Electrocardiographic changes during dobutamine stress testing in patients with recent myocardial infarction: relation with residual infarct artery stenosis and contractile recovery.

OBJECTIVE: The identification of viable but jeopardized myocardium after acute myocardial infarction (AMI) is of great importance for selecting patients who could benefit from a revascularization procedure. The aim of the study was to determine the accuracy of the dobutamine stress electrocardiogram (ECG) 1) for detecting significant stenosis of the infarct-related artery and 2) for predicting the occurrence of contractile recovery.

METHODS AND RESULTS: Ninety-four patients underwent dobutamine stress ECG and quantitative angiography within the first week after AMI. A follow-up resting echocardiogram was obtained in all patients at 1 month. Significant stenosis of the infarct-related artery was detected in 76 patients and functional recovery occurred in 56 patients. Dobutamine stress induced ST-segment elevation in 44 patients, ST-segment depression in 17 and T-wave normalization in 34. Increase in QT dispersion and dobutamine ST elevation were more sensitive than chest pain and ST-segment depression (79% and 53% vs. 24% and 17%, respectively; p<0.05) for detecting significant infarct-related artery stenosis. Four independent variables were selected for predicting contractile recovery: > or = 20 ms increase in QT dispersion from baseline to low-dose dobutamine (p = 0.00016), dobutamine-induced ST-segment elevation (p = 0.0009), elective angioplasty of the infarct-related artery (p = 0.001) and T-wave normalization (p = 0.005).

CONCLUSIONS: The analysis of predischarge dobutamine stress ECG is useful for predicting residual stenosis of the infarct-related artery and contractile recovery in the affected area. QT dispersion changes during the test are the most accurate parameter.