations that just do not fit in the body of the report. Anything that you feel is too large for the main part of the report or that you think would be distracting and interrupt the flow of the report is a good candidate for an appendix.

References & Attributions

Blicq, R., & Moretto, L. (2012).  Technically write. (8th Canadian Ed.). Pearson Canada.

OACETT. (2021).  Technology report guidelines . https://www.oacett.org/getmedia/9f9623ac-73ab-4f99-acca-0d78dee161ab/TR_GUIDELINES_Final.pdf.aspx

Attributions

Content is adapted from Technical Writing by Allison Gross, Annemarie Hamlin, Billy Merck, Chris Rubio, Jodi Naas, Megan Savage, and Michele DeSilva, which is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Writing in a Technical Environment (First Edition) Copyright © 2022 by Centennial College is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Implications or Recommendations in Research: What's the Difference?

• Peer Review

High-quality research articles that get many citations contain both implications and recommendations. Implications are the impact your research makes, whereas recommendations are specific actions that can then be taken based on your findings, such as for more research or for policymaking.

Updated on August 23, 2022

That seems clear enough, but the two are commonly confused.

This confusion is especially true if you come from a so-called high-context culture in which information is often implied based on the situation, as in many Asian cultures. High-context cultures are different from low-context cultures where information is more direct and explicit (as in North America and many European cultures).

Let's set these two straight in a low-context way; i.e., we'll be specific and direct! This is the best way to be in English academic writing because you're writing for the world.

Implications and recommendations in a research article

The standard format of STEM research articles is what's called IMRaD:

• Introduction
• Discussion/conclusions

Some journals call for a separate conclusions section, while others have the conclusions as the last part of the discussion. You'll write these four (or five) sections in the same sequence, though, no matter the journal.

The discussion section is typically where you restate your results and how well they confirmed your hypotheses. Give readers the answer to the questions for which they're looking to you for an answer.

At this point, many researchers assume their paper is finished. After all, aren't the results the most important part? As you might have guessed, no, you're not quite done yet.

The discussion/conclusions section is where to say what happened and what should now happen

The discussion/conclusions section of every good scientific article should contain the implications and recommendations.

The implications, first of all, are the impact your results have on your specific field. A high-impact, highly cited article will also broaden the scope here and provide implications to other fields. This is what makes research cross-disciplinary.

Recommendations, however, are suggestions to improve your field based on your results.

These two aspects help the reader understand your broader content: How and why your work is important to the world. They also tell the reader what can be changed in the future based on your results.

These aspects are what editors are looking for when selecting papers for peer review.

Implications and recommendations are, thus, written at the end of the discussion section, and before the concluding paragraph. They help to “wrap up” your paper. Once your reader understands what you found, the next logical step is what those results mean and what should come next.

Then they can take the baton, in the form of your work, and run with it. That gets you cited and extends your impact!

The order of implications and recommendations also matters. Both are written after you've summarized your main findings in the discussion section. Then, those results are interpreted based on ongoing work in the field. After this, the implications are stated, followed by the recommendations.

Writing an academic research paper is a bit like running a race. Finish strong, with your most important conclusion (recommendation) at the end. Leave readers with an understanding of your work's importance. Avoid generic, obvious phrases like "more research is needed to fully address this issue." Be specific.

The main differences between implications and recommendations (table)

Now let's dig a bit deeper into actually how to write these parts.

What are implications?

Research implications tell us how and why your results are important for the field at large. They help answer the question of “what does it mean?” Implications tell us how your work contributes to your field and what it adds to it. They're used when you want to tell your peers why your research is important for ongoing theory, practice, policymaking, and for future research.

Crucially, your implications must be evidence-based. This means they must be derived from the results in the paper.

Implications are written after you've summarized your main findings in the discussion section. They come before the recommendations and before the concluding paragraph. There is no specific section dedicated to implications. They must be integrated into your discussion so that the reader understands why the results are meaningful and what they add to the field.

A good strategy is to separate your implications into types. Implications can be social, political, technological, related to policies, or others, depending on your topic. The most frequently used types are theoretical and practical. Theoretical implications relate to how your findings connect to other theories or ideas in your field, while practical implications are related to what we can do with the results.

Key features of implications

• State the impact your research makes
• Helps us understand why your results are important
• Must be evidence-based
• Written in the discussion, before recommendations
• Can be theoretical, practical, or other (social, political, etc.)

Examples of implications

Let's take a look at some examples of research results below with their implications.

The result : one study found that learning items over time improves memory more than cramming material in a bunch of information at once .

The implications : This result suggests memory is better when studying is spread out over time, which could be due to memory consolidation processes.

The result : an intervention study found that mindfulness helps improve mental health if you have anxiety.

The implications : This result has implications for the role of executive functions on anxiety.

The result : a study found that musical learning helps language learning in children .

The implications : these findings suggest that language and music may work together to aid development.

What are recommendations?

As noted above, explaining how your results contribute to the real world is an important part of a successful article.

Likewise, stating how your findings can be used to improve something in future research is equally important. This brings us to the recommendations.

Research recommendations are suggestions and solutions you give for certain situations based on your results. Once the reader understands what your results mean with the implications, the next question they need to know is "what's next?"

Recommendations are calls to action on ways certain things in the field can be improved in the future based on your results. Recommendations are used when you want to convey that something different should be done based on what your analyses revealed.

Similar to implications, recommendations are also evidence-based. This means that your recommendations to the field must be drawn directly from your results.

The goal of the recommendations is to make clear, specific, and realistic suggestions to future researchers before they conduct a similar experiment. No matter what area your research is in, there will always be further research to do. Try to think about what would be helpful for other researchers to know before starting their work.

Recommendations are also written in the discussion section. They come after the implications and before the concluding paragraphs. Similar to the implications, there is usually no specific section dedicated to the recommendations. However, depending on how many solutions you want to suggest to the field, they may be written as a subsection.

Key features of recommendations

• Statements about what can be done differently in the field based on your findings
• Must be realistic and specific
• Written in the discussion, after implications and before conclusions
• Related to both your field and, preferably, a wider context to the research

Examples of recommendations

Here are some research results and their recommendations.

A meta-analysis found that actively recalling material from your memory is better than simply re-reading it .

• The recommendation: Based on these findings, teachers and other educators should encourage students to practice active recall strategies.

A medical intervention found that daily exercise helps prevent cardiovascular disease .

• The recommendation: Based on these results, physicians are recommended to encourage patients to exercise and walk regularly. Also recommended is to encourage more walking through public health offices in communities.

A study found that many research articles do not contain the sample sizes needed to statistically confirm their findings .

The recommendation: To improve the current state of the field, researchers should consider doing power analysis based on their experiment's design.

What else is important about implications and recommendations?

When writing recommendations and implications, be careful not to overstate the impact of your results. It can be tempting for researchers to inflate the importance of their findings and make grandiose statements about what their work means.

Remember that implications and recommendations must be coming directly from your results. Therefore, they must be straightforward, realistic, and plausible.

Another good thing to remember is to make sure the implications and recommendations are stated clearly and separately. Do not attach them to the endings of other paragraphs just to add them in. Use similar example phrases as those listed in the table when starting your sentences to clearly indicate when it's an implication and when it's a recommendation.

When your peers, or brand-new readers, read your paper, they shouldn't have to hunt through your discussion to find the implications and recommendations. They should be clear, visible, and understandable on their own.

That'll get you cited more, and you'll make a greater contribution to your area of science while extending the life and impact of your work.

The AJE Team

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Careers in Qual

Quick answers, conclusions and recommendations, related terms.

• Differences between a finding, a conclusion, and a recommendation: examples
• Learning Center

Table of Contents

• Defining the Terms: What Is a Finding, a Conclusion, and a Recommendation in M&E?
• Why It Matters: Understanding the Importance of Differentiating between Findings, Conclusions, and Recommendations in M&E
• How to Identify and Distinguish between Findings, Conclusions, and Recommendations in M&E
• How to Communicate Findings, Conclusions, and Recommendations Effectively in M&E Reports
• The Benefits of Clear and Accurate Reporting of Findings, Conclusions, and Recommendations in M&E

1. Defining the Terms: What Is a Finding, a Conclusion, and a Recommendation in M&E?

Monitoring and Evaluation (M&E) is a critical process for assessing the effectiveness of development programs and policies. During the M&E process, evaluators collect and analyze data to draw conclusions and make recommendations for program improvement. In M&E, it is essential to differentiate between findings, conclusions, and recommendations to ensure that the evaluation report accurately reflects the program’s strengths, weaknesses, and potential areas for improvement.

In an evaluation report, a finding, a conclusion, and a recommendation serve different purposes and convey different information. Here are the differences between these three elements:

1.1 Finding

A finding is a factual statement that is based on evidence collected during the evaluation . It describes what was observed, heard, or experienced during the evaluation process. A finding should be objective, unbiased, and supported by data. Findings are typically presented in the form of a summary or a list of key points, and they provide the basis for the evaluation’s conclusions and recommendations.

Findings are an important part of the evaluation process, as they provide objective and unbiased information about what was observed, heard, or experienced during the evaluation. Findings are based on the evidence collected during the evaluation, and they should be supported by data and other relevant information. They are typically presented in a summary or list format, and they serve as the basis for the evaluation’s conclusions and recommendations. By presenting clear and accurate findings, evaluators can help stakeholders understand the strengths and weaknesses of the program or initiative being evaluated, and identify opportunities for improvement.

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1.2 Examples of Finding

Here are some examples of findings in M&E:

• “Program participants reported a high level of satisfaction with the quality of training provided, with 85% rating it as good or excellent.”
• “The program was successful in increasing the number of girls enrolled in secondary school, with a 25% increase observed in the target communities.”
• “Program beneficiaries reported improved access to healthcare services, with a 40% increase in the number of individuals accessing healthcare facilities in the program area.”
• “The program’s training curriculum was found to be outdated and ineffective, with only 30% of participants reporting that the training was useful.”
• “The program’s monitoring and evaluation system was found to be inadequate, with data quality issues and insufficient capacity among staff to carry out effective monitoring and evaluation activities.”

These findings represent objective, measurable results of the data collected during the M&E process, and can be used to inform program design and implementation, as well as to draw conclusions and make recommendations for improvement.

1.3 Conclusion

A conclusion is a judgment or interpretation of the findings based on the evidence collected during the evaluation. It is typically expressed in terms of what the findings mean or what can be inferred from them. Conclusions should be logical, evidence-based, and free from personal bias or opinion.

Conclusions often answer the evaluation questions or objectives, and they provide insights into the effectiveness or impact of the program, project, or intervention being evaluated. By synthesizing the findings into a cohesive narrative, evaluators can provide stakeholders with a clear and actionable understanding of the program or initiative being evaluated. Conclusions can also inform future planning and decision-making, by identifying areas for improvement and highlighting successful strategies or interventions. Overall, conclusions are a crucial component of the evaluation process, as they help stakeholders make informed decisions about the programs and initiatives they are involved in.

1.4 Examples of Conclusion

Here are some examples of conclusions in M&E:

• Based on the data collected, it can be concluded that the program was successful in achieving its objective of increasing access to clean water in the target communities.”
• “The data indicates that the program’s training curriculum is ineffective and in need of revision in order to better meet the needs of participants.”
• “It can be concluded that the program’s community mobilization efforts were successful in increasing community participation and ownership of the program.”
• “Based on the data collected, it is concluded that the program’s impact on improving maternal and child health outcomes is limited and further efforts are needed to address the underlying health system and infrastructure issues.”
• “The data collected indicates that the program’s impact on reducing poverty in the target area is modest, but still significant, and further investment in complementary programs may be needed to achieve more substantial reductions in poverty rates.”
• These conclusions are based on the evidence presented in the findings and represent the interpretation or explanation of the meaning of the findings. They help to provide insight into the impact and effectiveness of the program and can be used to make recommendations for improvement.

1.5 Recommendation

A recommendation is a specific action or set of actions proposed based on the findings and conclusions of the evaluation. Recommendations should be practical, feasible, and tailored to the needs of the stakeholders who will be implementing them. They should be supported by evidence and aligned with the goals of the program, project, or intervention being evaluated.

Recommendations often provide guidance on how to improve the effectiveness or efficiency of the program, project, or intervention, and they can help to inform decision-making and resource allocation. By presenting clear and actionable recommendations, evaluators can help stakeholders identify and prioritize areas for improvement, and develop strategies to address identified issues. Recommendations can also serve as a roadmap for future planning and implementation and can help to ensure that the program or initiative continues to achieve its intended outcomes over time.

Overall, recommendations are an essential component of the evaluation process, as they help to bridge the gap between evaluation findings and programmatic action. By proposing specific and evidence-based actions, evaluators can help to ensure that evaluation results are translated into meaningful improvements in program design, implementation, and outcomes.

1.6 Examples of Recommendation

Here are some examples of recommendations in M&E:

• “To improve the effectiveness of the program’s training, the curriculum should be revised to better meet the needs of participants, with a focus on practical, hands-on learning activities.”
• “To address the data quality issues identified in the monitoring and evaluation system, staff should receive additional training on data collection and management, and the system should be revised to incorporate additional quality control measures.”
• “To build on the success of the program’s community mobilization efforts, further investments should be made in strengthening community-based organizations and networks, and in promoting greater community participation in program planning and decision-making.”
• “To improve the program’s impact on maternal and child health outcomes, efforts should be made to address underlying health system and infrastructure issues, such as improving access to health facilities and training health workers.”
• “To achieve more substantial reductions in poverty rates in the target area, complementary programs should be implemented to address issues such as economic development, education, and social protection.”

These recommendations are specific actions that can be taken based on the findings and conclusions of the M&E process. They should be practical, feasible, and based on the evidence presented in the evaluation report. By implementing these recommendations, development practitioners can improve program effectiveness and impact, and better meet the needs of the target population.

2. Why It Matters: Understanding the Importance of Differentiating between Findings, Conclusions, and Recommendations in M&E

Differentiating between findings, conclusions, and recommendations is crucial in M&E for several reasons. First, it ensures accuracy and clarity in the evaluation report. Findings, conclusions, and recommendations are distinct components of an evaluation report, and they serve different purposes. By clearly defining and differentiating these components, evaluators can ensure that the report accurately reflects the program’s strengths and weaknesses, potential areas for improvement, and the evidence supporting the evaluation’s conclusions.

Second, differentiating between findings, conclusions, and recommendations helps to facilitate evidence-based decision-making. By clearly presenting the evidence supporting the evaluation’s findings and conclusions, and making recommendations based on that evidence, evaluators can help program managers and policymakers make informed decisions about program design, implementation, and resource allocation.

Finally, differentiating between findings, conclusions, and recommendations can help to increase the credibility and trustworthiness of the evaluation report. Clear and accurate reporting of findings, conclusions, and recommendations helps to ensure that stakeholders understand the evaluation’s results and recommendations, and can have confidence in the evaluation’s rigor and objectivity.

In summary, differentiating between findings, conclusions, and recommendations is essential in M&E to ensure accuracy and clarity in the evaluation report, facilitate evidence-based decision-making, and increase the credibility and trustworthiness of the evaluation.

3. How to Identify and Distinguish between Findings, Conclusions, and Recommendations in M&E

Identifying and distinguishing between findings, conclusions, and recommendations in M&E requires careful consideration of the evidence and the purpose of each component. Here are some tips for identifying and distinguishing between findings, conclusions, and recommendations in M&E:

• Findings: Findings are the results of the data analysis and should be objective and evidence-based. To identify findings, look for statements that summarize the data collected and analyzed during the evaluation. Findings should be specific, measurable, and clearly stated.
• Conclusions: Conclusions are interpretations of the findings and should be supported by the evidence. To distinguish conclusions from findings, look for statements that interpret or explain the meaning of the findings. Conclusions should be logical and clearly explained, and should take into account any limitations of the data or analysis.
• Recommendations: Recommendations are specific actions that can be taken based on the findings and conclusions. To distinguish recommendations from conclusions, look for statements that propose actions to address the issues identified in the evaluation. Recommendations should be practical, feasible, and clearly explained, and should be based on the evidence presented in the findings and conclusions.

It is also important to ensure that each component is clearly labeled and presented in a logical order in the evaluation report. Findings should be presented first, followed by conclusions and then recommendations.

In summary, identifying and distinguishing between findings, conclusions, and recommendations in M&E requires careful consideration of the evidence and the purpose of each component. By ensuring that each component is clearly labeled and presented in a logical order, evaluators can help to ensure that the evaluation report accurately reflects the program’s strengths, weaknesses, and potential areas for improvement, and facilitates evidence-based decision-making.

4. How to Communicate Findings, Conclusions, and Recommendations Effectively in M&E Reports

Communicating findings, conclusions, and recommendations effectively in M&E reports is critical to ensuring that stakeholders understand the evaluation’s results and recommendations and can use them to inform decision-making. Here are some tips for communicating findings, conclusions, and recommendations effectively in M&E reports:

• Use clear and concise language: Use clear, simple language to explain the findings, conclusions, and recommendations. Avoid technical jargon and use examples to illustrate key points.
• Present data visually: Use tables, graphs, and charts to present data visually, making it easier for stakeholders to understand and interpret the findings.
• Provide context: Provide context for the findings, conclusions, and recommendations by explaining the evaluation’s purpose, methodology, and limitations. This helps stakeholders understand the scope and significance of the evaluation’s results and recommendations.
• Highlight key points: Use headings, bullet points, and other formatting techniques to highlight key points, making it easier for stakeholders to identify and remember the most important findings, conclusions, and recommendations.
• Be objective: Present the findings, conclusions, and recommendations objectively and avoid bias. This helps to ensure that stakeholders have confidence in the evaluation’s rigor and objectivity.
• Tailor the report to the audience: Tailor the report to the audience by using language and examples that are relevant to their interests and needs. This helps to ensure that the report is accessible and useful to stakeholders.

In summary, communicating findings, conclusions, and recommendations effectively in M&E reports requires clear and concise language, visual presentation of data, contextualization, highlighting of key points, objectivity, and audience-tailoring. By following these tips, evaluators can help to ensure that stakeholders understand the evaluation’s results and recommendations and can use them to inform decision-making.

5. The Benefits of Clear and Accurate Reporting of Findings, Conclusions, and Recommendations in M&E

Clear and accurate reporting of M&E findings, conclusions, and recommendations has many benefits for development programs and policies. One of the most significant benefits is improved program design and implementation. By clearly identifying areas for improvement, program designers and implementers can make adjustments that lead to more effective and efficient programs that better meet the needs of the target population.

Another important benefit is evidence-based decision-making. When M&E findings, conclusions, and recommendations are reported accurately and clearly, decision-makers have access to reliable information on which to base their decisions. This can lead to more informed decisions about program design, implementation, and resource allocation.

Clear and accurate reporting of M&E findings, conclusions, and recommendations also supports accountability. By reporting transparently on program performance, development practitioners can build trust and support among stakeholders, including program beneficiaries, donors, and the general public.

M&E findings, conclusions, and recommendations also support continuous learning and improvement. By identifying best practices, lessons learned, and areas for improvement, development practitioners can use this information to improve future programming.

Finally, clear and accurate reporting of M&E findings, conclusions, and recommendations can increase program impact. By identifying areas for improvement and supporting evidence-based decision-making, development programs can have a greater positive impact on the communities they serve.

In summary, clear and accurate reporting of M&E findings, conclusions, and recommendations is critical for improving program design and implementation, supporting evidence-based decision-making, ensuring accountability, supporting continuous learning and improvement, and increasing program impact. By prioritizing clear and accurate reporting, development practitioners can ensure that their programs are effective, efficient, and have a positive impact on the communities they serve.

Very interesting reading which clearly explain the M&E finding, recommendation and conclusion, which sometimes the terms can be confusing

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Conducting Biosocial Surveys: Collecting, Storing, Accessing, and Protecting Biospecimens and Biodata (2010)

Chapter: 5 findings, conclusions, and recommendations, 5 findings, conclusions, and recommendations.

A s the preceding chapters have made clear, incorporating biological specimens into social science surveys holds great scientific potential, but also adds a variety of complications to the tasks of both individual researchers and institutions. These complications arise in a number of areas, including collecting, storing, using, and distributing biospecimens; sharing data while protecting privacy; obtaining informed consent from participants; and engaging with Institutional Review Boards (IRBs). Any effort to make such research easier and more effective will need to address the issues in these areas.

In considering its recommendations, the panel found it useful to think of two categories: (1) recommendations that apply to individual investigators, and (2) recommendations that are addressed to the National Institute on Aging (NIA) or other institutions, particularly funding agencies. Researchers who wish to collect biological specimens with social science data will need to develop new skills in a variety of areas, such as the logistics of specimen storage and management, the development of more diverse informed consent forms, and ways of dealing with the disclosure risks associated with sharing biogenetic data. At the same time, NIA and other funding agencies must provide researchers the tools they need to succeed. These tools include such things as biorepositories for maintaining and distributing specimens, better guidance on informed consent policies, and better ways to share data without risking confidentiality.

TAKING ADVANTAGE OF EXISTING EXPERTISE

Although working with biological specimens will be new and unfamiliar to many social scientists, it is an area in which biomedical researchers have a great deal of expertise and experience. Many existing documents describe recommended procedures and laboratory practices for the handling of biospecimens. These documents provide an excellent starting point for any social scientist who is interested in adding biospecimens to survey research.

Recommendation 1: Social scientists who are planning to add biological specimens to their survey research should familiarize themselves with existing best practices for the collection, storage, use, and distribution of biospecimens. First and foremost, the design of the protocol for collec tion must ensure the safety of both participants and survey staff (data and specimen collectors and handlers).

Although existing best-practice documents were not developed with social science surveys in mind, their guidelines have been field-tested and approved by numerous IRBs and ethical oversight committees. The most useful best-practice documents are updated frequently to reflect growing knowledge and changing opinions about the best ways to collect, store, use, and distribute biological specimens. At the same time, however, many issues arising from the inclusion of biospecimens in social science surveys are not fully addressed in the best-practice documents intended for biomedical researchers. For guidance on these issues, it will be necessary to seek out information aimed more specifically at researchers at the intersection of social science and biomedicine.

COLLECTING, STORING, USING, AND DISTRIBUTING BIOSPECIMENS

As described in Chapter 2 , the collection, storage, use, and distribution of biospecimens and biodata are tasks that are likely to be unfamiliar to many social scientists and that raise a number of issues with which even specialists are still grappling. For example, which biospecimens in a repository should be shared, given that in most cases the amount of each specimen is limited? And given that the available technology for cost-efficient analysis of biospecimens, particularly genetic analysis, is rapidly improving, how much of any specimen should be used for immediate research and analysis, and how much should be stored for analysis at a later date? Collecting, storing, using, and distributing biological specimens also present significant practical and financial challenges for social scientists. Many of the questions they must address, such as exactly what should be held, where it should be held, and what should be shared or distributed, have not yet been resolved.

Developing Data Sharing Plans

An important decision concerns who has access to any leftover biospecimens. This is a problem more for biospecimens than for biodata because in most cases, biospecimens can be exhausted. Should access be determined according to the principle of first funded, first served? Should there be a formal application process for reviewing the scientific merits of a particular investigation? For studies that involve international collaboration, should foreign investigators have access? And how exactly should these decisions be made? Recognizing that some proposed analyses may lie beyond the competence of the original investigators, as well as the possibility that principal investigators may have a conflict of interest in deciding how to use any remaining biospecimens, one option is for a principal investigator to assemble a small scientific committee to judge the merits of each application, including the relevance of the proposed study to the parent study and the capacities of the investigators. Such committees should publish their review criteria to help prospective applicants. A potential problem with such an approach, however, is that many projects may not have adequate funding to carry out such tasks.

Recommendation 2: Early in the planning process, principal investigators who will be collecting biospecimens as part of a social science survey should develop a complete data sharing plan.

This plan should spell out the criteria for allowing other researchers to use (and therefore deplete) the available stock of biospecimens, as well as to gain access to any data derived therefrom. To avoid any appearance of self-interest, a project might empower an external advisory board to make decisions about access to its data. The data sharing plan should also include provisions for the storage and retrieval of biospecimens and clarify how the succession of responsibility for and control of the biospecimens will be handled at the conclusion of the project.

Recommendation 3: NIA (or preferably the National Institutes of Health [NIH]) should publish guidelines for principal investigators containing a list of points that need to be considered for an acceptable data sharing plan. In addition to staff review, Scientific Review Panels should read and comment on all proposed data sharing plans. In much the same way as an unacceptable human subjects plan, an inadequate data sharing plan should hold up an otherwise acceptable proposal.

Supporting Social Scientists in the Storage of Biospecimens

The panel believes that many social scientists who decide to add the collection of biospecimens to their surveys may be ill equipped to provide for the storage and distribution of the specimens.

Conclusion: The issues related to the storage and distribution of biospecimens are too complex and involve too many hidden costs to assume that social scientists without suitable knowledge, experience, and resources can handle them without assistance.

Investigators should therefore have the option of delegating the storage and distribution of biospecimens collected as part of social science surveys to a centralized biorepository. Depending on the circumstances, a project might choose to utilize such a facility for immediate use, long-term or archival storage, or not at all.

Recommendation 4: NIA and other relevant funding agencies should support at least one central facility for the storage and distribution of biospecimens collected as part of the research they support.

PROTECTING PRIVACY AND CONFIDENTIALITY: SHARING DIGITAL REPRESENTATIONS OF BIOLOGICAL AND SOCIAL DATA

Several different types of data must be kept confidential: survey data, data derived from biospecimens, and all administrative and operational data. In the discussion of protecting confidentiality and privacy, this report has focused on biodata, but the panel believes it is important to protect all the data collected from survey participants. For many participants, for example, data on wealth, earnings, or sexual behavior can be as or more sensitive than genetic data.

Conclusion: Although biodata tend to receive more attention in discussions of privacy and confidentiality, social science and operational data can be sensitive in their own right and deserve similar attention in such discussions.

Protecting the participants in a social science survey that collects biospecimens requires securing the data, but data are most valuable when they are made available to researchers as widely as possible. Thus there is an inherent tension between the desire to protect the privacy of the participants and the desire to derive as much scientific value from the data as possible, particularly since the costs of data collection and analysis are so high. The following recommendations regarding confidentiality are made in the spirit of balancing these equally important needs.

Genomic data present a particular challenge. Several researchers have demonstrated that it is possible to identify individuals with even modest amounts of such data. When combined with social science data, genomic data may pose an even greater risk to confidentiality. It is difficult to know how much or which genomic data, when combined with social science data, could become critical identifiers in the future. Although the problem is most significant with genomic data, similar challenges can arise with other kinds of data derived from biospecimens.

Conclusion: Unrestricted distribution of genetic and other biodata risks violating promises of confidentiality made to research participants.

There are two basic approaches to protecting confidentiality: restricting data and restricting access. Restricting data—for example, by stripping individual and spatial identifiers and modifying the data to make it difficult or impossible to trace them back to their source—usually makes it possible to release social science data widely. In the case of biodata, however, there is no answer to how little data is required to make a participant uniquely identifiable. Consequently, any release of biodata must be carefully managed to protect confidentiality.

Recommendation 5: No individual-level data containing uniquely identify ing variables, such as genomic data, should be publicly released without explicit informed consent.

Recommendation 6: Genomic data and other individual-level data con taining uniquely identifying variables that are stored or in active use by investigators on their institutional or personal computers should be encrypted at all times.

Even if specific identifying variables, such as names and addresses, are stripped from data, it is still often possible to identify the individuals associated with the data by other means, such as using the variables that remain (age, sex, marital status, family income, etc.) to zero in on possible candidates. In the case of biodata that do not uniquely identify individuals and can change with time, such as blood pressure and physical measurements, it may be possible to share the data with no more protection than stripping identifying variables. Even these data, however, if known to intruders, can increase identification disclosure risk when combined with enough other data. With sufficient characteristics to match, intruders can uniquely identify individuals in shared data if given access to another data source that contains the same information plus identifiers.

Conclusion: Even nonunique biodata, if combined with social science data, may pose a serious risk of reidentification.

In the case of high-dimensional genomic data, standard disclosure limitation techniques, such as data perturbation, are not effective with respect to preserving the utility of the data because they involve such extreme alterations that they would severely distort analyses aimed at determining gene–gene and gene–environment interactions. Standard disclosure limitation methods could be used to generate public-use data sets that would enable low-dimensional analyses involving genes, for example, one gene at a time. However, with several such public releases, it may be possible for a key match to be used to construct a data set with higher-dimensional genomic data.

Conclusion: At present, no data restriction strategy has been demonstrated to protect confidentiality while preserving the usefulness of the data for drawing inferences involving high-dimensional interactions among genomic and social science variables, which are increasingly the target of research. Providing public-use genomic data requires such intense data masking to protect confidentiality that it would distort the high-dimensional analyses that could result in ground-breaking research progress.

Recommendation 7: Both rich genomic data acquired for research and sensitive and potentially identifiable social science data that do not change (or change very little) with time should be shared only under restricted circumstances, such as licensing and (actual or virtual) data enclaves.

As discussed in Chapter 3 , the four basic ways to restrict access to data are licensing, remote execution centers, data enclaves, and virtual data enclaves. Each has its advantages and disadvantages. 1 Licensing, for example, is the least restrictive for a researcher in terms of access to the data, but the licensing process itself can be lengthy and burdensome. Thus it would be useful if the licensing process could be facilitated.

Recommendation 8: NIA (or preferably NIH) should develop new stan dards and procedures for licensing confidential data in ways that will maximize timely access while maintaining security and that can be used by data repositories and by projects that distribute data.

Ways to improve the other approaches to restricted access are needed as well. For example, improving the convenience and availability of virtual data enclaves could increase the use of combined social science and biodata without

a significant increase in risk to confidentiality. The panel notes that much of the discussion of the confidentiality risk posed by the various approaches is theoretical; no one has a clear idea of just what disclosure risks are associated with the various ways of sharing data. It is important to learn more about these disclosure risks for a variety of reasons—determining how to minimize the risks, for instance, or knowing which approaches to sharing data pose the least risk. It would also be useful to be able to describe disclosure risks more accurately to survey participants.

Recommendation 9: NIA and other funding agencies should assess the strength of confidentiality protections through periodic expert audits of confidentiality and computer security. Willingness to participate in such audits should be a condition for receipt of NIA support. Beyond enforce ment, the purpose of such audits would be to identify challenges and solutions.

Evaluating risks and applying protection methods, whether they involve restricted access or restricted data, is a complex process requiring expertise in disclosure protection methods that exceeds what individual principal investigators and their institutions usually possess. Currently, not enough is known to be able to represent these risks either fully or accurately. The NIH requirement for data sharing necessitates a large investment of resources to anticipate which variables are potentially available to intruders and to alter data in ways that reduce disclosure risks while maintaining the utility of the data. Such resources are better spent by principal investigators on collecting and analyzing the data.

Recommendation 10: NIH should consider funding Centers of Excellence to explore new ways of protecting digital representations of data and to assist principal investigators wishing to share data with others. NIH should also support research on disclosure risks and limitations.

Principal investigators could send digital data to these centers, which would organize and manage any restricted access or restricted data policies or provide advisory services to investigators. NIH would maintain the authority to penalize those who violated any confidentiality agreements, for example, by denying them or their home institution NIH funding. Models for these centers include the Inter-university Consortium for Political and Social Research (ICPSR) and its projects supported by NIH and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and the UK data sharing archive. The centers would alleviate the burden of data sharing as mandated of principal investigators by NIH and place it in expert hands. However, excellence in the design of data access and control systems

is likely to require intimate knowledge of each specific data resource, so data producers should be involved in the systems’ development.

INFORMED CONSENT

As described in Chapter 4 , informed consent is a complex subject involving many issues that are still being debated; the growing power of genetic analysis techniques and bioinformatics has only added to this complexity. Given the rapid pace of advances in scientific knowledge and in the technology used to analyze biological materials, it is impossible to predict what information might be gleaned from biological specimens just a few years hence; accordingly, it is impossible, even in theory, to talk about perfectly informed consent. The best one can hope for is relatively well-informed consent from a study’s participants, but knowing precisely what that means is difficult. Determining the scope of informed consent adds another layer of complexity. Will new analyses be covered under the existing consent, for example? There are no clear guidelines on such questions, yet specific details on the scope of consent will likely affect an IRB’s reaction to a study proposal.

What Individual Researchers Need to Know and Do Regarding Informed Consent

To be sure, there is a wide range of views about the practicality of providing adequate protection to participants while proceeding with the scientific enterprise, from assertions that it is simply not possible to provide adequate protection to offers of numerous procedural safeguards but no iron-clad guarantees. This report takes the latter position—that investigators should do their best to communicate adequately and accurately with participants, to provide procedural safeguards to the extent possible, and not to promise what is not possible. 2 Social science researchers need to know that adding the collection of biospecimens to social science surveys changes the nature of informed consent. Informed consent for a traditional social science survey may entail little more than reading a short script over the phone and asking whether the participant is willing to continue; obtaining informed consent for the collection and use of biospecimens and biodata is generally a much more involved process.

Conclusion: Social scientists should be made aware that the process of obtaining informed consent for the use of biospecimens and biodata typically differs from social science norms.

If participants are to provide truly informed consent to taking part in any study, they must be given a certain minimum amount of information. They should be told, for example, what the purpose of the study is, how it is to be carried out, and what participants’ roles are. In addition, because of the unique risks associated with providing biospecimens, participants in a social science survey that involves the collection of such specimens should be provided with other types of information as well. In particular, they should be given detail on the storage and use of the specimens that relates to those risks and can assist them in determining whether to take part in the study.

Recommendation 11: In designing a consent form for the collection of biospecimens, in addition to those elements that are common to social science and biomedical research, investigators should ensure that certain other information is provided to participants:

how long researchers intend to retain their biospecimens and the genomic and other biodata that may be derived from them;

both the risks associated with genomic data and the limits of what they can reveal;

which other researchers will have access to their specimens, to the data derived therefrom, and to information collected in a survey questionnaire;

the limits on researchers’ ability to maintain confidentiality;

any potential limits on participants’ ability to withdraw their speci mens or data from the research;

the penalties 3 that may be imposed on researchers for various types of breaches of confidentiality; and

what plans have been put in place to return to them any medically relevant findings.

Researchers who fail to properly plan for and handle all of these issues before proceeding with a study are in essence compromising assurances under informed consent. The literature on informed consent emphasizes the importance of ensuring that participants understand reasonably well what they are consenting to. This understanding cannot be taken for granted, particularly as it pertains to the use of biological specimens and the data derived therefrom.

While it is not possible to guarantee that participants have a complete understanding of the scientific uses of their specimens or all the possible risks of their participation, they should be able to make a relatively well-informed decision about whether to take part in the study. Thus the ability of various participants to understand the research and the informed consent process must be considered. Even impaired individuals may be able to participate in research if their interests are protected and they can do so only through proxy consent. 4

Recommendation 12: NIA should locate and publicize positive examples of the documentation of consent processes for the collection of biospeci mens. In particular, these examples should take into account the special needs of certain individuals, such as those with sensory problems and the cognitively impaired.

Participants in a biosocial survey are likely to have different levels of comfort concerning how their biospecimens and data will be used. Some may be willing to provide only answers to questions, for example, while others may both answer questions and provide specimens. Among those who provide specimens, some may be willing for the specimens to be used only for the current study, while others may consent to their use in future studies. One effective way to deal with these different comfort levels is to offer a tiered approach to consent that allows participants to determine just how their specimens and data will be used. Tiers might include participating in the survey, providing specimens for genetic and/or nongenetic analysis in a particular study, and allowing the specimens and data to be stored for future uses (genetic and/or nongenetic). For those participants who are willing to have their specimens and data used in future studies, researchers should tell them what sort of approval will be obtained for such use. For example, an IRB may demand reconsent, in which case participants may have to be contacted again before their specimens and data can be used. Ideally, researchers should design their consent forms to avoid the possibility that an IRB will demand a costly or infeasible reconsent process.

Recommendation 13: Researchers should consider adopting a tiered approach to obtaining consent. Participants who are willing to have their specimens and data used in future studies should be informed about the process that will be used to obtain approval for such uses.

What Institutions Should Do Regarding Informed Consent

Because the details of informed consent vary from study to study, individual investigators must bear ultimate responsibility for determining the details of informed consent for any particular study. Thus researchers must understand the various issues and concerns surrounding informed consent and be prepared to make decisions about the appropriate approach for their research in consultation with staff of survey organizations. These decisions should be addressed in the training of survey interviewers. As noted above, however, the issues surrounding informed consent are complex and not completely resolved, and researchers have few options for learning about informed consent as it applies to social science studies that collect biospecimens. Thus it makes sense for agencies funding this research, the Office for Human Research Protection (OHRP), or other appropriate organizations (for example, Public Responsibility in Medicine and Research [PRIM&R]) to provide opportunities for such learning, taking into account the fact that the issues arising in biosocial research do not arise in the standard informed consent situations encountered in social science research. It should also be made clear that the researchers’ institution is usually deemed (e.g., in the courts) to bear much of the responsibility for informed consent.

Recommendation 14: NIA, OHRP, and other appropriate organizations should sponsor training programs, create training modules, and hold informational workshops on informed consent for investigators, staff of survey organizations, including field staff, administrators, and mem bers of IRBs who oversee surveys that collect social science data and biospecimens.

The Return of Medically Relevant Information

An issue related to informed consent is how much information to provide to survey participants once their biological specimens have been analyzed and in particular, how to deal with medically relevant information that may arise from the analysis. What, for example, should a researcher do if a survey participant is found to have a genetic disease that does not appear until later in life? Should the participant be notified? Should participants be asked as part of the initial interview whether they wish to be notified about such a discovery? At this time, there are no generally agreed-upon answers to such questions, but researchers should expect to have to deal with these issues as they analyze the data derived from biological specimens.

Recommendation 15: NIH should direct investigators to formulate a plan in advance concerning the return of any medically relevant findings to

survey participants and to implement that plan in the design and conduct of their informed consent procedures.

INSTITUTIONAL REVIEW BOARDS

Investigators seeking IRB approval for biosocial research face a number of challenges. Few IRBs are familiar with both social and biological science; thus, investigators may find themselves trying to justify standard social science protocols to a biologically oriented IRB or explaining standard biological protocols to an IRB that is used to dealing with social science—or sometimes both. Researchers can expect these obstacles, which arise from the interdisciplinary nature of their work, to be exacerbated by a number of other factors that are characteristic of IRBs in general (see Chapter 4 ).

Recommendation 16: In institutions that have separate biomedical and social science IRBs, mechanisms should be created for sharing expertise during the review of biosocial protocols. 5

What Individual Researchers Need to Do Regarding IRBs

Because the collection of biospecimens as part of social science surveys is still relatively unfamiliar to many IRBs, researchers planning such a study can expect their interactions with the IRB overseeing the research to involve a certain learning curve. The IRB may need extra time to become familiar and comfortable with the proposed practices of the survey, and conversely, the researchers will need time to learn what the IRB will require. Thus it will be advantageous if researchers conducting such studies plan from the beginning to devote additional time to working with their IRBs.

Recommendation 17: Investigators considering collecting biospecimens as part of a social science survey should consult with their IRBs early and often.

What Research Agencies Should Do Regarding IRBs

One way to improve the IRB process would be to give members of IRBs an opportunity to learn more about biosocial research and the risks it entails.

This could be done by individual institutions, but it would be more effective if a national funding agency took the lead (see Recommendation 14).

It is the panel’s hope that its recommendations will support the incorporation of social science and biological data into empirical models, allowing researchers to better document the linkages among social, behavioral, and biological processes that affect health and other measures of well-being while avoiding or minimizing many of the challenges that may arise. Implementing these recommendations will require the combined efforts of both individual investigators and the agencies that support them.

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Recent years have seen a growing tendency for social scientists to collect biological specimens such as blood, urine, and saliva as part of large-scale household surveys. By combining biological and social data, scientists are opening up new fields of inquiry and are able for the first time to address many new questions and connections. But including biospecimens in social surveys also adds a great deal of complexity and cost to the investigator's task. Along with the usual concerns about informed consent, privacy issues, and the best ways to collect, store, and share data, researchers now face a variety of issues that are much less familiar or that appear in a new light.

In particular, collecting and storing human biological materials for use in social science research raises additional legal, ethical, and social issues, as well as practical issues related to the storage, retrieval, and sharing of data. For example, acquiring biological data and linking them to social science databases requires a more complex informed consent process, the development of a biorepository, the establishment of data sharing policies, and the creation of a process for deciding how the data are going to be shared and used for secondary analysis--all of which add cost to a survey and require additional time and attention from the investigators. These issues also are likely to be unfamiliar to social scientists who have not worked with biological specimens in the past. Adding to the attraction of collecting biospecimens but also to the complexity of sharing and protecting the data is the fact that this is an era of incredibly rapid gains in our understanding of complex biological and physiological phenomena. Thus the tradeoffs between the risks and opportunities of expanding access to research data are constantly changing.

Conducting Biosocial Surveys offers findings and recommendations concerning the best approaches to the collection, storage, use, and sharing of biospecimens gathered in social science surveys and the digital representations of biological data derived therefrom. It is aimed at researchers interested in carrying out such surveys, their institutions, and their funding agencies.

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O’Hara R, Johnson M, Hirst E, et al. A qualitative study of decision-making and safety in ambulance service transitions. Southampton (UK): NIHR Journals Library; 2014 Dec. (Health Services and Delivery Research, No. 2.56.)

A qualitative study of decision-making and safety in ambulance service transitions.

Chapter 8 conclusions and recommendations.

The aim of this study was to explore the range and nature of influences on safety in decision-making by ambulance service staff (paramedics). A qualitative approach was adopted using a range of complementary methods. The study has provided insights on the types of decisions that staff engage in on a day-to-day basis. It has also identified a range of system risk factors influencing decisions about patient care. Although this was a relatively small-scale exploratory study, confidence in the generalisability of the headline findings is enhanced by the high level of consistency in the findings, obtained using multiple methods, and the notable consensus among participants.

The seven predominant system influences identified should not be considered discrete but as overlapping and complementary issues. They also embody a range of subthemes that represent topics for future research and/or intervention.

The apparently high level of consistency across the participating trusts suggests that the issues identified may be generic and relevant to other ambulance service trusts.

In view of the remit of this study, aspects relating to system weaknesses and potential threats to patient safety dominate in the account of findings. However, it should be noted that respondent accounts also provided examples of systems that were said to be working well, for example specific care management pathways, local roles and ways of working and technological initiatives such as IBIS and the ePRF.

• Implications for health care

The NHS system within which the ambulance service operates is characterised in our study as fragmented and inconsistent. For ambulance service staff the extent of variation across the geographical areas in which they work is problematic in terms of knowing what services are available and being able to access them. The lack of standardisation in practice guidelines, pathways and protocols across services and between areas makes it particularly challenging for staff to keep up to date with requirements in different parts of their own trust locations and when crossing trust boundaries. Although a degree of consistency across the network is likely to improve the situation, it is also desirable to have sufficient flexibility to accommodate the needs of specific local populations. There was some concern over the potential for further fragmentation with the increased number of CCGs.

Ambulance services are increasingly under pressure to focus on reducing conveyance rates to A&E; this arguably intensifies the need to ensure that crews are appropriately skilled to be able to make effective decisions over the need to convey or not to convey if associated risks to patients are to be minimised. Our findings highlight the challenges of developing staff and ensuring that their skills are utilised where they are most needed within the context of organisational resource constraints and operational demands. Decisions over non-conveyance to A&E are moderated by the availability of alternative care pathways and providers. There were widespread claims of local variability in this respect. Staff training and development, and access to alternatives to A&E, were identified as priorities for attention by workshop attendees.

One of the difficulties for ambulance services is that they operate as a 24/7 service within a wider urgent and emergency care network that, beyond A&E, operates a more restricted working day. The study findings identify this as problematic for two reasons. First, it fuels demand for ambulance service care as a route to timely treatment, when alternatives may involve delay. Second, it contributes to inappropriate conveyance to A&E because more appropriate options are unavailable or limited during out-of-hours periods. Ultimately, this restricts the scope for ensuring that patients are getting the right level of care at the right time and place. Study participants identified some patient populations as particularly poorly served in terms of alternatives to A&E (e.g. those with mental health issues, those at the end of life, older patients and those with chronic conditions).

The effectiveness of the paramedic role in facilitating access to appropriate care pathways hinges on relationships with other care providers (e.g. primary care, acute care, mental health care, community health care). An important element relates to the cultural profile of paramedics in the NHS, specifically, the extent to which other health professionals and care providers consider the clinical judgements/decisions made by paramedics as credible and actionable. Staff identified this as a barrier to access where the ambulance service is still viewed primarily as a transport service. Consideration could be given to ways of improving effective teamworking and communication across service and professional boundaries.

Although paramedics acknowledged the difficulties of telephone triage, they also identified how the limitations of this system impact on them. Over-triage at the initial call-handling stage places considerable demands on both staff and vehicle resources. A related concern is the limited information conveyed to crews following triage. Initial triage was suggested as an area that warrants attention to improve resource allocation.

The findings highlight the challenges faced by front-line ambulance service staff. It was apparent that the extent and nature of the demand for ambulance conveyance represents a notable source of strain and tension for individuals and at an organisational level. For example, there were widespread claims that meeting operational demands for ambulance services limits the time available for training and professional development, with this potentially representing a risk for patients and for staff. Staff perceptions of risk relating to patient safety extend to issues of secondary risk management, that is, personal and institutional liabilities, in particular risks associated with loss of professional registration. The belief that they are more likely to be blamed than supported by their organisation in the event of an incident was cited by staff as a source of additional anxiety when making more complex decisions. This perceived vulnerability can provoke excessively risk-averse decisions. These issues merit further attention to examine the workforce implication of service delivery changes, including how to ensure that staff are appropriately equipped and supported to deal effectively with the demands of their role.

Paramedics identified a degree of progress in relation to the profile of patient safety within their organisations but the apparent desire within trusts to prioritise safety improvement was felt to be constrained by service demands and available resources. Attempts to prioritise patient safety appear to focus on ensuring that formal systems are in place (e.g. reporting and communication). Concerns were expressed over how well these systems function to support improvement, for example how incident reports are responded to and whether lessons learned are communicated to ambulance staff within and between trusts. Consideration could be given to identifying ways of supporting ambulance service trusts to develop the safety culture within their organisation.

Service users attributed the increased demand for ambulance services to difficulties in identifying and accessing alternatives. They were receptive to non-conveyance options but felt that lack of awareness of staff roles and skills may cause concern when patients expect conveyance to A&E.

• Recommendations for research

The workshop attendees identified a range of areas for attention in relation to intervention and research, which are provided in Chapter 6 (see Suggestions for potential interventions and research ). The following recommendations for research are based on the study findings:

• Limited and variable access to services in the wider health and social care system is a significant barrier to reducing inappropriate conveyance to A&E. More research is needed to identify effective ways of improving the delivery of care across service boundaries, particularly for patients with limited options at present (e.g. those with mental health issues, those at the end of life and older patients). Research should address structural and attitudinal barriers and how these might be overcome.
• Ambulance services are increasingly focused on reducing conveyance to A&E and they need to ensure that there is an appropriately skilled workforce to minimise the potential risk. The evidence points to at least two issues: (1) training and skills and (2) the cultural profile of paramedics in the NHS, that is, whether others view their decisions as credible. Research could explore the impact of enhanced skills on patient care and on staff, for example the impact of increased training in urgent rather than emergency care. This would also need to address potential cultural barriers to the effective use of new skills.
• Research to explore the impact of different aspects of safety culture on ambulance service staff and the delivery of patient care (e.g. incident reporting, communication, teamworking, and training) could include comparisons across different staff groups and the identification of areas for improvement, as well as interventions that could potentially be tested.
• The increased breadth of decision-making by ambulance service crews with advanced skills includes more diagnostics; therefore, there is a need to look at the diagnostic process and potential causes of error in this environment.
• There is a need to explore whether there are efficient and safe ways of improving telephone triage decisions to reduce over-triage, particularly in relation to calls requiring an 8-minute response. This could include examining training and staffing levels, a higher level of clinician involvement or other forms of decision support.
• There is a need to explore public awareness of, attitudes towards, beliefs about and expectations of the ambulance service and the wider urgent and emergency care network and the scope for behaviour change interventions, for example communication of information about access to and use of services; empowering the public through equipping them with the skills to directly access the services that best meet their needs; and informing the public about the self-management of chronic conditions.
• A number of performance measures were identified engendering perverse motivations leading to suboptimal resource utilisation. An ongoing NIHR Programme Grant for Applied Research (RP-PG-0609–10195; ‘Pre-hospital Outcomes for Evidence-Based Evaluation’) aims to develop new ways of measuring ambulance service performance. It is important that evaluations of new performance metrics or other innovations (e.g. Make Ready ambulances, potential telehealth technologies or decision-support tools) address their potential impact on patient safety.

Included under terms of UK Non-commercial Government License .

• Cite this Page O’Hara R, Johnson M, Hirst E, et al. A qualitative study of decision-making and safety in ambulance service transitions. Southampton (UK): NIHR Journals Library; 2014 Dec. (Health Services and Delivery Research, No. 2.56.) Chapter 8, Conclusions and recommendations.
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Why Scholars Should Consider Policy Recommendations

Understanding the policymakers’ dilemma, how to begin developing policy recommendations, questions to ponder, yes, you can, writing policy recommendations for academic journals: a guide for the perplexed.

Professor in the Edmund A. Walsh School of Foreign Service at Georgetown University and a Senior Fellow in the Transnational Threats Project at the Center for Strategic & International Studies.

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Daniel Byman; Writing Policy Recommendations for Academic Journals: A Guide for the Perplexed. International Security 2024; 48 (4): 137–166. doi: https://doi.org/10.1162/isec_a_00485

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Academic research can inform decision-makers on what actions to take or to avoid to make the world safer, more peaceful, and more equitable. There are many good works on bridging the gap between policymakers and academics but few on how scholars writing in academic journals can influence the policy process. In contrast to most policy-focused research, academic journals have long shelf lives and provide space for scholars to present heavily researched empirical evidence, theories, and analyses. Long, well-researched articles can, over time, shape the broader narrative for how to think about complex issues. Scholars also tend to be more objective and less partisan than policymakers. Despite the potential importance of academic work to the policy debate, many scholars receive little training on why and how to make policy recommendations. To remedy this problem, steps are offered to guide scholars as they begin developing policy recommendations for their articles. These include recognizing the dilemmas that policymakers themselves face, considering the audience before starting to write, identifying and using policy option menus, among others. When crafting recommendations, scholars should consider the long-term implications of their research on current policy as well as recommendations that might lead to more effective approaches. At the same time, scholars should consider the costs and limits of their recommendations.

Climate change. The rise of China and the U.S. response. The dangers posed by ISIS and other terrorist groups. The ability of the United Nations, the IAEA, the NPT, and other institutions to manage nuclear proliferation. Civil unrest and the potential for peaceful change. Globalization's benefits and perils. These are among the most important security issues facing the world today—and they are issues that scholars can, and do, speak to regularly. Thomas Homer-Dixon's “Environmental Scarcities and Violent Conflict,” John Mearsheimer's “The False Promise of International Institutions,” Andrew Kydd and Barbara Walter's “The Strategies of Terrorism,” Maria Stephan and Erica Chenoweth's “Why Civil Resistance Works,” and Henry Farrell and Abraham Newman's “Weaponized Interdependence” are among the most-cited articles ever published in International Security , and their scholarly impact is considerable. 1 Beyond their theoretical contributions, these articles illustrate the potential that International Security and other academic journals have for speaking to policy issues. All of them contain important ideas proposing what decision-makers should consider, do, and not do to make the world a better place.

Despite the potential importance of academic work to the policy debate, new scholars receive little training on why and how to make policy recommendations. Some academic journals only pay lip service to policymaking or ignore it altogether. There are many insightful works on the gap between policymakers and academics and why it should be bridged, and a host of training workshops, government funding programs, and other efforts push in this direction, often with valuable results. 2 Other articles stress how to craft relevant recommendations in general. 3 Yet almost all these efforts focus on activities outside publishing in top academic journals, ignoring the important role that scholarly journals should play in shaping thinking on policy. This article seeks to fill this gap, advising contributors on how to write policy recommendations for articles in both International Security and, I hope, other high-quality academic publications that seek to inform the policy debate.

Providing helpful commentary on policy is challenging—as difficult as the academic research that leads to publication in a top journal—and it is doubly difficult when doing so for an academic journal. Publication time is measured in months or even years, in contrast to blogs and current affairs journals that offer more immediate turnaround. Policymakers rarely have time to read long articles, which are the staples of journals like International Security , and indeed “rarely have time to read what's not urgent in their inbox,” as one senior policymaker noted. 4 Perhaps most important, it is often difficult for academics to understand a policy, let alone the pressures that policymakers face and the conflicting objectives that they try to juggle.

Yet it is vital for scholars to learn the dilemmas that policymakers face and to be relevant to public and private policy debates so that their research can help make the world a better place. Engaging policy also makes for better research. By focusing on questions important to the policy world, scholars avoid the trap of scholasticism—that is, when they concentrate on internal debates rather than on the original problems that first inspired academic research. But writing serious policy recommendations requires considerable modesty: crafting effective policy is hard, and academics should recognize the limits of their findings and the difficulties of moving the policy needle.

When crafting recommendations, scholars should take advantage of their objectivity and ability to challenge the prevailing wisdom. They are also well-placed to use history to learn lessons and to draw insights from large datasets. Academic journals, for their part, endure: they have long shelf lives and allow deep dives, providing space for scholars to present heavily researched empirical evidence, theories, and analyses. Long, well-researched articles can, over time, shape the broader narrative for how to think about a complex issue such as the potentially peaceful nature of democracy or how to make deterrence more robust. 5 They may also help provide context when unexpected events occur and the policy community has little to draw on but theory and analogy.

As scholars begin crafting their articles, they should try to determine their policy audience—including leaders outside government in industry and civil society—to identify who might read their work and who might act on it. They should consider their variables, identifying ways to maximize better outcomes or minimize worse ones. To help academics think of ways to use their findings to influence policy, one strategy is to create or draw on existing menus of policy instruments (“What can diplomats do?” “How might financial tools assist with coercion or another goal?” and so on). At the same time, scholars should consider the costs and limits of their arguments, conveying enabling conditions and the level of certainty of their findings as well as their overall recommendations. Finally, they should use their academic journal work as a springboard for writing shorter pieces in policy journals, blogs, and opinion pages.

The remainder of this article has five sections. The first section explains why academic authors should speak to policy issues and why offering policy recommendations contributes to better scholarship. It also highlights the unique role of academic publications like International Security . The second section describes the dilemmas that policymakers themselves face—difficulties that scholars must recognize even if their ultimate advice criticizes or transcends these dilemmas. In section three, the heart of the article, I explain how an academic author might begin thinking about policy relevance. For some scholars, this process may involve identifying steps to take from the start of their research project. For others, it may involve considering how work undertaken with an academic audience in mind might also speak to policymakers. Section four poses a set of questions that scholars should consider as they craft their recommendations. It also illustrates how to apply the article's framework. The article concludes with a brief exhortation for scholars to engage the policy world in their academic research.

Policy-relevant scholarship is intended to produce findings that feature in the deliberations of government officials and others involved in policy decisions. This section makes three arguments. First, journals like International Security value policy relevance, as do most of the scholars who work on international security, and policy-relevant research can improve scholarship as well as inform policy. Second, academics have much to contribute to the broader policy debate. Third, academic journals have their own niche in the broader policy analysis ecosystem, complementing blogs, the opinion pages of major newspapers, and policy journals like Foreign Affairs .

the so what of the so what

Not every International Security article should be policy relevant, but most should. Scholarship seeks to expand human knowledge, but for international security, much of that knowledge is interwoven with policy challenges. 6 The vast majority of articles that appear in International Security speak to some aspect of policy, ranging from avoiding international and civil wars to improving alliances to the nature of the international system. 7

The editors of International Security consider the “so what” hurdle when they evaluate a submission—Why should a reader bother with your article when there are so many other ones to read instead? 8 This hurdle is much easier to clear if the author makes the policy connection unambiguous. If an article's central question matters to those responsible for waging war, preserving the peace, maintaining fiscal stability, improving governance, and otherwise trying to promote security, then that article—and its recommendations for avoiding dangerous outcomes and increasing the chances of positive ones—is worth considering for inclusion in a journal.

Aside from this important question regarding publication, many scholars seek to do relevant research. 9 It is likely that a policy question or world event piqued a scholar's interest in international relations. Many scholars believe (rightly!) that they can contribute to both internal government debates and broader, more public discussions of complex policy issues.

what scholars bring to the policy table

Scholars have much to offer the policy debate. Although scholars may be removed from the policymaking fray, that distance gives them a chance to present new ways of thinking about a problem and to take the long view. Unlike some policymakers, scholars are not driven by their inbox. This flexibility allows scholars to set long-term agendas. As the policy community celebrated the fall of the Soviet Union, for example, Graham Allison, Owen Cote, Richard Falkenrath, and Steven Miller presciently identified the threat of loose nuclear weapons and material from the former Soviet Union. Their evidence spurred policy attention and eventually action. 10

In the near term, scholars can challenge prevailing wisdoms. In 2002, John Mueller questioned the post-9/11 consensus that Al Qaeda would continue to conduct numerous mass-casualty attacks like 9/11 or even more destructive ones. As time went on, Mueller built on his research and proved his initial argument that 9/11 was an outlier for U.S. casualties. 11

Scholars have time to dig deep: research for an article can take many years, a luxury the policy community lacks. Scholars can also create large datasets and survey significant amounts of open-source material. Some of this analysis occurs within the intelligence community, but scholars often create better-designed datasets and have more time to read and digest publicly available material.

In addition, scholars are bureaucratically (though not politically) neutral. 12 They do not have a vested interest in whether the State Department or the Defense Department oversees a peacekeeping operation, for example. Policymakers often reason by analogy, whereas scholars are trained to thoroughly research particular cases in an unbiased way and draw conclusions across cases, both of which add more insight than using a simple analogy. 13 Perhaps most important, International Security and other leading journals publish rigorous, peer-reviewed articles that use precise and careful research methods and analyses to answer questions, challenge the conventional wisdom, validate empirical findings, and advance understanding about complex topics.

This reasoning may seem Pollyannaish, but imagine if scholars rejected policy contributions in their writing. There would be less work that is deeply informed, methodologically rigorous, and carefully reviewed. Daniel Drezner points out that many nonacademic public intellectuals are more partisan and less open to criticism than their academic counterparts. Such partisanship decreases the quality of public intellectuals’ work though not their influence. 14

More focus on policy can also lead to better scholarship. Making policy is difficult, and making good policy is even harder. By speaking to these challenges, scholars are forced to ask themselves knotty questions and to better understand what they study and the data on which they rely for their analyses. For example, an academic who engages policy seriously may recognize that the paper trail of memoranda and strategy documents is often more spin than substance. 15 With policy concerns in mind, scholars are less likely to emphasize elegant scholarship that elides real-world difficulties. As Rebecca Adler-Nissen argues, “Part of the reason why ‘bad ideas’ are allowed to develop in the first place is that we have established a hierarchy of prestige that values ‘clean’ and ‘elegant’ scholarly ideas over the ‘messy’ ones of practitioners.” 16 She adds that policy engagement forces scholars to “begin to develop ideas that acknowledge the complexities, paradoxes, and hidden politics of ‘policy.’ We become curious about what practitioners find appropriate, shameful, or important.” 17

Policy recommendations can be dangerous things. Policymakers might take them out of context to “prove” that their desired outcome is the best option. Work on the democratic peace, for example, was used to justify the 2003 invasion of Iraq. But this justification overlooked important context: many findings that extol the benefits of the peace do not focus on forced regime change. 18 Paul Musgrave warns of “lab leaks” in political science, whereby magazines like the Atlantic and Foreign Policy present concepts with little context and fewer caveats, making them more likely to be misused. 19 Scholars may also fear being labeled as activists if they promote particular policies. They are also taught to avoid normative language—a luxury that policymakers do not share.

The cures for these potential ills, however, are not to avoid policy engagement but to take it more seriously. Scholars cannot control the conclusions that people draw from reading their work. But clear writing and speaking directly to policy concerns make it more difficult for others to misuse a scholar's ideas for their misguided policies. As Erica De Bruin argues, “If irresponsible public scholarship is the issue, then developing a more rigorous ethic of public engagement is vital.” 20 Similarly, activism is a good thing when it reduces the risk of war, improves human rights, and otherwise makes the world a better place. In addition, as Charli Carpenter points out, engaging with advocacy organizations often helps researchers overcome academic biases because it requires them to consider different issues and learn about new problems. 21 The key for scholars is to ensure that their work remains rigorous and objective, which at times means recognizing that their preferred approach has flaws and limits.

the unique role of academic journals in the policy debate

Academic journals like International Security are part of a vast ecosystem of outlets that all claim to speak to policy issues. These include foreign-policy-oriented long-form journals like Foreign Affairs and Survival , general media outlets such as the New York Times , Yomiuri Shimbun , and the Economist , podcasts like those featured at War on the Rocks , specialized outlets like Arms Control Wonk and Lawfare , and numerous others. As articles on policy relevance argue, scholars should publish in these outlets—and many do! These platforms publish articles more quickly than academic ones, enabling scholars to speak directly to the issues of the day.

Academic journals have their niche as well. In some cases, particularly when the danger is possible but not imminent (e.g., if China were to invade Taiwan), an academic journal might be an ideal outlet for in-depth work. Michael O'Hanlon wrote such a piece in 2000, and its findings remained relevant for years even as the international environment and China's military capabilities changed. 22 Scholars can try to provide general guidance on a more specific problem. A 2020 piece explaining the sources of Russian bellicosity, for example, would still be helpful to policymakers in 2022, though it would need to be updated with insights on the invasion of Ukraine.

The longer length of an academic article also has trade-offs. A typical International Security article has 10,000–15,000 words, and some are even longer. For Foreign Affairs , the recommended length is 2,000–5,000 words, and for the New York Times it is 800–1,200 words. 23 Shorter pieces are more likely to be read, especially by more senior policymakers with crammed schedules. Conversely, it is harder to go into depth in a short piece.

The flip side of a long review process and longer length is a long shelf life. 24 Articles for International Security deliberately speak to broader issues and long-term problems. Consequently, they may remain relevant for many years. Twenty years after publication, Andrew Kydd and Barbara Walter's work on the strategies of terrorism still speaks to terrorist groups’ goals and methods. 25 Similarly, Caitlin Talmadge's focused study on Iran's possible blocking of the Strait of Hormuz remains highly relevant almost fifteen years later, identifying the many challenges to Iran, the possible responses for the United States, and so on. 26 Additional scholarly work, technological advances, and geopolitical change may affect the issues discussed in both articles, but the authors provide a set of concepts that create a valuable foundation on which to build policy.

In addition, the long shelf life changes the readership and value of the piece, allowing scholars to shape worldviews that inform a host of decisions. An International Security article may be on a syllabus for years or even decades after publication, framing how an issue is thought of for years to come, as RAND research on nuclear strategy did in the 1950s and 1960s. 27 It is plausible that a twenty-year-old student who reads an academic piece may retain its concepts and arguments as a mid-level policymaker two decades later. In the words of John Maynard Keynes, “practical men, who believe themselves quite exempt from any intellectual influence, are usually the slaves of some defunct economist.” 28 Be that defunct economist.

Journals like International Security are also more open to historical deep dives and reinterpretations. Because analogical reasoning is so prevalent, changing an understanding of an important historical event, such as the outbreak of World War I or the Cuban missile crisis, can inform how to think about what to do in the present. Keir Lieber points out that historians and policymakers like Henry Kissinger misunderstood World War I as an inadvertent conflict. This misreading has profound implications for how to gauge the likelihood of small great power disagreements accidentally spiraling into major war. 29

In some cases, rare ones but with high impact, a discontinuous event takes an article off the shelf. Should China invade Taiwan in 2025, an in-depth piece written in 2020 in a journal like International Security might be among the most comprehensive external guides to a policy challenge that would consume world attention, even if it does not discuss this specific crisis. Naazneen Barma and James Goldgeier note that Swedish Nobel laureate Gunnar Myrdal's The American Dilemma , a masterful 1944 study of race in the United States, was largely ignored when published, and its sponsors disowned it for years. In 1956, however, its findings helped shape the Brown v. Board of Education decision, one of the most consequential Supreme Court rulings in U.S. history. 30

Because academic articles are often explicitly theoretical, they also offer insights into new or related but distinct situations. For example, the 2011 Arab Spring upended long-standing policies toward area regimes. Even though pre-2011 articles on democratic transitions, the impact of military coup-proofing, civil war resolution, and similar topics that are common in security-related academic journals do not necessarily focus on the conditions in Egypt, Tunisia, or other affected countries, they nevertheless offered many potential insights during the turbulence. 31 Policymakers might have learned ways to promote successful elections, avoid (or predict) coups, prepare for civil violence, and so on. The key concepts endure, even if the dates and places are different.

Bureaucracies often amass considerable knowledge on complex issues, and policymakers are rarely stupid. Yet many policies seem foolish and ill-informed, especially in hindsight. To understand why the policy outcome often differs from the ideal, it is vital to understand the many pressures and restrictions that policymakers face. Academics should not treat these difficulties as immutable or even excusable, but recommendations should reflect an understanding of the policy itself and how to improve outcomes. Identifying the actual policy is a difficult aspect of research that should accompany the broader academic research process. Perhaps most important, academics should approach policy influence with considerable humility: in providing advice to smart, knowledgeable people, often the academic is not aware of all, or even most, of the challenges confronting the policy community.

policy constraints

Policymakers make their own policies, but they do not make them just as they please. Some factors, such as geography or the polarity of the international system, are invariable. Although many elements that constrain decision-making and agency are malleable, these constraints are often tight, making it hard for policymakers to break out of a narrow set of options.

Policymakers are beholden to their publics and to elites. These limits apply in both democratic and authoritarian systems, albeit in different ways and to different degrees. 32 It is tempting to urge “leadership” as a recommendation, and at times policymakers do go against the preferences of their constituents and supporters. But leaders are understandably wary of jeopardizing their political status.

Competing priorities and limited resources also constrain policymakers. The many issues that scholars examine—civil wars in sub-Saharan Africa, refugee flows in Southeast Asia, the destabilizing effects of new weapons systems, and problems with security assistance, to name only a few—compete with one another and with numerous other concerns. For the most senior policymakers, they also compete with domestic priorities, which are usually more salient. Recommendations that call for more aid to a region, more training to an ally's military, and so on all come at a cost, with other priorities receiving less money and attention as a result.

Policymakers also must act with only limited information. Colin Powell recalled that if he waited for enough facts to be 100 percent right, it meant it was too late to act. 33 Although U.S. intelligence proved remarkably prescient about the likelihood of the 2022 Russian invasion of Ukraine, the Joe Biden administration did not know if Ukrainian forces would hold out, how key allies in Europe would respond, or how a then-unpopular leader like Ukrainian President Volodymyr Zelensky would respond when greatness was thrust upon him. 34 Policymakers also had to worry about less probable but potentially catastrophic concerns like nuclear escalation. Recommendations must recognize the many uncertainties and scenarios that policymakers are likely to face after a terrorist attack, as a civil war is breaking out, or when a peaceful movement seeks to overthrow a dictatorial regime.

In short, policymakers are in a proverbial box, constrained by politics, resources, competing priorities, and limited information. For academics to think outside this box, they must understand why policymakers are in it, which parameters are possible to shift, and which are likely to hold firm.

the difficulties of understanding policy

Understanding policy takes time, and it is easy to get wrong or caricature. First, policies often embody multiple strategic, bureaucratic, and political interests. Second, an administration may provide conflicting or confusing signals as to what its true policy is. Third, the resulting complexity makes coding difficult. Fourth, policies are often bad because alternative policies are worse; criticism should recognize this reality.

One barrier to understanding policy is that a single issue may be interwoven with a wide array of interests. Take, for example, negotiations with Iran as embodied in the Joint Comprehensive Plan of Action. In this instance, U.S. policymakers balance a range of goals, including: stopping Iran's nuclear weapons program altogether; pausing the program for several years; shoring up international regimes like the 1968 Treaty on the Non-Proliferation of Nuclear Weapons (NPT); leading allies in Europe and elsewhere that also oppose Iran's nuclear program but are more eager for commercial ties to Tehran; reassuring regional allies that are suspicious of Iran; condemning Iran's support for militant and terrorist groups in the greater Middle East; supporting Iranian demonstrators seeking regime change; and winning over a domestic population that is highly suspicious of any relationship perceived as forgiving to Iran. 35 Judging success is difficult, as some of these goals are incompatible. Policymakers maximize some interests, satisfice others, and “fail” on still others. 36 A recommendation that improves the odds for success in one area may hinder it in others. For example, the Barack Obama administration succeeded in nuclear negotiations with Iran in part because U.S. policymakers avoided entangling the nuclear discussions with demands regarding Iran's support for terrorist groups.

Multiple signals from an administration make determining the actual policy difficult. Governments issue public strategy documents but engage in private and even covert diplomacy that can be more consequential. Diplomats may join treaty negotiations but have private instructions to ensure that negotiations fail. Officials use public statements not only to delineate a policy but also to close off rival approaches. For example, an administration publicly condemning the assassination of Saudi journalist Jamal Khashoggi on one day would find it more difficult to sell Riyadh weapons the next. At times, the public statement is virtue signaling, staking the moral high ground even as most administration policies either do not follow through on lofty goals such as promoting human rights or opposing aggression or even go in the opposite direction. Western leaders, for example, called for Syrian dictator Bashar al-Assad's ouster but did not provide the Syrian opposition with sufficient military support to make it happen. 37 Was regime change truly their goal?

The many interests involved in policy decisions, the multiplicity of signals coming out of governments, and the possibility of virtue signaling all pose coding problems. It is challenging for scholars to determine success or failure or to assign values to other binary measures of policy that are often used in large datasets. Similarly, the signaling confusion makes it hard to for researchers to know which coding they should use.

For academics, the many interests and confusing signaling also pose a data problem. Official strategy documents can be great sources, but they can also be misleading. President Donald Trump's 2017 National Security Strategy seemed to bear little relationship to his administration's overall foreign policy. Indeed, in some ways actual policy contradicted the guidance, with the strategy embracing a strong role for U.S. leadership in the face of great power competition when President Trump was highly critical of traditional U.S. allies and was cozying up to Moscow. 38 Often deliberations occur in private before a formal meeting. The meeting record is thus a ratification, not a reflection of discourse. Understandably, scholars often have a bias toward the written word, whereas it is the briefing or private conversation that matters the most to many policymakers. Some written policy documents may accurately reflect the authors’ views. But policymakers are less likely to document their political and bureaucratic interests, which leads scholars to have a bias toward strategic explanations.

Indeed, almost every policy addressing a complex problem is insufficient and often the only alternatives are bad ones—so which bad one is the best? As David Baldwin notes in his assessment of economic sanctions, “If the menu of choice includes only the options of sinking or swimming, the observation that swimming is a ‘notoriously poor’ way to get from one place to another is not very helpful. And if the principal alternative to economic sanctions is appearing to condone communism, racism, terrorism, or genocide, the observation that they are a ‘notoriously poor tool of statecraft’ may miss the point. In the context of the logic of choice, the evaluation of one policy alternative in isolation from others makes little sense.” 39 Policymakers may have an ambitious declared goal (“stopping human rights abuses”), but in practice they may settle for a range of lesser achievements, such as slightly reducing human rights abuses by making it more difficult for a regime to access resources, signaling disapproval to gain allied support, avoiding pressure to use military force that may backfire, and so on. Recommendations that do not at least acknowledge the poor range of options available to policymakers will not be convincing.

Taylor Fravel and Charles Glaser's work on the South China Sea and U.S. policy is an excellent example of how scholars can avoid these traps. 40 Fravel and Glaser are careful not to caricature current policy as they describe alternatives such as greater retrenchment and more intense military resistance. They detail the conditions under which different alternatives might be appropriate and suggest specific policies to accompany the alternatives, such as clarifying ambiguous treaty arrangements, imposing substantial economic sanctions, implementing shaming measures when China violates norms, and deploying surface and air forces, among many others. Overall, the reader is left with a better understanding of the balance that current U.S. policy is trying to strike, which Chinese actions would suggest the policy is failing, and the many potential downsides of different approaches, particularly how more aggressive efforts risk unwanted escalation.

the need to transcend the dilemma

Scholars must understand the policymakers’ dilemma and factor it into their recommendations, but they should not be bound by it. Pointing out the weakness of a policy in addressing a problem is an important service, and strong arguments can help policymakers advocate for more resources, shift priorities, or even take political risks in the face of domestic and elite opinion. Even better, however, is offering a plausible alternative. A particularly important role for scholars is to help policymakers reconsider factors that the policy community sees as insurmountable rather than malleable, such as identifying ways to overcome long-standing animosities, to reshape public support, to reprioritize regional objectives, and so on.

Scholars are taught to dissect complex problems, but often they focus on a lacuna in the literature rather than the policy implications of their research findings. 41 If they focus more on the advantages of a particular method or on why a variant of one major paradigm is better than another, such elements by themselves are of little interest to the policymaker. Below I both offer advice for authors as they begin to craft a piece designed to increase policy influence and list factors to consider as their research progresses. Some of these steps may prove useful even if the scholar sees the research as primarily academic.

step one: help a policymaker solve a problem

For those interested in speaking directly to policymakers as well as academics, start with the “so what” that motivated the research in the first place to determine how it fits into the policy world. What factors shape current policies, how malleable are they, and what alternatives are on the table? What will policymakers learn from reading the article that may improve their understanding about the problems they face and that may offer potential solutions? The article's focus should help solve a problem that is in a policymaker's inbox or, just as important, should be in their inbox. As the then deputy secretary of state James Steinberg noted, policymakers are “desperate” for ideas and solutions. 42

step two: consider, realistically, the audience

Before scholars begin their research, they should examine the issues that different kinds of policymakers or policy influencers see as important. Make sure to include those topics in the essay in a way that their audience can recognize, understand, and appreciate. Some policymakers write strategic documents, others evaluate weapons systems, still others negotiate treaties, and so on. Sometimes scholars decide that their work will have the greatest impact if they inform the media. The research findings should help reporters enlighten the public and ask nuanced and informed questions of government officials. Likewise, if the research will have the greatest impact by shaping the thinking of undergraduates and masters’ candidates—the next generation of policymakers—consider how to structure the whole essay, and possibly the research more broadly, to be most useful and effective for that audience.

With the issue in mind, identify the target policy audience. For those writing on a common topic like alliances and war, North Atlantic Treaty Organization (NATO) countries’ ministries of defense and foreign affairs, the leaders of Asian democracies, and intelligence chiefs are some (ambitious) possibilities. But authors should think broadly, beyond just governments, even if their piece is focused on traditional interstate security issues. For example, social media companies have emerged as important players in the information realm. With three billion monthly active users, Facebook's decisions on who to allow on its platform and what can be discussed are often more consequential than various foreign ministries’ statements. Companies’ content moderation policies and crisis response protocols, or lack thereof, can hinder or enable genocide. 43 Schools can teach new subjects (or old subjects differently), affecting reconciliation between once-embittered communities and public attitudes toward age-old problems like the impact of discrimination. Civil society and advocacy organizations such as the International Campaign to Ban Landmines can shift discourse, rally domestic coalitions (remember the box and how domestic politics shapes it!), and advance international law. Also consider where on the policy food chain your audience is. The U.S. president can change things more quickly than the assistant secretary of state for the Bureau of International Security and Nonproliferation, and the assistant secretary has more power than a desk officer. But guess which one has more time to read your article?

Authors who want to speak directly to policymakers should think of ways to infuse their entire project—puzzle, theoretical approach, hypothesis testing, and presentation of findings—with answers to both scholarly and policy questions. In addition to presenting rigorous methods and building on existing literatures, an article's theoretical and hypothesis sections must also make sense to a curious policymaker. Why is comparing many states’ approaches to military training better than delving deep into one example (or vice versa)? Why present some explanations but not others? A policymaker working on this issue should nod her head as she goes along rather than wonder why vital, obvious details that are necessary to make progress on a problem are missing from an article's analysis.

step three: emphasize useful variables and proper linkages

Scholars can also emphasize certain variables in their analyses to identify ways that policymakers can achieve the best results. If civil wars are correlated with ethnic disputes, economic inequality, or poor governance, then policies that foster ethnic harmony, greater equality, and reduced corruption should be encouraged. Policymakers would eagerly listen to scholars who provide specifics on what has worked. Articles that focus on methods can also be useful to policymakers, though drawing policy insights from such works often requires a bit more effort. Nicolas Sambanis, for example, argues that changes to both the threshold of violence used to define a civil war and the coding of intrastate, interstate, and extrastate wars can dramatically alter findings regarding peace duration and the causal power of economic problems, among many others. 44 If articles that draw on such findings are not robust, as Sambanis's research suggests, then policy recommendations built on them should be reconsidered.

Some scholars may prefer to skip the above steps and instead focus on the article's contributions to the academic literature. If they do so, however, they can still write useful policy recommendations. Having read a scholar's research, the intended current or future policymaker may be more informed about the causes of war, why alliances fracture, barriers to ethnic reconciliation, and other grave problems and perhaps better equipped to reduce these dangers. The author should now ask, “Given the findings from my research, what makes desirable policy outcomes more likely?” This might involve pointing out tensions between different policy approaches. Lindsey O'Rourke, for example, finds that policymakers prefer covert regime change over overt measures because they can deny responsibility for failures and reduce criticism for meddling in general. Efforts to ensure deniability, however, make the operations less likely to succeed. Highlighting this trade-off between two competing benefits (deniability versus improved chances of success) is important and increases the article's utility to policymakers. 45 This step tends to be easier if scholars have designed their work with policy concerns in mind from the start. Even so, articles that are more academic facing may still make desirable policy outcomes more likely.

Scholars’ recommendations should flow from their analyses. Such a point seems straightforward, even obvious. But often policy recommendations stray from the analytic foundations on which they claim to rest. For example, the 9/11 Commission issued a powerful report condemning intelligence failures and calling for major structural reforms, particularly to centralize intelligence under a director of national intelligence. 46 As Richard Posner pointed out, however, among intelligence agencies it was only the Federal Bureau of Investigation (FBI) that demonstrated major structural failures in combating terrorism. 47 The 9/11 Commission nevertheless recommended major institutional changes elsewhere in the intelligence community but not in the FBI. Although the report indicated that post-9/11 information sharing worked well and that Central Intelligence Agency (CIA) paramilitary operations were effective and agile, it recommended centralizing information sharing and moving the CIA's operations under the Defense Department. To be clear, such recommendations may have been good ones, but they did not match the substance of the commission's findings on information sharing or paramilitary operations.

Finally, avoid offering hackneyed recommendations. A recommendation that urges policymakers to focus on economic growth may be vacuous. A call for more intelligence may be hard to enact. Instead, provide thoughts on why intelligence is currently lacking. 48

step four: create a menu of policy options

Depending on the research topic, there are many practicable ways to influence policy. It is useful to consider all options, even if most do not end up being relevant to your findings. The U.S. military teaches its students that the instruments of power are summarized by the acronym DIME (diplomatic, informational, military, and economic)—and that is one place to start. 49 What might a diplomat do to sail the ship of state in the right direction? Is more intelligence needed? If so, could government education or propaganda campaigns help? What about the many variations of military force? Do economic tools such as sanctions help? Sometimes the answer to such questions is a clear and quick “no.” But combining these tools can often move policy forward. There are numerous variations of DIME, such as MIDFIELD (military, informational, diplomatic, financial, intelligence, economic, law, and development), which brings in financial and economic tools, international and domestic law, and so on. 50 In other cases, changes to education policy might be appropriate. Regardless of the preferred abbreviation, if any, thinking through a list of tools is a useful way to start.

Combinations are particularly important. Policymakers rarely rely on one instrument, and saying that such an instrument succeeds or fails, by itself, is less persuasive than discussing combinations.

Another approach is to think of a checklist for policymakers. Alexander George's writing on coercive diplomacy, for example, offers both contingent generalizations on when it works and factors for policymakers to think through. In essence, George shows how structured, focused comparisons of past cases help policymakers assess what they need to know and do for current developments. 51

step five: consider costs and limits of your policy recommendations

Some policy recommendations may be highly effective but also involve high costs in lives or money. Others help solve one problem but introduce others. Considering the findings, what current policies are making things worse or simply wasting money? Similarly, what costs and trade-offs are likely if a policymaker implements the article's recommendations? In general, it is always useful to ask, “Why is this not being done already?”

The findings that promoting regime change in Iran would lead to many casualties and would foster anti-Americanism would be useful to share with policymakers. Yet a recommendation to avoid foreign intervention might mean accepting a hostile, nuclear-armed Iran. It is easier for policymakers to dismiss research that fails to consider the latter possibility. Other policies are just expensive. Asking Asian countries to respond to China's rise by vastly increasing their anti-access/area denial capabilities may be sensible, but doing so is costly. Political leaders have other uses for the money.

By contrast, examining the cost of existing policies can generate new recommendations. For example, Kenneth Pollack finds that U.S. efforts to train Arab militaries using a U.S. military model is a recipe for failure given different political, cultural, and institutional settings. This seems like a finding that would lead to a recommendation to stop training altogether. Even though ineffective training is often useless in a military sense, stopping it would anger allied elites and harm bilateral relationships. Pollack thus recommends that the United States shift how it trains foreign militaries to better recognize these differences. 52

With the above in mind, make recommendations that are distinctive and clear. In her work on military training, Renanah Miles Joyce contends, “Liberal providers should emphasize building institutions that help to regulate military behavior rather than prioritizing individual or unit-level training with a normative component tacked on.” 53 This sentence packs a lot of substance: it identifies the actors (liberal states that provide military assistance), the policy that needs to change (prioritizing individual and unit-level training), and the proposed alternative (building institutions).

Another approach is to think about the policy box and where you stand in relation to it. It is tempting for scholars to ignore politics and simply point out the best answers. Yet recommendations that incorporate political realities are potentially more influential. Often, a mix is best. A scholar might note that today's political reality makes the ideal policy infeasible. Instead, the author might recommend a suboptimal but still useful set of steps: “As long as U.S. domestic politics makes a return to the Trans-Pacific Partnership [TPP] difficult, a less effective but valuable step would be to engage in a series of bilateral trade agreements that, cumulatively, offer lesser but still important security benefits similar to TPP.” This recommendation acknowledges the preferred solution (TPP) and offers a more politically plausible middle ground (bilateral agreements) that a policymaker could consider. Similarly, it is important to acknowledge resource constraints but not be bound by them: “Ideally, Taiwan would purchase a suite of anti-access/area denial capabilities rather than rely on more traditional systems like tanks, and it should begin with Harpoon anti-ship missiles.” 54

step six: use research as a springboard for other outputs

After conducting exhaustive research and developing informed recommendations, a scholar can repackage their research for podcasts and as shorter pieces for magazines like Foreign Affairs , outlets like Lawfare , and newspapers. These shorter pieces come to the attention of policymakers at multiple levels and make it more likely that at least a few of them may engage the longer work. After Keir Lieber and Daryl Press published their deeply researched findings on challenges to nuclear deterrence in International Security , they reached broader audiences by sharing their results in Foreign Affairs and the Atlantic . 55

Believe it or not, many editors welcome pitches from informed, serious scholars, even if the scholars have not previously written for popular publications. Most outlets have information on where and how to submit on their websites. Emailing editors directly is also an option. 56 In many cases, busy editors will not respond to inquiries or will otherwise not give a pitch the time it deserves. So be it. Curse to yourself, move on, and submit elsewhere, repeating as necessary. After initial contact is made, subsequent submissions are often easier, especially if an author proves to be authoritative, responsive, and otherwise easy to work with. I edit the “Foreign Policy Essay” at Lawfare and regularly feature content that draws on long academic articles. A simple email to me usually leads to a response—the author and I discuss if a piece might be suitable and, if so, how it might draw on the original research but reach a different, policy-focused audience.

After following some form of steps one through six, there are several important questions that scholars should pose to themselves as they draft policy recommendations for their articles. These questions have no right answers—but considering them will help properly situate the research in ways that policymakers find useful.

It is fine to think big, and it is also fine to think small—each category has different audiences and different impacts. Mid- or senior-level officials are more likely to act on smaller, more fine-grained recommendations. They can use their bureaucratic power to advocate purchasing a particular weapons system, strengthening an international organization, or using financial tools instead of military force to coerce an adversary. They cannot, however, easily establish a new norm on a controversial topic, jettison the 1947 National Security Act, or dump a long-standing ally in favor of a new one. Yet such broad recommendations, even if infeasible in the short or medium term, are part of what academics contribute to a debate. By changing public and elite perceptions over time, scholars can give policymakers more agency to overhaul their approach, thereby loosening the constraints of the policy box. Another factor to consider is the timing of a recommendation. For example, proposing that the European Union change its aid recipients as the deadline for doing so approaches might be more influential than making that same recommendation months or years after the deadline has passed.

do the recommendations solve the problem or move the needle?

A related question is whether a recommendation focuses on either solving or mitigating a problem. The former, obviously, is better, but in most cases it is unrealistic. If scholars have solutions for how to finally end civil wars, reconcile embittered ethnic groups, or ensure that nuclear war is an impossibility, then they should propose them! Yet small improvements in dangerous situations are tremendously valuable. Recommendations that make a civil war a little less likely, reduce the odds of a counterproductive intervention, or minimize wasted time or resources have measurable consequences. Offering a recommendation that reduces the number of refugees from one million to 950,000 is less consequential than preventing the disaster that created one million refugees. But it is still monumental to have fifty thousand fewer refugees, even if the reduction seems insufficient to the scale of the suffering. Most scholarship at best slightly shifts policy, and academics should be comfortable, indeed proud, that it does so. Academic authors should recognize that sometimes only limited progress is possible given resources, the limits of policy instruments, and political realities.

conveying uncertainty

Policymakers and government analysts are often wrong. And so are academics. A powerful advantage of academics, however, is (or should be) that mistakes are learning opportunities. Scholars can revisit foreign policy decisions and, by understanding why people were wrong, identify neglected variables or scope conditions. This power, however, comes with responsibility. Just as methods and sources have inevitable limits and gaps, so do policy recommendations. Small variations in findings—“sanctions always fail” versus “sanctions usually fail”—have profound policy implications, and those variations should be made clear. In addition, scholars should reevaluate their work and highlight their mistakes as ways to ensure their integrity. 57 Scholars can and will be wrong, and refusing to acknowledge this by making excuses or otherwise avoiding responsibility misses a learning opportunity and reduces the scholar's credibility. In conveying uncertainty, scholars should strike a balance between showing humility by acknowledging research limitations and offering policymakers clear advice despite unknown or conflicting variables.

are you writing implications or recommendations?

Although this article focuses on policy recommendations, an important (and at times easier) variant is to consider policy implications: How do research findings inform existing policies? This differs from a recommendation, which asks: “What should policymakers do differently in light of the research findings?” Consider this statement: “There is no need to stop Iran from acquiring nuclear weapons because it is unlikely to use them.” If policymakers are convinced by the argument, they might abandon efforts to coerce Iran or otherwise dramatically change their approach. Another variant is to warn of possible problems with a current approach: “Efforts to stop Iran from acquiring nuclear weapons will face challenges from Iran's insecurity about its own defense capabilities, from the different interests of Iran's trading partners, and from a distrust of U.S. credibility following the U.S. withdrawal from the Joint Comprehensive Plan of Action under President Trump.” This latter example offers no new policy but warns current policymakers about potential obstacles to success. Presumably, policymakers could try to mitigate these constraints, such as by providing side payments to trading partners, but the author is not making a specific recommendation.

By contrast, consider an approach that focuses on recommendations: “To stop Iran from acquiring nuclear weapons, the United States and its allies should focus less on military pressure and more on tightening economic sanctions.” Ideally, a scholar would provide examples for how to do such tightening. When in doubt, it is better to be direct than to let others draw their own conclusions.

Pointing out both policy recommendations and policy implications is valuable for the reasons discussed above. Policymaking is difficult, and solutions are not always obvious. Relatedly, sometimes a particular recommendation is uncomfortable (e.g., don't do humanitarian intervention or otherwise help a vulnerable population). This discomfort does not mean that scholars should avoid highlighting unpopular policy implications. Ideally, scholars would embrace this role as they are less likely than someone in government to suffer career harm from an unpopular position.

Table 1 presents five International Security articles that were published in the last five years. These examples highlight a wide range of topics that might matter to policymakers. 58 Some focus on a clear policy issue like civil-military relations or on an instrument like military training. Others seem more abstract, examining the nature of the international system or hostile uses of water. The authors represent a mix of both senior scholars and people at earlier career stages. Without claiming expertise on any of these issues myself, I identify potential audiences, policy recommendations, and other policy platforms for each article. (Note: the scholars themselves may disagree with my read on the implications of their work.)

Examples of Policy Audiences, Policy Recommendations, and Policy Implications of Select International Security Articles

SOURCES: See note 58 for the citations for these five International Security articles. The spin-offs listed in column four include: John J. Mearsheimer, “The Inevitable Rivalry: America, China, and the Tragedy of Great Power Politics,” Foreign Affairs , Vol. 100, No. 6 (November/December 2021), https://www.foreignaffairs.com/articles/china/2021-10-19/inevitable-rivalry-cold-war ; Isaac Chotiner, “Why John Mearsheimer Blames the U.S. for the Crisis in Ukraine,” New Yorker , March 1, 2022, https://www.newyorker.com/news/q-and-a/why-john-mearsheimer-blames-the-us-for-the-crisis-in-ukraine ; The U.S.-China Technology Relationship in Flux,” panel discussion (transcript), Brookings Institution, Washington, DC, October 4, 2019, https://www.brookings.edu/wp-content/uploads/2019/10/fp_20191004_china_tech_transcript.pdf ; Andrea Kendall-Taylor et al., “Henry Farrell and Abraham Newman Discuss ‘Weaponized Interdependence,’” Brussels Sprouts , podcast, Center for a New American Security, March 6, 2020, https://www.cnas.org/publications/podcast/henry-farrell-and-abraham-newman-discuss-weaponized-interdependence ; Henry J. Farrell and Abraham L. Newman, “This is What the Future of Globalization Will Look Like,” Foreign Policy , July 4, 2020, https://foreignpolicy.com/2020/07/04/this-is-what-the-future-of-globalization-will-look-like/ ; Henry J. Farrell and Abraham L. Newman, “The U.S. Is the Only Sanctions Superpower. It Must Use That Power Wisely,” New York Times , March 16, 2022, https://www.nytimes.com/2022/03/16/opinion/us-russia-sanctions-power-economy.html ; Henry J. Farrell and Abraham L. Newman, “America Weaponized the Global Financial System. Now Other Countries Are Fighting Back,” Monkey Cage (blog), Washington Post , December 19, 2019, https://www.washingtonpost.com/politics/2019/12/19/america-weaponized-global-financial-system-now-other-states-are-fighting-back/ ; Risa Brooks, “The Erosion of Civil-Military Relations,” Power Problems , podcast, Cato Institute, November 16, 2021, https://www.cato.org/multimedia/power-problems/erosion-civil-military-relations ; Risa Brooks, Jim Goldby, and Heidi Urben, “Crisis of Command: America's Broken Civil-Military Relationship Imperils National Security,” Foreign Affairs , Vol. 100, No. 3 (May/June 2021), https://www.foreignaffairs.com/articles/united-states/2021-04-09/national-security-crisis-command ; Risa Brooks, “What Can Military and Civilian Leaders Do to Prevent the Military's Politicization,” War on the Rocks , April 27, 2020, https://warontherocks.com/2020/04/what-can-military-and-civilian-leaders-do-to-prevent-the-militarys-politicization/ ; Sam Ratner, “The Stuff of Life and Death: Part II,” The World , May 4, 2021, https://theworld.org/stories/2021/05/04/stuff-life-and-death-part-ii ; Renanah Miles Joyce, “Rethinking How the United States Trains Foreign Militaries,” Lawfare , August 14, 2022, https://www.lawfaremedia.org/article/rethinking-how-united-states-trains-foreign-militaries .

To illustrate the framework and some of the points above more fully, consider a hypothetical article that examines alliances, a staple topic in international relations. The scholar asks, “What causes major power alliances to fail?” To make the work more policy relevant, the author should investigate the policies of the United States or other relevant countries, seeking to understand why they do what they do. Why did alliances with a particular focus, strength, and scope emerge, and what limits did they have? This investigation might involve reviewing government records, interviewing diplomats, and otherwise treating this baseline question as its own research topic. When doing interviews, it is useful to ask counterfactuals to determine why different results did not occur: Why were certain desirable countries excluded or problematic countries included in the alliance? Why was a particularly difficult coordination mechanism included or an alternative excluded? Overall, the scholar should try to get a sense of why the status quo emerged the way that it did.

With this background in mind, it is time to look forward. The question—what causes major power alliances to fail—is of obvious interest to a U.S. or an Asian diplomat, a NATO leader, or another official who might be involved in strengthening alliances. Nonetheless, it is hard to consider a specific audience for this topic. If the piece is highly relevant to the United States, the audience might be the regional bureaus at the State Department, which manage diplomatic relations for their parts of the world. Another option is the Office of the Secretary of Defense for Policy, which has departments that focus on the Indo-Pacific region, Strategy and Plans, and International Security Affairs, among others. Other entities, perhaps less central but also important, might include the International Finance office at the Department of Treasury and various shops within the intelligence community that monitor relations with countries around the world. The more scholars learn about these audiences’ agendas, remits, and resources, the better scholars’ recommendations will be.

Although the variables in play will of course depend on the research, it is worth considering two hypothetical alternative variables: shared interests versus institutional design. The former, of course, is out of the hands of almost all policymakers. But at least some (very senior) policymakers have input into institutional design.

This hypothetical example also illustrates how recommendations and implications may differ. The implications of different interests may lead to problems that are difficult to solve but must be anticipated and managed, perhaps to the point of not relying on allies under certain conditions or expecting only fitful cooperation. In contrast, a scholar may recommend a specific change to institutional design, such as a new entity, or greater powers for or new members of an existing entity. Here, as in other instances, it is important to consider the scope of the recommendation. Academics might rightly propose an entirely new alliance structure, such as an Asian version of NATO. Or they might focus more narrowly (but with more chance of influencing the debate) on how to tweak an existing structure to make it more effective.

Similarly, it is useful to consider how different elements of national power might help, and drafting a basic policy menu is a useful first step. The scholar should ask how diplomats, intelligence officers, the military, and economic actors like the Treasury Department might contribute. Imagine holding a meeting (or, ideally, interviewing people from different agencies) and think about how each might play a role.

It is also valuable for scholars to think ahead about likely problems with their recommendations. If, say, the recommendation is more resources to help gain the goodwill of a particular country, the trade-off is one that senior policymakers always face: fewer resources for other countries. But there may be less obvious costs and trade-offs. Might strengthening the alliance alarm a neighbor, perhaps leading to a dangerous spiral? Might the ally become more aggressive, creating a moral hazard, or, conversely, fear being chain-ganged into a conflict? Such possibilities need not be covered exhaustively, but it is important to acknowledge the limits of a recommendation. Again, interviewing and engaging with relevant policymakers can highlight these limits.

When the research is completed and published, it is time to consider additional publishing options. Many of these should be tied to current events: For a scholar writing in early 2024, what does research on alliance weakness tell us about how the Australia-United Kingdom-United States alliance might hold up or how Sweden and Finland's accession to NATO might be best managed? Leading newspapers might find these topics of interest, as would more specialized outlets like Foreign Affairs and Foreign Policy . When possible, scholars should give briefings on their work or otherwise promote it.

Writing policy recommendations can seem daunting, and in many ways it is. It can be done poorly and at times even counterproductively. When done well, however, recommendations can help guide decision-makers and the public on the world's more difficult issues.

In many ways, the process is the same for crafting both a better policy recommendation and a better article. Use clear, jargon-free prose and structured arguments to make recommendations more convincing. 59 Authors should seek out criticism, ideally from those with policy experience as well as from fellow scholars. The editors at International Security are an invaluable resource: they can help scholars think through and fully consider both ideas and implications. By making policy recommendations, scholars join a broader community that seeks to make the world a better place. It is not an easy task, but it is a necessary and rewarding one.

The author would like to thank Michael Desch, James Goldgeier, Matthew Kirchman, Ines Oulamene, Kenneth Pollack, Jeremy Shapiro, and the anonymous reviewers for their comments and excellent feedback on previous versions of this article.

As of April 2024, these articles are among the thirty most-cited contributions to International Security , according to data obtained by MIT Press. Thomas F. Homer-Dixon, “Environmental Scarcities and Violent Conflict: Evidence from Cases,” International Security , Vol. 19, No. 1 (Summer 1994), pp. 5–40, https://doi.org/10.2307/2539147 ; John J. Mearsheimer, “The False Promise of International Institutions,” International Security , Vol. 19, No. 3 (Winter 1994/95), pp. 5–49, https://doi.org/10.2307/2539078 ; Andrew H. Kydd and Barbara F. Walter, “The Strategies of Terrorism,” International Security , Vol. 31, No. 1 (Summer 2006), pp. 49–80, https://doi.org/10.1162/isec.2006.31.1.49 ; Maria J. Stephan and Erica Chenoweth, “Why Civil Resistance Works: The Strategic Logic of Nonviolent Conflict,” International Security , Vol. 33, No. 1 (Summer 2008), pp. 7–44, https://doi.org/10.1162/isec.2008.33.1.7 Henry Farrell and Abraham L. Newman, “Weaponized Interdependence: How Global Economic Networks Shape State Coercion,” International Security , Vol. 44, No. 1 (Summer 2019), pp. 42–79, https://doi.org/10.1162/isec_a_00351 .

See, among others, Naazneen H. Barma and James Goldgeier, “How Not to Bridge the Gap in International Relations,” International Affairs , Vol. 98, No. 5 (September 2022), pp. 1763–1781, https://doi.org/10.1093/ia/iiac102 ; Michael C. Desch, Cult of the Irrelevant: The Waning Influence of Social Science on National Security (Princeton, NJ: Princeton University Press, 2019); Stephen M. Walt, “The Relationship between Theory and Policy in International Relations,” Annual Review of Political Science , Vol. 8 (2005), pp. 29–32, https://doi.org/10.1146/annurev.polisci.7.012003.104904 ; Alexander L. George, Bridging the Gap: Theory and Practice in Foreign Policy (Washington, DC: United States Institute of Peace, 1993); Bruce W. Jentleson, “The Need for Praxis: Bringing Policy Relevance Back In,” International Security , Vol. 26, No. 4 (Spring 2002), pp. 169–183, https://doi.org/10.1162/016228802753696816 ; Henry Farrell, “Why Do Policy Makers Hate International Relations Scholarship?,” Monkey Cage (blog), Washington Post , September 18, 2013, https://themonkeycage.org/2013/09/why-do-policy-makers-hate-international-relations-scholarship ; Nicholas Kristof, “Professors, We Need You!,” New York Times , February 16, 2014, https://www.nytimes.com/2014/02/16/opinion/Sunday/kristof-professors-we-need-you.html . For workshops and other initiatives, see, for example, the Bridging the Gap project ( https://www.bridgingthegapproject.org ) as well as the Scholars Strategy Network ( https://scholars.org ). In the United Kingdom, the Research Excellence Framework ( https://www.ref.ac.uk ) links public engagement and policy relevance to funding, as have efforts like the Minerva Research Initiative ( https://minerva.defense.gov ).

Bruce W. Jentleson and Ely Ratner, “Bridging the Beltway–Ivory Tower Gap,” International Studies Review , Vol. 13, No. 1 (March 2011), pp. 6–11, http://dx.doi.org/10.1111/j.1468-2486.2010.00992.x ; Paul C. Avey and Michael C. Desch, “What Do Policymakers Want from Us?,” International Studies Quarterly , Vol. 58, No. 2 (June 2014), pp. 227–246, https://doi.org/10.1111/isqu.12111 ; Daniel Byman and Matthew Kroenig, “Reaching beyond the Ivory Tower: A How To Manual,” Security Studies , Vol. 25, No. 2 (2016), pp. 289–319, https://doi.org/10.1080/09636412.2016.1171969 .

James B. Steinberg, “Universities and Public Policy,” presentation at Presidents’ National Dialogue, University of Ottawa, October 22, 2009, https://www.cips-cepi.ca/wp-content/uploads/2011/01/steinberg.pdf .

See Michael W. Doyle, “Kant, Liberal Legacies, and Foreign Affairs,” in Arthur Ripstein, ed., Immanuel Kant (London: Routledge, 2017), pp. 503–533. For a critique, see Sebastian Rosato, “The Flawed Logic of Democratic Peace Theory,” American Political Science Review , No. 97, No. 4 (November 2003), pp. 585–602, https://doi.org/10.1017/S0003055403000893 . A foundational deterrence book is Thomas C. Schelling, The Strategy of Conflict (Cambridge, MA: Harvard University Press, 1981).

For an argument that policy recommendations are not essential for policy relevance, see Daniel Maliniak et al., eds., Bridging the Theory-Practice Divide in International Relations (Washington, DC: Georgetown University Press, 2020), pp. 8–10. For a critique, see Desch, Cult of the Irrelevant , pp. 250–255.

For a comparison of International Security 's focus on explicit policy recommendations with other security journals, see Jack Hoagland et al., “The Blind Men and the Elephant: Comparing the Study of International Security across Journals,” Security Studies , Vol. 29, No. 3 (2020), pp. 425–426, https://doi.org/10.1080/09636412.2020.1761439 .

Teresa Pelton Johnson, “Writing for International Security: A Contributor's Guide,” International Security , Vol. 16, No. 2 (Fall 1991), pp. 171–180, https://www.belfercenter.org/publication/writing-international-security-contributors-guide .

See the question “Does your research tend to be basic or applied?” in the 2017 TRIP Faculty Survey. Daniel Maliniak et al., 2017 TRIP Faculty Survey, Teaching, Research, and International Policy Project, Global Research Institute, Williamsburg, VA, https://trip.wm.edu/research/faculty-surveys .

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John Mueller, “Harbinger or Aberration? A 9/11 Provocation,” National Interest , Vol. 69 (Fall 2002): pp. 45–50, https://www.jstor.org/stable/42895558 .

Byman and Kroenig, “Reaching beyond the Ivory Tower,” p. 295.

Yuen Foong Khong, Analogies at War: Korea, Munich, Dien Bien Phu, and the Vietnam Decisions of 1965 (Princenton, NJ: Princeton University Press, 1992), pp. 3–18.

Daniel W. Drezner, The Ideas Industry: How Pessimists, Partisans, and Plutocrats are Transforming the Marketplace of Ideas (Oxford: Oxford University Press, 2017), pp. 43–101.

David D. Newsom, “Foreign Policy and Academia,” Foreign Policy , No. 101 (Winter 1995/96), p. 56, https://doi.org/10.2307/1149406 .

Rebecca Adler-Nissen, “Leaving the Lab,” Duck of Minerva (blog), September 2, 2021, https://www.duckofminerva.com/2021/09/leaving-the-lab.html .

John M. Owen IV, “Review: Iraq and the Democratic Peace: Who Says Democracies Don't Fight?,” Foreign Affairs , Vol. 84, No. 6 (November/December 2005), pp. 122–127, https://doi.org/10.2307/20031781 .

Paul Musgrave, “Political Science Has Its Own Lab Leaks,” Foreign Policy , July 3, 2021, https://foreignpolicy.com/2021/07/03/political-science-dangerous-lab-leaks/ .

Erica De Bruin, “How Can We Vaccinate against Viral Political Science?,” Duck of Minerva (blog), August 31, 2021, https://www.duckofminerva.com/2021/08/how-can-we-vaccinate-against-viral-political-science.html . De Bruin points to the program Rigor, Relevance, and Responsibility at the University of Denver's Sié Center as one such effort.

Charli Carpenter, “‘You Talk of Terrible Things So Matter-of-Factly in This Language of Science’: Constructing Human Rights in the Academy,” Perspectives on Politics , Vol. 10, No. 2 (June 2012), pp. 363–383, https://doi.org/10.1017/S1537592712000710 .

Michael O'Hanlon, “Why China Cannot Conquer Taiwan,” International Security , Vol. 25, No. 2 (Fall 2000), pp. 51–86, https://doi.org/10.1162/016228800560453 .

“Submissions,” Foreign Affairs , accessed February 21, 2023, https://www.foreignaffairs.com/submissions ; “New York Times Opinion Guest Essays,” New York Times , accessed February 21, 2023, https://help.nytimes.com/hc/en-us/articles/115014809107-New-York-Times-Opinion-Guest-Essays .

For International Security , see “Submission Guidelines,” International Security , Belfer Center for Science and International Affairs, Harvard Kennedy School, https://www.belfercenter.org/journal-international-security/overview#!submission-guidelines .

Kydd and Walter, “The Strategies of Terrorism.”

Caitlin Talmadge, “Closing Time: Assessing the Iranian Threat to the Strait of Hormuz,” International Security , Vol. 33, No. 1 (Summer 2008), pp. 82–117, https://doi.org/10.1162/isec.2008.33.1.82 .

Barma and Goldgeier, “How Not to Bridge the Gap,” p. 1768.

John Maynard Keynes, The General Theory of Employment, Interest and Money (1936; repr., London: Macmillan, 2007), pp. 383–384.

Keir A. Lieber, “The New History of World War I and What It Means for International Relations Theory,” International Security , Vol. 32, No. 2 (Fall 2007), pp. 155–191, https://doi.org/10.1162/isec.2007.32.2.155 .

Barma and Goldgeier, “How Not to Bridge the Gap,” p. 1781.

James T. Quinlivan, “Coup-proofing: Its Practice and Consequences in the Middle East,” International Security , Vol. 24, No. 2 (Fall 1999), pp. 131–165, https://doi.org/10.1162/016228899560202 ; Lise Morjé Howard and Alexandra Stark, “How Civil Wars End: The International System, Norms, and the Role of External Actors,” International Security , Vol. 42, No. 3 (Winter 2017/18), pp. 127–171, https://doi.org/10.1162/ISEC_a_00305 ; Edward D. Mansfield and Jack Snyder, “Democratic Transitions, Institutional Strength, and War,” International Organization , Vol. 56, No. 2 (Spring 2002), pp. 297–337, https://doi.org/10.1162/002081802320005496 .

Elizabeth N. Saunders, “Elites in the Making and Breaking of Foreign Policy,” Annual Review of Political Science , Vol. 25, No. 1 (2022), pp. 219–240, https://doi.org/10.1146/annurev-polisci-041719-103330 ; Mary E. Gallagher and Jonathan K. Hanson, “Power Tool or Dull Blade? Selectorate Theory for Autocracies,” Annual Review of Political Science , Vol. 18, No. 1 (2015), pp. 367–385, https://doi.org/10.1146/annurev-polisci-071213-041224 .

Colin L. Powell and Joseph E. Persico, My American Journey (New York: Ballantine, 1995), p. 393.

Shane Harris et. al., “Road to War: U.S. Struggled to Convince Allies, and Zelensky, of Risk of Invasion,” Washington Post , August 16, 2022, https://www.washingtonpost.com/national-security/interactive/2022/ukraine-road-to-war/ ; Afiq Fitri, “How President Zelensky's Approval Ratings Have Surged,” New Statesman , March 1, 2022, https://www.newstatesman.com/chart-of-the-day/2022/03/how-president-zelenskys-approval-ratings-have-surged .

Suzanne Maloney and Fred Dews, “Iran's Nuclear Aspirations,” Brookings Cafeteria , podcast, February 18, 2022, https://www.brookings.edu/podcast-episode/irans-nuclear-aspirations/ ; Mark Fitzpatrick, “Assessing the JCPOA,” Adelphi Series , Vol. 57, No. 466–467 (2017), pp. 19–60, https://doi.org/10.1080/19445571.2017.1555914 .

Steinberg, “Universities and Public Policy.”

Nikolaos van Dam, “What the West Got Wrong in Syria,” Foreign Policy , August 22, 2017, https://foreignpolicy.com/2017/08/22/what-the-west-got-wrong-in-syria/ . On variations on signaling in general, see Kai Quek, “Four Costly Signaling Mechanisms,” American Political Science Review , Vol. 115, No. 2 (2021), pp. 537–549.

Donald J. Trump, National Security Strategy of the United States of America (Washington, DC: White House, 2017), https://trumpwhitehouse.archives.gov/wp-content/uploads/2017/12/NSS-Final-12-18-2017-0905.pdf .

David A. Baldwin, “The Sanctions Debate and the Logic of Choice,” International Security , Vol. 24, No. 3 (Winter 1999/2000), p. 84, https://doi.org/10.1162/016228899560248 .

M. Taylor Fravel and Charles L. Glaser, “How Much Risk Should the United States Run in the South China Sea?,” International Security , Vol. 47, No. 2 (Fall 2022), pp. 88–134, https://doi.org/10.1162/isec_a_00443 .

Lawrence M. Mead, “Scholasticism in Political Science,” Perspectives on Politics , Vol. 8, No. 2 (June 2010), p. 454, https://doi.org/10.1017/S1537592710001192 .

Daniel Byman and Aditi Joshi, “Social Media Companies Need Better Emergency Protocols,” Lawfare , January 14, 2021, https://www.lawfaremedia.org/article/social-media-companies-need-better-emergency-protocols .

Nicholas Sambanis, “What Is Civil War? Conceptual and Empirical Complexities of an Operational Definition,” Journal of Conflict Resolution , Vol. 48, No. 6 (2004), pp. 814–858, https://doi.org/10.1177/0022002704269355 .

Lindsey A. O'Rourke, “The Strategic Logic of Covert Regime Change: U.S.-Backed Regime Change Campaigns during the Cold War,” Security Studies , Vol. 29, No. 1 (2020), pp. 92–127, https://doi.org/10.1080/09636412.2020.1693620 .

National Commission on Terrorist Attacks, The 9/11 Commission Report: Final Report of the National Commission on Terrorist Attacks upon the United States , Vol. 3 (Washington, DC: Government Printing Office, 2004), pp. 399–428.

Richard A. Posner, “The 9/11 Report: A Dissent,” New York Times , August 29, 2004, https://www.nytimes.com/2004/08/29/books/the-9-11-report-a-dissent.html .

Daniel Byman and Jeremy Shapiro, “‘What U.S. Foreign Policy Really Needs Is …’: The 11 Worst Washington Insider Policy Clichés,” Foreign Policy , June 5, 2015, https://foreignpolicy.com/2015/06/05/the-11-worst-useless-foreign-policy-pundit-cliches/ .

Joint Chiefs of Staff, Strategy , Joint Doctrine Note 1–18 (Washington, DC: Joint Force Development, 2018), pp. II-5–II-11, https://www.jcs.mil/Portals/36/Documents/Doctrine/jdn_jg/jdn1_18.pdf .

Joint Chiefs of Staff, Strategy , p. II-8.

Alexander L. George and William E. Simons, eds., The Limits of Coercive Diplomacy (Boulder, CO: Westview Press, 1994), pp. 53–55, 267–294.

Kenneth M. Pollack, Armies of Sand: The Past, Present, and Future of Arab Military Effectiveness (Oxford: Oxford University Press, 2018), pp. 439–451.

Renanah Miles Joyce, “Soldiers’ Dilemma: Foreign Military Training and Liberal Norm Conflict,” International Security , Vol. 46, No. 4 (Spring 2022), p. 89, https://doi.org/10.1162/isec_a_00432 .

Edward Wong and Amy Qin, “U.S. Presses Taiwan to Buy Weapons More Suited to Win against China,” New York Times , May 7, 2022, https://www.nytimes.com/2022/05/07/us/politics/china-taiwan-weapons.html .

Keir A. Lieber and Daryl G. Press, “The End of MAD? The Nuclear Dimension of U.S. Primacy,” International Security , Vol. 30, No. 4 (Spring 2006), pp. 7–44, https://doi.org/10.1162/isec.2006.30.4.7 ; Keir A. Lieber and Daryl G. Press, “The Rise of U.S. Nuclear Primacy,” Foreign Affairs , Vol. 85, No. 2 (March/April 2006), pp. 42–54, https://doi.org/10.2307/20031910 ; Keir A. Lieber and Daryl G. Press, “Superiority Complex: Why America's Growing Nuclear Supremacy May Make War with China More Likely,” Atlantic , July/Aug. 2007, pp. 86–92, https://www.theatlantic.com/magazine/archive/2007/07/superiority-complex/305989/ .

See, for example, submission information for Foreign Policy at https://foreignpolicy.submittable.com/submit and for Foreign Affairs at https://www.foreignaffairs.com/submissions-0 .

Barma and Goldgeier, “How Not to Bridge the Gap,” p. 1773.

John J. Mearsheimer, “Bound to Fail: The Rise and Fall of the Liberal International Order,” International Security , Vol. 43, No. 4 (Spring 2019), pp. 7–50, https://doi.org/10.1162/isec_a_00342 ; Farrell and Newman, “Weaponized Interdependence”; Risa Brooks, “Paradoxes of Professionalism: Rethinking Civil-Military Relations in the United States,” International Security , Vol. 44, No. 4 (Spring 2020), pp. 7–44, https://doi.org/10.1162/isec_a_00374 ; Charlotte Grech-Madin, “Water and Warfare: The Evolution and Operation of the Water Taboo,” International Security , Vol. 45, No. 4 (Spring 2021), pp. 84–125, https://doi.org/10.1162/isec_a_00404 ; Joyce, “Soldiers’ Dilemma.”

Johnson, “Writing for International Security.”

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EU Member States adopt recommendations to enhance research security

Today, the EU made an important step towards ensuring that international research and innovation cooperation can take place in a way that is both open and safe. At the meeting of the Council of the EU, research ministers adopted a Recommendation on enhancing research security, which puts forward measures designed to protect research and innovation from misuse.

Iliana Ivanova, Commissioner for Innovation, Research, Culture, Education and Youth, said:

“Openness and international cooperation are at the core of great science and innovation, but they also make it particularly vulnerable to security threats. With these recommendations, the EU responds to the calls for clarity and guidance from researchers and innovators. We will work together to safeguard sensitive knowledge from being misused, supporting research organisations in fulfilling their responsibilities while protecting academic freedom and building a resilient ecosystem.”

The Recommendation is based on a Commission proposal tabled on 24 January 2024 as part of measures underpinning the European Economic Security Strategy. It strikes a balance between being open and safe, while respecting and safeguarding crucial principles such as academic freedom, institutional autonomy and non-discrimination.

Today’s agreement will enable the Member States to address research security in a collective and coordinated way. Alignment and consistency across the EU are key to an effective response to these threats. 

With the adoption of this Recommendation, EU Member States commit to work jointly on the issue. Next steps on their part include developing a coherent set of policy measures and support structures for the research sector, introducing research security questions in grant application forms and encouraging research performing organisations to introduce research security risk management.

For its part, the Commission will follow up on the recommendations by leveraging the European Research Area governance structures bringing together Member States’ experts, funding organisations, and EU level stakeholders.

The Commission has already started to explore possibilities for establishing a European Centre of Expertise on Research Security and for supporting capacity building and peer learning for national administrations.

The Commission will continue to actively engage with our key partners around the globe to seek alignment between safeguarding measures. The first European Flagship Conference on Research Security, expected to take place in autumn 2025, will take stock of the progress made.

The Commission tabled its  proposal for a Council Recommendation on enhancing research security on 24 January 2024 as part of a  follow-up package to the European Economic Security Strategy, which was launched on 20 June 2023 by a  joint Communication . 

For its proposal the Commission took into account the  policy debate on knowledge security and responsible internationalisation that Ministers of Research had at their meeting of 23 May 2023, as well as the feedback from stakeholders received following a  call for evidence , end of 2023. It is also in line with the 2021 Commission  Communication on the Global Approach to Research and Innovation : Europe's strategy for international cooperation in a changing world.

Following today’s adoption by the Council, the official publication of the Council Recommendation is expected in the coming days.

More information  

Factsheet: Council recommendation on research security

Factsheet: Building blocks for risk appraisal

Press contact:

EC Spokesperson for Research, Science and Innovation

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• Published: 03 June 2024

The assessment of left ventricular diastolic function: guidance and recommendations from the British Society of Echocardiography

• Shaun Robinson 1 ,
• Liam Ring 2 ,
• David Oxborough 3 ,
• Allan Harkness 4 ,
• Sadie Bennett 5 ,
• Bushra Rana 1 ,
• Nilesh Sutaria 1 ,
• Francesco Lo Giudice 1 ,
• Matthew Shun-Shin 1 ,
• Maria Paton 6 ,
• Rae Duncan 7 ,
• James Willis 8 ,
• Claire Colebourn 9 ,
• Gemma Bassindale 6 ,
• Kate Gatenby 6 ,
• Mark Belham 10 ,
• Graham Cole 1 ,
• Daniel Augustine 8 &
• Otto A. Smiseth 11  

Echo Research & Practice volume  11 , Article number:  16 ( 2024 ) Cite this article

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Impairment of left ventricular (LV) diastolic function is common amongst those with left heart disease and is associated with significant morbidity. Given that, in simple terms, the ventricle can only eject the volume with which it fills and that approximately one half of hospitalisations for heart failure (HF) are in those with normal/’preserved’ left ventricular ejection fraction (HFpEF) (Bianco et al. in JACC Cardiovasc Imaging. 13:258–271, 2020. 10.1016/j.jcmg.2018.12.035), where abnormalities of ventricular filling are the cause of symptoms, it is clear that the assessment of left ventricular diastolic function (LVDF) is crucial for understanding global cardiac function and for identifying the wider effects of disease processes. Invasive methods of measuring LV relaxation and filling pressures are considered the gold-standard for investigating diastolic function. However, the high temporal resolution of trans-thoracic echocardiography (TTE) with widely validated and reproducible measures available at the patient’s bedside and without the need for invasive procedures involving ionising radiation have established echocardiography as the primary imaging modality. The comprehensive assessment of LVDF is therefore a fundamental element of the standard TTE (Robinson et al. in Echo Res Pract7:G59–G93, 2020. 10.1530/ERP-20-0026). However, the echocardiographic assessment of diastolic function is complex. In the broadest and most basic terms, ventricular diastole comprises an early filling phase when blood is drawn, by suction, into the ventricle as it rapidly recoils and lengthens following the preceding systolic contraction and shortening. This is followed in late diastole by distension of the compliant LV when atrial contraction actively contributes to ventricular filling. When LVDF is normal, ventricular filling is achieved at low pressure both at rest and during exertion. However, this basic description merely summarises the complex physiology that enables the diastolic process and defines it according to the mechanical method by which the ventricles fill, overlooking the myocardial function, properties of chamber compliance and pressure differentials that determine the capacity for LV filling. Unlike ventricular systolic function where single parameters are utilised to define myocardial performance (LV ejection fraction (LVEF) and Global Longitudinal Strain (GLS)), the assessment of diastolic function relies on the interpretation of multiple myocardial and blood-flow velocity parameters, along with left atrial (LA) size and function, in order to diagnose the presence and degree of impairment. The echocardiographic assessment of diastolic function is therefore multifaceted and complex, requiring an algorithmic approach that incorporates parameters of myocardial relaxation/recoil, chamber compliance and function under variable loading conditions and the intra-cavity pressures under which these processes occur. This guideline outlines a structured approach to the assessment of diastolic function and includes recommendations for the assessment of LV relaxation and filling pressures. Non-routine echocardiographic measures are described alongside guidance for application in specific circumstances. Provocative methods for revealing increased filling pressure on exertion are described and novel and emerging modalities considered. For rapid access to the core recommendations of the diastolic guideline, a quick-reference guide (additional file 1) accompanies the main guideline document. This describes in very brief detail the diastolic investigation in each patient group and includes all algorithms and core reference tables.

Ventricular anatomy, physiology and mechanics

Myocardial architecture and function.

To appreciate the myocardial mechanics that enable global LV contraction and relaxation, it is important to understand the composition of the LV myocardium that enables these processes.

Myocyte alignment defining myocardial layers

It is the shortening and lengthening of cardiac myocytes along planes of alignment that enables the ventricular cavity to decrease and increase volume, producing systolic ejection and diastolic filling. The bulk of the ventricular myocardium is composed of contractile myocytes that branch at each end to form connections with adjacent myocytes [ 3 ]. This branch-connectivity creates an interconnected network of cardiomyocytes that forms the basis of the multi-layered architecture of the ventricular myocardium, enabling the complex processes of ventricular contraction and relaxation. When considered according to myocyte alignment and orientation, the LV myocardium consists of three layers, albeit without distinct borders between them: the sub-epicardium, mid-wall and sub-endocardium. Sub-epicardial fibres are orientated in a left-handed (LH) helical arrangement and account for around 25% of the total myocardial wall thickness [ 4 ]. Aligned obliquely longitudinal, they extend from the level of the atrioventricular valves at the base of the ventricles. When viewed from an anterior perspective, the sub-epicardial fibres run down obliquely leftward and continue to the apex; the fibres originating from the base of the left ventricle extend towards the diaphragmatic surface of the heart, crossing the posterior interventricular groove [ 3 , 4 , 5 ]. Contraction of this layer is largely responsible for torsion of the apex relative to the base [ 6 ]. Fibres in the mid-wall account for around 53–59% of the myocardial thickness, increasing in the elderly [ 7 ], and are arranged circumferentially and in near parallel alignment with the mitral valve (MV) annulus; these fibres largely generate radial contraction [ 6 ]. The sub-endocardial layer is the thinnest layer, accounting for < 20% of the total myocardial thickness. These fibres are arranged in a right-handed (RH) helix and obliquely longitudinal pattern, generating longitudinal and rotational contraction of this layer [ 8 ]. Fundamentally, the LV consists of two muscular helixes that surround the midventricular circumferential layer of muscular fibres.

Helical arrangement of myocardial fibres—Nakatani, 2011 [ 8 ]

Myocardial mechanics and ventricular contraction

This complex configuration of myocyte alignment (sub-epicardial—LH helix, sub-endocardial—RH helix, mid-wall—circumferential) enables three-dimensional contraction that results in rotation, shortening and inward contraction of the myocardium with the net effect of reducing LV cavity dimensions in all planes.

Contraction of sub-epicardial fibres, arranged in a LH helix, causes anti-clockwise rotation of the apical sub-epicardium and clockwise rotation of the base, while contraction of the sub-endocardial fibres, arranged in a RH helix, causes clockwise rotation of the apical sub-endocardium and anticlockwise rotation at the base (Fig.  1 ) [ 8 , 9 ]. However, because the rotational radius of the outer layer is greater than that of the inner layer and therefore produces greater torque, the sub-epicardial direction of contraction dominates when both layers contract simultaneously [ 9 ]. Consequently, global apical rotation is clockwise very briefly during isovolumetric contraction before reversing and rotating anti-clockwise during the ejection phase (Fig. 2 ). Global basal contraction mirrors this process, rotating anti-clockwise very briefly during isovolumetric contraction before reversing to clockwise rotation during systolic ejection. Therefore, global LV systolic rotation is predominantly anti-clockwise at the apex and clockwise at the base (Fig. 3 ).

Basal and apical rotational direction of myocardial contraction—Nakatani, 2011 [ 8 ]

From a mechanistic perspective, twisting of the myocardium along these planes helps maintain a uniform myocardial fibre stress and shortening that produces a high global contraction percentage (LVEF ~ 60%) from relatively small myocyte shortening (~ 20%) [ 10 , 11 , 12 ]. Importantly for the efficiency of diastolic filling, twisting and deformation of the myocardial matrix throughout systole causes a progressive build-up of potential energy [ 13 ]. This energy is released following peak contraction resulting in rapid recoil of the circumferential fibres and untwisting of the sub-epi and sub-endocardial helices during isovolumic relaxation and the early period of diastolic filling. The clockwise untwisting of the apex and simultaneous anti-clockwise untwisting of the base generates rapid relaxation of the LV cavity and consequently early diastolic suction [ 14 , 15 , 16 ].

Subendocardial and subepicardial rotational directions at the base and apex—from Nakatani, 2011 [ 8 ]

Due to the tomographic nature of routine 2D TTE, this complex three-dimensional contraction is viewed, and therefore measured, in 2D orthogonal planes: mitral annular Tissue-Doppler Imaging (TDI) and GLS measure longitudinal lengthening/shortening of the LV, while LVEF predominantly measures radial contractility with some minor contribution from longitudinal shortening. Therefore, because contraction and relaxation of the cardiomyocytes is not purely longitudinal or radial in direction, 2D indices of deformation in these planes are not precisely reflective of LV myocardial contraction. Nonetheless, these echocardiographic measures of longitudinal and radial contraction are well validated and provide important diagnostic and prognostic insight into disease processes and their effect on myocardial function.

Normal left ventricular function throughout the cardiac cycle

The LV cardiac cycle is broadly divided into two phases: systole and diastole. Although these phases are often considered independently when being investigated by echocardiography, the proficiency of the ventricle to fill and eject reflects global myocardial performance. Given that the extent of systolic contraction and ejection must be equal to that of diastolic relaxation and filling (as the ventricle cannot perpetually eject more volume than has entered the chamber during the preceding filling period, and vice-versa), there exists a crucial interdependence between LV systolic and diastolic function. Consequently, both phases are simultaneously susceptible to deterioration secondary to disease processes and although dysfunction of one phase may be the predominate cause of symptoms, it is highly likely that this will be accompanied by some degree of impairment of the other. Therefore, in order to fully understand the physiological mechanisms that govern the timings and pressure differentials that enable ventricular filling, and to appreciate the importance of systolic/diastolic interdependence, it is essential to understand ventricular function throughout the cardiac cycle and how this determines filling, filling pressure (LVFP) and ejection.

Left ventricular systole

LV systole is defined as the period between MV closure and aortic valve (AV) closure and consists of two phases that are termed according to the changes of LV volume: isovolumetric contraction and the ejection phase.

Isovolumetric contraction

LV diastole and filling end when LA contraction is complete and LA-LV pressures are close to equal, leading to the start of MV closure (Fig. 4 ) [ 17 ]. With the onset of systolic contraction, LV cavity pressure increases above LA pressure (LAP) and the MV closes. Although LV pressure is increasing and exceeds LAP, it remains below the pressure within the aorta and the AV remains closed [ 18 ]. Therefore, because the ventricle is within the contractile phase but internal pressure prevents blood from entering or leaving the chamber, this period is referred to as the isovolumetric contraction time (IVCT).

Recording of simultaneous LV and Ao pressures (the representation of LAP has been added)—O.Smiseth’s own work

Systolic ejection

Once LV pressure exceeds aortic pressure, the AV is thrust open and blood is ejected from the LV; this period is referred to as the ejection phase. Although peak systolic contraction and deformation is achieved in late systole, peak LV pressure, and consequently outflow velocities, peak in mid systole before falling as the ventricular volume decreases towards end-systole. The AV closes following peak LV contraction when the cavity pressure falls below the pressure in the aorta, thus defining the end of the systolic period.

Left ventricular diastole

Diastole is defined as the period between AV closure and MV closure and includes periods of isovolumetric relaxation and ventricular filling. In sinus rhythm (SR) with normal heart rate (HR) and no conduction delay between the atria and ventricles, diastole is a four-phase process that comprises periods of: isovolumetric relaxation, early rapid filling, a period of little or no filling (diastasis) and atrial contraction (Fig. 4 ).

Isovolumetric relaxation

Throughout systole, compression and torsion of the myocardium generates a progressive build-up of potential energy within the elastic elements of the cardiomyocytes and extracellular matrix [ 19 ], peaking at end-systole. This energy is then released in early diastole as the twisted and compressed cardiomyocytes recoil and relax back to their unstressed/resting orientation, resulting in rapid recoil and untwist of the LV. Combined with a contribution from active myocyte relaxation, this leads to a rapid increase in LV cavity dimensions that causes an equally rapid fall in intracavity pressure. This near constant rate of LV relaxation causes a near exponential rate of pressure decay that can be measured by the time constant, Tau (τ). Since the rate at which intracavity pressure falls is determined by τ, the rate of pressure-decay can be measured as an indicator of LV relaxation and therefore diastolic myocardial function [ 20 ].

The onset of diastole is defined mechanically by closure of the AV. LV pressure at the start of diastole is therefore high and just below aortic pressure (Fig. 5 ). For a short period following AV closure, despite falling, pressure within the rapidly relaxing LV continues to exceed LAP and the MV remains shut with consequently no ventricular filling [ 21 ]. Given that both the AV and MV are shut and LV volume is unchanged from the point of AV closure, this phase is described as the Isovolumetric Relaxation Time (IVRT) (Fig. 5 ) and lasts between AV closure and MV opening. In both normal and disease states, the rate of relaxation is constant with a near linear relationship with τ; because a normal τ is typically less than 45 ms in most age groups, the IVRT is short in those with normal diastolic function [ 22 ].

Pressure–volume loop demonstrating changes in ventricular volume during filling and ejection with corresponding changes in intracavity pressure. The isovolumetric relaxation and contraction periods are highlighted [ 21 ]

Early filling

Continued untwisting and relaxation of the LV causes intracavity pressure to fall. Once pressure in the LV falls below pressure in the LA, suction effect causes the MV to open and blood flows from the LA into the LV, marking the onset of the rapid early filling phase and the end of the IVRT (Fig. 6 ). For a very brief period of 30 – 40 ms following MV opening, the rapid rate of LV relaxation is such that pressure within the LV continues to fall despite the initial increase in volume, creating a pressure gradient from the LA to LV apex that results in flow accelerating out of the LA [ 24 , 25 , 26 ]; minimal LV diastolic pressure is therefore typically reached at around 3.5 × τ [ 22 ]. With continued LV relaxation and rapidly increasing LV volume towards its relaxed capacity, LV cavity pressure rises with a progressive reduction in the LA-LV pressure difference and resultant fall in the transmitral flow velocity. In young healthy hearts and at a normal HR, between 80 and 90% of total LV filling occurs during the early diastolic filling phase with the majority of early LV filling completed by 140 ms.

The four phases of diastole shown on a spectral Doppler trace of mitral inflow ( A ) and mitral annular tissue-Doppler imaging ( B )—(1) IVRT, (2) early filling, (3) diastasis, (4) late filling from atrial contraction

As the early filling period ends and the LV reaches its relaxed volume, LV diastolic pressures increase with little to no pressure difference existing between the LA and LV. Consequently, transmitral flow volume and velocity fall significantly and the MV leaflets return to a semi-open or even almost closed position. This period of little to no flow following early passive filling and before atrial contraction is termed diastasis. With a normal P-R interval, the duration of diastasis is determined by the diastolic period and therefore HR, with bradycardia resulting in a longer period between the early filling phase and atrial contraction and therefore longer diastasis.

Late filling from atrial contraction

The final phase of ventricular filling occurs when LA contraction increases LA pressure, forcing the MV to open and ejecting blood into the LV. In the setting of normal diastolic function, the relaxed LV offers very little resistance to additional filling and the majority of blood ejected by the LA enters the LV, with only a small proportion being ejected back into the pulmonary veins. During this final stage of diastole, because the LV cardiomyocytes are completely relaxed, highly compliant and distensible, the 10–20% additional volume from atrial contraction is achieved with a < 5 mmHg increase in EDP [ 27 ]. This enables the LV to fill at very low pressure with consequently low pressure within the LA, pulmonary veins (PV) and therefore pulmonary capillary bed (Fig. 6 ).

Atrial function and pulmonary vein flow

As a reservoir for blood prior to early LV diastolic filling and through pump contribution in late diastole, LA function modulates LV filling and is therefore an important component of LVDF. In connection with the LA, flow from the PV’s reflects the phases of LA filling and contraction and therefore provides insight into LVDF, LVFP and LAP [ 28 ]. In SR, there are three phases of LA function, each of which are identifiable during TTE by alterations in LA chamber dimensions and by blood flow into and out of the LA [ 29 ] (Fig. 7 ).

The phases of atrial function demonstrated using pressure volume loop—adapted from Negishi et al. The phases of the cardiac cycle have been highlighted on image A. Diastole has been divided into: E—early filling, D—diastasis and A—atrial contraction. The reservoir phase (red trace—1) occurs during ventricular systole: pulmonary venous blood enters the LA resulting in LA volume increasing from minimum to maximum. In normal circumstances, the associated increase in LA pressure is small, owing to atrial compliance and distensibility. Immediately after mitral valve opening, there is reduction in LA volume and pressure as blood enters the LV during the conduit phase (green trace—2). At a low enough HR there is a period between early and late diastolic filling where LA and LV pressures are close to equal with consequently minimal transmitral flow (dark blue trace—3). Finally, the atrium contracts, marking the onset of the pump phase (grey trace—4). This is accompanied by a rapid increase in LA pressure and blood is ejected from the LA into the LV with some retrograde flow into the PV’s (the A-reversal wave). Immediately after contraction, the LA recoils and relaxation commences (light blue trace—5), leading to the start of the reservoir phase [ 29 ]

Reservoir phase

The LA reservoir phase occurs during LV systolic contraction with PV flow during this period occurring over two phases. At the very start of LV systole, elastic recoil of the LA immediately after atrial contraction causes dimensions to increase and LAP to fall, drawing blood in from the PV’s and marking the initial phase of PV systolic flow. Ongoing systolic contraction and shortening of the LV leads to descent of the MV annulus towards the LV apex. As the roof of the LA is relatively fixed in position, this motion stretches the LA and increases dimensions from a contracted minimum at end-diastole to a maximum volume at ventricular end-systole (Fig. 7 ).

The increase in LA dimensions causes LAP to fall further while right ventricular (RV) systolic pressure is simultaneously propagated through the pulmonary vasculature. These actions combine to create a pressure differential that drives blood flow through the lungs and PV’s into the LA—noted as the second phase of PV flow [ 30 ] (Fig. 8 ). The LA therefore functions as a ‘reservoir’ of blood during LV systole. As LA filling during this phase relies on a combination of chamber stretch (through LV longitudinal shortening), RV systolic pressure propagated through the lungs [ 30 ] and intrinsic LA distensibility, this aspect of LA function is broadly related to LV stroke volume (SV) and atrial compliance [ 31 , 32 ]. The total LA reservoir volume is ejected into the LV over two phases: passive LA contraction/compression in early diastole (secondary to LV recoil and relaxation) and active contraction (pump) in atrial systole.

Pulsed Wave Doppler spectral display of pulmonary vein flow. S1 and S2 waves reflect left atrial filling during LV systole (LA reservoir phase). The D wave reflects pulmonary vein flow during early ventricular diastole (LA conduit phase). The Ar wave reflects flow reversal within the pulmonary veins secondary to atrial contraction (LA pump phase)

Conduit phase

The LA conduit phase starts with MV opening and continues until active atrial contraction. However, in atrial fibrillation (AF), the absence of atrial contraction means that this phase continues until end-diastole. The conduit phase is represented by the volume of blood that is transported from the PV’s to the LV without being stored in the atrium and can be estimated by considering changes in LA dimensions in comparison to LV SV, as follows:

In normal circumstances (absence of aortic or mitral regurgitation), the volume of blood ejected by the LV in systole, the SV, is equal to the volume of blood that it fills with in diastole (total filling volume). This total diastolic filling volume (and therefore SV) is achieved by two filling mechanisms that occur simultaneously:

emptying of the LA from its maximum volume at end-systole to a minimum volume following atrial contraction at end-diastole— LA reservoir volume .

blood drawn into the LV by suction effect, secondary to LV relaxation in early to mid-diastole, that simply passes through the LA from PV’s— LA conduit volume .

The contribution of LA reservoir volume to LV filling is calculated as the difference between maximum LA volume and minimum LA volume. Therefore, because the total LV filling volume and SV are equal, the contribution of conduit volume to LV filling is calculated as the difference between LA reservoir volume and SV.

For example:

Although this calculation does not consider the volume of blood ejected back into the PV’s during the LA pump phase, this volume of blood is insignificant and cannot be measured by echocardiography.

Active contraction phase

The final stage of LA function is the pump phase, sometimes described as the contractile phase, when blood is actively ejected into the LV. LA contraction contributes between 10–15% of total filling in the healthy young [ 32 ], increasing up to 35–40% in the healthy elderly [ 33 ]. When LVEDP is normal, the majority of blood ejected from the LA enters the LV and is identified as the A wave on transmitral Doppler. However, even in normal healthy hearts, LA contraction results in a small volume of blood being ejected backward into the pulmonary veins (Fig. 8 ). The LA pump phase is an important mechanism by which LV filling can be maximised and SV maintained.

The spectrum of impaired diastolic function

Although sudden cardiac events may have an immediate adverse effect on LVDF and LVFP, the development of impaired diastolic function is typically a chronic process where deterioration is usually determined by aetiology and the effectiveness of medical management of the underlying disease. Many pathological processes affect myocardial function and consequently alter the properties of left ventricular relaxation and compliance, thus limiting the capacity of LV filling and causing LV and LA diastolic pressures to increase. Although impaired diastolic function broadly describes the complex continuum from normality to restrictive filling, three important physiological aspects define LV filling capability and should be considered by echocardiography: myocardial relaxation, chamber compliance and LVFP [ 34 ]. While there is no certainty of progression, impaired diastolic function will initially present in the very early stages as a subclinical abnormality of relaxation with no significant effect on LVFP or associated symptoms. If progressive, it may advance through the spectrum of impairment to restrictive ventricular filling with the significant haemodynamic consequences of markedly raised LVFP and pulmonary hypertension (PH) that cause the symptoms of HF.

Impaired relaxation, normal LV compliance

The earliest stage of diastolic impairment is characterised by impaired relaxation but with normal chamber compliance. Impaired relaxation is defined by a longer τ and reduced relaxation velocities [ 20 ]. Given that τ is linearly related to the rate of pressure fall within the LV, a slower rate of LV relaxation results in a slower rate of pressure fall and consequently longer time period between AV closure at the very start of diastole and MV opening with the onset of LV filling. Impaired LV relaxation is therefore reflected by a longer IVRT. Following the extended IVRT, the MV opens and the LV begins to fill. However, because the early diastolic filling rate is proportional to the rate of pressure decay, which in turn is determined by the rate of relaxation (τ), the early diastolic ventricular filling rate, and therefore volume and velocity, is reduced when relaxation is impaired [ 35 ]. In essence, for the same filling period, impaired relaxation reduces the early diastolic filling rate and therefore volume with a greater proportion of total filling, approaching 35–40%, occurring through atrial contraction in late diastole in order to maintain SV and cardiac output (CO).

Despite relaxation being impaired the LV remains compliant, meaning that the chamber is able to distend/stretch to accommodate the filling volume and maintain low LVFP. Minimum LV diastolic pressure is closely related to the relaxation properties of the LV and therefore occurs very early in diastole [ 36 ]. With normal relaxation and filling, the minimum filling pressure is low—in the young and athletic, low minimum pressure increases the transmitral pressure difference while LAP remains normal, creating a suction effect that facilitates rapid early filling at normal filling pressure. However, as relaxation becomes impaired and the rate of pressure decay falls, minimum LV diastolic pressure increases and reduces the early diastolic pressure difference, therefore attenuating the suction force for flow between the LA and LV [ 37 ] and reducing early diastolic transmitral velocities. Although impaired LV relaxation leads to increased minimum pressure, because the LV remains compliant and is able to distend to accommodate atrial pump volume, LVFP, and therefore LAP, remain normal (Fig. 9 ). Importantly, impaired relaxation may cause a mild increase in LV EDP that although not contributory to symptoms, is an early indicator of impaired diastolic function [ 38 ].

Adapted from Panesar, Dilveer and Burch

Relative changes in LA and LV diastolic pressures in different stages of impaired diastolic function. LAP remains normal when relaxation is impaired but becomes elevated when LV compliance is decreased. [ 42 ]

Impaired relaxation, reduced LV compliance

Worsening diastolic function is characterised by continued deterioration of LV relaxation rate and velocities with increasing myocardial stiffness and reduced chamber compliance. Increasing LV stiffness and consequently reduced LV compliance leads to increased LV diastolic pressure even at normal filling volume. As the myocardium becomes stiffer and LV compliance deteriorates further, LV filling becomes restrictive with significantly elevated LV diastolic pressure, and therefore LAP, for even low filling volumes (Fig. 9 ).

Elevation of LV diastolic pressures and LAP has a significant impact on all phases of ventricular filling. Whereas impaired relaxation with normal LAP results in a longer IVRT, elevated LAP causes the MV to open sooner and therefore shortens the IVRT. Although relaxation is impaired with marked attenuation of the diastolic suction effect, filling in early diastole is now dominated by elevated LAP. Therefore, upon MV opening, high LAP causes high transmitral flow velocity in early diastole. Due to reduced LV compliance, LV pressure rises rapidly with rapid equalisation between LA-LV pressures and an equally rapid deceleration of early diastolic transmitral flow velocity—the early diastolic filling period is therefore typically shortened when LV diastolic pressure and LAP are elevated. Following early diastolic filling, flow between the LA and LV during diastasis is typically low volume and low velocity when LAP is normal. However, LA incompliance due to raised LAP (secondary to LV impaired diastolic function) may result in continued flow between the LA and LV during this period (as flow from the PV’s into a stiff LA continues during diastasis, LAP increases resulting in transmitral forward flow (L-wave)) [ 39 ]. With reduced LV compliance causing elevated diastolic pressure, LA contraction at end-diastole is against a higher resistance (afterload) and causes further elevation of LV EDP. Increased resistance to LA contraction reduces the transmitral forward flow volume, velocity and duration and results in a greater proportion of blood being ejected back into the PV’s and for a longer duration than forward flow [ 39 ]. When LVEDP is significantly raised, LA pump function deteriorates in the face of significantly increased afterload. Consequently, because the LV, LA and PV’s are in continuity with the pulmonary capillary bed, increased LV diastolic pressure is transmitted back through the LA and PV’s leading to increased pulmonary capillary pressure and consequently PH [ 40 , 41 ].

Effect of normal aging on LV filling

The effect of normal aging on LV filling mimics the early stages of impaired diastolic function such that a slower rate of myocardial relaxation and lower relaxation velocities are expected findings in the elderly. Therefore, an extended IVRT, reduced early diastolic filling and increased late diastolic filling are normal findings. Mean LAP does not increase with aging, although LV EDP may become mildly elevated but is not typically associated with symptoms [ 43 ]. Although these findings are similar to the initial stages of impaired LV diastolic function, they should be expected in those over the age of 65 years. In fact, a short IVRT and predominance of early diastolic filling in the elderly should raise the suspicion of impaired LV diastolic function with raised LVFP.

Echocardiographic measurements: routine, supplementary and non-routine measures

Given the multiple aspects of diastolic mechanics and associated LVFP, there is no single parameter or measure that accurately describes ventricular diastolic function and the response of intracavity pressure. The echocardiographic assessment of LV diastole must therefore incorporate multiple parameters of intracardiac blood flow velocity, myocardial relaxation velocity and left atrial size and function in order to consider the presence and degree of diastolic impairment. Optimisation of all two-dimensional images and Doppler waveforms should be in accordance with the recommendations made with the BSE Minimum Dataset [ 2 ]. Within this guideline, diastolic measures have been categorised into: routine —measures that are anticipated to be performed in all patients; supplementary —additional measures that may be required to confirm LVDF and LVFP; and non-routine— measures that are occasionally performed and only in specific scenarios. Practical guidance for how to acquire images and perform the routine , supplementary and non-routine measurements can be found in tables at the end of each section.

Routine echocardiographic measures of LV diastolic function

Transmitral e wave.

The transmitral Doppler E wave represents early LV filling from rapid relaxation. Although measurement of peak E is not a direct measure of LAP when applying the simplified Bernoulli equation (due to inertial resistance of blood within valve [ 44 , 45 ]), the peak E velocity is determined by the LA to LV pressure difference and is therefore reflective of LAP. As such, E velocity can be considered alongside other measures for the interpretation of diastolic function and LVFP. In the young healthy heart, rapid relaxation causes low minimum LV pressure that increases the transmitral pressure difference. This creates a suction effect in the setting of normal LAP that enables the majority of ventricular filling to occur in the early diastolic phase and at high velocity, resulting in a high E velocity [ 46 ]. With normal aging, slowing of the rate of ventricular relaxation causes the suction effect to become attenuated, in-turn leading to a higher minimal pressure, a reduction in the early diastolic transmitral pressure gradient and a fall in the transmitral E velocity.

Transmitral E velocity—impaired diastolic function

Similar to normal aging, impaired LV relaxation results in a slower rate of pressure fall within the LV, an increase in the minimum diastolic pressure and therefore attenuated suction effect. In the setting of normal LAP, this reduces the transmitral pressure difference and results in lower inflow velocities. Peak E velocity therefore falls as LV relaxation becomes impaired (Table  1 ). As diastolic impairment progresses and LV compliance decreases, LAP becomes elevated causing the E velocity to increase. The relationship between LV diastolic function and E wave velocity is therefore U-shaped, with E velocity falling in the early stages of diastolic impairment before increasing as disease progresses.

Limitations of E wave velocity

Valve disease: significant MV disease causing elevated LAP will cause the E velocity to increase, altering the E/A ratio irrespective of LV diastolic function [ 47 ]. Furthermore, because the peak A wave velocity is flow/load dependent, the E/A ratio may also be affected by moderate or severe aortic regurgitation (AR) that increases LVEDP, decreases the end-diastolic LA-LV pressure difference and therefore decreases A wave velocity [ 48 ]. LV disease: in patients with coronary artery disease (CAD) or hypertrophic cardiomyopathy (HCM) and normal LVEF (≥ 50%), peak E velocity correlates poorly with LAP [ 49 ]. Peak E velocity is heavily influenced by changes in LV volume and LV elastic recoil (and therefore systolic contractility) and should not be utilised as a standalone indicator of LVFP in any scenario. Flow timing: although not typically considered for the assessment of diastolic function, it is important when considering timing of flow to bear in mind that flow response to changing pressure is not instantaneous. Transmitral flow velocity increases so long as there is an accelerating force and therefore positive pressure gradient, while a reversal of the pressure gradient acts as a decelerator of flow. The inertial effect of pooled blood in early diastole therefore explains the temporal difference between peak pressure gradient and peak transmitral flow velocity, meaning that the peak pressure gradient and peak transmitral velocity do not coincide to provide exact timings [ 50 ].

Transmitral E deceleration time

E wave deceleration measures the time between peak early transmitral flow velocity (peak E) and the point when flow ends, or the point at which atrial contraction occurs. Onset of mitral E-deceleration corresponds to LA-LV pressure crossover and reversal of the transmitral pressure gradient which acts as a deceleration force. In patients with a remodelled and stiff ventricle, a large early filling volume, as reflected in a high E velocity, leads to rapid rise in LV pressure and a high deceleration gradient which causes a short E deceleration time. E-deceleration time is therefore a marker of LV diastolic stiffness, although in milder degrees of diastolic impairment E-deceleration time is more influenced by LV relaxation. In young healthy hearts, rapid LV recoil and relaxation result in highly efficient filling and a large volume of blood entering the LV very quickly with consequently rapid equalisation of pressure between the LA and LV [ 51 ]. The deceleration of flow is therefore equally rapid with a short time period between peak E velocity and the end of early diastolic flow, reflected as short E wave deceleration. However, as LV relaxation slows with normal aging, the rate and volume of LV filling falls, and there is lengthening of the E wave deceleration time. An extended E deceleration time is therefore expected in the elderly [ 52 ].

Transmitral E deceleration time—impaired diastolic function

The early stages of impaired diastolic function are characterised by slowing in the rate of LV relaxation with therefore extended E wave deceleration time, as seen with normal aging—typically > 220 ms in those < 50 years and > 280 ms in those > 50 years [ 53 ]. As diastolic impairment progresses and LV compliance decreases, LAP increases to maximise LV filling and maintain SV. The early diastolic flow into an incompliant LV causes LV pressure to rise rapidly and LA-LV pressures to equalise quickly with a consequently rapid deceleration of flow. The E wave deceleration time is therefore short (< 150 ms) when diastolic impairment is advanced and LVFP increased. Hence, the relationship between impaired LVDF and the E deceleration is inverse U-shaped (increasing with impaired relaxation before decreasing as LVFP increases), with an inverse relationship between rising LAP and E deceleration time.

In those with confirmed heart disease, decreased LV compliance and restrictive filling are associated with worsening mortality. Given that the E deceleration time relates to LV compliance and therefore filling, there is a demonstrable association with heart failure (HF) symptoms, death and hospitalisation in both those presenting with acute myocardial infarction or HF with reduced ejection fraction (HFrEF). The E deceleration time is therefore of significant prognostic importance in patients with known heart disease [ 54 , 55 , 56 ].

Limitations of E wave deceleration time

Normal LVEF: when LV systolic function is normal, the E deceleration time is not a consistently accurate measure of LVDF [ 51 ]. E/A fusion: the deceleration time may be unmeasurable when E and A waves are fused due to tachycardia, raised pre-A velocity or first-degree AV block. MV disease: the deceleration time is likely determined by the severity of stenosis in patients with mitral stenosis (MS) [ 47 ].

Transmitral A wave velocity

In SR, LV filling concludes with atrial contraction in late diastole, represented as the transmitral A wave on Doppler imaging. A distensible and compliant LV is able to increase end-diastolic volume with only a small increase in pressure. With normal diastolic function, the majority of total LV filling occurs in early diastole with a small contribution of LA contraction to overall filling, usually 10–20%. Therefore, with normal LV compliance, the low pressure difference between the LA and LV in late diastole and the low volume contribution from LA contraction result in a transmitral A wave velocity that is typically lower than the E wave velocity. In young individuals, the A velocity is usually < 50 cm/s [ 46 ] . However, the age-related decline in LV relaxation reduces early diastolic filling with consequently reduced emptying of the LA [ 57 , 58 , 59 ]. Reduced emptying leads to an increase in LA volume (preload) prior to contraction in late diastole resulting in greater LA pump volume and therefore greater A wave velocity, often to around 75 cm/s in the elderly.

Transmitral A wave velocity—impaired diastolic function

Similar in physiology and echocardiographic appearance to normal aging, impaired LV relaxation but with normal compliance causes the transmitral A velocity to increase. As diastolic impairment progresses and LV compliance decreases, raised LV end-diastolic pressure increases LA afterload and therefore resistance to LA ejection, leading to a reduction in the transmitral A volume, velocity and duration of flow. Therefore, the relationship between impaired LVDF and A velocity is inverse U-shaped, where A velocity initially increases as relaxation slows before decreasing as LV diastolic pressure increases.

Limitations of A wave velocity

E/A fusion: may prevent identification of the MV A wave duration and peak velocity. Aortic regurgitation: transmitral A velocity is affected by increases in LA afterload. When severe AR significantly increases LVEDP, LA afterload is markedly increased with reduced LA-LV pressure difference and consequently reduced LA pump volume and therefore low A wave velocity and reduced duration [ 48 ]. Pre-A velocity: the pre-A velocity describes the cross-over point between fused E and A waves. With normal diastolic function and normal resting HR, the pre-A velocity is typically < 20 cm/s. When diastolic function is impaired, the slower rate of relaxation may extend into the later diastolic period (reflected by longer E deceleration time), causing early diastolic flow to continue to the point of atrial contraction and consequently fusing the E and A waves; E/A fusion can also be seen secondary to dyssynchronous relaxation (left bundle branch block (LBBB)), 1st degree AV block or by sinus tachycardia. If atrial contraction occurs at a point when the pre-A velocity exceeds 20 cm/s, the higher starting blood-flow velocity of the associated A wave results in a higher peak A wave velocity that may cause E/A ratio reversal, irrespective of LAP [ 60 ]. This discordant finding is common in elderly hypertensive patients with HFpEF where E velocity is increased and exceeds 1 m/s, therefore suggesting increased LAP, while the E/A ratio is reduced, and may be less < 1 due to the pre-A velocity exceeding 20 cm/s. However, the algorithm for the assessment of LVFP remains accurate for the global assessment of LVDF and should be utilised. As with all measures of blood-flow Doppler, signal clarity and consequently measurement accuracy are limited by artefact and the signal-to-noise ratio. Given the relatively low velocity of flow, measurement of the pre-A velocity should be performed once pulsed-wave Doppler (PW) signals have been optimised (minimised wall-filter/low-velocity reject) and transit time artefacts reduced. In cases of eccentric AR where regurgitant flow contaminates the assessment of transmitral forward flow, the pre-A velocity may not be clearly identified and may prevent a measurement from being made.

The ratio of transmitral E and A velocities reflects the ratio of early and late LV diastolic filling. Efficient relaxation in young healthy hearts enables the majority of LV filling to occur in early diastole, with relatively low contribution from atrial contraction and at low velocity. The E/A ratio in young healthy individuals is therefore typically > 1. In those who are athletically trained, highly efficient early diastolic relaxation can result in an E/A ratio of up to 2 [ 61 ]. Natural aging leads to a slower rate of LV relaxation with a reduction in the early diastolic filling volume and fall in E velocity, normal SV is maintained by an increase in the atrial contraction filling volume [ 62 ]. This increase in atrial contraction volume is reflected by an increase in A velocity to exceed E velocity and therefore a shift in the E/A ratio to < 1 [ 63 ].

E/A ratio—impaired diastolic function

As with normal aging, the early stages of LVDF impairment are characterised by impaired (slowed) relaxation but with normal chamber compliance. As such, E velocity falls and A velocity increases with a reduction in E/A ratio to < 1 (Table  1 ). As diastolic impairment progresses, LV compliance decreases and both LV diastolic pressure and LVFP increase. The increase in LAP causes E velocity to increase while increased LV end-diastolic pressure increases LA afterload and decreases the end-diastolic LA - LV pressure difference, causing A velocity to decrease; E/A ratio therefore returns to > 1 as LVFP increase. As the LV becomes progressively less compliant, filling becomes restrictive with normal or even low filling volumes causing a significant increase in LV diastolic pressure and consequently LAP. Higher LAP leads to increasing E velocity while significantly increased LA afterload results in further reduction of A velocity and subsequently increasing E/A ratio, typically > 2, as restrictive filling develops. Therefore, the relationship between E/A ratio and diastolic function is, like E wave velocity, U-shaped.

Limitations of E/A ratio

When the E and A are fused and pre-A velocity exceeds 20 cm/s, the A wave velocity is increased and E/A ratio altered irrespective of LAP. E/A fusion may also prevent identification of the MV A wave duration and peak velocity. LA afterload: transmitral A velocity is affected by increases in LA afterload. When severe AR significantly increases LV end-diastolic pressure, LA afterload is markedly increased with consequently reduced LA pump volume and therefore low A wave velocity and reduced duration [ 64 ]. LA function: when LA pump function is reduced due to cardiomyopathy, CAD, following heart transplantation or stunning following cardioversion to SR from an atrial arrhythmia, the ejected volume is reduced with consequently low A velocity. E/A ratio will therefore be altered by a lower peak A velocity. Short P-R interval: the A wave duration may be truncated by a shortened PR interval when LV systolic contraction occurs before atrial contraction has been completed. Atrial Flutter: because of the very high atrial rate with consequently low atrial pump volume and velocity, the E/A ratio should not be measured during atrial flutter.

Early diastolic mitral annular Tissue Doppler Imaging (TDI)—e′

As the fibrous boundary between the LA and LV, motion of the MV annulus throughout the cardiac cycle reflects longitudinal shortening and lengthening of both the LV and LA. In systole, the LV shortens, pulling the MV downwards and towards the LV apex, therefore stretching the LA and increasing its dimensions. Following peak systolic contraction and shortening, the LV relaxes and lengthens in early diastole, pushing the mitral annulus upwards and shortening/compressing the LA. In late diastole, atrial contraction causes further LA shortening, pulling the MV annulus further upwards. The phasic velocity of mitral annular motion therefore reflects myocardial function throughout the cardiac cycle and can be measured by TDI as an indicator of systolic contractility and diastolic relaxation and compliance – S′ reflecting LV systolic shortening, e′ reflecting early diastolic LV relaxation and a′ reflecting atrial contraction in late diastole.

In the healthy heart of the young and middle-aged, MV annular velocities are high during both systolic descent and diastolic ascent [ 46 ] reflecting the dynamic function of both the LA and LV. In those who are athletically trained, adaptive cardiac remodelling leads to super-efficient cardiac function and marked predominance of early diastolic filling, typically reflected by systolic and early diastolic MV annular velocities that are supra-normal [ 61 ]. With normal LV filling, due to the rapid and efficient relaxation of the healthy heart the onset of early diastolic transmitral blood flow occurs near simultaneously with e′. However, even in the normal heart there are expected regional differences in peak relaxation velocities. Due to differences in the extent of longitudinal motion between septal and lateral walls, septal annular velocities are typically lower in comparison to that of the lateral wall [ 64 ]. As the relationship between peak e′ velocity and τ is inverse, where slower relaxation leads to increasing τ and decreasing e′, e′ velocities typically fall with normal aging (Table  2 ).

Similar to the process of aging, impaired LV relaxation and longer τ leads to both a delay in onset of e′ and a fall in peak velocity [ 65 , 66 ]. When LV relaxation is normal, e′ velocities may be preload dependent (e′ increases as the transmitral gradient increases). When LV relaxation is impaired, the effect of increased LAP on e′ velocity is negligible such that e′ remains low [ 67 , 68 ]; an e′ below the age-specific cut-off is therefore considered an indicator of impaired LV relaxation. However, due to the wide range of normal e′, with some patients having naturally very high values, a value greater than the age-specific cut-off does not confirm normal LV relaxation.

In normal hearts with normal LVDF and relaxation, e′ velocity is directly related to the transmitral pressure gradient and indexing to E velocity for E/e′ does not correlate with LVFP. When LVFP are normal but the rate of LV relaxation is reduced secondary to either normal aging or impaired LVDF, both E and e′ velocities are reduced. However, because the reduction in both E and e′ is almost proportional, the ratio between them remains relatively unchanged and < 14 in the majority of individuals across all age groups [ 46 ]. Progression of impaired diastolic function is characterised by worsening of LV relaxation, with further reduction of e′ velocity, and decreasing LV compliance leading to elevated LVFP and therefore increased E velocity. An increased E/e′ ratio is therefore a marker for increased LVFP and LAP. A value < 8 is specific for normal LVFP and an average of septal and lateral E/e′ > 14 is highly specific for a PCWP of > 15 mmHg and therefore raised LVFP [ 69 , 70 ]. Where only a single site measure is possible or valid, a lateral ratio > 13 or septal ratio > 15 may be used. Although a progressive age-related decline is observed for of both E and e′ velocity, the proportional decline in e′ is greater than for E with a consequent increase in E/e′ ratio with normal aging, although rarely to a level that suggests elevated LVFP [ 46 ]. An E/e′ ratio > 14 is therefore a supportive finding for elevated LVFP for the majority of individuals across all age groups and certainly in those ≤ 40 years.

Limitations of E/e′

Doppler alignment: Measures of peak e′ velocity may be underestimated when Doppler alignment is not parallel. Although lateral annular velocities are typically higher than septal, parallel Doppler alignment is more easily achieved with the septal annular motion. Doppler alignment with lateral annulus motion should be considered when interpreting annular velocity and diastolic function. Regional variation and annular tethering: The correlation between E/e′ and LVFP is not strong in those with LBBB or paced rhythm but is strong when LV systolic function is globally impaired and the LVEF is reduced [ 71 , 72 ]. As a measure of peak annular velocity, differentiation between active motion and translational motion through tethering with normally functioning myocardium cannot be made by peak velocity alone. Regional differences in myocardial function may therefore complicate the assessment of LV filling and should be considered. The presence of: severe annular calcification; mitral annular repair ring; or MV replacement will also reduce annular velocities and alter the E/e′. The interpretation of septal and lateral e′ is also important during the assessment of pericardial disease with pericardial adhesion often causing reduced lateral wall longitudinal motion and therefore reduced lateral e′ velocity, thus complicating the assessment of intrinsic LV diastolic function [ 73 , 74 ]. The septal e′ may be reduced post-cardiac surgery, during atrial arrhythmia and in conditions that significantly affect right heart pressure and volume [ 70 , 75 , 76 ]. LVEF: the correlation of E/e′ with LVFP is less strong in those with normal LVEF in comparison to those with impaired LV systolic function [ 69 , 77 ]. Load dependency: although less load dependent than E velocity, e′ is not entirely independent of LV loading conditions with septal and lateral annular velocities possibly affected to different degrees by changes in LV preload [ 78 , 79 ]. e′ may also be increased by alterations in LV preload secondary to severe mitral regurgitation (MR). When increased LV afterload causes a reduction in LV contractility, LV recoil and relaxation are attenuated with an increase in τ and an associated decline in e′ velocity. e′ parameters should therefore be considered alongside the effect of systolic blood pressure (SBP) on LV function. Age: e′ reflects LV relaxation and therefore decreases with age; age-specific limits for abnormal velocities should be used to avoid over-classification of the elderly as abnormal. However, although an E/e′ < 14 does not confirm normal LVFP, a ratio > 14 is extremely uncommon in young and middle-aged individuals with normal hearts and is only seen in a very small number of elderly patients with normal LVFP [ 46 ].

Although numerous studies have confirmed the utility of E/e′ for the assessment of raised LVFP, it is a single value that should be considered alongside all other parameters of LVDF. It should be viewed in the context of its limitations and should not be considered as a deciding parameter for the assessment of LVDF.

In the normal healthy heart, the LA is a thin-walled chamber that functions under low pressure, usually at a mean of around 8 mmHg. LA dimensions are primarily determined by patient lean body mass and because LA size does not increase due to mere aging alone, LA dilation is therefore considered an abnormal finding across all age groups. A detailed description of LA function can be found in the earlier section of this document.

LA volume—impaired diastolic function

The extent to which the LA dilates secondary to impaired LV diastolic function is determined not only by LAP, but also intrinsic LA compliance, general hydration/volume status and compliance of the left atrial appendage to help off-load LAP [ 80 ]. Therefore, because the relationship between LA volume and pressure is not linear, a specific LAP does not correlate directly with a specific LA volume. Consequently, the direct correlation between LAP and LA volume is not strong [ 81 , 82 ]. However, LA maximum and minimum volumes are related to LAP and increase in response to chronic elevation. LA dilation is therefore an expected finding in those with impaired LVDF and chronically raised LVFP.

Importantly, LA compliance is a major determinant of LAP. A stiff and incompliant LA causes increased LAP but limits the degree of LA dilation. For example, patients with dilated cardiomyopathy (DCM) and more compliant LV and LA myocardium are likely to have more severe LA dilation with greater maximum volume than those with restrictive cardiomyopathy (RCM) in whom decreased LA compliance limits the degree of dilation (because a stiff chamber cannot dilate to the same extent as a compliant chamber). However, despite lower LA volume, the stiffer incompliant LA in patients with RCM causes higher LAP in comparison to those with DCM and larger but more compliant LA [ 83 , 84 ].

Limitations of LA volume

Normal LAP: There are a number of limitations when interpreting LA size as an indicator of LAP. Although LA dilation is present in the vast majority of patients with elevated LAP, not all patients with large LA have elevated LAP. Other causes of LA dilation should always be excluded, including: atrial arrhythmia, significant MV disease, transplanted hearts, bradycardia, ventricular septal defects, athletic remodelling and high output states [ 85 ]. Normal variation: LA dimensions do not increase significantly with normal aging. However, the normal range of LA volume is wide across all age groups [ 46 , 86 ]. In around 90% of non-obese patients with normal healthy hearts, the biplane Simpson’s Method of Disks (MoD) LA volume does not exceed 34 mL/m 2 when indexed (LAVi) to body surface area (BSA). This value is considered the upper reference interval of normal LA size and therefore the recommended cut-off when assessing LVDF. However, even in entirely normal hearts, LA volume measures > 34 mL/m 2 in around 10% of patients and > 37 mL/m 2 in around 5% [ 85 ], with some studies reporting LAVi up to 43–45 mL/m 2 in normal males and females across most age-groups [ 46 ]. LA volume alone is therefore not a reliable indicator of LAP. Obesity: furthermore, increasing obesity limits the utility of indexing to BSA. Cardiac size is primarily determined by fat-free lean muscle mass—LA dimensions do not increase in response to obesity alone. However, when indexing heart size to patient habitus during echocardiography, BSA is estimated according to simple measures of patient height and weight. The normal age-related decline in adult height has a minimal impact upon BSA. However, increasing weight can significantly increase the BSA, consequently ‘normalising’ chamber volumes when dividing their absolute dimensions by a larger BSA value. The utility of indexed LA measures is therefore reduced in obese patients with decreasing utility as BSA increases. For this reason, and because obesity is common in patients with impaired diastolic function, it has been suggested that a lower LAVi cut-off value may be considered to describe LA dilation in obese patients [ 66 ]. However, because the same LA volume will result in progressively lower LAVi as BSA increases, applying a single dichotomous cut-off parameter to this continuous variable for all patients is inherently limited. Interpretation of LA size should therefore be based on a global judgement of cardiac function and alongside the Doppler based parameters of LV filling. Chronicity: LA dilation is a chronic process and reverse remodelling is not immediate. LA volume may therefore remain persistently increased despite normalisation of LVFP, for example with the introduction of medical treatment [ 87 ]. Similarly, sudden increases in LAP secondary to acute deterioration in LV function (myocardial infarction, myocarditis) may be associated with normal LAVi. However, sudden increases in LAP would likely be reflected clinically and by other parameters of diastolic function.

TR velocity

The continuity between the LA, pulmonary veins and the pulmonary capillary system causes elevation of LAP to be transmitted through the pulmonary vasculature, leading to elevated pulmonary pressures. Therefore, in the absence of other causes of PH, the velocity of tricuspid regurgitation (TR) can be considered indicative of systolic pulmonary artery pressure (SPAP) and therefore incorporated into the assessment of LVDF and estimation of LVFP.

Limitations of TR velocity

Doppler: like all Doppler measures of blood flow, estimation of TR velocity is subject to error associated with the angle of insonation and alignment between the transmitted sound and the blood flow. Although perfect parallel alignment is not achieved in most cases, the degree of velocity underestimation increases as the angle of misalignment increases. Crucially, some degree of TR is required in order to measure the peak velocity. However, even when present, it is very often of insufficient volume to provide a complete Doppler waveform and therefore of measurable peak velocity [ 46 ]. Other causes: as any cause of PH will cause TR velocity to increase, the presence of undiagnosed pulmonary disease may lead to a TR velocity that exceeds 2.8 m/s [ 88 ]. Very severe/torrential TR: when TR becomes very severe or massive/torrential, the large volume of blood entering the RA causes RAP to rise rapidly and become markedly elevated, leading to rapid equalisation of RA and RV pressure. Although systolic pulmonary pressures may be elevated, the very high RAP results in low pressure difference between the RV and RA and therefore low TR velocity with consequently underestimated SPAP. In this scenario, the waveform of the TR continuous wave (CW) Doppler can help identify when the severity of regurgitation is such that the peak velocity is underestimated. The CW Doppler waveform of non-torrential TR is typically parabola in shape due to the pressure difference between the RV an RA being sustained throughout systole, and therefore sustaining the velocity of regurgitant flow. However, torrential TR causes RAP to rise to very high levels and rapidly, equalising with RV pressure and leading to a rapid cessation of TR. This rapid equalisation of pressures with no sustained pressure difference throughout systole results in a triangular CW Doppler waveform and subsequently underestimated peak TR velocity. Therefore, a velocity of ≤ 2.8 m/s does not confirm normal SPAP when TR is massive/torrential. Underestimation of RAP: as the TR velocity merely reflects the pressure difference between the RV and RA, any increase in RAP will reduce the velocity of TR. As such, a TR velocity below the threshold of 2.8 m/s may be seen in the setting of elevated SPAP when RAP is also raised.

LA function—strain analysis

Although atrial function can be assessed by measuring LA volume at specific points of the cardiac cycle, this is a time-consuming process and is limited by low temporal resolution (low frame-rates) at higher heart rates. Strain analysis is considerably quicker and is largely automated, and therefore lends itself more readily for use in clinical medicine. The analysis of LA strain (LAs) provides parameters for all phases of LA function, the reservoir phase (LARs) and pump phase (LAPs) being important for the assessment of LVDF.

Two methodologies for the assessment of atrial strain have been established yet differ according to the zero-reference point (i.e., the defined starting point of analysis; Fig. 10 ). The convention for measuring LV strain is that relative fibre shortening is associated with compression of the myocardium and therefore a ‘negative’ strain value, and relative fibre lengthening with a ‘positive’ value. Although this remains the principle for assessment of LAs, the point in the cardiac cycle at which the measurement starts will determine the calculated strain value.

Atrial strain, with examples of different zero-reference points. Figure ( a ) displays a typical LA strain waveform while ( b ) demonstrates measured atrial strain parameters. On the lower left ( c ), the onset of the QRS has been chosen as the zero-reference point. With this method, the atrium is at the beginning of the reservoir phase and initially expands, resulting in a positive deflection ( c ). On the right, the p-wave is used as the zero-reference, and consequently the first deflection is negative as the atrium enters the pump phase ( d ). Red vertical arrow demonstrates peak reservoir strain, blue vertical arrow the passive contraction strain (conduit phase), and green vertical arrow active pump (contractile) strain ( c and d ). The choice of zero-reference point will systematically alter the values obtained, with the QRS-onset methodology ( c ) leading to systematically larger strain values than the p-wave methodology

When the peak of the R-wave (i.e., onset of ventricular systole) is used as the starting point for LAs analysis (R–R gating), the zero-reference point coincides with the onset of the ‘reservoir’ phase. In this setting, because analysis starts at the point when LA dimensions are at their smallest, the first observed change in LA myocardial length occurs as the LA increases from its minimum to its maximum size; the associated fibre elongation therefore results in a strain value that is positive in reference to the pre-lengthening baseline. Alternatively, if the onset of the P-wave is chosen as the zero-reference point (P–P gating), analysis will begin immediately prior to the onset of the pump phase and LA shortening, in which case the initial strain deflection will be negative as the atrial myocardium contracts and shortens. Therefore, because strain assessment describes the proportional change in myocardial length, the differences in zero-reference point becomes important. For example: if strain analysis starts with a pre-contractile atrial fibre length of 4 cm, and the contracted length shortens to 2 cm, this reflects a strain of -50%. However, if analysis of the same segment of atrial tissue starts at a contracted length of 2 cm, which then relaxes to a length of 4 cm, strain is calculated at + 100%. Although significantly different values, both describe the same absolute change. For this reason, the choice of zero reference point systematically alters the strain values obtained, with the QRS-gating providing systematically larger values for atrial strain than the p-wave gating. However, the proportional values of reservoir vs. pump strain will remain the same irrespective of the method chosen.

In the majority of published data, the QRS is defined as the zero-reference point and is therefore the preferred method of the BSE [ 89 ]. According to vendor, strain analysis may be performed in a single A4C view or a global average by biplane from both the A4 and A2C views optimised for maximal LA dimensions [ 2 ]. As with estimates of LA maximum volume, A2C and A4C views optimised for the LV do not provide the greatest LA volume and therefore overestimate LAs values [ 90 ]. LAs values do not differ between men and women and normal reference intervals have been described by both meta-analysis and study of normal healthy hearts [ 91 ] (Table  3 ).

LA reservoir strain— LA dimensions increase from a post contraction minimum at end-diastole to a maximum at end-systole. The positive reservoir strain therefore reflects total LA lengthening.

LA pump strain— LA dimensions decrease as the LV lengthens in early diastole with further reduction in LA dimensions following atrial contraction. Pump strain values are therefore negative.

LA strain in the assessment of LV diastolic function

It is well recognised that dilated atria are associated with a poorer prognosis across a range of cardiovascular disease states [ 92 ]. However, increased LA volume does not confirm increased LA pressure, nor does it identify LA function. For instance, LA dilation is known to occur secondary to certain normal physiological conditions, including athletic conditioning and prolonged bradycardic states. In both scenarios, LA pressure and function remain normal, suggesting that function rather than volume may be more relevant when investigating diseases that affect LVDF [ 93 ].

The clear and evidenced disturbances of LA function in a variety of cardiac diseases [ or = 65 years of age. Am J Cardiol. 2008;101:1626–9." href="#ref-CR94" id="ref-link-section-d386317e3463">94 , 95 , 96 , 97 , 98 , 99 , 100 ] reflects the sensitivity and utility of LAs for the assessment of impaired LV diastolic function. The measurement of LAVi has long been considered crucial for the assessment of LVDF on the premise that chronically increased LAP leads to LA dilatation [ 85 ]. While this is often the case in the long-term, overlap with normal physiological variation and the low sensitivity of LAVi for the early detection of increased LAP limit the accuracy of LAVi as a reliable and sensitive marker for abnormal increases in LAP. However, because the LA is exposed to LV pressures throughout the diastolic period and because LA function and emptying is influenced by LA afterload and properties of LV systolic shortening and diastolic lengthening, parameters of LAs can be considered indicative of LV diastolic relaxation and filling pressures and are therefore a useful parameter in the assessment of LV diastolic function.

When LV relaxation is impaired but with normal LVFP and normal LAP, reduced lengthening of the LV in early diastole causes a reduction in LA shortening and consequently reduced LAs during this period (conduit phase), while the shift to proportionally greater LV filling from LA contraction causes an increase in LAPs. However, LAPs is also affected by properties of intrinsic LA contractile function and LA afterload at end-diastole (LVEDP), therefore directly correlating with MV A and a′ velocity. Given the influence by LVEDP, LAPs is also related to A-wave transit time and inversely related to Ar-A duration (see later sections) [ 85 ].

Although studies have demonstrated an inverse relationship between LARs and LAPs for both PCWP and LVEDP irrespective of LVEF, the correlation is not strong enough to justify LAs as a standalone measure of LVFP and therefore diastolic function. However, the correlation is stronger than that of LAVi and may be help differentiate severity. When individuals with impaired diastolic function and similar LV size, mass, ejection fraction and, most importantly, left atrial volume were compared, LAs parameters were found to be significantly lower in those with symptoms of HFpEF, thus reinforcing the importance of LA function over size alone [ 101 ]. Furthermore, and suggesting potential prognostic importance of LA function, when comparing patients with HFrEF and HFpEF, although those with reduced LVEF tend to have larger LAVi, those with preserved LVEF have greater LA stiffness with consequently lower LAs values and more AF [ 83 , 84 ].

A step-wise reduction in LARs is observed as LVDF worsens, with LARs found to be the only parameter of LV filling that consistently deteriorated as LV diastolic impairment worsened, thus distinguishing all grades of diastolic function [ 102 ] (Fig. 11 ).

Step-wise reduction in LA strain parameters as LV diastolic function worsens and LVFP increase. From Singh et al. [ 102 ]

In contrast, conventional measures of LVDF, LAVi and E/e′, increase and therefore differentiate normality from impaired diastolic function with raised LVFP, before plateauing with no identifiable differentiation between higher grades of diastolic impairment (raised LVFP versus restrictive filling). Consistent with a continuous deterioration in LA function as diastolic impairment progresses, the prevalence of abnormal LARs appears to be significantly linked with the severity of impaired diastolic function, with a reported increase from 62.9% in those with normal LVFP, to 88.6% in those with raised LVFP and 95.7% in those with restrictive filling. A step-wise decline in LARs is also observed as LVDF worsens, from 22.2% (± 6.6%) in those with normal LVFP, 16.6% (± 7.4%) in those with raised LVFP and 11.1% (± 5.4%) in those with restrictive filling [ 84 ].

Despite this continuous stepwise reduction in mean LARs across all grades of diastolic impairment, there exists an overlap in strain values between the normal cohort and those with impaired relaxation but normal LVFP, such that LARs may be insensitive to accurately identify the early stages of LV diastolic impairment [ 102 ]. However, the significant differences in LARs between those with normal filling and those with raised LVFP identifies LAs as a useful adjunct to the assessment of LVDF. In those with confirmed cardiac disease, PCWP > 12 mmHg was identified by LARs < 18% and absolute LAPs < 8%, while < 16% and < 6% identified PCWP > 15 mmHg [ 103 , 104 ]. Importantly, in those with normal LV systolic function and absolute GLS 18%, high-normal LA pump strain (> 14%) identified normal LVFP with 92% accuracy [ 103 ]. In the same study, the authors reported 83% accuracy of the 2016 ASE algorithm for differentiating normal from raised LVFP, this level of accuracy remained the same when LAs was incorporated into the assessment. However, because a parameter was missing in 10% of patients, most commonly TR, feasibility of the 2016 algorithm improved from 90 to 99% by adding LAs [ 103 ]. On this basis, LARs and LAPs can be considered during the assessment of LVDF with a cut-off of < 18% and < 8% suggesting increased LVFP [ 104 ].

Reproducibility of LAs: inter/intra-observer and vendor variability

Reproducibility of LA strain measures was found to be high during inter-observer variability analysis with inter-class correlation coefficient (ICC) for LARs and LAPs of 0.89 and 0.82 respectively. Intra-observer ICC for LARs and LAPs was also found to be excellent at 0.93 and 0.92 respectively [ 103 ].

Limitations of LA strain

Image axis: off-axis imaging leading to foreshortening of the LA (when apical views are optimised for the LV) overestimates LAs values. Feasibility: measurement of LAs is considered feasible in 95% of patients but training and validation may be required for those unfamiliar with LAs measurements. Normal systolic function: the correlation between LAs and LVFP is weaker in those with LVEF ≥ 50% in comparison to those with LVEF < 50%. Atrial arrhythmia: in patients with AF, LARs is routinely low and typically < 20% [ 103 ]. Vendor variability: when comparing measures performed on different analysis platforms, there is overall minor variation in the strength of the correlation between measures of LAs and invasively measured LAP across multiple vendors. However, the referenced cut-offs within this guideline have been derived from aggregated data collected by multiple vendors and can therefore be applied irrespective of the ultrasound system manufacturer [ 103 ]. To minimise the risk of vendor variation influencing LAs measures and therefore the diagnosis of LV diastolic function, it is recommended, where possible, that surveillance/repeat echocardiography is performed using the same vendor analysis platform as previous studies. Where this is unfeasible, potential vendor differences should be considered within the global interpretation of LV diastolic parameters (Table 4 ).

Supplementary parameters of LV diastolic function

Transmitral a wave duration (for ar–a duration).

The transmitral A wave and pulmonary venous a-wave (PVa) flow are caused by atrial contraction and therefore occur simultaneously at end-diastole. When the LV is compliant, EDP is low and offers low resistance to atrial contraction, resulting in greater volume of flow moving forward into the LV than that of flow ejected back into the PV’s. However, despite the differences in volume and velocity, there is no difference in duration between MV A and PVa flow when diastolic function is normal [ 108 ].

Transmitral A wave and duration—impaired diastolic function

Similar in physiology and echocardiographic appearance to normal aging, impaired LV relaxation but with normal compliance causes the transmitral A velocity to increase but with no reduction in the duration of flow. As diastolic impairment progresses and LV compliance decreases, elevated LV EDP increases LA afterload and therefore resistance to LA ejection, leading to a reduction in the transmitral A volume, velocity and duration of flow.

Limitations of A wave velocity and duration

Doppler optimisation: measurement of the MV A wave duration may be prevented if the start and end of flow cannot be identified due to poorly optimised spectral Doppler signals. Aortic regurgitation: transmitral A duration is affected by increases in LA afterload. When severe AR significantly increases LVEDP, LA afterload is markedly increased with consequently reduced LA pump volume and therefore low A wave velocity and reduced duration [ 48 ]. Short P-R interval: the A wave duration may be truncated by a shortened PR interval when LV systolic contraction occurs before atrial contraction has been completed. Doppler alignment: sampling of PV flow becomes increasingly difficult as LA volume/dimensions increase, a common finding in those with impaired diastolic function or atrial fibrillation.

Pulmonary vein flow

Phasic flow through the PV’s in governed by LV relaxation, compliance of both the LV and LA and by LA function. As such, PV flow profiles provide insight into LV filling and diastolic function. In SR, PV flow occurs over three phases (Fig. 12 ). Although the deceleration times for the PV S and PV D waves are not supplementary parameters within the diastolic algorithms (they are considered non-routine measures), they are described below within the broader description of pulmonary vein flow.

PV Doppler: S 1 and S 2 waves occur in systole, contributed to by elastic recoil of the LA, LV systolic shortening and RV SV/SPAP propagating through the lungs. The D waves occurs with LV relaxation in early diastole while the Ar wave occurs in late diastole following atrial contraction

PV S wave velocity and deceleration

The PV S wave may have two identifiable peaks that correspond to the two phases of flow during this period: S 1 and S 2 . During LV systole and immediately after contraction, elastic recoil of the LA causes dimensions to increase and pressure to fall, drawing a small volume of blood from the PV’s into the LA by suction effect—identified as the S 1 wave. During mid and late systole, ongoing shortening of the LV and descent of the mitral annulus towards the apex further increases LA dimensions, while RV SV and systolic pressure are propagated through the lungs. The combination of these processes drives a second S wave—identified as S 2 . Overall, because the volume of PV flow generated by LA recoil is minimal, S 2 is the predominant contribution to the peak S wave velocity (Fig. 12 ). Consequently, the PV S wave velocity is not only influenced by LV diastolic properties and LAP, but also by LA contraction (that determines the magnitude of elastic recoil), LA relaxation and compliance, LV compliance as well as LV and RV contractility.

PV D wave velocity and deceleration

Rapid early diastolic relaxation of the LV causes pressure to fall below LAP, creating a suction-effect that opens the MV and draws blood into the LV from the LA. As the LA empties, the fall in LAP causes blood to flow from the PV’s through the LA and into LV—identified as the PV D wave (Fig. 12 ). The reduction in LA dimensions during this period is secondary to relaxation and lengthening of the LV, pushing the MV annulus upwards and towards the roof of the LA, with no real mechanical contribution by the LA. After peaking in early diastole, PV D flow gradually decelerates until the end of early diastolic filling, corresponding to the deceleration of transmitral flow. As PV D velocity and deceleration reflect transmitral forward flow, it is therefore altered by variations in LV relaxation rate and LAP.

PV Ar velocity and duration

Following the early LV filling phase, atrial contraction at end-diastole contributes to the remainder of total LV filling. However, while normal LV compliance and normal/low EDP allows for most of the blood ejected by the LA to enter the LV, a small volume of blood is ejected back into the PV’s (Fig. 12 ). The velocity and duration of retrograde flow into the PV’s is therefore determined by a number of factors, including: atrial preload, afterload and intrinsic LA pump function. When LVDF is normal, the duration of retrograde flow into the PV’s is equal or very similar to that of transmitral flow into the LV.

PV flow—impaired diastolic function

Pvs/pvd ratio and systolic fraction.

When diastolic function is normal, PV S velocity is typically equal to or higher than PV D velocity and the ratio of S/D is therefore typically > 1; in athletes or the young and fit, highly efficient and rapid relaxation and predominance of early filling often causes the PV D velocity to exceed the PV S velocity and a ratio of < 1. Reduced LA compliance and pump function and increased LAP secondary to impaired diastolic function may cause the PV S 1 velocity to fall with a consequent reduction in the combined PV S velocity [ 109 ], thus reducing the PV S/D ratio to < 1. The PV systolic fraction describes the ratio of PV S and D flow and can be calculated by PVS VTI /(PVS VTI  + PVD VTI ). A systolic fraction of < 40% in those with reduced LVEF provides high specificity for raised LAP [ 110 , 111 ].

Deceleration of PVS slope

The deceleration slope of the PV S wave can be measured as an indicator of LA compliance and therefore LAP (Fig. 13 ). When the LA is compliant, chamber distensibility results in a gradual increase in pressure and therefore gradual deceleration of the PV S wave. Increased LAP decreases LA compliance and causes pressure to rise more rapidly with filling from the PV’s, leading to rapid equalisation of pressure between the PV’s and LA and therefore rapid deceleration of PV S flow [ 112 ]. Although no validated diagnostic parameters are available in order for this measure to be considered routinely, sudden or interval changes in PV S deceleration may provide insight into alterations in LAP [ 113 , 114 ].

Deceleration slope of the PVS wave—DT PVS

PVD deceleration slope

Early diastolic LV filling (MV E wave) and PV D flow occur simultaneously. Because LA function provides no real contribution to PV flow during this phase, both MV E and PV D flow profiles are influenced primarily by LV relaxation, while PV D flow is additionally influenced by LA compliance and LAP rise. The peak velocity of PV D flow increases as LAP increases while the deceleration slope of the PV D wave (DT PVD ) reflects the rate of pressure equalisation between LA and LV (Fig. 14 ) and, therefore, the rate of LAP increase. When impaired diastolic function is confirmed, shorter DT PVD is suggestive of elevated LAP while longer deceleration time is suggestive of normal/low LAP [ 109 ]. A DT PVD of < 175 ms was found to have 100% sensitivity and 94% specificity for identifying LAP ≥ 17 mmHg, while a deceleration time of > 275 ms had sensitivity of 88% and specificity of 95% for LAP of ≤ 6 mmHg in patients in SR with normal LVEF and undergoing cardiac surgery (coronary artery bypass grafting and/or aortic valve replacement) [ 109 ]. As no validated diagnostic parameters are available for this measure across large patient groups, it is not recommended in routine practice. However, sudden or interval changes in PV D deceleration may provide insight into alterations in LAP.

Deceleration slope of the PVD wave—DT PVD

PV Ar velocity and duration 

Increased LV diastolic pressure secondary to decreased LV compliance increases LA afterload and resistance to LA ejection. Consequently, the volume, velocity and duration of transmitral forward flow from atrial contraction (MV A) decreases when LV EDP is increased. Simultaneously, because resistance to LA ejection is lower in the PV’s than in the LV, a greater volume of blood is ejected back into the PV’s and over a longer duration [ 69 , 115 , 116 ]. The PV Ar velocity and the difference in duration between MV A and PV Ar (Ar-A duration) can therefore be considered as indicators of raised LV diastolic pressures, with an Ar-A duration of > 30 ms or a PV Ar velocity > 35 cm/s suggesting increased LAP [ 82 , 117 , 118 ]. As the only echocardiographic measure of LV pressure at end-diastole, this parameter may help differentiate patients with impaired relaxation but normal LVFP from those with raised EDP only, the first haemodynamic indicator of impaired diastolic function.

Limitations of PV Doppler

Doppler: measurement of PV flow by PW Doppler may be unattainable due to poor signal quality and in some cases may not be detected at all. Even when attainable, spectral Doppler waveforms of PV flow velocity and deceleration times may be inaccurate when the direction of sound and blood flow are not parallel. However, sampling of the right upper or right lower PV (RU/LPV) in the A4C view usually provides near-parallel alignment with flow. Although measurement of PV S and PV D velocity is possible with good spectral Doppler signals, the PV Ar signal is of lower velocity and short in duration; measurement of PV Ar is therefore subject to greater measurement error, limiting the accuracy of Ar-A duration estimates. The very short time-interval being measured may also be affected by the non-simultaneous method of measuring MV A and PV Ar signals. MV disease: the deceleration of PV S wave may not be specific for LV diastolic function. When significant MV disease causes elevated LAP with consequently reduced LA compliance, the PV S deceleration time may be reduced irrespective of LV diastolic properties; even non-severe jets of mitral regurgitation directed into the RUPV can reduce the PV S velocity and consequently reduce the PVS/PVD ratio, irrespective of LVDF and LAP [ 47 ]. Additionally, because the PV S velocity is also influenced by the degree of LV longitudinal shortening and RV SV (thereby RV systolic function), the PV S/D ratio may not be consistently < 1 when RV function remains normal despite impaired diastolic function and raised LAP. LVEF: the correlation between S/D ratio and LAP is best in those with reduced LVEF [ 110 , 119 ]. Although these limitations prevent the PV S/D ratio from being routinely considered for the diagnosis of LV diastolic function, in patients with confirmed impaired diastolic function and raised LVFP (irrespective of LVEF), mortality is markedly increased in those where the PV S/D ratio is < 1 in comparison to those where the ratio is > 1, suggesting a possible prognosticating role in those where impaired diastolic function is confirmed [ 120 , 121 ]. HR: HR should be considered when interpreting PV flow for the assessment of LVDF. At lower HR, the low PV flow-rate towards the end of the PV D phase creates little resistance to retrograde flow following atrial contraction and flow reversal is seen during the PV Ar period. However, at higher HR, the shorter diastolic period results in atrial contraction occurring earlier in diastole when PV D forward flow-rates are higher and offer greater resistance to retrograde ejection. Therefore, despite increased LAP, PV Ar waves may not be present during periods of tachycardia [ 122 ]—if present, velocity and duration are likely to be affected. The assessment of Ar-A duration is therefore less valid in sinus tachycardia and long PR intervals with E and A fusion and cannot be measured in AF or atrial flutter. Accuracy of the systolic fraction is reduced when LVEF is normal or in the presence of AF, MV disease or HCM. Healthy young: in healthy young individuals and athletes, enhanced LV relaxation causes a suction effect that increases the PV D velocity and may lead to S/D ratio reversal. Although this PV pattern may also be accompanied by high E/A ratio and possibly larger LA size in athletes (potentially giving the impression of impaired diastolic function), this is easily recognised as a normal finding by analysis of the e′ velocity, E/e′, TR velocity and LA function (see later section).

Although LA and LV pressures are near equal during diastasis, continued PV flow during this period causes a continued rise in LAP. In normal healthy hearts, this momentum of pulmonary vein flow entering the LA and causing LAP to rise results in very low velocity transmitral forward flow, usually measuring < 20 cm/s [ 39 ].

L-wave—impaired diastolic function

Continued PV flow into a dilated and incompliant LA may cause consistent elevation of LAP following early LV filling, leading to transmitral flow during diastasis with a velocity that reflects the degree of LAP elevation [ 22 ]. Although some degree of transmitral flow may be seen in normal circumstances, high velocity flow (> 20 cm/s) during diastasis reflects impaired relaxation and elevated LAP [ 23 ].

Limitations of L-wave

The limitations for measuring and interpreting both the L-wave and pre-A velocity are similar given that both describe the point in mid-diastole between early and late LV filling. E/A fusion: whereas the pre-A measure describes the velocity of transmitral blood-flow at the cross-over point between E and A waves, the L-wave velocity is a measure of transmitral flow occurring between two identifiably separate E and A waveforms . Tachycardia or extended PR interval with subsequent E/A fusion therefore prevents the measure of L-wave velocity. Aortic regurgitation: in cases of eccentric AR where regurgitant flow contaminates the assessment of transmitral forward flow, an L-wave velocity may not be clearly identified and may prevent a measurement from being made (Table 5 ).

Non-routine measures of diastolic function

Although the following parameters are not recommended for routine clinical practice, they may provide insight into LVDF in certain scenarios.

Mitral annular tissue Doppler imaging (TDI)—e′/a′ ratio

In the normal heart, the TDI diastolic pattern at the mitral annulus mirrors that of transmitral blood-flow Doppler where the both E wave and e′ velocity are high, due to the predominance of rapid early diastolic filling, while the A wave and a′ are comparatively low. Therefore, high e′ velocities and relatively low a′ velocities result in an e′/a′ ratio that exceeds 1, is typically high in the young and fit, and increases with athletic conditioning and supra-normal early diastolic relaxation [ 65 , 123 , 124 ]. As expected, the age-related decrease in global LV relaxation rate leads to a continuous decline in peak e′ velocities with normal aging (Table  2 ). The age-related shift in early to late filling ratio is also reflected by a reversal of the e′/a′ ratio to less than 1 [ 125 ].

e′/a′—impaired diastolic function

With impaired LVDF, MV annular velocities and pattern reflect the decline in LV relaxation and shift in ratio between early and late LV filling. As such, when LV relaxation is impaired but LVFP and LAP remain normal, the onset of the e′ is subtly delayed [ 68 , 126 ] and the velocity decreases, falling below that of a′ resulting in an e′/a′ ratio of < 1. Although decreased LV compliance and increased LVFP causes the transmitral blood flow E/A ratio to increase to above 1 (when not affected by pre-A velocity), this shift in ratio is secondary to an increase in E velocity due to elevated LAP and a reduction in A velocity due to increasing LA afterload and consequently reduced end-diastolic pressure difference between the LA and LV. Although MV annular velocities are affected by loading conditions and left heart pressures, they are much less load dependent than transmitral Doppler. Therefore, the absolute MV annular velocity continues to fall and the e′/a′ ratio remains < 1 when LVFP and LAP initially become elevated.

Limitation of e′/a′:

When LV filling becomes restrictive, significantly increased LA afterload leads to a marked reduction in LV filling from atrial contraction and although total filling volume is reduced, the majority of LV filling occurs in early diastole. Mitral annular velocities may reflect this physiology and explains why an e′/a′ ratio of > 1 may be seen in those with restrictive filling [ 127 ].

As described, in those with normal hearts, the IVRT is influenced by the rate of LV relaxation and therefore age. In the young and those who are athletic, rapid recoil and untwisting of the LV causes intracavity pressure to fall rapidly, resulting in a very short time between AV closure and MV opening and a consequently short IVRT (Table  5 ). With aging, the rate of myocardial relaxation slows with a corresponding increase in the rate of intra-cavity pressure fall and a consequent increase in the IVRT [ 58 ].

IVRT—impaired diastolic function

When LV relaxation is impaired but with normal compliance and normal LVFP, the slower rate of relaxation results in a slower rate of pressure decay within the LV and a consequently longer period between AV closure and MV opening. Although less accurate than direct measures of τ, the IVRT therefore reflects the rate of pressure decay and is increased when LV relaxation is impaired—similar to the physiology seen in normal aging hearts. When LVFP is elevated, the LV to LA diastolic pressure difference is reduced causing the MV to open sooner. Impaired LV diastolic function with elevated LAP therefore leads to shortening of the IVRT. For a healthy adult < 60 years old, a normal IVRT is typically < 80 ms. Impaired relaxation but with normal LAP results in a lengthened IVRT [ 128 ], typically > 100 ms. Conversely, decreased LV compliance with increased LAP results in an IVRT that shortens to a ‘normal’ range of 60–100 ms. When LV filling becomes restrictive and mean LAP is significantly raised, the MV opens sooner and the IVRT shortens further and may be as brief as 40–60 ms [ 129 , 130 , 131 ]. The relationship between impaired LVDF and the IVRT is therefore U-shaped, increasing in the early stages of diastolic impairment before decreasing as LAP increases (Table 6 ).

Limitations of IVRT

Short duration: IVRT is typically very short in duration and is therefore subject to measurement error, particularly during periods of tachycardia, limiting its routine application. Variations in pressure: as the duration is entirely determined by pressure differences, the IVRT varies according to alterations in pressure either side of the MV. When LV systolic pressure is increased, LV relaxation will start from a higher pressure and therefore extend the time period between AV closure and MV opening, thus extending the IVRT [ 51 ]. Conversely, when SBP is low, relaxation starts from a lower pressure and IVRT will be shorter. IVRT is also affected by alterations in LAP and will therefore decrease in scenarios where significant MR or MS cause elevated LAP, irrespective of LV relaxation properties. Given the very short time-period being measured and the continuous nature of the variable, and therefore overlap in parameters between normal and abnormal filling, IVRT interpretation is most accurate and robust at the extreme ends of the spectrum where very long periods indicate slower LV relaxation while very short periods are likely to indicate elevated LAP.

Velocity propagation (Vp)

Combining colour flow Doppler (CFD) with M-Mode (CMM) provides a spatiotemporal map of flow within the LV that is relatively independent of loading conditions and may be helpful for the assessment of LVDF. In the healthy heart, normal elastic recoil creates small mitral-to-apex pressure gradients that help generate the suction for early diastolic LV filling, causing blood to accelerate from the LA in early diastole and rapidly propagate to the apex [ 132 , 133 , 134 ]. This flow propagation velocity (Vp) can be mapped by CMM and measured as an indicator of LVDF. When diastolic function is normal, blood flow from base to apex is rapid with a Vp of ≥ 45 cm/s. Impaired relaxation leads to slower rate of pressure decay and therefore slower rate of early diastolic filling with a reduced Vp (< 45 cm/s). Vp is therefore an indirect measure of τ [ 135 , 136 ].

Combining Vp (as a measure of LV relaxation) with peak E velocity (as an indicator of LAP) may be helpful for the assessment of LVFP. Although a direct estimation of LVFP is theoretically possible [ 135 ], the calculation is limited by inaccurate measures of the CMM slope for Vp estimation. However, utilising the E/Vp ratio may differentiate normal from raised PCWP (thereby LVFP) in both SR and AF [ 137 ]; an E/Vp ≥ 1.4 is suggestive of raised LVFP. In patients with impaired LV systolic function and low LVEF, an E/Vp ratio of > 2.5 predicts LVEDP of > 15 mmHg [ 71 ].

The E/Vp ratio may also hold prognostic value in the setting of HF. A ratio > 1.5 following acute myocardial infarction (MI) predicts in-hospital HF while a separate study found that a ratio of > 1.8 not only predicted HF in those with low or normal LVEF, but also correlated well (r = 0.73) with LV EDP [ 138 ]; in those with systolic HF, a ratio of > 2.7 predicted death, transplantation or HF hospitalisation [ 139 ].

Limitations of Vp and E/Vp

Other determinants: Vp is not solely determined by LV diastolic properties and is also affected by: LV geometry, ratio of MV orifice size to LV cavity size and by dyssynchronous relaxation [ 140 , 141 , 142 ]. The Vp slope may be erroneously normal in patients with impaired relaxation but where the LV cavity is small and hypertrophied. Measurement reproducibility and standardisation: Different measurement techniques exist (non-colour/colour flow interface vs slope of the first aliasing velocity) while interobserver variability has been reported to be as high as 20% [ 143 ]. Lack of standardisation limits the reproducibility of findings and hinders the comparison of studies, therefore restricting the application of results.

Intracavity flow during the IVRT

In the normal healthy heart, there is very little movement of blood within the LV cavity during the IVRT. However, when abnormal and dyssynchronous relaxation is present, either due to LBBB or CAD, temporal differences in regional relaxation may create a pressure difference between the base and apex of the LV that results in intracavity flow during the IVRT. CW interrogates flow along the length of the LV cavity and is therefore the most suitable modality to identify and measure this abnormal flow. Flow is typically towards the apex with a velocity in the range of 20–60 cm/s, reaching 2 m/s in extreme cases. Although this parameter is not recommended for the routine assessment of LVDF, it’s presence may help identify abnormal LV relaxation, especially in the scenarios where LV dyssynchrony is present or expected.

IVRT/T E-e′

When diastolic function and LAP are normal, the onset of early myocardial relaxation and LV filling is almost simultaneous, with little to no measurable time difference between the onset of the E and e′ Doppler signals (Fig. 15 ) (Table  7 ). However, as impaired diastolic function with elevated filling pressures develops, slower LV relaxation causes a delay in the onset of e′ while increased LAP causes earlier opening of the MV and therefore earlier onset of the MV E wave. The time difference between the onset of the E and e′ waves therefore increases as diastolic function worsens. Measurement of this time difference (T E-e′ ) therefore relates directly with τ [ 140 ]. Combined with IVRT, to incorporate LAP, the IVRT/T E-e′ ratio can be calculated as an indicator of LVFP, with a value < 2 suggesting a PCWP of > 15 mmHg [ 144 ]. Because the IVRT/T E-e′ considers the timing of e′ onset relative to the IVRT and E signal onset, this measure can be applied for the assessment of LVDF in those with significant MV disease [ 144 ]; LV diastolic pressures are likely raised when the ratio is < 4.2 in those with MS and < 5.6 in those with significant MR [ 145 ].

Measurement of the time difference between the onset of E and e′. Note the optimisation to decrease transit-time artefact and reduction of wall-filter/low-velocity reject to ensure signal onset is clearly seen

A-wave transit time

Flow entering the LV during early and late diastole causes a movement of blood towards the AV that is detectable within the LVOT by Doppler imaging, described as Er and Ar waves (Fig. 16 ). These waves do not occur instantaneously with transmitral forward flow, however, and a time-delay exists between LV inflow and the onset of the Er and Ar within the LVOT. This time-delay is referred to as the Er or Ar transit-time with the Ar transit-time being typically shorter than that of the Er (Table  7 ).

Measurement of A-wave transit time. The time-to-peak A wave has been measured in this case with the R-wave defined as the starting point. The short transit time of 22 ms is suggestive of decreased LV compliance

In patients with impaired diastolic function and increased myocardial stiffness, the A wave propagates rapidly through the LV with a consequently short Ar transit time. A peak-to-peak transit time of ≤ 45 ms or onset-to-onset transit time of ≤ 50 ms suggests decreased LV compliance and increased end-diastolic stiffness, consistent with impaired diastolic function [ 146 , 147 ].

Other indicators of impaired LV relaxation

The parameters described below reflect global myocardial function and are therefore considered indicative of impaired LV relaxation when they fall below the normal expected range.

Impaired myocardial function – LVEF and strain analysis

There are certain clinical scenarios in which impaired LV relaxation can be assumed to be present. Impaired systolic contractility identifies impaired myocardial function and indicates that LV relaxation is likewise impaired. Therefore, an LVEF of < 50% or absolute GLS < 16% [ 149 ] is consistent with impaired LVDF; an assessment of LVFP should then be made. Additionally, impaired relaxation should also be assumed in those with left ventricular hypertrophy, regional wall motion abnormalities or known myocardial disease of other aetiology. However, reduced GLS or LVEF are not ubiquitous amongst those with impaired diastolic function and may be within the normal range despite diastolic impairment and raised LVFP. As such, LVEF ≥ 50% or absolute GLS ≥ 16% do not confirm normal diastolic function and wider consideration of secondary parameters may be required. In athletically fit individuals, physiological adaptation of the heart may result in low-normal parameters of systolic contraction (LVEF and GLS) at rest as the larger ‘athletes’ heart’ is able to deliver the required stroke volume and cardiac output at a lower magnitude of contractility. In this scenario, normal or supra-normal diastolic parameters usually help to differentiate normal athletic adaptation from myocardial impairment [ 42 ]. However, if parameters of both systolic and diastolic function are at the lower limits of normal, further imaging (incorporating exercise testing) may be required to confirm normality/pathology.

Algorithms for the assessment of LV diastolic function

Normal systolic function, normal versus impaired systolic function.

Although previous diastolic guidelines provided recommendations that applied to all patients, the diastolic assessment is simplified by consideration of key parameters of LV systolic function. When LVEF is < 50%, GLS < 16% or the presence of myocardial disease is confirmed (ischaemic heart disease with regional wall motion abnormalities, cardiomyopathy, pathological LVH), abnormal relaxation is extremely likely and therefore assumed—the focus of the diastolic assessment is to investigate whether LVFP are consequently elevated. However, when LV systolic function is normal, relaxation must be investigated along with LVFP. Furthermore, the accuracy of LVDF parameters to identify elevated LVFP is greatest when LV systolic function is impaired. The process of investigating LVDF is therefore subtly but necessarily different between those with normal LV systolic function and those with confirmed abnormal systolic function or known myocardial disease.

Normal systolic function algorithm

Systolic function is considered impaired when either LVEF is < 50% or absolute GLS < 16%, whereas LVEF ≥ 55% and GLS ≥ 18% are consistent with normal systolic function. There exists, therefore, a grey-zone of LVEF (50–54%) and GLS (16.0–17.9%) where analysis of systolic function requires interpretation of other factors, including: LV volumes and TDI, prior echo reports, clinical history, cardiovascular symptoms, family history, and potentially functional assessment [ 86 ]. Consequently, LVEF and GLS cannot provide binary normal/abnormal cut-offs for systolic function. As such, the LVDF algorithm for those with normal systolic function cannot be defined by specific LVEF or GLS ranges. Instead, confirmation of normal systolic function should be made by global assessment and in accordance with the previously published guidance [ 86 ].

In those with normal systolic function and no evidence of myocardial disease, there exists significant overlap between normal and abnormal for parameters of LV relaxation. As such, the assessment of LVDF in those with normal systolic function must start with the assessment of LVFP (Fig. 17 ). This assessment centres on three key variables: E/e′ > 14, TR velocity > 2.8 m/s and indexed LA volume > 34 mL/m 2 . When two or three of these parameters are negative (ie, below the referenced cut-off), LVFP are considered normal. If two or three parameters are positive (ie, above the referenced cut-off), diastolic function is impaired and LVFP are elevated.

Algorithm for the assessment of LVDF in those with normal systolic function. It is recommended that the algorithm is not applied in the following conditions: severe MR/MS or MAC or MV replacement or repair

When only two criteria are available, typically in the absence of TR, with one positive and one negative, the missing parameter can be replaced by LAs. In those with normal systolic function, high-normal values of LARs (> 30%) and LAPs (> 14%) indicate normal LVFP with very high accuracy [ 103 ]; LV relaxation should then be reported according to age-specific e′. As diastolic impairment progresses and LVFP increase, parameters of LA function typically deteriorate. When replacing a missing key parameter, LARs < 18% is suggestive of elevated LVFP [ 103 ]. However, when systolic function is normal, there is overlap in LAs parameters across normal and elevated LVFP, such that a range of LARs > 18% is seen in both normal diastolic function as well as impaired diastolic function with elevated LVFP [ 103 ]. The accuracy of each parameter to identify elevated LVFP is therefore weaker when systolic function is normal and further analysis of diastolic parameters is therefore required when LARs falls within a range of 19–29%. In this setting, the supplementary parameters of Ar-A duration > 30 ms and L-wave velocity > 20 cm/s correlate well with elevation of LVFP and should therefore be considered. If one or both of these parameters are positive, the diagnosis of impaired diastolic function with elevated LVFP is made. If not, LVFP are considered normal and LV relaxation is reported according to age-specific e′.

Importantly, replacement of the missing parameter does not improve the accuracy of the algorithm. However, because TR is absent in a significant number of patients (between 40 and 60% in some studies [ 150 , 151 ]), replacement with LAs analysis improves algorithm feasibility to around 95% and reduces the number of indeterminate outcomes [ 104 ]. Feasibility studies have reported that LA strain can be measured in between 92–95% of patients [ 103 ]. However, in those with one positive and one negative key variable and where LA strain analysis is not possible, the assessment of LVFP is indeterminate and LV relaxation is reported according to age-specific e′, although the supplementary parameters described within the algorithm may provide some insight into LVFP.

Impaired systolic function or known myocardial disease algorithm

When LV systolic function is impaired or known myocardial disease is present, LV relaxation is almost certainly impaired—the focus of the diastolic assessment is therefore to determine whether LVFP are elevated using the three key variables of LVFP (Fig. 18 ). When two or three of these parameters are negative, LVFP are considered normal. If two or three parameters are positive, diastolic function is impaired and LVFP are elevated. When only two criteria are available with one positive and one negative, the missing parameter can be replaced by LAs. However, the cut-offs are subtly different to those with normal LVEF. In those with impaired systolic function, absolute LAPs < 8% or LARs < 18% indicate elevated LVFP while ≥ 14% and ≥ 24% indicate normal LVFP with high accuracy. Due to the overlap in LA strain parameters between normal and elevated LVFP, LAPs values of 8–13% and LARs 18–23% may be seen in the settings of both normal and elevated LVFP [ 103 ] and supplementary parameters should be considered. In addition to Ar-A duration > 30 ms and L-wave velocity > 20 cm/s, a PV S/D ratio < 1 and MV E deceleration time < 150 ms are accurate indicators of elevated LVFP with high sensitivity and specificity when LV systolic function is impaired. If one or more of these supplementary parameters are positive, elevated LVFP should be reported. If all are negative, LV relaxation is impaired but LVFP are normal. As impaired relaxation has been established, age-specific e′ are not considered in those with impaired systolic function or known myocardial disease. In those with one positive and one negative key variable but LA strain analysis is not possible, the assessment of LVFP cannot be performed and LV relaxation is therefore impaired but with indeterminate LVFP. However, the supplementary parameters described within the algorithm may provide some insight into LVFP.

Algorithm for the assessment of LVDF in those with impaired systolic function or known myocardial disease. It is recommended that the algorithm is not applied in the following conditions: LBBB, RV apical pacing or resynchronisation pacing (CRT); LV assist devices

Atrial fibrillation algorithm

Although the assessment of LVDF is complicated by cardiac arrhythmia, AF is a common finding in those with impaired diastolic function (AF being commonly caused by abnormalities of LV structure and/or function) and often seen in patients with HF; the echocardiographic investigation of diastolic function should not be omitted because of the presence of AF alone. However, because it is not possible for all measures of diastolic function to be made during the same cardiac cycle, the R-R variability, and therefore beat-to-beat variation of loading conditions that is characteristic of AF risks invalidating the assessment of diastolic function if appropriate measurement methods are not followed. The writing group recommend that if the HR is < 100 bpm (ideally < 90 bpm), Doppler parameters can be obtained from a single beat if the two preceding R-R intervals are of similar duration (within 60 ms of one another). When deriving the E/e′ ratio, it is important that the E velocity and the e′ velocity are measured from cardiac cycles that are similar length [ 107 ].

The algorithm for the assessment of LV diastolic function in those with AF incorporates parameters that when combined provide an overall accuracy of 75% for the detection of elevated filling pressures in those in AF [ 152 ]; the assessment of LV relaxation cannot be performed accurately in AF. This algorithm should be used in all patients in AF, irrespective of LV systolic function.

Step 1 incorporates four key variables: septal E/e′, MV E velocity, MV E deceleration time, and TR velocity. When ≥ 3 parameters are positive, LVFP are considered elevated. When ≤ 3 are negative, LVFP are considered normal. In scenarios where ≤ 3 parameters are available and only ≤ 2 are positive or negative, filling pressures are unclassified and further supplementary parameters should be considered in Step 2: LARs, PV S/D ratio and BMI. When ≥ 2 of these 3 are positive, filling pressures are considered elevated. When ≤ 2 of 3 are negative, filling pressures are considered normal. If these criteria in STEP 2 are not met, LV filling pressures are indeterminate (Fig. 19 ).

Algorithm for the estimation of LVFP in patients with AF. None of the parameters listed in the algorithm are of sufficient accuracy to be considered adequate stand-alone measures for the assessment of LVDF. The algorithm is not recommended for application in the following conditions: complex congenital heart disease, cardiac transplants, end-stage liver disease, mitral stenosis or mitral annular calcification resulting in significant mitral stenosis, prosthetic mitral valve, severe aortic stenosis, severe mitral or tricuspid regurgitation, and atrial fibrillation with rapid average ventricular rate at rest (> 120 bpm) [ 152 ]

Septal wall E/e′

In the setting of AF, greater variability of the R-R interval results in greater variation of the lateral e′ velocity than that of septal e′. It is therefore recommended that the E/e′ ratio is calculated using septal wall e′ alone. When considered within the AF algorithm, a ratio of > 11 provides greatest accuracy for detecting elevated LVFP.

Mitral E peak velocity ≥ 100 cm/s and deceleration time ≤ 160 ms

The transmitral peak E velocity is reflective of the early diastolic pressure difference between the LA and LV. When LV diastolic function is normal, rapid and efficient LV relaxation generates a suction effect that increases the LA-LV pressure gradient without elevation of LAP. When LV diastolic function is impaired with elevated LVFP, increased LAP causes MV E velocity to increase while decreased LV compliance causes rapid equalisation of LV and LAP, resulting in rapid deceleration of flow velocity. As the most common cause of AF is an abnormality of LV structure and or function [ 153 ], an E velocity > 100 cm/s and deceleration time ≤ 160 ms in this setting are therefore supportive of impaired LVDF with consequently elevated LVFP and LAP.

TR velocity > 2.8 m/s

Although the cut-off for TR velocity remains the same as in SR at > 2.8 m/s, care should be taken to avoid measurement following short R-R intervals that may be associated with underestimated peak TR velocity.

Obesity—body-mass index (BMI) > 30

The relationship between obesity and HFpEF has become clearer in recent years. Rather than merely a mechanical cause of dyspnoea that is associated with comorbidities for HFpEF (hypertension (HTN), diabetes mellitus (DM), CAD etc.), the metabolic consequences of obesity have system wide effects on the cardiovascular system that lead to systemic inflammation, mitochondrial dysfunction, autonomic dysregulation and altered haemodynamic loads. In turn, causing abnormal myocardial structure, function and metabolism that is the basis for the independent relationship between obesity and HFpEF that is not explainable by the associated cardiovascular risk factors alone [ 154 ]. Given the relationship between obesity and HFpEF and that AF is a recognised consequence of chronically elevated LVFP (the haemodynamic correlate of HFpEF), a BMI of > 30 is therefore considered supportive of elevated LVFP in the setting of AF.

Irrespective of LVFP, due to the absence of LA contraction/pump phase, parameters of LARs are routinely lower in AF than in SR [ 97 ]. Consequently, the cut-off for identifying elevated LVFP in AF is lower at < 16% [ 152 ].

PV S/D ratio

As described, decreased LA compliance (common in AF) and increased LAP causes a reduction in PV D velocity, leading to a reduction in the PV S/D ratio to below 1.

Assessment of diastolic function in special groups

Valvular disease.

Mitral stenosis

In those with moderate or severe MS, under filling of the LV results in normal or even low LV diastolic pressure while MV obstruction increases LAP, causing the E velocity, E/A ratio, E/e′, LA volume and SPAP to increase; if MS is calcific in nature and extends into the MV annulus, e′ velocities may also decrease. Although impaired LV diastolic function is not a typical finding in those with rheumatic MS, when moderate or severe MS is present the transmitral blood flow velocity and MV annular relaxation velocities are predominantly determined by the severity and extent of MV disease rather than diastolic properties of the LV; however, because even mild MS can lead to increased transmitral E velocity and alter the E/A and E/e′ ratios, the diastolic assessment should incorporate absolute e′, TR velocity, LA volume and parameters of LV geometry and function (including mass and GLS) in order to make a global judgement of diastolic function and the likelihood of impairment. Ultimately, it may not be possible to determine LVDF by echocardiography in the presence of moderate or severe MS and invasive catheterisation procedures may be required. Understanding the clinical presentation of the patient to identify the likelihood of LV myocardial impairment (DM, HTN, CAD etc.) can help determine whether impaired diastolic function is likely.

Although both IVRT < 60 ms and MV A velocity > 1.5 m/s suggest raised PCWP in those with MS [ 145 ], this does not differentiate the cause. By incorporating the time difference between the onset of MV annular motion and blood-flow, IVRT/T E-e′ may identify impaired relaxation. Although parameters of LV systolic function are likely affected by LV under filling in those with moderate or severe MS, low GLS may help identify abnormal myocardial function when other parameters of diastolic function cannot be interpreted. AF is common in those with severe MS and should be considered when reporting GLS and LVDF. Markers suggestive of impaired relaxation—IVRT/T E-e′  < 4.2

Mitral regurgitation

When the LV and LA are compliant, moderate or severe primary MR results in chamber dilation that negates an increase in LAP. However, once the regurgitant volume exceeds the compliance capacity of the LA to accommodate the additional volume loading, LAP becomes elevated, leading to increased E velocity, E/A ratio, E/e′, LA volume and SPAP; significant MR may also lower or completely diminish PV S velocity. Even when LAP is normal and MR moderate, the additional regurgitant volume increases the early diastolic transmitral volume and may elevate E velocity, causing the E/A and E/e′ ratios to increase and PV S velocity to reduce. The increase in LAP and forward flow volume caused by moderate or severe primary MR causes an elevation in E velocity that consequently confounds the assessment of LVDF. Although the below markers may be of some utility in identifying elevated LAP, it may not be possible to differentiate the cause of raised LVFP or accurately assess LVDF in the presence of moderate or severe primary MR. LV diastolic pressure measurements may require cardiac catheterisation if impaired diastolic function is suspected and of clinical importance. In patients with severe MR secondary to LV disease, the parameters of LVFP and LAP reflect the combination of disease processes.

Markers of raised LAP: IVRT < 60 ms, Average E/e′ > 14 (only if impaired LV systolic function), Ar–A ≥ 30 ms, IVRT/T E-e′  < 5.6 if normal LVEF (more specific if < 3). GLS is affected less by loading conditions than LVEF and may help identify abnormal myocardial function in the setting of severe primary MR.

Mitral annular calcification

In the presence of mitral annular calcification (MAC) and mild calcific MS, the assessment of LVDF can be challenging. Absolute e′ velocities may be reduced due to tethering of the MV annulus and consequently reduced relaxation velocities, while E velocity may be increased due to accelerated flow through the decreased mitral valve area. E/e′, E/A ratio, and LA size may all increase secondary to MAC. However, MAC is commonly associated with hypertensive heart disease, chronic kidney disease and CAD and is therefore seen in patients with impaired diastolic function. Consideration of timings may be helpful alongside assessment of the degree of valvular obstruction. For instance, if no significant obstruction is present but the IVRT is 20 ms less than expected for age, LAP may be increased. Conversely, if the E wave is increased but the IVRT is within normal range, then E velocity is likely raised due to the decreased MVA. In the absence of pulmonary disease, elevated TR velocity may suggest increased LAP. Given the comorbidities associated with MAC, a simple estimate of E/A can help differentiate normal LAP (< 0.8) from raised LAP (> 1.8); for those with an intermediate ratio (0.8–1.8), an IVRT of < 80 ms suggests raised LAP [ 155 ].

MV repair/replacement

Assessment of LV relaxation and LVFP is difficult following mitral valve surgery. Decreased MV orifice area will lead to increased transmitral flow velocity while annular velocities are very likely to be reduced due to the presence of an annuloplasty ring or replacement valve—LA volume will very likely be increased and function possibly reduced due to previously severe regurgitation or stenosis. As with MS/MR, TR velocity and flow timings (IVRT and IVRT/TE-e′) may be of value alongside LV GLS and understanding the clinical background to determine the likelihood of impaired diastolic function.

Aortic regurgitation

Chronic severe AR is well tolerated in those with a distensible and compliant LV (typically young individuals with bicuspid aortic valve because the additional diastolic filling is matched by an increase in LV size to maintain low diastolic pressure [ 156 ]). Once the AR volume exceeds the capacity for LV preload to adapt, LV diastolic pressure will rise progressively throughout diastole [ 157 , 158 , 159 ] leading to increased EDP and therefore LA afterload with consequently low A velocity with increased E/A ratio; the E deceleration time may also decrease as LV diastolic pressure rises more rapidly. In chronic AR, a combination of increased E/e′, LA volume and TR velocity are suggestive of raised LAP.

When severe AR is acute, the LV is not instantaneously distensible to accommodate the sudden onset of significant additional diastolic volume. The inability to distend renders the LV incompliant with diastolic pressures becoming markedly elevated [ 160 ]. This rapid increase in LV diastolic pressure may cause early closure of the MV and an abbreviated filling period with potentially some degree of diastolic MR due to significantly raised LV EDP [ 161 ]. However, these findings merely reflect the haemodynamic consequence of sudden onset severe AR overloading an LV that may be entirely normal. Although acute severe AR may prevent an accurate assessment of intrinsic myocardial diastolic function, it is poorly tolerated and the detailed assessment of LV relaxation is unlikely to be of immediate clinical importance.

Intrinsic diastolic impairment and decreased compliance limit the capacity of the LV to dilate in the face of volume overload. A normal end-diastolic volume in the setting of severe chronic AR may therefore be suggestive of decreased LV compliance, especially when combined with parameters suggestive of raised LV EDP.

Cardiomyopathies

Hypertrophic cardiomyopathy (hcm).

Due to increased LV mass, reduced chamber compliance, microvascular ischaemia and myocardial fibrosis, impaired diastolic function is common in HCM and results in elevated LVFP and LA dilatation [ 162 , 163 ]. Accurate classification of diastolic function severity is essential for appropriate therapy decisions, yet challenging in HCM due to the concomitant presence of LVOTO and MR in many patients. Many independent echo variables have weak correlations with LVFP, including E/e′ [ 164 ]. As such, integration of several parameters is necessary to quantify diastolic function accurately [ 165 ]. For appropriate medical management and identification of those who may be suitable for advanced heart failure therapy, it is essential to identify patients with preserved LVEF but a restrictive diastolic filling pattern [ 166 ]. The algorithmic approach to assessing LVDF in the setting of myocardial disease should be undertaken in those with HCM [ 167 ], although LA volume and function should be interpreted in caution when moderate or severe MR is present.

Restrictive cardiomyopathy

This group of cardiomyopathies of variable aetiology have been described according to their impact on LV filling. Unsurprisingly, therefore, some degree of diastolic impairment is expected in those with infiltrative and storage disorders that fall into the category of a restrictive cardiomyopathy. The standard algorithm for assessing diastolic function remains valid in this group. Although diastolic function may be markedly abnormal in the chronic stages of these processes, impairment may be subtle in the early stages with slower relaxation but normal LVFP. A restrictive filling pattern can be found in a number of disease groups however (ischaemia, valvular disease, HCM, DCM) and the aetiology of the underlying myocardial disease may not be identifiable from the echocardiogram alone [ 168 ].

Sinus tachycardia

Measurement of timings, especially those of brief duration, will be challenging during sinus tachycardia. A sweep-speed of 100 mm/s should be utilised. Fusion of the transmitral E and A waves makes assessment of E velocity and E/A ratio difficult or may even prevent measurement. Although it is possible to perform measures of diastolic function during the compensatory pauses that follow ectopics, the effect of persistent tachycardia on cardiac loading conditions should be considered and how this might affect LVFP and therefore echocardiographic parameters of diastolic function. Although an accurate assessment of LV relaxation may not be possible, the following parameters and associated cut-off values are suggestive of raised LVFP:

Markers of raised LVFP: average E/e′ (> 14 provides highest specificity, > 10 is more sensitive but less specific), PV systolic filling fraction ≤ 40% (if good tracings possible), IVRT ≤ 70 ms, TR velocity > 2.8 m/s, E/A > 1 in patient with LVEF < 50% (if pre-A velocity < 20 cm/s).

AV block, LBBB and paced rhythms

A long PR interval, LBBB or ventricular pacing may result in fused E/A waves, causing elevated pre-A velocity. A very long PR interval (> 320 ms) or similar paced AV delay will result in marked E/A fusion and potentially diastolic MR. E/A fusion increases atrial pump SV and may result in a longer A wave duration, altering the Ar-A duration, and higher pulmonary venous systolic velocity leading to altered PV S/D ratio. If the fusion is minimal, grading of diastolic function may still be possible according to the standard algorithm. Decreased IVRT may help identify raised LAP.

Markers of raised LVFP: average E/e′ > 14, LA volume > 34 mL/m 2 , Ar-A duration > 30 ms (if E/A not fused), TR velocity > 2.8 m/s.

Pulmonary arterial hypertension - differentiating pre and post-capillary PH

In the absence of lung disease, raised LVFP translates to raised PCWP and consequently raised SPAP, causing PH. A TR velocity > 2.8 m/s is therefore an important indicator of impaired diastolic function. However, PH may occur for reasons other than abnormal LV diastolic function. Distinguishing pre-capillary PH (pulmonary vascular remodelling) from post-capillary PH (left-heart disease) has important prognostic and therapeutic implications. The definition of pre-capillary PH requires the PCWP to be ≤ 15 mmHg [ 169 ]. Thus, identifying elevated LVFP effectively excludes the diagnosis of pre-capillary PH (although occasionally some patients may have both conditions). Differentiating which patients have pre-capillary versus post-capillary PH (or both) is challenging. Markers suggesting that PH may be pre-capillary [ 76 , 88 ] and not due to LVDF and elevated LVFP are listed:

Fixed dilated inferior vena cava, LV eccentricity index > 1.2, RV > LV size, RV dysfunction, E/e′ < 10 (if significant septal flattening, use lateral e′ only), normal LA size and function, mid-systolic notch in right ventricular outflow tract, PW Doppler or pulmonary valve Acceleration Time < 80 ms and medical condition associated with PH. However, by combining transmitral E/A ratio, LA reservoir strain and lateral E/e′, LVFP can be investigated as a potential cause of PH (Fig. 20 ) [ 170 ].

Algorithm for differentiating pre and post-capillary PH—reproduced with permission [ 170 ]. Accuracy to differentiate between normal and elevated LV filling pressure: Mitral E/A and LA reservoir strain: 85% accuracy. Mitral E/A and lateral E/e′ < 8 or > 13: 86% accuracy

Heart transplantation

Before diastolic assessment is made, it is essential to consider the parameters being measured in the context of the heart age, rather than the age of the recipient patient. Donor hearts are commonly those of healthy and young individuals and may present with very different diastolic flow profiles to those expected of an older recipient patient. Bi-atrial surgery will result in enlarged atria with clearly abnormal atrial function. Bicaval surgery may not affect left atrial function. Reduced atrial contraction often leads to a reduced A wave velocity and consequently abnormally raised E/A ratio. Reduced e′ velocities due to bi-atrial surgery may lead to abnormally raised E/e′ [ 170 ]. A tachycardia is commonly seen despite normal systolic and diastolic function. If bi-atrial surgery has been performed, competing atrial signals may cause discordant atrial contractions, significantly altering transmitral flow profiles. The only reliable marker of raised LVFP may be a raised SPAP in the absence of pulmonary disease.

Provocative manoeuvres to unmask increased LVFP

Diastolic stress-echocardiography, indications for diastolic stress-echocardiography.

In patients with symptoms of exertional dyspnoea of unknown cause and impaired relaxation but normal LVFP at rest and no other identifiable cause on resting echocardiography, exercise stress echocardiography (ESE) for the assessment of diastolic function can be considered [ 171 ].

Diastolic function during exercise

The normal heart is able to increase SV and CO without a significant increase in LVFP. During exercise, augmented elastic recoil and relaxation causes the minimum diastolic pressure to fall, generating a greater transmitral pressure gradient that enhances early diastolic suction and facilitates greater LV filling without an increase in LAP [ 172 , 173 , 174 ]. These acute physiological adaptions to exercise are observed echocardiographically as an increase in septal and lateral annular velocities (augmented LV relaxation) and an increase in the E velocity (greater transmitral gradient). As the increase in both E wave and MV annular velocities is roughly proportional, the E/e′ ratio is not elevated by exercise in the normal heart and remains relatively unchanged throughout the test [ 175 ]. Excluding exercise induced ischaemia, increasing HR does not induce impaired diastolic function. In those with impaired diastolic function, the relaxation response is attenuated during exercise so that LV minimal pressure does not decrease significantly and the greater transmitral pressure gradient required to augment LV filling volume is achieved by an increase in LAP [ 172 ]. Peak E velocity increases proportionally with LAP while impaired myocardial relaxation results in persistently low e′ velocities throughout exercise, thus leading to an increased E/e′ ratio. With rising LAP, elevated SPAP causes TR velocity to increase [ 85 ].

An assessment of diastolic function during ESE is therefore indicated in those experiencing exertional symptoms and whose resting echo demonstrates impaired relaxation with normal LVFP (ESE is very unlikely to reveal elevated LVFP during exercise when resting LV diastolic function is entirely normal). When LVFP are raised at rest, diastolic-specific ESE does not add clinical benefit as the likely cause of exertional symptoms has been identified by resting TTE. However, if performed for the investigation of myocardial ischaemia, correlating patient symptoms with diastolic and systolic function may be beneficial [ 173 ].

Performing a diastolic ESE—exercise protocol

As pharmacological agents (Dobutamine, Adenosine, Atropine etc.) do not provide the same level of physiological stress as physical exercise and do not generate the same degree of venous return, the diastolic stress test is performed using either a treadmill or semi-supine bike. Assessment of diastolic function at any point, whether at rest or during exercise, relies on separation of the early (E, e′ and E deceleration time) and late (A and a′) filling Doppler signals. As increasing HR decreases the diastolic filling period and causes early and late diastolic waveforms to merge, identification of the E max velocity becomes increasingly difficult at HR around 100–105 bpm.

When performed using the treadmill, the assessment of diastolic function is made during the recovery phase. With bike stress echo, assessment of diastolic function is not limited to recovery alone and can be performed during exercise. This not only offers the additional benefit of correlating symptom onset with the estimation of LVFP at that time, but also allows the exercise protocol to be tailored to the patient’s symptoms, exercise capacity and echo findings.

Once the patient is connected to all monitoring equipment (usually 12-lead ECG, BP and O 2 saturation monitor) the bike is reclined and tilted leftward until images of diagnostic quality are obtainable. Once in the exercise position, the echo windows should be optimised. Parameters that are to be measured during exercise should be re-measured with the patient in the exercise position to establish baseline reference values in the new windows. For those who are physically able, a protocol starting with 25W resistance and increasing by 25W at 2-min intervals is appropriate. For those who have a low level of exercise capacity, a lower resistance protocol should be considered (starting resistance of 10W with 2-min increments of 10W). A standard cycle protocol directs a cycle rate of 55–65 rpm, although this can be tailored to control HR response and enable image acquisition at the required HR. As part of the ESE, assessment of significant CAD and valve disease may also be considered. The test for ischaemia typically aims to achieve 85% of target HR (maximum age predicted) in the absence of symptoms. Measures of diastolic function can therefore be performed both pre and post maximal exertion when heart rates are between 95 and 105 bpm.

Performing a diastolic ESE—measurement protocol

The measurement protocol for assessing diastolic function during exercise incorporates the Doppler parameters that are performed at rest (Table  8 ). During each stage, at peak exercise and during recovery, the following diastolic parameters are acquired:

Mitral annular septal and lateral e′

Transmitral E velocity

Where exclusion of CAD is the main indication, a maximal stress test is performed and 2D images prioritised for assessment of regional wall motion abnormalities (RWMA). If contrast is required for improved endocardial definition, tissue Doppler signals for diastolic assessment may be unobtainable; TR velocity (if measurable) maybe the only indicator of mean LVFP in this case. At peak exercise, assessment of RWMA and systolic function can be performed for 60 s post-peak stress. If both E/A and e′/a′ signals remain fused after this time, continue to assess TR velocity until HR allows diastolic assessment. It is important to bear in mind that pulmonary artery pressure is the product of flow (SV) and pulmonary artery (PA) vasculature resistance. SPAP may therefore become raised during exercise in those who are elderly with reduced PA compliance (resistance), or in athletes who have normal PA compliance but augment SV and CO massively (flow). Caution must therefore be exercised when interpreting TR velocity alone.

Interpretation of results

Interpreting the results of the diastolic stress echocardiogram should incorporate exercise induced symptoms, haemodynamic factors (HR and BP) and patient age. Echocardiographic parameters are suggestive of impaired diastolic function with exercise induced elevation of LVFP when E/e′ > 14 and TR velocity > 2.8 m/s [ 85 ]. However, irrespective of LV diastolic function, SPAP and therefore TR velocity may increase at higher HR and CO in the elderly. Importantly, the E/e′ ratio remains a single parameter within the algorithm for assessing LV diastolic function. As such, although a ‘positive’ test, where E/e′ ratio exceeds 14 during exertion, is strongly suggestive of exercise-induced elevation of LVFP, a ‘negative’ test with an E/e′ < 14 throughout exercise does not confirm normal LVFP [ 174 , 176 ]. In this situation, the findings of the test should be considered within the clinical context and alongside patient symptoms.

Diastolic ESE Summary

ESE is a non-invasive, physiological, and convenient investigation to evaluate symptomatic patients with suspected diastolic heart failure. Diastolic stress testing is particularly suited for those with evidence of impaired relaxation yet normal LVFP at rest, and where pulmonary disease and other significant cardiac causes have been excluded. In comparison to the treadmill, bike stress testing offers the major advantage of real time assessment of diastolic haemodynamic parameters in conjunction with patient symptoms.

Leg-raises and preload increase

LV diastolic pressures are determined by LV compliance and filling volume, manoeuvres to increase LV preload can therefore help unmask elevated LVFP [ 177 ]. Although this is more definitively achieved by exercise, passive leg-raise (PLR) increases LV preload through increasing venous return and can be considered as an ad-hoc addition to routine TTE in those with symptoms of exertional dyspnoea, impaired LV relaxation on TTE yet normal LVFP at rest and with no identifiable cardiac cause of symptoms. When positive, the increased LV preload into an incompliant LV causes elevated LVFP that are identifiable by the standard diastolic algorithm. However, a negative test does not rule-out more significant diastolic function impairment and ESE for diastolic assessment may be considered. Although PLR may increase LV preload and cause LVFP to become elevated, active leg raises, where each leg is alternatively raised and lowered, introduces an element of exercise and may help augment this response.

Valsalva manoeuvre

Given the load dependency of diastolic pressures, performing manoeuvres that offload the left heart, such as the Valsalva manoeuvre, can have the opposite effect of the diastolic stress-test and can reveal an impaired relaxation filling pattern (ratio < 1) when LVFP is otherwise increased and the E/A ratio ‘pseudo-normalised’ to > 1 [ 178 ]. When the Valsalva manoeuvre is performed effectively, increased thoracic pressure decreases venous return and thus reduces left heart filling. With a reduction in left sided volume, LAP and LV diastolic pressures fall, leading to a decrease in E velocity. Reduction in LV pressure in late diastole decreases LA afterload, allowing LA contraction volume, and therefore velocity, to increase and thus causing the E/A ratio to reverse [ 179 ]. When restrictive filling physiology is present but Valsalva manoeuvre offloads the left heart, reducing E velocity and E/e′ and reversing the E/A ratio, LV filling is considered restrictive but reversible. However, when an effective Valsalva manoeuvre does not offload the left heart and LVFP and LAP remain high, filling is considered restrictive and irreversible, portending a poorer prognosis. Although the resting E/A ratio alone may not differentiate normal from raised LVFP, other standard measures of diastolic assessment should help diagnose impaired diastolic function and identify raised LVFP. Therefore, the Valsalva manoeuvre may only be required to distinguish fixed from reversible restrictive filling.

Performing the Valsalva manoeuvre

Measurements should be taken at inspiration and throughout 10 s of forced expiration against a closed glottis. A slow sweep-speed can capture the full manoeuvre. It is difficult to perform well—the expiratory pressure must be maintained for 10 s and the sample volume kept at the same position throughout. A decrease in the MV E-wave of 20 cm/s suggests a good technique. If the E/A ratio decreases by ≥ 50% or the A-wave increases (but not due to E & A fusion) then this is highly specific for raised LVFP. A normal response is a balanced reduction in E and A velocities and an increased heart rate.

Future directions of the diastolic function assessment

Lv untwisting and diastolic strain analysis.

Since myocardial deformation is altered despite normal LVEF in diseases that predispose to impaired diastolic function and HFpEF (obesity, DM, renal disease, HTN and age) [ 180 ], diastolic strain and parameters of LV untwisting may be useful indicators of LV diastolic function. Whereas GLS measures longitudinal deformation of the myocardium in systole and is reflective of global systolic function, untwist and torsional mechanics are important components of LV diastolic recoil and LV filling and can be described according to: the degrees of basal or apical rotation, rotation relative to ventricular length and the rate at which this occurs. Therefore, assessment of untwisting and torsion mechanics may help identify impairment of LV filling [ 181 ].

Given that over 40% of LV untwisting is achieved within the first 15% of the diastolic period [ 182 ], untwist during the IVRT appears to be important for global diastolic function. In one hybrid animal-human study, diastolic strain rate (DSR) was able to identify impaired LV relaxation with a significant inverse correlation existing between SR during the IVRT (DSR IVR ) and τ in animals (r = 0.83) and in humans (r = 0.74); a positive yet less strong correlation was found in animals between DSR IVR and -dP/dt (r = 0.71) [ 183 ]. When considered alongside Doppler parameters of LV filling, diastolic strain analysis was also able to predict LVFP. The ratio of transmitral E to DSR IVR and SR in early diastole (DSR E ) were found to correlate directly with PCWP, with E/DSR IVR demonstrating the strongest relationship (r = 0.79) [ 183 , 184 ]. Although E/DSR IVR could not predict a specific PCWP, all patients, except one, with a ratio of < 236 had a PCWP of < 15 mmHg, whereas all patients, except one, with a ratio > 300 had a PCWP of > 15 mmHg; 75% of the patients in this study with a ratio of 236–300 had a PCWP of > 15 mmHg. In addition, E/DSR IVR was found to be more accurate than E/e′ at predicting raised LVFP in patients with normal LVEF or regional impairment. The correlation of PCWP with E/DSR E was significant but weak in comparison (r = 0.46). Although DSR IVR is preload dependent (increasing when LVFP increases), the load dependency only becomes significant when LV relaxation is normal, similar to E/e′. When LV relaxation is impaired the influence of preload is less significant and DSR IVR is reduced in the setting of impaired diastolic function [ 183 ]. In another animal study, the authors measured the peak untwisting velocity in healthy pigs in comparison to pigs with induced metabolic syndrome. At three months, the peak untwisting velocity was unchanged in the healthy pigs yet significantly reduced in those with induced metabolic dysfunction, despite no significant change in E/A ratio or E/e′ [ 185 ], suggesting a role for untwisting velocities in the assessment of subclinical diastolic impairment.

However, in canine studies, LV untwisting rate (UR) was found to be heavily influenced by loading conditions, LV end-systolic volume (ESV) and systolic contractility, such that decreasing LV ESV or increasing LV twist through Dobutamine infusion resulted in a greater rate of LV untwisting in early diastole but without a significant change in τ [ 186 ]. Even when τ was significantly lengthened by beta-blocker infusion, the LV UR remained unchanged when ESV was reduced, suggesting that UR is significantly dependent on LV ESV. In HFpEF and HFrEF patients, the peak UR was related to indicators of LV contractility (LV twist and ESV) and was only related to τ in those with reduced LVEF. In the same study, irrespective of the presence of HF, LV twist, a seemingly important factor influencing untwist, was found to be decreased at rest in those with reduced LVEF yet normal in those with impaired diastolic function but normal LVEF, further supporting the notion that systolic twist is a key determinant of diastolic UR. Importantly, LV UR is reduced during exercise in patients with HFpEF.

As with other parameters of LV filling, age influences the rate of diastolic recoil and therefore strain parameters measured during this period. As previously described, LV recoil during the IVRT and early filling period is achieved, in part, through release of potential energy stored within the elastic elements of myocytes during systolic deformation and twist. However, degenerative changes through normal aging reduce the elastic resistance of the myocardium and attenuates the degree of potential energy stored within the twisted myocardium, thereby reducing the relative peak diastolic untwisting velocity and untwisting rate and delaying the time to peak untwisting velocity [ 9 , 187 , 188 ].

The assessment of diastolic strain appears promising for future iterations of diastolic guidelines but remains a research tool at this time and is not currently recommended for the routine application of LV diastolic assessment.

Multivariate reference regions

Assessment of diastolic parameters according to multivariate reference regions may be considered more broadly in future diastolic function guidelines. When large-scale studies have sought to identify normal echocardiographic reference intervals for given parameters, the data for each measure is typically presented as the mean value accompanied by the standard deviation (SD) [ 91 , 189 ]. As 2SD either side of the mean value provides us with a measurement range within which 95% of all measures lie, we are provided with lower and upper limits of normal (LLN/ULN); measures that fall outside of this reference interval are considered highly likely to be abnormal. However, although this method provides us with an expected normal reference interval for individual univariate parameters, considering multiple univariate parameters side-by-side and simply dichotomising each one as normal or abnormal, as is required for the assessment of LVDF, is problematic. For example, three separate variables at the very lower end of their normal reference interval (ie, e′ velocity, E velocity and E/A ratio) may be individually normal as they are all (just) within a normal reference interval, but the combination of three very low-normal values may be abnormal and indicative of disease. When considering age-specific multivariate reference regions for identifying abnormal filling patterns, using multiple univariate reference intervals side-by-side to confirm abnormality in this way is not advisable [ 189 ]. By doing so: (a) increases the risk of false-positives, (b) reduces test sensitivity and (c), because discrepancies are common among groups of measurements with univariate reference intervals, large proportions of patients may be deemed unclassifiable. When reviewing multiple univariate parameters of diastolic function, Selmeryd et al. demonstrate multivariate analysis for age-specific patterns of LV inflow (E/A) that incorporates velocity of E, A and e′, identifying expected E and A velocity, E/A ratio and E/e′ according to age and e′ velocity [ 189 ] (Fig. 21 ). By doing so, a more global consideration of these parameters is possible and within the context of other univariate parameters.

Age-specific datasets plotted for E, A and e′ result in a three-dimensional skewed ellipsoid reference region. Here, the colour-coded ellipsoids have been sliced and displayed to demonstrate the expected E and A velocity and therefore E/A ratio according to six incremental e′ velocities. For example, it would be expected that for an individual in their thirties with an average e′ of 16 (centre-bottom graph), the E and A velocity would fall within the red ellipsoid and the E/A ratio would not be expected to fall below 1. Furthermore, the E/ e′ would not be expected to exceed 8. From Selmeryd et al. [ 189 ]

The authors go on to report that in those with normal healthy hearts without impaired diastolic function, the multivariate upper limit of E/e′ in the young is around 8, whereas a ratio of 15 may be considered normal in older subjects with normal hearts if the E/A ratio is < 1 and/or e′ is < 7 cm/s, highlighting the contextual role of E/e′ in the assessment of diastolic function. However, current guidance continues to apply a single and high E/e′ cut-off value for all ages. Although this provides high specificity for elevated LVFP, it renders the ratio insensitive to the detection of impairment leading up to this point. While a cut-off of > 14 is optimal for identifying PCWP > 15 mmHg, there is clearly a period prior to the development of elevated LVFP when E/e′ is increasing and potentially indicative of impaired diastolic function in the young, but not yet at the required cut-off for suggesting raised LVFP and therefore diastolic impairment. Conversely, and as described, E and e′ are continuous variables with significant dependency on age. However, because of the disproportionate age-related decline between the two variables (e′ decreasing to a greater extent than E), the E/e′ ratio increases with normal aging (8.2 ± 2.2 at age < 45 years and 12.4 ± 3.3 at ≥ 75 years) [ 91 ]. Despite this progressive increase with age, a single cut-off for diagnosing impaired diastolic function applies to all age groups. This naturally impairs the ability of E/e′ to detect impaired diastolic function in the young (where an E/e′ > 9 is extremely uncommon [ 91 , 189 , 190 ]) and risks over-diagnosis and false positives in the elderly. Applying such multivariate reference regions may improve the diagnosis of impaired diastolic function in the future.

LA stiffness index

The LA stiffness index is a measure that incorporates echocardiographic estimates of LAP (E/e′) and LA function (LARs) to describes the compliance properties of the LA in the setting of impaired diastolic function [ 191 ] – (E/e′) / LARs. In those with diastolic impairment and raised LVFP, elevated LAP causes increased LA wall stress, decreasing LA compliance and leading to reduced LA filling [ 87 , 192 ].

Greater LA stiffness has been identified in HFpEF patients [ 83 , 101 , 193 ] with reportedly greater accuracy for the diagnosis of HFpEF than LARs alone [ 193 , 194 ], although this is likely due to LA stiffness indicating a well-established and more advanced stage of impaired diastolic function than raised LVFP alone, therefore explaining the closer correlation with adverse outcomes [ 195 ]. Furthermore, although LVFP may be reduced through optimal medical management, the chronic morphological and functional alterations of the LA persist and identifies an increased risk of adverse outcomes that would be missed by assessment of LVFP alone [ 195 ]. Additionally, it is very common in patients with impaired diastolic function for LVFP to be normal at rest but for LA function and stiffness to be abnormal and therefore detectable by assessment of LA stiffness [ 195 ]. Prognostically, increased LA stiffness is recognised in patients with chronic AF due to the development of LA myocardial fibrosis and is associated with higher rates of AF recurrence following AF ablation [ 196 ].

Although reference value cut-offs have been published that identify an increased risk of heart failure hospitalisation and mortality in patients with increased LA stiffness (an index of > 0.26 identified patients who were at greater risk of heart failure hospitalisation or death at five years in those with HFpEF (LVEF ≥ 50%) and LVEDP > 16 mmHg [ 190 ]), these parameters have not been validated. Furthermore, no data is currently available for LA stiffness index in those with normal and compliant LA [ 195 ]. Although the published data suggests that the LA stiffness index provides important diagnostic and prognostic value, this important physiological and haemodynamic concept may be considered but is not recommended for routine clinical practice.

LV diastolic function reporting recommendations

Previous guidelines for the assessment of LVDF have classified the degree of impairment into grades I, II and III or mild, moderate and severe, where: grade I/mild impairment identifies impaired ventricular relaxation but with no evidence of raised LVFP; grade II/moderate indicates a more advanced degree of diastolic impairment with raised LVFP; grade III/severe identifies restrictive filling with significantly raised LVFP and is further defined as reversible or irreversible according to the response of LVFP to Valsalva manoeuvre. In this guideline, the BSE have departed from reporting diastolic function according to numerical grades (I, II, III) or grades of inferred severity (mild, moderate or severe). These grading systems are largely unfamiliar to clinicians outside of cardiology and infer a degree of significance that may be contradictory to the clinical context—impaired LV relaxation with normal LVFP in a young athlete is of markedly different clinical significance than for a 75 year-old hypertensive patient, yet would be described as mildly impaired for both. Furthermore, the role of echocardiography is to describe diastolic function and its effect on LVFP. Although there are instances where medical management may reverse the process that has caused impaired diastolic function (for example, enzyme replacement therapy for Anderson-Fabry’s disease, LV mass regression following aortic valve replacement), in many cases the medical optimisation of patients with more significant diastolic function impairment includes off-loading of the left heart in order to reduce LVFP, leading to symptomatic improvement. As such, reduction in LVFP through medical management may give the false impression of improving myocardial function on serial echocardiography when reported by grades or perceived severity (‘improving’ from moderate to mild, grades II to I), when in fact it is merely a reduction in LVFP. Rather, the BSE recommend that the spectrum of diastolic function should be reported according to the continuum of physiology that it is, ranging from a prolonged rate of ventricular relaxation and with no significant increase in LVFP in the initial stages, through to decreased myocardial compliance and consequently elevated LAP. The BSE therefore recommend that the reporting of impaired diastolic function is in accordance with the observed physiology and haemodynamic sequelae; the recommended reporting statements are as follows:

Normal diastolic function for age

Impaired LV diastolic function with normal filling pressure at rest

Impaired LV diastolic function with elevated filling pressure at rest

In those with elevated LVFP, LVEF ≥ 50%, no more than moderate left-sided valve disease and symptoms of exertional breathlessness with unknown cause, the following statement may be considered for inclusion within the report:

these findings may be consistent with HFpEF and should be considered in the context of clinical presentation and symptoms.

The assessment of LVDF is complex, requiring a multiparametric approach to the investigation of relaxation, chamber compliance and filling pressures. However, by considering the recommendations within this guideline alongside the patient’s clinical presentation, and therefore identifying the pre-test probability of impaired diastolic function, a successful investigation of diastolic function and LVFP is possible is most patients.

Availability of data and materials

All data generated or analysed during this study are included in this published article [and its supplementary information files].

Abbreviations

Atrial fibrillation

Aortic valve

Blood pressure

Body surface area

Coronary artery disease

Colour Flow Doppler

Colour M-mode

Cardiac output

Continuous wave

Diastolic strain rate

Diastolic strain rate during isovolumetric relaxation time

Early diastolic strain in sinus rhythm

Exercise stress echocardiography

End systolic volume

Global longitudinal strain

Heart failure

Hypertrophic cardiomyopathy

Heart failure with preserved ejection fraction

Heart failure with reduced ejection fraction

Isovolumetric contraction time

Isovolumetric relaxation time

Left atrium

• Left atrial pressure

Left atrial conduit strain

Left atrial pump strain

Left atrial reservoir strain

Left atrial strain

Left atrial volume index

Left bundle branch block

Left ventricle

Left ventricular filling pressure

Left ventricular diastolic function

Left ventricular end diastolic pressure

Left ventricular ejection fraction

Left ventricular outflow tract

Myocardial infarction

Method of disks

Mitral valve

Pulmonary artery

Pulmonary capillary wedge pressure

Pulmonary hypertension

Pulmonary vein

Pulse wave Doppler

Right atrium

Right atrial pressure

Right ventricular / right ventricle

Regional wall motion abnormalities

Systolic blood pressure

Systolic pulmonary artery pressure

Sinus rhythm

Stroke volume

Tissue Doppler imaging

Tricuspid regurgitation

Transthoracic echocardiography

Untwisting rate

Propagation velocity

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Acknowledgements

Many thanks to the echocardiography teams at both Imperial College Healthcare NHS Trust and North West Anglia Foundation Trust for the images presented within.

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Contributions

SR is the primary author of the document. OS provided expert oversight and guidance, particularly for left atrial strain discussion. LR, DO and DA provided expert contribution for overall guideline creation and left atrial strain analysis and algorithm development. AH, SB, BR, NS, FLG, MS-S, MP, RD, JW, CC, GB, KG, MB and GC provided expert review and content guidance. All authors read and approved the final manuscript.

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Correspondence to Shaun Robinson .

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Competing interests

Otto A. Smiseth is co-inventor of “Method for myocardial segment work analysis”, has filed patent on “Estimation of blood pressure in the heart”, and has received one speaker honorarium from GE Healthcare. SR is co-Editor-in-Chief of Echo Research and Practice. LR, DA, DO, AH, MS-S and MP are Associate Editors of Echo Research and Practice. NS is a member of the Echo Research and Practice Editorial Board.

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Supplementary Information

Additional file 1..

Compliance describes the change in intracavity pressure secondary to an increase in cavity volume such that a highly compliant chamber is able to increase volume significantly (distensibility) with only a small associated increase in internal pressure (compliance = ΔV/ΔP where V = volume and P = pressure). Within an incompliant (stiff) chamber, pressure rises rapidly with only small increases in volume

Describes the ability of a chamber to stretch/expand to increase volume. A highly compliant chamber is therefore distensible whereas an incompliant and stiff chamber is unable to stretch/expand and is therefore of low distensibility

Left atrial pressure varies throughout the cardiac cycle. The V-wave occurs during ventricular systole peaking at 6–12 mmHg, while the A-wave occurs during atrial contraction peaking at 4–16 mmHg. Mean LAP is between 2–12 mmHg

LV end-diastolic pressure occurs following atrial contraction and immediately prior to the rapid increase in pressure at the onset of systole. LVEDP is normally between 4–12 mmHg

Due to the continuity between the LA, pulmonary veins and pulmonary vasculature, left atrial pressure can be measured by ‘wedging’ a balloon-tipped catheter within a distal pulmonary artery

Due to the wide range of pressure throughout diastole, LV filling pressures is used as a general term within this guideline to describe the pressures under which LV diastolic filling occurs—ie, normal versus elevated LV filling pressure

Describes the degree of myocyte stretch prior to LV contraction. As this cannot be measured directly by echocardiography, LV end-diastolic volume is considered a surrogate of LV preload. LV preload is increased by severe aortic or severe mitral regurgitation

Describes the resistance against which the LV fibres contract against in systole. Elevated systolic blood-pressure and aortic stenosis increase LV afterload

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Robinson, S., Ring, L., Oxborough, D. et al. The assessment of left ventricular diastolic function: guidance and recommendations from the British Society of Echocardiography. Echo Res Pract 11 , 16 (2024). https://doi.org/10.1186/s44156-024-00051-2

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Received : 18 September 2023

Accepted : 13 May 2024

Published : 03 June 2024

DOI : https://doi.org/10.1186/s44156-024-00051-2

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