Monday, June 16, 2014

The vicissitudes of mitral valve prolapse

MVP was once thought to be rare and was under recognized. It became much more commonly diagnosed in the 1970s due to a couple of developments. First, it was realized that early systolic clicks were commonly of mitral origin and not always of aortic origin. Secondly, M mode echocardiography was coming into common usage and criteria were developed. Fascination with the condition increased as it was purported to be associated with cardiomyopathy, cerebral ischemic events, arrhythmias, skeletal abnormalities, sudden cardiac death and a variety of minor maladies. For a while in the 1980s it seemed that the condition had increased to pandemic proportions. Was it a case of true increase in incidence or just increased recognition? Actually it was more complex than either of those. Interest in the condition rose then waned. This graphic from PubMed shows the number of citations by year through the span of 1966 through 2012. Publications peaked in 1985.

Over the last two decades we have achieved clarity due largely to two developments. First was refinement of the original echo criteria which lacked specificity for patients who truly had degenerative change of the valve leaflets or supporting structures. Second was the realization that we had been inappropriately lumping diverse groups of patients under the category of MVP. As our understanding of the condition evolved it became apparent that there were two main groups of patients, one with true MVP characterized by pathologic changes in the valve or supporting structures. The other group, perhaps the more commonly diagnosed, represented a dysautonomia, a hyperadrenergic state. The resulting hyperdynamic state of the heart could give the appearance of prolapse under the old echocardiographic criteria and be associated with clicks and murmurs. The current thinking is that, while there may be some overlap, many patients in this second group do not have valvular pathology.

So what is this hyperadrenergic state? It's a condition that's been recognized for over a century but under different names, as discussed in Wooley's classic paper from1976. These names included DaCosta's syndrome, effort syndrome and, by the early 70s, neurocirculatory asthenia. Over the following decade it became incorporated with MVP only to split off again as our understanding grew. Now many of these patients are labeled as postural orthostatic tachycardia syndrome (POTS).

The current thinking on true MVP is summarized in this paper. It makes the point that while the severity and complications of MVP are variable they depend, in our current understanding, almost entirely on the severity of mitral regurgitation.

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