Pathology of the myocardium and the conduction system in sudden coronary death

This review summarizes previously unpublished and recently published autopsy findings of prehospital sudden coronary death (SCD) in four different counties (Olmsted, Minnesota; Albany, New York; Dade, Florida; and San Francisco Bay Area, California), totaling 868 patients. The prevalence of cardiomegaly and significant coronary atherosclerosis, and the relative infrequency of acute coronary thrombosis in prehospital SCD, well documented in the past, have been reaffirmed in current studies. Differences in the patient populations and laboratory techniques notwithstanding, these independent autopsy studies showed that 62% to 74% of cases of SCD had either acute or old myocardial infarction (MI); the incidence of acute MI ranged from 12% to 47%, and that of old MI from 22% to 53%. The prospective autopsy study of 120 Olmsted County SCD cases showed that among those with established acute MI, subendocardial lesions outnumbered transmural lesions by the ratio of 2:1, and the infarcts ranged in histological age from less than 24 hours to 4 weeks. Evidence of acute myocardial ischemia, as determined by the histological criteria of myofibrillar degeneration, sinuous fibers, and positive HBFP staining, was present in 52% to 81% of patients. Such high incidence of myocardial ischemia is compatible with the proposed mechanism of the terminal event in SCD, namely ventricular fibrillation or asystole, and underscores the importance of presymptomatic diagnosis of coronary heart disease. The lack of specific or acute anatomical lesions in the conduction system in SCD, however, does not preclude the possibility of bradyarrhythmias occurring shortly before death.