Two-dimensional echocardiography and infarct size: relationship of regional wall motion and thickening to the extent of myocardial infarction in the dog.

Abstract

SUMMARY To study endocardial wall motion and thickness as indexes of infarction, we used two-dimensional echocardiography to examine regional percentages of systolic wall thickening (%Th) and endocardial motion (%EM) in infarcted canine hearts. Thirteen dogs were studied 48 hours after occlusion of the circumflex or left anterior descending coronary artery. Two-dimensional echocardiographic cross sections obtained every 16 msec at 1-cm intervals from apex to base in an open-chest, anesthetized preparation were analyzed with a computer-aided contouring system for quantification of segmental %EM and %Th at 16 equally spaced points per slice. Slices corresponding to each two-dimensional echocardiographic cross section were examined pathologically for evidence of infarction.Comparing histologically infarcted with distant normal zones in each slice, %Th and %EM both yielded clear separation with little overlap (-12.5% infarcted vs 37.4% normal for thickness; -11.3 vs 25.7% for motion, p << 0.001 for both). Endocardial motion was less precise than thickening, however, in distinguishing infarct from either distant normal zones or zones directly adjacent to infarct.Although wall thickening was useful in separating out true subendocardial infarct, change in systolic thickening was not accurate in detecting the transmural extent of infarction. In 827 individual two-dimensional echocardiographic segments with varying degrees of transmural involvement, segments with 1-20% extent of transmural infarction showed reduced thickening compared with noninfarcted segments (39.9 vs 15.2%, p < 0.001), whereas myocardial segments with 21-100% transmural infarction showed systolic thinning (-8.9 to -13.3%). There was no significant augmentation in the severity of systolic thinning as the extent of transmural infarction increased from 21% to 100%.We conclude that: (1) Wall motion abnormalities are less precise than thickening in discriminating between infarcted and noninfarcted zones and could lead to overestimation of infarct size. (2) There is an abrupt deterioration in systolic thickening in segments containing more than 20% transmural extent of infarction. (3) There is no significant augmentation in the degree of systolic thinning as the transmural extent of infarct increases from 21% to 100%. This "threshold" phenomenon may therefore preclude accurate estimation of infarct size by two-dimensional echocardiography. (4

Regional function and perfusion at the lateral border of ischemic myocardium.

“…Two echocardiographic studies have suggested that wall thickening may be more specific than endocardial motion for demonstrating myocardial necrosis. 17,42 Although use of endocardial motion to assess regional performance may potentially represent a limitation of our study, our data relating the area of dysfunction to area of ischemia are quite similar to those obtained in studies using wall thickening. '7' 18, 42, 43 In this study, consistency of echocardiographic imaging and correlation with pathologic material was achieved with echogenic markers.…”

Persistent reduction in left ventricular asynergy in patients with acute myocardial infarction by intravenous infusion of nitroglycerin.

“…1-3 "1Since twodimensional echocardiography (2D-echo) provides tomographic images of the heart, 16 we used a modification of existing 2D-echo methods for assessing left ventricular asynergy'2-14 [17][18][19][20][21] in parastemal short-axis views. We also expressed total left ventricular asynergy as percent of left ventricular surface area for correlation with EST and CK infarct size.…”

Importance of temporal heterogeneity in assessing the contraction abnormalities associated with acute myocardial ischemia.

“…This alignment was similar to that used to orient the echocardiographic coordinates, and echocardiographic rays falling within the region of histologically defined infarction were thus determined. Once these radii were identified they were analyzed individually for (1) the presence of dyskinesis at any point in the contraction sequence, (2) the point in the contraction sequence at which maximal dyskinesis alonig each radius occurred, and (3) the total number of radii within the infarct zone showing dyskinetic motion at each sampling period.…”

“…The purpose of this study, therefore, was to determine (1) whether there is significant temporal variability in the dyskinetic motion that characterizes ischemic myocardial dysfunction, and (2) whether temporal variability, if present, has an important effect on the echocardiographic analysis of abnormal wall motion.…”