Infective endocarditis and mitral prolapse: a comparison with other types of endocarditis.

We compared clinical features, response to therapy, and outcome of infective endocarditis in ten patients with mitral valve prolapse and 23 patients with endocarditis involving other types of left-sided valvular lesions. Signs of endocarditis were more subtle in patients with mitral valve prolapse, and antimicrobial therapy was instituted later in those patients. Nevertheless, nine of ten patients with mitral valve prolapse and endocarditis responded optimally to antimicrobials; only five of 23 patients with other types of endocarditis responded similarly. Four patients with mitral valve prolapse experienced increasing valvular dysfunction during the year after treatment of endocarditis; one died. We conclude that endocarditis in patients with mitral valve prolapse is more responsive to antimicrobial therapy even though recognition of the infection often is delayed. However, mitral valve prolapse endocarditis is not a benign infection, because progressive valvular dysfunction is a frequent sequel.