Characterization of Transmural and Subendocardial Infarction by Typing and Grading of Ischemic Lesions in Autopsied Human Hearts

Abstract

Two types of myocardial infarction, transmural and subendocardial, were macroscopically examined, and the gross and microscopic findings were correlated. The transmural type usually consisted of yellowish-brown coagulation necrosis in the center of an infarcted focus and coagulative myocytolysis at the marginal zone. The subendocardial type was characterized by coagulative myocytolysis throughout the entire focus. Wavy fiber and colliquative myocytolysis of non-specific ischemic lesions were seen only microscopically in both peripheral and subendocardial areas of infarcted foci. Coagulation necrosis was associated with obstructive thrombus formation in 79% of cases as a result of absolute ischemia in the transmural type. Coagulative myocytolysis was associated with obstruction by plaque hemorrhage in 27% of cases, and multivessel disease was frequently encountered in the subendocardial type due to insufficient blood supply. Based on histochemical and immunohistochemical examinations, the ischemic lesions were graded in descending order of coagulation necrosis, coagulative myocytolysis, wavy fiber, and colliquative myocytolysis. The close relation between coagulation necrosis and the transmural type as well as that of coagulative myocytolysis with the subendocardial type suggests two different pathogenetic mechanisms of transmural and subendocardial infarction.