Mitral leaflet in functional regurgitation: passive bystander or active player?

In a population-based study, mitral regurgitation (MR) has been found to be the most common form of valvular heart disease in the United States.1 The incidence of MR rises sharply at ≈65 years of age: moderate or severe MR is estimated to occur in 1% of the 55 to 64 age group, increasing to 6.4% for individuals aged 65 to 74 and to 9.3% for those older than 75.1 In view of the increasing life expectancy of the general population, we can anticipate encountering a substantial rise in the number of patients with hemodynamically significant MR. Because heart failure, ischemic heart disease, and other disorders affecting the left ventricle become more prevalent with older age, one can speculate that it is particularly functional MR that will contribute to the overall increase in MR cases, with the numbers caused by degenerative disease rising less dramatically with age. Article see p 334 As the rate of rheumatic disease has decreased dramatically in the Western world, degenerative disease, largely resulting from myxomatous degeneration, constitutes the most common reason for mitral valve surgery. The true incidence of functional MR, in which the primary cause of regurgitation does not originate from the leaflets themselves, is not well known. Many patients with functional MR never undergo surgery, and the disease can remain silent for some time or can be masked by the underlying pathology of the left ventricle and the coronary arteries. Functional MR is an entity that was poorly understood until some years ago. Whereas it was believed that in the setting of ischemic heart disease, MR is often caused by “papillary muscle dysfunction,”2 we now know that in the absence of rupture, isolated ischemia or even infarction of a papillary muscle rarely causes regurgitation3 unless accompanied by displacement of the …