Left ventricular dilatation after acute myocardial infarction is caused by infarct expansion and compensatory dilatation of noninfarct area. This study was done to investigate the contributory topographical change of left ventricle to left ventricular dilatation after acute myocardial infarction.

24 first acute myocardial infarction was studied with 2-dimensional echocardiography serielly. First study was done at 7days and second study was done 9 months after an infarction attack. Left ventricular volume was measured by Simpson's method in end-diastolic frame and change of end diastolic left ventricular surface area was measured in apical 4 chamber view. Left ventricular surface area was devided by ischemic(noncontraction) and nonischemic(contracting) area by connecting central point of long axis of left ventricle and the junction of dyssynergic motion and normal motion point in outer rim of left ventricle in end diastolic frame of apical 4 chamber view.

Mean left ventricular end-diastolic volume at entry was 114±23ml and increased to 121±27ml at 9 months after acute myocardial infarction in whole group(p=0.02). In a subgroup of anterior infarction, the left ventricular surface area was increaed in 9 cases with increared left ventricular volume(34.8±5.1cm² to 36.4±4.1cm², p=0.02) and ischemic surface area did not change in these group. In 7 patients without increase in left ventricular volume, the left ventricular surface area did not change and ischemic surface area decreased(9.4±4cm² to 8±3.2cm², p=0.03) at 9 months.

Thus the increase in left ventricular end-diastolic volume between 13 days and 9 months after acute myocardial infarction is considered to be a consequence of noninfarct ventricular area dilatation.