Exercise versus dobutamine-induced ST elevation in the infarct-related electrocardiographic leads: clinical significance and correlation with functional recovery.

BACKGROUND: The clinical significance of stress-induced ST elevation early after acute myocardial infarction and its relation to functional recovery remain controversial. The aims of this study were (1) to determine the incidence of ST elevation during dobutamine and exercise tests and (2) to assess the relative accuracy of exercise and dobutamine ST elevation for predicting functional recovery after acute myocardial infarction.

METHODS AND RESULTS: We investigated 52 patients who underwent supine exercise (from 25 W to maximal charge) and dobutamine (from 5 to 40 microg/kg per minute and up to 1 mg atropine) stress electrocardiography in the same position. ST elevation was defined as new or worsening at >1 mm, 80 ms after J point. Echocardiography and quantitative angiography were available in all patients before hospital discharge. The follow-up resting echocardiogram was recorded 30 +/- 6 days after the acute event. ST elevation developed during 30 (58%) dobutamine and 24 (46%) exercise tests. The sum of ST elevation was higher during dobutamine testing (7.7 +/- 3.8 mm) than during exercise (5.5 +/- 2.5 mm) (P =.03). A low peak creatine kinase level was the single independent predictor of dobutamine-induced ST elevation. Functional improvement occurred in 35 patients. Two independent predictors of functional recovery were selected from multivariate analysis: dobutamine ST elevation (chi(2) = 9.1; P =.0026) and low peak creatine kinase level (chi(2) = 5.1; P =.025). When dobutamine ST elevation was not included in multivariate analysis, exercise-induced ST elevation emerged as an independent predictor of functional recovery (chi(2) = 5.0; P =.023). Significant linear correlation was found between the sum of ST elevation at peak dobutamine stress and the extent of functional recovery (r = 0.87; P <.0001). In contrast, no correlation was observed with exercise ST elevation (r = 0.06; P = not significant).

CONCLUSIONS: Stress-induced ST elevation is an ancillary sign of viable myocardium that can recover. The sum of ST elevation at peak dobutamine stress correlates with the extent of functional recovery.