Mitral valve prolapse and cerebral infarction.

SEVERAL RECENT REPORTS, including the one by Scharf et al. in this issue, have firmly established the association of mitral valve prolapse (MVP) and cerebral infarction, especially in young adults with unexplained stroke (table 1). It is not surprising that this association is more difficult to demonstrate in older stroke patients, in whom atheroembolic mechanisms predominate. Assuming that the incidence of MVP-associated cerebral ischemia does not vary with patient age, as suggested by Sandok and Giuliani in this issue, and even if one-third of all cerebral infarctions in young adults are related to MVP, the incidence of MVP-related strokes is only 1/100,000/year. In older adults who have a stroke incidence of 80/ 100,000/year, the contribution of MVP (estimated to be 1.25%) could easily be overlooked. MVP is an important cause of cerebral infarction in young patients with otherwise unexplained cerebral ischemia. Nevertheless, MVP-associated ischemia remains a diagnosis of exclusion and other causes of cerebral ischemia must be vigorously excluded before attributing stroke to MVP. Barnett et al. reported MVP as the only abnormality in 30% of unselected patients under age 45 with cerebral ischemia. In a population-based, retrospective survey of causes of cerebral infarction in 135 patients under age 40, MVP was the only association in 7 (5%). Smith and McKnight reported MVP as the presumed cause in 5% of 96 consecutive patients who were evaluated for cerebrovascular symptoms. It is clear that cerebral ischemia rarely occurs in unselected young adults with MVP. The apparent paradox found in the low risk of stroke in unselected people with MVP and the high prevalence of MVP in young patients with unexplained stroke, as noted by Jones et al. in this issue, is easily explained. Again assuming that one-third of stroke in young adults is due to MVP (probably an over-estimate), a stroke incidence of 3/100,000/year in patients under age 40," and a 6% prevalence of MVP in all young adults, it is quickly calculated that the risk of stroke in all young adults with MVP is only 1/6,000/year. Clearly, no prophylactic treatment to prevent stroke is warranted in asymptomatic people with MVP.