Assessment of location and size of myocardial infarction with contrast-enhanced echocardiography

Abstract

The ability of contrast-enhanced echocardiography to localize and quantify myocardial infarction was studied in 16 open chest dogs. Both routine and contrast-enhanced two-dimensional echocardiograms were recorded at baseline and 4 hours after occlusion of the left anterior descending (n = 11) or circumflex (n = 5) coronary artery. Ultrasound contrast was produced by injection into the aortic root of 3 ml of 0.3% hydrogen peroxide mixed with 6 ml blood. Systolic wall thickening was also measured and quantified as a marker of myocardial infarction. Dogs were sacrificed after 4 hours of coronary occlusion. The slice of the left ventricle that corresponded to the two-dimensional echocardiogram was stained with nitro-blue tetrazolium to localize the infarct. The size of the myocardial infarct was determined by planimetry. The oxygen bubbles produced by mixing hydrogen peroxide with blood produced an excellent intramyo-cardial ultrasound contrast effect. Complete data were available in 12 dogs. Contrast echocardiography accurately localized the infarction in all 11 dogs with an infarct documented by nitro-blue tetrazolium. The area of the infarct, determined by planimetry and expressed as a fraction of total myocardial area from the nitro-blue tetrazolium study, correlated well with the size of the infarct determined with contrast echocardiography (correlation coefficient [r] = 0.92, standard error of the estimate [SEE] = 0.05, probability [p] < 0.001). Intra-and interobserver correlations were excellent for the determination of fraction of infarcted myocardium by contrast echocardiography (r = 0.93, p < 0.001, SEE = 0.04; r = 0.89, p < 0.001, SEE = 0.07, respectively). Absence of systolic wall thickening also accurately localized myocardial infarction, but correlated poorly with the extent of infarction (r = 0.29, p = not significant). It is concluded that contrast-enhanced two-dimensional echocardiography, using a combination of hydrogen peroxide and blood to provide ultrasound contrast, accurately and reproducibly localizes and quantifies myocardial infarction.