[Coronary atherosclerosis in acute myocardial infarct. Anatomic profile of diverse causes of death]

Abstract

Objective: to study the degree of coronary obstruction by atherosclerotic plaques in a population dying with acute myocardial infarction. We defined subgroups by the degree of the obstructive lesion and compared the severity and distribution of coronary atherosclerotic lesions in different groups according to cause.

Study design: systematic prospective study in patients dying in the acute phase of myocardial infarction in a University Hospital Coronary Unit during a four years period.

Population and methods: we studied 193 patients corresponding 77% of the patients dead in the same period. 24 patients were excluded by technical reasons related to the preparation of necropsic material. The clinical protocol included 64 parameters and were considered the following causes of death: left ventricular failure (shock or acute pulmonary edema), left ventricular free wall rupture, interventricular septum rupture, primary asystole, pulmonary embolism and ventricular fibrillation. To study of the heart we performed the transverse slices technic after fixation; to study the epicardial coronary arteries we isolated the coronaries after fixation and made 5 mm transverse slices. The slices were macroscopic and microscopic evaluated for the degree of coronary obstruction in every 5 mm segment. We classified the degree of coronary obstruction in five grades: less than or equal to 25%; greater than 25% e less than or equal to 50%; greater than 50% e less than or equal to 75%; greater than 75% e less than 100%; and total obstruction.

Results: the degree of coronary obstruction in each epicardial segment were: Right ostium--grade I = 21%, grade II = 46%, grade III = 26%, grade IV = 7%, grade V = 0; Right coronary--grade I = 5%, grade II = 10%, grade III = 19%, grade IV = 28%, grade V = 38%; Left ostium--grade I = 27%, grade II = 50%, grade III = 19%, grade IV = 4%, grade V = 0; Left main--grade I = 16%, grade II = 43%, grade III = 28%, grade IV = 10%, grade V = 2%; Anterior descendent--grade I = 1%, grade II = 5%, grade III = 11%, grade IV = 34%, grade V = 49%; Left circumflex--grade I = 2%, grade II = 14%, grade III = 22%, grade IV = 40%, grade V = 22%. The number of coronary arteries with more than 75% obstruction for each group of one, two or three vessel disease were: 1 vessel--41 cases; 2 vessels--56 cases; 3 vessels--68 cases. The number of vessels with more than 75% obstruction for each cause of death were: Wall rupture--1 vessel = 20, 2 vessels = 18, 3 vessels = 11; Septum rupture--1 vessel = 0, 2 vessels = 2, 3 vessels = 2; Shock--1 vessel = 12, 2 vessels = 21, 3 vessels = 30; Acute pulmonary edema--1 vessel = 1, 2 vessels = 9, 3 vessels = 7; Asystole--1 vessel = 4, 2 vessels = 1, 3 vessels = 8; Pulmonary embolism--1 vessel = 2, 2 vessels = 5, 3 vessels = 8; Ventricular fibrillation--1 vessel = 2, 2 vessels = 0, 3 vessels = 2.

Conclusion: in most patients dying with acute myocardial infarction, the coronary atherosclerotic lesions were present in two or three epicardial coronary arteries. The left anterior descendent artery was the more frequent artery with major lesion (greater than 75%). Major atherosclerotic lesion in just one vessel were more frequent in patients dying by cardiac rupture.