Detection of acute myocardial infarction in closed-chest dogs by analysis of regional two-dimensional echocardiographic gray-level distributions.

We hypothesized that acute myocardial infarction could be detected in standard two-dimensional echocardiograms of closed-chest dogs by evaluating regional echo amplitude distributions using computerized image analysis. We tested this hypothesis by performing standard, 2.4 MHz two-dimensional echoes before and 2 days after circumflex coronary occlusion in seven closed-chest dogs. Control and infarcted regions of interest were studied in digitized stop-frame images. Average gray level was calculated for each region of interest, and the shape of the gray-level distribution was analyzed by calculation of skewness and kurtosis and by qualitative features of shape. Average gray level increased significantly from the pre- to postocclusion images in the infarcted regions (16.7 +/- 4.2 vs. 32.4 +/- 4.4 units, P less than 0.01), but not in the control regions (17.4 +/- 4 vs. 22.3 +/- 5.5., P = NS). Average gray level could not distinguish between infarcted and normal regions within the postocclusion images (36 +/- 5.2 vs. 33.6 +/- 5.8, P = NS). Three independent observers qualitatively evaluated histogram shape and correctly identified 7/7 MI regions (100% sensitivity) and 14/20 normal regions (70% specificity). Quantitatively, infarct regions exhibited a significant decrease in kurtosis from pre- to postocclusion images (7.1 +/- 4.0 vs. 5.2 +/- 2.9, P = NS). Within postocclusion images, infarcted regions displayed a significantly lower kurtosis than did normal regions (0.27 +/- .47 vs. 2.5 +/- 1.0, P less than .01). We conclude that acute myocardial infarction may be detected in closed-chest dogs by analyzing regional echo amplitude data from standard two-dimensional echocardiograms.