Ischemic expansion during acute myocardial infarction and reversal by coronary reperfusion.

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 less than 0.01) and central ischemic epicardial (1.84 +/- 0.06 to 1.93 +/- 0.06 cm, p less than 0.05) segment lengths were significantly increased. There were no significant changes in segment lengths or wall thickness in the normal zone. After 2 hours of occlusion, there was significant diastolic left ventricular (LV) dilatation (LV area increased from 18.2 +/- 1.3 to 21.0 +/- 1.3 cm2, p less than 0.01). Furthermore, central ischemic endocardial and epicardial segment length changes from baseline to occlusion correlated significantly with LV dilatation (r = 0.56, p less than 0.003; r = 0.55, p less than 0.004 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)