DR. LIEBSON: I am Dr. Philip Liebson from the Section of Cardiology, Rush University Medical Center, Chicago. I am joined today by two of my colleagues from the Section of Cardiology and Echocardiography: Dr. Rami Doukky, Associate Professor of Medicine, Radiology and Dr. Melissa Tracy, Associate Professor, Cardiology, both of whom have been very active in the area of echocardiography.
The topic for discussion is “Evaluation of Diastolic Function, How Practical Is It?” and encompasses an area in which there has been much research and, I have to admit, much confusion. If you have seen the report of an echocardiogram on one of your patients with the information on diastolic function, indicating “impaired relaxation,” “pseudo-normal function,” or “reversible or fixed restrictive dysfunction,” you may have wondered what it means, especially when accompanied by a normal left ventricular ejection fraction (LVEF). We will consider the importance of these findings and the role of diastolic dysfunction and diastolic heart failure in the management of cardiac patients, especially when systolic performance is considered to be normal. We will also discuss some of the more recent advances in the evaluation of diastolic function in echocardiography and other noninvasive measurement.
Let’s start out with the question, what is the importance of diastolic function?
DR. DOUKKY: Diastolic function assessment sheds light on left ventricular (LV) performance beyond systolic function. Clinicians are often fixated on the EF, which is certainly important and many of our management decisions are based on it. However, cardiac function is not completely summed up in the EF. A good deal of information about contractility could also be assessed by other means such as myocardial strain, but this is not the subject of our discussion today.
Diastolic function assessment, on the other hand, provides additional insight, particularly in symptomatic patients. It helps us better understand the physiology in patients with normal or impaired systolic function by providing additional information regarding the loading condition of the patient, ie, the LV filling pressure. It also provides valuable prognostic information beyond EF.
DR. LIEBSON: Dr. Tracy, what is the difference between the terms diastolic dysfunction and diastolic heart failure? Is there an important difference?
DR. TRACY: I would like to echo a couple of points that Dr. Doukky stated. The reason why we need to discuss diastolic function on every echocardiogram is that diastolic dysfunction (abnormal filling/relaxation) is present in virtually all patients with heart failure. In addition, 50% of patients who are admitted for congestive heart failure (fluid overload) actually have normal LVEF, ie, normal pumping function to their heart, but abnormal diastolic function coupled with signs and symptoms of heart failure, ie, diastolic heart failure.1
If the echocardiogram comes back and the referring physicians read “normal systolic function or normal LVEF” with no mention of diastolic function, they may immediately think that this patient does not have any issues regarding the filling/relaxation of the heart and/or cardiac etiology for the heart failure symptoms, which would be incorrect. If we avoid and ignore the fact that there are both systolic (pumping) and diastolic (filling) physiological factors working together for hemodynamic stability as well as other parameters such as those in a physical exam, chest radiograph, and biomarkers, we may actually not treat our patients appropriately. These patients will definitely have progression of disease with admissions/readmissions for heart failure and a worse risk of mortality. Recently, an article2 in the Journal of Cardiovascular Translational Research identified several biomarkers in the plasma, which can be measured. These biomarkers included brain natriuretic peptide and markers of collagen homeostasis and fibrosis. Since there are several etiologies leading to diastolic dysfunction, it would be a reasonable conclusion that multiple biomarkers used independently and in combination will need to be followed to better diagnose, treat, and improve outcomes for patients with diastolic dysfunction.
Looking at all of the parameters of an echocardiogram for diastolic function is important. The difference between diastolic dysfunction and diastolic heart failure is that the latter presents with signs and symptoms consistent with heart failure in the absence of depressed LVEF. There are 4 different levels of diastolic dysfunction.
Therefore, what you were alluding to in your first statement, Dr. Liebson, is that we use these scientific words, but we don’t really know what they mean. I think it is important that the referring physicians understand that there are 4 different stages of diastolic dysfunction, and a patient can actually fluctuate between stage 1 to stage 3, but stage 4 tends to be irreversible.
Stage 1 is a mild form of diastolic dysfunction. At this stage, if, for example, the patient’s blood pressure is treated well, he/she may be able to prevent the level of diastolic dysfunction from progressing. Stage II, is called pseudonormal and is a moderate degree of diastolic dysfunction. Stage III and IV are severe forms of diastolic dysfunction, with stage IV typically being irreversible. Therefore, diastolic dysfunction is a big problem, and it is very important that we have discussions, so that when the referring physician gets the echocardiogram, he/she understands the verbiage.
DR. LIEBSON: I have to emphasize that diastolic dysfunction and isolated diastolic dysfunction are quite common, especially in the elderly, and there are population studies3–6 to indicate that at least half of the elderly with heart failure have LVEFs greater than 45%, and in some studies,3,7,8 diastolic heart failure is present, apart from systolic heart failure, in up to 75% of elderly patients.
DR. DOUKKY: I would like to elaborate on Dr. Tracy’s remarks. Heart failure is a clinical diagnosis manifesting with well-known signs and symptoms. This should not be confused with diastolic dysfunction, which is an echocardiographic finding not necessarily associated with clinical heart failure syndrome.
It is not unusual for some to confuse diastolic dysfunction with diastolic heart failure. When patients with preserved systolic function present with classic symptoms of heart failure, they are usually at more advanced stages of diastolic dysfunction, manifesting as diastolic dysfunction grade 2, 3, or 4 on echocardiography.
I agree with Dr. Liebson that the prevalence of diastolic heart failure is increasing among the elderly, especially at the community level. In referral centers, we tend to see more patients with systolic heart failure. At the community level, nonetheless, diastolic heart failure is certainly on the rise, particularly in the elderly. In our lifetime, diastolic dysfunction with preserved EF will probably be the most common cause of heart failure.
DR. LIEBSON: In every type of evaluation, you need to have a gold standard, and I would like to ask what we consider the gold standard to be for the evaluation of diastolic function.
DR. TRACY: The gold standard would definitely be echocardiography.
DR. LIEBSON: Can echocardiography be compared to another standard, which may be more direct? That really is the thrust of my question.
DR. DOUKKY: The “tau”, which can be measured with left-heart catheterization, is widely accepted as a standard invasive indicator of the rate of LV relaxation, while catheter-measured LV end-diastolic pressure is the gold standard for assessing the filling pressure. Certainly, no one uses these invasive tools for the routine assessment of diastolic function. Therefore, the practical gold standard remains echocardiography, which can reliably assess the state of diastolic function and the filling condition of the patient in the vast majority of the cases. Occasionally, conflicting diastolic indices may limit our ability to evaluate diastolic function echocardiographically. In such situations, invasive assessment is still an option.
DR. TRACY: In general, a lot of our measurements are based on cardiac catheterization, but if you look at the last 10 years, the amount and reproducibility of data that we can get from an echocardiogram allow you to evaluate filling parameters, valvular dynamics, and pressure gradients from the noninvasive and highly reproducible echocardiogram and compare it to the invasive cardiac catheterization.
We refer back to cardiac catheterization, but in the last 10 years, the area of echocardiography has exponentially grown to the point that you will have an invasive cardiologist and/or a surgeon come to echocardiography laboratory asking the echocardiographer to assist him/her with a particular case based on the findings from the echocardiogram. This is because, as Dr. Doukky mentioned, the information does not always fit together perfectly like a puzzle, so there are many different findings on the echocardiogram that should be looked at for classification of a patient’s report as normal or abnormal. If the echocardiogram is not normal, then where does the patient fit in the paradigm of diastolic dysfunction?
If you only focus on the mitral valve inflow or the tissue Doppler alone in a vacuum, you will have a difficult time accurately diagnosing diastolic dysfunction. I definitely want to echo what Dr. Doukky has said, that diastolic dysfunction is not a diagnosis that you can make at the bedside.
If you have a patient who does not have a history of systolic dysfunction or a weak heart muscle and is admitted with heart failure, the echocardiogram helps you decide whether the patient has systolic dysfunction, diastolic dysfunction, or a combination of systolic and diastolic dysfunction or heart failure and whether you need to look at possible pulmonary issues.
So, echocardiography is really paramount in being able to diagnose a patient’s condition correctly.
DR. LIEBSON: I would like to follow-up this discussion with what specifically are the echocardiography techniques for best assessment of diastolic function and what echocardiogram abnormalities are best to differentiate between diastolic and systolic dysfunction?