Infective endocarditis complicating mitral valve prolapse: epidemiologic, clinical, and microbiologic aspects.

Cases of infective endocarditis superimposed upon prolapsing mitral valves were first described two decades ago. In the intervening years 72 reports in the English-language literature have described 267 such cases. Men predominated numerically in cases occurring after the age of 40 years and in surgical and autopsy series. In cases with auscultatory abnormalities documented before the onset of infective endocarditis, murmurs-and not merely isolated systolic clicks--were usually present. Complications of infective endocarditis were relatively common, and at least 42 patients required valve replacement in the acute phase of illness or during convalescence. Although viridans streptococci were the most frequent etiologic agents (46% of cases), deaths occurred primarily among patients infected with other organisms and among those over 40 years of age. Mitral valve prolapse is increasingly being recognized as a precursor of infective endocarditis because of its high prevalence in the general population and the wider availability of echocardiographic diagnostic techniques. The risk/benefit and cost/benefit ratios for endocarditis prophylaxis in patients with prolapsing mitral valves remain controversial.