Experimental evaluation of the extent of myocardial dyssynergy and infarct size by two-dimensional echocardiography.

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Abstract
The extent of left ventricular (LV) dyssynergy was assessed noninvasively in 19 dogs with two-dimensional echocardiographic short-axis sections during myocardial ischemia and infarction. After coronary occlusion, two-dimensional echocardiography uniformly indicated an increase in LV end-diastolic volume and a decrease in LV ejection fraction. Two-dimensional echocardiographic measurements of dyssynergy were evaluated and compared in three subgroups against (1) the extent of LV dyssynergy determined by force-gauge mapping during 10 coronary occlusions of 30-60 minutes' duration in eight open-chest dogs, (2) infarct size delineated by nitroblue tetrazolium (NBT) staining of left ventricular slabs after 48 hours of left anterior descending coronary artery (LAD) occlusion in five closed-chest dogs, and (3) NBT infarct size after 3-hour LAD occlusion followed by 45 hours of reperfusion in six closed-chest dogs. Linear regression analysis of results from these three comparisons gave good correlations (r = 0.89) for groups 1 and 2; in group 2, the extent of dyssynergy by two-dimensional echocardiography was consistently greater than infarct size by NBT. In group 3, the correlation was poor (r = 0.39). These results suggest that an adequate estimate for the extent of LV dyssynergy or infarct size may be obtained with two-dimensional echocardiography during myocardial ischemia or infarction, but not in the presence of coronary reflow, which causes an acute discrepancy between myocardial viability and function.