SIGNIFICANCE OF ST SEGMENT ELEVATION ON Q -LEADS AT REST AND DURING EXERCISE AFTER ACUTE MYOCARDIAL-INFARCTION

Introduction. ST segment elevation on Q-leads has been related to a gr eater infarct size and to the existence of ventricular aneurysm. On th e other hand, ST elevation during exercise testing has been related to the presence of myocardial viability. Objectives. In the present stud y we investigated the relation between ST segment elevation on infarct -related electrocardiographic leads at rest and during exercise with: a) the extension and severity of the regional dysfunction; b) the pres ence of myocardial viability (response to dobutamine), and c) the resi dual stenosis in the culprit artery. Material and methods. The study g roup was composed of 51 patients; cardiac cathetherism (8 +/- 3 days) and exercise testing (8 +/- 2 days) were performed during the pre-disc harge period. In contrast ventriculography (centerline method) we dete rmined the circumferencial extension (rads) and the severity (SD/rad) of the regional dysfunction at rest and after dobntamine (10 mu g/kg/m in). The minimal luminal diameter (MLD) in the culprit artery was also measured. Results are expressed as median [Q1-Q3] and the differences among the groups were assessed by Mann-Whitney U. Results. Patients w ith ST segment elevation in two or more leads at rest (n = 36) showed a greater (41 [30-51] rads vs 20 [14-41] rads; p = 0.007) and more sev ere regional dysfunction (1.9 [1.5-2.5] SD/rad vs 0.6 [0.5-2.4] SD/rad ; p = 0.01), less response to dobutamine (% of reduction of the dysfun ction extension after dobutamine) (17 [0-42]% vs 50 [24-100]%; p = 0.0 04) and smaller MLD (0.5 [0-0.9] mm vs 0.8 [0.6-1.1] mm; p = 0.03). Li kewise, patients with exercise-induced ST segment elevation (n = 28) s howed less response to dobutamine (15 [0-45]% vs 40 [21-57]%; p = 0.03 ) and smaller MLD (0.5 [0-0.7] mm vs 0.9 [0.5-1] mm; p = 0.02). There were non significant differences between patients with and without ST elevation during exercise in the extension or severity of the regional dysfunction. ST segment elevation both at rest (RR 0.2; CI 95%: 0.04- 0.85) and during exercise (RR 0.19; CI 95%: 0.05-0.69) decreased the p robability of improvement with dobutamine. Conclusions. We conclude th at ST segment elevation on Q-leads at rest is related to a more extend ed and severe dysfunction. Patients with ST segment elevation (at rest or during exercise) show less response to dobutamine (myocardial viab ility less likely) and a more severe residual coronary stenosis.