The enigma of the risk of stroke in mitral valve prolapse.

THE POSSIBILITY THAT A COMMON CARDIAC ABNORMALITY, mitral valve prolapse, might be responsible for embolic stroke has generated substantial interest and controversy among cardiologists and neurologists. The interest reflects the hope for a measure of stroke prevention in specific individuals but the controversy surrounds our inability to produce absolute proof that a true relationship exists. Evidence linking the two disorders is compelling" and is supported further by the article of Barletta et al contained in this issue (219-223). However, the difficulties involved in establishing the relationship revolve around several issues touched on by the letter of Hart and Sherman (334). The occurrence of stroke in mitral valve prolapse (MVP) patients is indeed a rare event. Numerous studies, including those of the Framingham group, have set the incidence of mitral valve prolapse in the otherwise normal adult population at about 5-7%. This reported incidence has been demonstrated in echocardiographic studies of various population groups and agrees with the autopsy incidence of 7.4% identified by Lucas and Edwards in a series of 1376 deaths at a community hospital. Yet despite the common occurrence of this valvular lesion, the risk of stroke in someone with mitral prolapse and the factors governing that risk remain unknown. Originally, the relationship of mitral valve prolapse with stroke was suggested not by examining a group of MVP patients but by examining a group of young stroke patients for evidence of an associated cardiac lesion.In those studies, an unexpected number of patients were found to have mitral valve prolapse. It should be remembered however, that in many patients the heart was shown to be normal and the etiology of the stroke remained a mystery. In those studies, 15% of the subjects had no identifiable lesion to account for their stroke and, in Barletta's series, 35% are similarly identified. Mitral valve prolapse is