Enhanced detection of the evolution of tissue changes after acute myocardial infarction using color-encoded two-dimensional echocardiography.

Acute myocardial infarction was produced in 26 dogs by ligation of the left anterior descending coronary artery. Two-dimensional echocardiograms (2-D echoes) were performed through the chest wall before and serially after coronary ligation. The dogs were then killed in four groups at the following intervals: 24-48 hours, 1-2 weeks, 3 weeks and 6-8 weeks. Each 2-D echo was processed through a video quantizer, which encoded echo amplitudes progressively into eight regions of color. The myocardium was graded with respect to color composition in regions that showed any abnormally contracting segment (ACS). The ACS exhibited a progressive increase in echo intensity that became maximal 6-8 weeks after coronary ligation. Histopathologic and histochemical studies verified that these increases in echo amplitude correlated with the evolution of healing and myocardial scar formation. At 6-8 weeks, the mean collagen content of infarcted myocardium had increased by a factor of 4; concurrently, ACS echo amplitude had increased two- to threefold. These observations suggest that color-encoded 2-D echo promotes facile perception of serial changes in tissue characteristics that result from acute myocardial infarction.