We retrospectively reviewed 52 hearts from patients who had heart valve replacement more than one month prior to death. In 37 cases death was sudden (less than 6 hours after symptoms). These 37 cases were divided as Group I (15 cases, sudden death related to valve prosthesis); and Group II (22 patients, sudden death not related to valve prosthesis). Causes of death in Group I were valve thrombosis (n = 4), embolization of valve thrombi (n = 2), strut fracture (n = 2), anticoagulation-related hemorrhage (n = 2), perivalvular fistula (n = 1) and left ventricular outflow obstruction (n = 1). Causes of death in Group II were presumed arrhythmia in 14, myocardial infarction in six and aortic rupture in two cases. Severe coronary atherosclerosis (> 75% cross-sectional area luminal narrowing) was present in five of 14 cases dying of arrhythmia and in all six cases with myocardial infarction; in the remaining cases, there was marked cardiac hypertrophy (mean weight 728 +/- 177 grams). The mean age (54 +/- 18 vs. 54 +/- 13 years, respectively) was similar in both groups. Seven of 21 deaths after aortic, 6/12 deaths after mitral, 10/25 deaths after mechanical, and 5/11 after porcine valve replacement were secondary to valve complications. The mean left ventricular thickness was 1.7 cm in both groups, the mean left ventricular cavity dimension 2.8 +/- 1.4 cm in Group I vs. 3.5 +/- 1.4 cm in Group II, and the mean heart weight was 550 grams in Group I vs. 734 +/- 211 in Group II (p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)