Significance of coronary arterial thrombus in transmural acute myocardial infarction. A study of 54 necropsy patients.

In 54 necropsy patients with transmural acute myocardial infarction (AMI) and coronary arterial thrombi, histologic sections of coronary arteries that contained the thrombi were examined by video-planimetry to determine if the amount of luminal narrowing caused by thrombi was comparable to that produced by underlying atherosclerotic plaques, and to determine the amount of luminal narrowing by plaques immediately proximal and distal to the thrombi. The 54 coronary arteries in the 54 patients were narrowed 33-98% (mean 81%) by atherosclerotic plaque alone in cross-sectional area at the site of the thrombus (occlusive in 47 and nonocclusive in seven), from 26-98% (mean 75%) within the 2-cm segment proximal to the thrombus, and from 43-98% (mean 79%) within the 2-cm segment distal to the thrombus. Of the 54 arteries, 52 (96%) were narrowed 76-98% in cross-sectional area by atherosclerotic plaque alone at or immediately proximal or distal to the thrombus and 26 (48%) were narrowed 91-98% by plaque alone. The thrombi were 0.1--6.0 mm2 (mean 1.4 mm2) in cross-sectional area and the underlying atherosclerotic plaques were 3.0-21.0 mm2 (mean 8.7 mm2). Thus, among necropsy patients with transmural AMI, coronary thrombi occur at sites already severely narrowed by atherosclerotic plaques.