Relation between Perfusion of Infarcted Myocardium and Exercise-induced ST Shift in Acute Myocardial Infarction

ABSTRACT

BACKGROUND: It has been demonstrated that within 2 weeks following acute myocardial infarction (AMI), exercise-induced ST-segment depression (STD) indicates subendocardial ischemia in the viable myocardium within infarcted or remote area from the infarction. Exercise-induced ST-segment elevation (STE) in leads with abnormal Q wave is associated with left ventricular dysfunction or aneurysm rather than transmural ischemia. We studied whether each pattern of ST-segment shift on exercise ECG during recovery phase following AMI is correlated with the perfusion status of infarcted myocardium evaluated by myocardial contrast echocardiog-raphy (MCE), regardless of findings of coronary angiography (CAG). METHOD: Study population was consisted of 25 patients with AMI (anteior wall 11 patients, inferior wall 14 patients, mean age=57.3+/-8.9years). Patients underwent exercise ECG and coronary angiography at 10 days post-AMI. After CAG, sonicated Hexabrix was injected into both coronory arteries alternatively and 2-D echocardiography was taken in parasternal short axis, apical 4, and 2 chamber views. To analyze the echocardiographic image semiquantitively, left ventricle was divided into 20 segments and perfusion status was graded as good, partial, and no opacification. RESULT: All patients with exercise-induced STE (n=8) in Q-leads had patent infarcted-related artery and poor collaterals on CAG, which was associated with poor or no opacification of infarcted myocardium on MCE. Patients with exercise-induced STD (n=9) frequently had closed infarct-related artery (67%), but good opacification of infarcted myocardium was shown by retrograde perfusion via collaterals, which was commonly seen in patients with multivessel disease. CONCLUSION: In early recovery phase of acute myocardial infarction, exercise-induced ST elevation in Q leads was associated with poor perfusional status in infarcted myocardium, even with patent infarct-related artery on CAG, while exercise-induced ST depression was frequently seen in the good perfusional status despite of closed infarted-related artery, which was commonly observed in patients with multivessel disease.