PATHOGENESIS OF CARDIAC RUPTURE FOLLOWING ACUTE MYOCARDIAL INFARCTION

摘要

Myocardial rupture is a known complication of acute infarction (Datta, 1975 and Becker, 1975). The morphological variation associated with this phenomenon can be explained by the formation of an endocardial tear followed by a dissecting hemorrhage. The model explains the correlation between rupture, hypertension, and the age of an infarct. However, it is incomplete as it fails to predict what causes the endocardial tear. Infarcted myocardium remains irreversibly more compliant than non-infarcted muscle and passive (Baroldi, 1991). Rupture usually occurs early post infarction, at the margin of the infarct, and is most often associated with transmural infarcts (Whittaker, 1991 and Lewis, 1969). This suggests that stress concentration effects, due to a material mismatch at the border of the infarcted and non-infarcted muscle, are the cause of an endocardial tear. Some degree of aneurysm formation is almost always present with acute infarction. Thus, a common mechanism exists between myocardial rupture post infarction and the formation of a left ventricular (LV) aneurysm. Because of the common mechanism in rupture and aneurysm formation, prior LV aneurysm models are reviewed. Radhakrishnan (1986) described an ellipsoidal shell model (Fig. 1) of the LV with isotropic layered walls. Myocardial rupture was not predicted with infarctions of less than 70% of the wall thickness. For a fixed LV geometry, increases in the angle-of-damage of the infarct were associated with a smaller thickness of infarction to avoid rupture. Similarly, for a fixed thickness of the infarct, increases in the angle-of-damage of the infarct were associated with larger ratios of b{sub}0/a{sub}0 to avoid rupture. Myocardial rupture was more dependent upon the percentage of infarcted wall thickness and LV shape than the angle-of-damage of the infarct. These generalizations were based upon average wall stress and deformations. Although insightful in general terms, insufficient detail in the stress distributions is available for correlation to the morphologic data for rupture.