Clinicopathological study of myocardial infarction with normal or nearly normal extracardiac coronary arteries. Quantitative analysis of contraction band necrosis,coagulation necrosis,hemorrhage, and infarct size

Summary In order to clarify the pathogenesis of acute myocardial infarction (MI) in hearts with normal coronary arteries, infarct size, and the extent of contraction band necrosis (CBN), coagulation necrosis, and hemorrhage were quantitatively examined using an image analyzer in 5 autopsy cases of MI with normal or nearly normal extracardiac coronary arteries. One patient died 40 h after acute MI. A second patient with acute MI due to severe spasm of segment 6, confirmed by cineangiography, died three days later. The third patient had already suffered a subarachnoid hemorrhage, and died 10 h after the onset of acute MI. The fourth patient had aortic stenosis and regurgitation. She developed acute MI due to total occlusion of segment 6, confirmed by cineangiography 4 h after the onset, and died 61 days later. Autopsy revealed old anteroseptal MI with normal coronary arteries and valvular thrombi. The fifth patient had a malignancy, and died one day after the onset of acute MI. Autopsy revealed multiple occlusive thrombi in the small intramural coronary arteries of the left ventricular wall supplied by segment 14, without any stenosis in the feeding vessel. Most infarcts were localized in the territory supplied by 1 or 2 of the 3 epicardial coronary arteries, and coincided with the clinically diagnosed infarct site. The infarct size ranged from 3%–26% of the left ventricular wall, and infarcts were generally localized to the inner third of the wall (67±20%). Histological examination of the four patients with acute MI revealed diffuse CBN (86±14% of the infarcted area) and/or hemorrhage. The findings suggested that MI associated with normal coronary arteries was caused by transient coronary arterial occlusion due to spasm and/or thromboembolism, with the CBN seen in these hearts representing reperfusion injury.