Pathobiology of sudden death: coronary causes

The single most common cause of sudden death in the western world is coronary artery disease. Sudden death from coronary causes occurs equally in asymptomatic patients, patients with angina, and patients with a known history of myocardial infarction. The mechanism of sudden coronary death in most patients is ventricular fibrillation secondary to ischemia. Microthrombi in intramyocardial coronary arteries may also play a role. Instability of atherosclerotic plaques, in terms of thrombosis and vasoreactivity, underlies the syndrome of unstable angina as well as many cases of acute myocardial infarction. Sudden coronary death falls within this spectrum of ischemic heart disease. Development of these syndromes depends on the abruptness of onset and the completeness and duration of coronary occlusion. Thus a rapidly evolving coronary artery lesion, with plaque fissure, rupture, and luminal thrombosis, can lead to myocardial ischemia, with fatal electrical instability of the myocardium as the first clinical manifestation. The diagnosis of sudden coronary death in the absence of myocardial infarction is determined by the degree of coronary artery narrowing and the exclusion of other causes of death. The presence of acute coronary artery lesions, which may be present in a significant number of sudden coronary death patients, lends support to the pathologic diagnosis. Thus the coronary arteries in victims of sudden coronary death may exhibit established atherosclerotis or acute lesions, whereas the myocardium may appear normal or show healed or acute infarction or hypertrophy. Although less common, nonatherosclerotic coronary artery diseases can account for sudden death as well, particularly in younger patients. Therefore, when sudden death occurs in children and young adults, coronary causes related to congenital anomalies, fibromuscular dysplasia, arteritis, or metabolic diseases should be considered.