Diagnostic Value of Exercise-Induced ST-Segment Elevation in Q-Wave Leads. After Recent Myocardial Infarction

Abstract

Background: Exercise-induced ST-segment elevation in an infarct territory with abnormal Q waves is a known marker for more severe left ventricular wall-motion abnormalities. However, it is reported, that exercise-induced ST-segment elevation in infarct leads may indicate residual viability in the intarctregion. The aim of the study was to test whether exercise-induced ST-segment elevation is related to left ventricular (LV) dysfunction or to persistent viability in patients with previous myocardial infarction (MI). Methods: 145 consecutive patients (119 men, 26 women, age 58 ± 11 years) 2–3 weeks after Q-wave Ml but without ST elevation at rest ECG were enrolled in the study. All patients underwent a target heart rate or symptom-limited exercise testing (ET) with Bruce protocol. Exercise-induced ST-segment elevation < 1 mm above the baseline ST segment level (80 ms after J point) in more than 1 ECG lead with Q wave was considered to be significant. Patients were divided in two groups according to ET results: group I, 25 patients with significant exercise-induced ST-segment elevation and group II, 120 patients without exercise-induced ST-segment elevation. All patients underwent rest ECHO and low dose dobutamine stress echo (LOSE) within 7 days after ET. LV function was estimated using ejection fraction (EF). Results: More severe LV dysfunction was observed in patients from group 1 (EF 31 ± 8.16% vs EF 45 ± 10.3%). Myocardial viability (defined as an improvement of regional systolic wall thickening in the regions with resting regional wall-motion abnormalities during LOSE 5 to 15 g/kg/min was recognized in 8 patients (32%) in group I and 31 patients (25.8%) in group II. There was no relation between exercise-induced ST-segment elevation and myocardial viability (chi-square test: 2,809; NS). Conclusions: Exercise-induced ST-segment elevation in most cases is associated with left ventricular dysfunction. Patients with exercise-induced ST-segment elevation have a lower EF than those without and greater severity of resting wall-motion abnormalities. Our results suggest that exercise-induced ST-segment elevation is not related to residual myocardial viability.