Sudden death occurs in a small but important subset of patients with mitral valve prolapse (MVP). Clinical criteria for identifying patients at risk for sudden death have been elusive. To determine if certain morphologic characteristics were present in hearts from patients with sudden cardiac death and MVP, autopsy hearts from persons with sudden death and isolated MVP who were previously asymptomatic or had a history of cardiac arrhythmias (n = 27) were compared with (1) hearts from patients with congestive heart failure (CHF) and mitral regurgitation (MR) secondary to MVP (n = 14), and (2) hearts from persons dying from non-cardiac causes in which MVP was an incidental finding (n = 19). Patients who died suddenly were younger than both patients with MR/CHF and incidental cases (37 +/- 10 vs 65 +/- 16 and 58 +/- 21 years, respectively, p less than 0.001). Mitral valve annular circumference, anterior and posterior mitral valve leaflet lengths, posterior mitral valve thickness, and presence and extent of endocardial plaque were greater in hearts from patients with sudden death than hearts from those with incidental MVP. Hearts from patients with MR/CHF weighed significantly more, had greater left and right atrial cavity sizes and left ventricular cavity diameter than hearts from both sudden death and incidental cases.