Ischemic expansion during acute myocardial infarction and reversal by coronary reperfusion

Abstract

Previous studies have shown that infarct expansion occurs at least 1 day after a large transmural infarction. To assess whether regional left ventricular expansion is evident within hours of an acute myocardial infarction, 25 adult mongrel dogs underwent left circumflex coronary artery occlusion for 2 hours and 22 of these were subsequently reperfused. Two-dimensional echocardiography was used to record left ventricular topography and function at baseline, at 2 hours of occlusion, and following reperfusion. Short-axis midpapillary echocardiograms were analyzed using a microcomputer digitizing routine by establishing a 360-degree circumferential map of the left ventricle. The central ischemic zone was defined as that region with the most depressed contractility after 2 hours of occlusion, and the normal zone was set at 180 degree away from the central ischemic zone. Endocardial and epicardial segment lengths and wall thickness were measured for both the normal zone and the central ischemic zone at end diastole. After 2 hours of occlusion, diastolic central ischemic endocardial (1.3 +/- 0.05 to 1.42 +/- 0.04 cm, p p 2, p r = 0.56, p R = 0.55, p < 0.004 respectively). Following 2 hours of reperfusion, central ischemic endocardial, epicardial, and LV area decreased significantly and approached baseline values. We conclude that ischemic expansion exists and can be identified using two-dimensional echocardiography; that it occurs early following coronary artery occlusion; and that it is reversed by reperfusion.