The myxomatous mitral valve and sudden death.

The clincopathologic features of 14 cases of sudden death attributable to dysrhythmias associated with the myxomatous mitral valve are described. The patients were 14-59 years old (mean 27 +/- 11 years). Eleven were female and three male. Of the seven ECGs available, none showed prolongation of the QT interval, but two showed repolarization abnormalities. The material was classified according to the degree of prolapse in the pathologic specimen. When obvious prolapse was found, the expected auscultatory findings had been documented. In three cases there was minimal prolapse, casting some doubt on the hypothesis that traction on the papillary muscles or diastolic dumping of the leaflets may be implicated in the pathogenesis of the dysrhythmias. In one of the cases with minimal prolapse there was a strong family history of sudden death. Endocardial friction lesions were present in 11 cases, including two of the three with minimal prolapse. In five cases there was a thrombotic lesion in the angle between the posterior leaflet and the left atrial wall containing fibrin and platelets. These abnormalities may be important in the pathogenesis of the ventricular dysrhythmias.