Q&A: The value of strain for echocardiography
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Professor Paul Leeson Professor of Cardiovascular Medicine at the University of Oxford and co-founder of Ultromics. |
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Director, Noninvasive Cardiac Imaging Laboratory |
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Clinical Research Fellow at the University of Oxford |
Current echocardiography guidelines from the ASE and other societies recommend strain as a valuable complement to traditional function parameters. [1]
In particular, decades of research has shown the importance of global longitudinal strain (GLS) to detect heart failure (HF), most notably heart failure with preserved ejection fraction (HFpEF). [2]
But these recommendations for GLS reporting might be challenging to navigate, especially with the extra time it can take to measure and analyze studies. This is not to mention variability issues: if we look at the same images with different operators and software vendors, we get different values that can affect diagnostic accuracy.
With this in mind, Ultromics brought together experts in the field for an FAQ session involving strain – including GLS – and how to successfully implement these measurements as part of routine diagnosis and risk stratification. Dr. Roberto Lang (University of Chicago) and Professor Paul Lesson (Oxford University and Chief Medical Officer at Ultromics) speak with moderator Dr. Rizwan Sarwar (Oxford University) about the clinical benefits of analyzing strain, when to use strain, and how new advances in technology have given clinicians the ability to interpret strain with accuracy, precision, and without additional time.
Below are some of the key takeaways from the FAQ session:
1. What Are the Clinical Benefits of Strain?
The use of strain in echocardiography increases diagnostic precision compared to ejection fraction (EF) alone, and has significant incremental prognostic value for predicting outcomes.
Dr. Lang mentions the importance of a holistic approach to analyzing strain. “I think that by using all the different components of strain, there's a lot of physiology and clinical things that we can learn.
“[I] was studying a patient with cardiac amyloidosis,” he continues, “and I was struck by the fact that this patient had preserved a left ventricular ejection fraction, but the global longitudinal strain was low.”
Dr. Lang and his team measured again, and they confirmed the finding.
“So there must be something that is making this patient preserve the ejection fraction despite the fact,” he says, mentioning the GLS was very low. “And we actually have now some software that allows us to look at the circumferential strain. And we did that and the circumferential strain was very high. So the preservation of ejection fraction was in this amyloid patient based on the fact that the circumferential strain was compensating for the longitudinal strain.”
As Dr. Lang illustrates, taking a more comprehensive look at strain and how interactions can affect reporting is key to successful risk stratification.
Dr. Lang additionally notes, “the left ventricular (LV) strain is the bread and butter. And it's part of the evolution from ejection fraction to measuring systolic function.”
2. When Should You Use Strain?
Both Dr. Lang and Professor Lesson agree that practitioners and clinicians should consider including strain measurements in routine reporting.
“When we're looking at left ventricular function, at the moment, we just rely on one EF measurement, which we've been doing since the dawn of echocardiography,” Dr. Lang says. “We used to do it with a method of discs (MOD) slice to get the measurement of how it changes in diameter. And it's been around a long time, but actually, it's one single measure. And what strain gives us . . . [is a] much more sophisticated look at how we're assessing left ventricular function.”
That extra information about LV functioning, Dr. Lang continues, should be used within a “holistic approach of understanding what's going on with the left ventricle.”
Professor Lesson also mentions that the evolving strain reporting technology allows for more regular implementation in diagnosis and risk stratification. “What we need to do is start reporting strain as a measurement and start working with it, because it's going to be there and it's available,” Professor Lesson says. “And then you start seeing, actually, if you have a normal EF . . . and you have normal strain, that gives you huge confidence about what you're looking at. Whereas actually, if you have a normal EF but the strain is a little bit different, then you can start to understand and start to explore a little bit about what might be going on. I think having this ability to handle strain as one of those metrics which we can work with is going to be great as uptake increases.”
Later in the chat, Professor Lesson says, “you could argue that actually, any patient receiving a left ventricular function assessment should receive a strain measurement as well.”
Dr. Lang adds, “In a busy lab in the United States, we do over a hundred records a day. So [it’s] very difficult to say we're going to do GLS only in certain patients. It's much easier if we do it on everybody, because if you start picking and choosing, it doesn't really work.”
3. How Easy Is It To Get Started Using Strain?
Professor Lesson says that a good starting point is to use global measurements in patients with LV function. “If it's abnormal and the EF is normal . . . it's no different from what we do if we get an ECG which has a bit of abnormality in it – you don't stop there. You start by understanding where there needs to be some further investigations.”
While current guidelines recommend measuring GLS alongside EF, there are some challenges to consider. [1] These include the extra imaging time and training needed to measure GLS, and ensuring low variability in strain analysis to accurately assess risk stratification.
Technology, however, has answered these challenges. AI in echocardiography allows for faster imaging time with zero variability. It can be adopted easily into any clinical practice and allows every healthcare professional to use strain alongside EF, even if you don’t have the infrastructure or resources to do so.
The unique concept of providing simplified reports, rather than having clinicians use software to manually calculate measurements and adjust contours, means strain can be used regardless of a user’s familiarity.
The right AI can be connected to any vendor, PACS or IT infrastructure, without the need for any upfront costs, updates to current software, or training. A technology like this is system-wide and can be deployed seamlessly without any disruption to clinical workflow.
4. How Can AI Help Clinicians Routinely Utilize Strain in Clinical Practice?
The value of strain in echo reporting is clear, and AI has answered the call to more easily implement strain in clinical settings. With AI, clinicians can evaluate strain without the manual effort, extra time, or potential variability in analysis. Busier clinics can quickly and accurately process studies without the need for extra staff training.
In responding to Dr. Sarwar’s question about the popular perception of high variability in strain reporting, Dr. Lang says, “I think that very few people have truly experienced state-of-the-art software that does these measurements in an automated way. If you experience that, you can see that the variability would decrease quite a lot.“
Learn More About the Value of Strain for Echocardiography
This article summarised some key takeaways from the Value of Strain Fireside Chat, however, Dr. Lang and Professor Lesson had many more insights during the webinar. These included stories from their own clinical experience of strain, how oncology patients are affected, and discussion on including a wider variety of subjects in future research.
You can watch the full webinar here to learn more about the value of strain to risk stratification, including how technology has shifted the echo reporting environment.
References:
- Edvardsen T, Asch FM, Davidson B, et al. Non-invasive imaging in coronary syndromes: recommendations of the European Association of Cardiovascular Imaging and the American Society of Echocardiography, in collaboration with the American Society of Nuclear Cardiology, Society of Cardiovascular Computed Tomography, and Society for Cardiovascular Magnetic Resonance. European Heart Journal - Cardiovascular Imaging. 2021;23 7.
- Nagueh SF, Smiseth OA, Appleton CP, et al. Recommendations for the Evaluation of Left Ventricular Diastolic Function by Echocardiography: An Update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. Journal of the American Society of Echocardiography. 2016;294:277–314.:e6–33.
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