Contribution of the sST elevation/T-wave normalization in Q-wave leads during routine, pre-discharge treadmill exercise test to patient management and risk stratification after acute myocardial infarction: a 2.5-year follow-up study.

OBJECTIVES

This study investigated whether ST-segment elevation and T-wave normalization (TWN) in Q-wave leads on pre-discharge exercise electrocardiogram (ECG) can contribute to patient management after a recent myocardial infarction (MI).

BACKGROUND

The clinical relevance of these exercise ECG changes remains controversial despite accumulating evidence of their association with myocardial viability. Because discrepancies of previous studies may depend on patient selection, the value of these ST/T abnormalities in the thrombolytic era should be better defined.

METHODS

One-hundred one patients, age 58 +/- 11 years, with a recent, first Q-wave MI (57% thrombolyzed, ejection fraction 43 +/- 7%) underwent pre-discharge, submaximal treadmill testing followed, in the absence of severe ischemia, by dobutamine stress echocardiography, thallium-201 single photon emission computed tomography, and coronary angiography.

RESULTS

ST elevation at peak exercise, but not TWN, was associated with more severe infarctions as indicated by higher peak creatine kinase (p < 0.05) and with a greater number of scarred segments both on echocardiography (p < 0.05) and scintigraphy (p < 0.01). However, the incidence of myocardial viability and ischemia did not differ between groups with or without these ST/T changes. Anterior infarction location and >or=3 echocardiographically scarred segments were among the independent predictors of ST elevation at peak ergometric exercise. During follow-up (31 +/- 13 months), the rate of hard events was low (8%) and similar between the study groups.

CONCLUSIONS

In patients after acute Q-wave MI without severe ischemia according to clinical and standard ECG criteria, exercise-induced ST elevation, but not TWN, is associated with larger infarctions. The contribution of these ST/T abnormalities toward identifying patients with myocardial viability or ischemia and determining risk stratification is poor. In-hospital management of such patients based on routine clinical practice is sufficient for selection of a population with a relatively low long-term risk.