Comparison of degree and extent of coronary narrowing by atherosclerotic plaque in anterior and posterior transmural acute myocardial infarction

The percentage of cross-sectional area narrowing by atherosclerotic plaques in each 5-mm-long segment of the right, left main, left anterior descending and left circumflex coronary arteries was determined at necropsy in 50 patients who died of a first acute transmural myocardial infarction (AMI). The amount and extent of the coronary narrowing were compared in the 2 patients with anterior wall AMI and in the 28 patients with posterior wall AMI. Although the percentage of coronary arteries narrowed 76-100% was similar in the anterior and posterior wall AMI patients (74% vs 75%; average 3.0 of 4 coronary arteries per patient), the patients with anterior wall AMI had less severe narrowing of each of the 5-mm segments of the four major coronary arteries than did the patients with posterior wall AMI. Of the 1166 5-mm coronary segments examined in the 22 anterior wall AMI patients, 23% were narrowed 76-100% in cross-sectional area by atherosclerotic plaque, and of the 28 patients with posterior wall AMI, 39% of the segments were 76-100% narrowed (p<0.001). Among the anterior AMI patients, a higher percentage of the 5-mm segments of the left anterior descending coronary artery was severely (> 75%) narrowed than either posterior perfusing coronary artery. The percentage of segments narrowed 76-100% for each of the major coronary arteries in the posterior AMI patients, however, was similar. Thus, our necropsy patients with posterior wall AMI had more extensive and severe coronary artery narrowing than did our patients with anterior wall AMI. If the coronary arteries had not been examined quantitatively, this difference in severity would not have been apparent.