Assessment of ischemic regional myocardial dysfunction and its reversibility.

BY ITS very nature, significant disease of the coronary arteries results in regional ischemia or infarction, with sparing of other areas of the heart. Therefore, it is intuitively reasonable that assessment of the consequences of ischemic events on cardiac contraction would be best reflected in regional myocardial performance. On the other hand, if a regional contractile abnormality is sufficiently severe or extensive it can impair global ventricular function, so that a fall in the ejection fraction also can be a useful marker of regional ischemic events. Although other measures of ischemia or infarction are available. including electrocardiographic events, metabolic abnormalities, and reduced coronary perfusion, the generally close coupling between contractile performance and ischemia or ischemic damage frequently has led to its use for the study of changes in regional myocardial function. Nevertheless, dissociations can occur between regional contraction and tissue metabolism or viability, as in delayed but reversible postreperfusion dysfunction. Also, when acute infarction develops into regional scar, when abnormal loading conditions exist, or when compensatory hypertrophy produces hyperfunction of nonischemic zones, measurements of regional contraction are often needed to understand the net effect of an ischemic event on global ventricular function. It will be the purpose of this brief analysis to examine the characteristics of regional contraction, its usefulness and limitations in relation to global left ventricular function for the detection of myocardial ischemia and infarction, and its role in assessing responses to experimental reperfusion and clinical thrombolytic therapy. Although diastolic abnormalities can be important as well, the brevity of the review will limit discussion to that of systolic function.