Intermittent complete atrioventricular block masquerading as epilepsy in the mitral valve prolapse syndrome.

A 24-year-old white man had a history of "epilepsy" since the age of eight years. Prolapse of the mitral valve was documented by auscultation and echocardiographic and left ventriculographic studies. At 120 hours after stopping therapy with phenobarbital and diphenylhydantoin (Dilantin) sodium, continuous electrocardiographic monitoring (Holter monitor) revealed episodes of complete atrioventricular block lasting up to 23 seconds. The results of hemodynamic studies were normal. The patients' symptoms were all totally corrected by implantation of an epicardial demand pacemaker. This report raises the possibility that sudden death in association with the mitral valve prolapse syndrome may be due to intermittent severe disturbances in conduction, in addition to ventricular arrhythmias.