Morphologic comparison of frequency and types of acute lesions in the major epicardial coronary arteries in unstable angina pectoris, sudden coronary death and acute myocardial infarction

The frequency and type of acute lesions in the four major (right, left main, left anterior descending, left circumflex) epicardial coronary arteries were examined at necropsy in 14 patients with unstable angina pectoris, 21 patients with sudden coronary death and 32 patients with a fatal first acute myocardial infarction. None of the 67 patients had a grossly visible left ventricular scar (healed myocardial infarct) and only the group with acute myocardial infarction had left ventricular myocardial necrosis. Although the frequency of intraluminal thrombus was similar in patients with unstable angina (29%) and sudden death (29%) and significantly lower than in those with acute infarction (69%) (p = 0.02), the thrombus in the patients with unstable angina and sudden death consisted almost entirely of platelets and was nonocclusive, whereas the thrombus in the group with acute infarction consisted almost entirely of fibrin and was occlusive. The frequency of plaque rupture was insignificantly different in the groups with unstable angina (36%) and sudden death (19%), and was significantly lower than in the group with acute infarction (75%) (p = 0.02). The frequency of plaque hemorrhage was insignificantly different in the groups with unstable angina (64%) and sudden death (38%) and was significantly lower than in the group with acute infarction (190%) (p = 0.04). The frequency of atherosclerotic plaques containing multiluminal channels was similar in patients with unstable angina, sudden death and acute infarction (100%, 81% and 90%, respectively), but the percent of 5-mm long segments of the four major coronary arteries containing multiluminal channels (probably the result of organization of thrombus) was greatest in the unstable angina pectoris group (12% vs. 7% vs. 1%, respectively: p = 0.04). Thus, the frequency of thrombus, plaque rupture and plaque hemorrhage in the coronary arteries among patients with unstable angina pectoris and sudden coronary death was similar and significantly less than in the patients with acute myocardial infarction. The type of thrombus and the amount of lumen obstructed by thrombus were similar in the groups with unstable angina pectoris and sudden coronary death and quite different from those in the group with acute myocardial infarct group.