Exercise versus recovery electrocardiography in predicting mortality in patients with uncomplicated myocardial infarction

BACKGROUND: Exercise testing after acute myocardial infarction has limited prognostic accuracy. We prospectively used stress-recovery, heart rate-adjusted, ST-segment analysis to predict cardiac death in this clinical setting. METHODS: The stress-recovery index, defined as the difference in absolute values of the areas designated by ST depression in the heart-rate domain during exercise and recovery, was derived in 708 survivors of a first myocardial infarction. To assess whether it contributed additional prognostic information to routinely obtained information, clinical data, resting ejection fraction, and exercise testing data were entered into a sequential Cox model; the stress-recovery index was entered last. Model validation was performed by bootstrapping adjusted for the degree of optimism in estimates. Survival curves were set up using Kaplan-Meier analysis and compared by the log-rank test. RESULTS: Hypertension (OR 1.3, 95%CI 0.9-4.6), exercise capacity (OR 0.6, 95%CI 0.3-1.1 for the interquartile difference in kilopounds per minute), and the stress-recovery index (OR 0.7, 95%CI 0.5-0.9 for the interquartile difference) were independent predictors of cardiac death at a median follow-up of 32 months. However, the stress-recovery index enhanced the prognostic power of the model on top of clinical and exercise testing variables in all diagnostic subgroups according to ST-segment analysis and significantly discriminated survival. A simple nomogram was generated from the fitted Cox model to estimate risk in individual patients. CONCLUSIONS: Stress-recovery, heart rate-adjusted, ST-segment analysis predicts cardiac death after acute myocardial infarction and provides additional prognostic information over clinical and exercise testing data.