What's the BIG DEAL about Diastolic Dysfunction? Here's What....

Diastolic dysfunction is a very under-appreciated condition in medical practice. It's very important for the heart's overall purpose -- that is to pump an adequate amount of blood every minute (i.e. which should be around a 5 liters/min.) -- known as the Cardiac Output (CO). If the heart does not fill properly - that is, if the left ventricle -"the main pumping chamber of the heart" does not fill well in diastole, then it will not be primed well in order to pump enough blood when the left ventricle (LV) contracts in systole.

Diastole actually has two components (i.e. E' / A'). There is actually both a passive and active phase to diastole. In the first phase, the ventricles fill passively (i.e. blood flows from the atriums to the ventricles due to a pressure gradient differential between the atriums and ventricles, with the atrial pressure being higher than the ventricular) and actually for a normal, healthy patient, under around 60 years of age, this first phase should provide the majority of the blood volume filling. The second, active phase, is when the atriums contract (i.e. represented by the "P-wave" on an EKG; the first bump before the QRS complex). This phase completes the filling of the ventricles. In a normal patient, for example, a healthy, active 30 year old, the second phase should only consist of around 10-20% of filling, whereas the passive phase should provide 80-90% of the filling.

In the field of echocardiography, we measure the ratio of phases I & II of diastole as the E' / A' ratio. Once that ratio falls below 1.0, then a patient can be diagnosed with "diastolic dysfunction", meaning that the ventricles are no longer filling efficiently. Contrast that with some student athletes whom I've performed an echo on and their E' / A' ratio is around 2.1! Therefore, their heart fills quite optimally. You see, their ventricles are very flexible or pliable and present very little resistance to filling. In cardiology we say that their heart is very "compliant" (i.e. as opposed to non-compliant in the other example). 

The reason why that E' / A' ratio decreases with age is because the ventricular muscle fibers become stiffer and more restricted, which impinges on how well they receive the blood from the ventricles. Because of this, the second phase, atrial contraction has to do more work in filling the ventricles. With age, the arteries also become stiffer and less pliable. The way one can fight the onset of diastolic dysfunction is cardiovascular exercise, a heart healthy diet, getting enough Omega 3s (i.e. fish oil, cold water fish, flaxseed, etc.). And actually vigorous exercise is very beneficial because you are giving your arteries a "work-out". Your arteries have to expand to allow for the sometimes tripling of blood flow which occurs during exercise, so they are expanding and contracting.

Now, in extreme cases of diastolic dysfunction where a patient's ventricles become very stiff, they have high blood pressure, and hence, there is a great deal of resistance to ventricular filling, phase I of diastole contributes less to filling and I've seen cases where their E' / A' ratio drops to around 0.2. Many of these types of patients have Congestive Heart Failure (CHF). And actually studies have been done to demonstrate that in approximately 30% of heart failure cases, the underlying reason is diastolic dysfunction, NOT ventricular function. Meaning, these patients’ ventricles are contracting normally (i.e. have an ejection fraction (EF) of at least 55%), however their diastolic filling is very inefficient, straining the atrial muscle fibers. In-fact sometimes, I've seen with echo, that these patients’ ventricles are "hyper-contractile" (i.e. with an abnormally high EF of >80%; the normal upper limit is 70%).

The reason why I think this condition is not given much attention in clinical practice (i.e. outside of cardiology and echocardiography) is that it is hard to diagnose. The physician may hear changes with auscultation, but it is hard to measure without performing an echo on the patient. A practitioner cannot measure diastolic function with an EKG. It is a hemodynamic consequence. But, the thing is, you are not going to send every patient with diastolic dysfunction for an echo. It's actually normal with age, starting at around 60 years of age (i.e. a general approximation subject to variability for each individual patient), to have declining compliance or an E' / A' ratio which falls close to 1.0 or slightly below.

I write this to educate people about this important condition and to highlight some of the key parameters around it. Throughout my echo career, I've been passionate about educating those outside of echo about the clinical implications of diastolic dysfunction. I've actually gone out of my way to talk with medical residents about it and tried to convey this strongly to my echo students (i.e. I was formerly an echo teacher & instructor at a healthcare training institute). The reality is, is that, many internists in the U.S. do not have the awareness level that they should with regard to this condition. I think because it's a vague thing. There's really no surgery to cure this and it's hard to medicate. From what I’ve read, the best cure for diastolic dysfunction is to engage in regular exercise / physical activity. I've actually read that you can improve your diastolic function through exercise.

If you have an interest in learning more about this condition, here are some articles which shed additional light on this topic:

“New Concepts in Diastolic Dysfunction and Diastolic Heart Failure: Part I”, Michael R. Zile and Dirk L. Brutsaert, Circulation, American Heart Association, 2002; 105: 1387-1393

“The less familiar side of heart failure: Symptomatic diastolic dysfunction”, Spencer A. Morris, PharmD, BCPS, Mark Van Swol, MD, Bela Udani, MD, The Journal of Family Practice, 2005 June; 54(6): 501-511

Please share this information with others who can benefit from it. I'm on a mission to educate as many people as I can about this important issue!