Exercise-induced ST-segment elevation in leads over infarcted area and residual myocardial ischemia in patients with previous myocardial infarction.

Abstract

The purpose of this study was to evaluate the clinical significance of exercise-induced ST elevation in patients who had previous myocardial infarction. Electrocardiographic leads were placed over the infarcted area in 65 patients who had previous myocardial infarction (PMI; isolated left anterior descending coronary artery disease). All patients also had stress thallium scan. Exercise-induced ST changes in leads placed over patients' infarcted areas were compared with the extent of both their myocardial ischemia [thallium ischemic score (TIS)] and the area of their infarcted tissue [defect score (DS)]. The latter was derived from a circumferential profile analysis. In patients who had PMI less than three months after the onset of myocardial infarction (n = 36), the left ventricular ejection fraction (LVEF) and the extent of abnormal left ventricular wall motion did not significantly differ from those in patients with exercise-induced ST elevation (greater than 2 mm, n = 26; less than 2 mm, n = 10). In patients who had PMI more than three months after the onset of myocardial infarction (n = 29), patients with high exercise-induced ST elevation (greater than 2 mm, n = 15) showed left ventricular dyskinesis more frequently than those with low ST elevations (less than 2 mm, n = 14). In addition, the former showed higher DS and lower TIS than the latter. In patients who had PMI less than three months after onset (n = 26), 73% of those with ST elevations with prominent upright T waves (n = 15) also had transient thallium defects in their infarcted areas. They also had higher LVEF and TIS than those with low ST elevations (less than 2 mm, n = 11). These results indicated that exercise-induced ST elevations in leads placed over the infarcted areas are to be interpreted differently depending on the degree of recovery of injured myocardial tissue.(ABSTRACT TRUNCATED AT 250 WORDS)