Evaluation of Diastolic Function: How Practical Is It?

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Statins may have a favorable pleiotropic effect on diastolic function19; statins and beta-blockers in patients with heart failure and preserved LVEF may prevent mortality.12 Statins have been used for heart failure patients using ACE inhibitors, but mostly in patients whose LVEFs have been low.

And finally, there are some interesting studies20,21 showing that sildenafil, which has a phosphodiesterase-5A–inhibition effect, may suppress chamber and myocyte hypertrophy in animal models and clinical studies. These studies have found that endothelium-receptor antagonists, when added to standard therapy, did not improve outcomes.

Now, I would like to go to the next topic, some of the newer echocardiography evaluators of diastole, which I think should be very interesting. Dr. Doukky, do you have any comments about this? What is new in echocardiography for diastole evaluation in terms of evaluation of strain?

DR. DOUKKY: Myocardial strain assessment does provide additional information in the assessment of systolic and diastolic function. Strain imaging can uncover systolic impairment that may not be apparent by simply looking at the EF.

Furthermore, it may also be helpful in assessing diastolic function to some extent, since tissue Doppler imaging is limited by a couple of factors. First, it has the angle-dependency problem, which leads to underestimation of the measured velocities. Second, tissue Doppler may be erroneously normal due to the translational motion of the heart. These 2 factors may lead to errors in the tissue Doppler assessment of diastolic function.

Strain imaging, on the other hand, implements speckle-tracking technique, rather than Doppler, to evaluate the displacement of 2 echo speckles within the myocardium relative to each other. Therefore, it is not affected by the angle-dependency problem or the translational motion of the heart. Strain imaging, however, is not widely used clinically in the assessment of diastolic impairment.

DR. LIEBSON: Dr. Tracy, about what Dr. Doukky has said, do you feel that in the next 5 years, the evaluation of strain and strain rate would be important as a general adjunct in the echocardiography laboratory or just as a research tool?

DR. TRACY: I think that in the next 5 years, if the technology across the vendors can become reproducible, the strain and strain rate could be very valuable. To elaborate a little on what Dr. Doukky was saying, if you only look at mitral inflow or tissue Doppler, there are absolute limitations.

One is age, because we know that beyond the age of 65 years, mitral valve inflow pattern alone becomes less reliable as a tool. We also haven’t talked about the fact that if a patient has a prosthetic valve or a significant amount of mitral annular calcification, tissue Doppler becomes unreliable.

So, I definitely think that the limitation on strain and strain rate indices is due to a few factors. One of the limitations is that the specific indices are not reproducible by all of the vendors. So, we cannot reproduce what one vendor is doing with another vendor’s equipment, and thus, we rely on information that is vendor specific. This results in confusion and bias.

The other limitation is that there is a learning curve with new and evolving technology. In addition, with the currently available equipment, a long time may be required to obtain accurate information. In order to implement strain and strain rate into our everyday workflow, the sonographers, fellows, and faculty must be adequately trained and the time necessary to measure these indices accurately must not be fraught with hindrance and limitations.

DR. LIEBSON: Thank you, Dr. Tracy. Just for the sake of completeness, magnetic resonance imaging (MRI) has been used for diastolic dysfunction. Do either of you have any comments about the use of MRI? Not that it would be an everyday procedure, but any comments on the benefit, if any?

DR. TRACY: MRI is the ideal method to quantitate LV mass and volume. However, I don’t believe the current technology by means of MRI can surpass what can be assessed by echocardiogram based on scientifically proven measures, reproducibility, timeliness, and cost. Finally, there’s still the issue of patients who cannot undergo MRI because of prosthetic equipment and/or claustrophobia.

The images and the information that are obtained from a cardiac MRI are great, but in my opinion, their use will be more related to research rather than every day clinical practice.

DR. LIEBSON: Nonetheless, there is valuable information in certain situations where MRI can provide information on diastolic dysfunction.

DR. TRACY: I agree with you completely, Dr. Liebson. Extrapolating your question of where we think MRI may be going in the next 5 years, I remember talking about cardiac computed tomography (CT) and cardiac MRs 20 years ago and thinking that this is a big thing and that echocardiograms were going to become obsolete. I couldn’t have been further from the truth. I do believe that the data obtained from cardiac CT and cardiac MR will also continue to grow, but you are not going to be able to get around the limitations of prosthetic devices. There are newer prosthetic devices (artificial heart valves and pacemakers), which will not be perturbed by the MRI procedure, but we will still have many generations of patients with prosthetics that can’t safely utilize this advanced cardiac imagery.

There are also patients who are claustrophobic. Finally, the way our healthcare system is going, these other advanced imaging procedures are not portable and are expensive. They will never take the place of a good echocardiogram. They will be able to add data to a patient’s clinical scenario. You may do it to confirm a diagnosis, but with the speed and accuracy in which echocardiography is continuing to advance, I don’t believe you’re going to need either of those 2 modalities to make a diagnosis, specifically, for diastolic function and valvular pathology.

DR. LIEBSON: Well, I would like to thank you both for an excellent discussion. Are there any final words either of you have on this topic?

DR. TRACY: As new technology and new areas in echocardiography are developing, it would be important to make sure that we are educating our sonographers and educating our fellows, so that if they do a complete echocardiography with the latest technology, we will be able to deliver the information to the referring physician.

I think that at an academic institution, such as Rush Medical College, we have a great service offer for our sonographers and fellows to make sure that we’re educating them, so that they’re able to understand diastolic function and dysfunction and are able to develop the technology.

DR. DOUKKY: I completely agree with Dr. Tracy, and I would like to stress again that it is important for us to report diastolic function, particularly the filling pressure status, as it is most useful clinically. It is important, within every institution, to have some sort of agreement on what elements of diastolic function to report clinically. The American Society of Echocardiography (ASE) guidelines22 on the evaluation of diastolic function are probably our best resource for that.

In addition, it is important to educate our referring physicians on the meaning and implications of various terms commonly used in the description of diastolic function.

DR. LIEBSON: Thank you both for an excellent discussion. Let me just summarize our discussion. There is no question of whether diastolic dysfunction is important not only in its prevalence, but also as a prognostic indicator, especially in patients with normal systolic function. The important thing is that clinicians must know how to interpret the results of echocardiography, which, again, currently is the gold standard, the easiest way to determine diastolic function or dysfunction.

At present, I think the major concern that many clinicians have is that they do not understand what the echocardiographic findings mean, and it is extremely important for the echocardiographers to educate their clinicians, so that they know how to interpret the echocardiographic report. Nonetheless, there will be some excellent, important, new findings in echocardiography over the next few years. We have touched upon some of them, and I feel echocardiogram will remain an important procedure for evaluating cardiac function, especially in diastole.

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