Contrast echocardiography in acute myocardial ischemia: I. In vivo determination of total left ventricular “area at risk”

Myocardial contrast echocardiography has been shown recently to accurately assess the “area at risk” for necrosis after acute coronary occlusion in the experimental model. Risk area quantitation, however, has been studied primarily from single tomographic planes. Because the three-dimensional extent of myocardial necrosis depends on the total volume of myocardium at risk, the total left ventricular “area at risk” was determined in 11 dogs (Group A) with either left anterior descending or left circumflex artery occlusion using contrast echocardiography and compared with risk area determined by technetium autoradiography. An excellent correlation was found between the two methods (r = 0.96, y = 0.91x + 1.5, p < 0.001, SEE = 3.17). A comparison of risk area for individual levels of the left ventricle using both methods, however, showed some variation in the degree of correlation, with the poorest fit being apparent at the apex. To identify the source of the variation, errors caused by data registration were minimized in six additional dogs (Group B) by implanting epicardial markers at a single level and measuring “area at risk” at this level using both methods. When no registration error was present, the correlation between the two methods was excellent (r = 0.99, y = 0.92x + 2.6, p < 0.001, SEE = 0.55). In conclusion, the “area at risk” for infarction after acute coronary occlusion can be determined accurately for the entire left ventricle as well as for a single tomographic slice using myocardial contrast echocardiography. This was validated using technetium autoradiography, which is an established method of determining “area at risk” in the experimental setting.