Use of echocardiographic regional contraction abnormalities for the estimation of infarct size

In summary, regional myocardial function in the presence of transmural myocardial infarction is markedly depressed at the center of the infarcted area, and preserved, or even increased, in regions located distant from the injured segments of the LV wall. Because systolic thickening, as measured by echocardiography, increases progressively from the border of the ischemic or infarcted zone towards the remote regions, different degrees of overestimation or underestimation of the infarcted territory will be obtained depending on the threshold chosen as the cutoff point between normal and abnormal function. Variable but consistent overestimation of infarct size by wall motion abnormalities has been reported repeatedly from both experimental and human studies, even when dyskinesis or systolic thinning are used as the sine qua non criterion for dysfunction. The absence of a predictable, or in some studies, even reliable relationship between either the extent of infarction and dysfunction indicates that echocardiography is imprecise in sizing myocardial infarction by the extent or degree of wall motion abnormalities. The clinical application of infarct size quantification by echocardiography is further complicated by the fact that therapeutic reperfusion is now common practice in clinical cardiology, and in that setting, stunned myocardium cannot readily be distinguished from ischemic, infarcted, or merely overloaded segments of the LV, rendering the correlation between systolic thinning or dyskinesis and infarct mass even more complex and unreliable. Improvements in our ability to assess regional myocardial function with less dependence on external systems of reference will enhance the noninvasive quantification of infarct size. However, true distinction between infarcted and contiguous noninfarcted myocardium will, in all likelihood, ultimately require methods independent of regional wall motion as an index of the extent of myocardial injury.