Prognostic significance of risk stratifiers of mortality, including T wave alternans, after acute myocardial infarction: results of a prospective follow-up study.

INTRODUCTION

Occurrence of sustained microvolt-level T wave alternans (TWA) at a specified heart rate has been suggested to predict life-threatening arrhythmic events, but its prognostic value has not been well established in patients who survived an acute myocardial infarction (AMI). The purpose of this prospective study was to assess the predictive significance of various noninvasive risk indicators of mortality, including TWA, in consecutive post-AMI patients with optimized medical therapy.

METHODS AND RESULTS

In addition to a symptom-limited predischarge exercise test with measurement of TWA, mortality risk was assessed using heart rate variability, 24-hour ECG recordings, baroreflex sensitivity, signal-averaged ECG, QTc interval, QT dispersion, and echocardiographic wall-motion index in 379 consecutive patients. Twenty-six patients (6.9%) died during a mean follow-up of 14 +/- 8 months. Sustained TWA was found in 56 patients (14.7%), none of whom died. Several risk variables, e.g., incomplete TWA test (inability to perform the exercise test or reach the required target heart rate of 105 beats/min), increased QRS duration on signal-averaged ECG, increased QT dispersion, long QTc interval, nondiagnostic baroreflex sensitivity result, and low wall-motion index, predicted all-cause mortality in univariate analyses. In multivariate analysis, the incomplete TWA test was the most significant predictor of cardiac death (relative risk 11.1, 95% confidence interval 2.4 to 50.8; P < 0.01).

CONCLUSION

Sustained TWA during the predischarge exercise test after AMI does not indicate increased risk for mortality. An incomplete TWA test and several common risk variables provided prognostic information in this post-AMI population.