Predictive Value of Microvolt T-Wave Alternans for Sudden Cardiac Death in Patients With Preserved Cardiac Function After Acute Myocardial Infarction : Results of a Collaborative Cohort Study

ObjectivesWe conducted a collaborative cohort study to evaluate the predictive power of microvolt T-wave alternans (TWA) in patients with preserved left ventricular ejection fraction (LVEF) after myocardial infarction (MI).BackgroundThere is little information available about the prognostic value of risk stratification markers in this population. Although these patients have a relatively good prognosis, identifying high-risk patients is important in clinical practice.MethodsThis study enrolled 1,041 post-MI patients with an LVEF ≥40% (average 55 ± 10%). Microvolt TWA testing was performed 48 ± 66 days after acute MI, and 10 other risk variables were also evaluated. The end points were prospectively defined as sudden cardiac death or life-threatening arrhythmic events.ResultsDuring a follow-up of 32 ± 14 months, 38 patients (3.7%) died of nonarrhythmic causes and were not considered for analysis. Of the 1,003 evaluable patients, 18 (1.8%) reached an end point. Microvolt TWA was positive in 169 patients (17%), negative in 747 (74%), and indeterminate in 87 (9%). A positive microvolt TWA test, nonsustained ventricular tachycardia, and ventricular late potentials were predictors of events, and percutaneous coronary intervention decreased the risk rate. On multivariate analysis, a positive microvolt TWA test was the most significant predictor, with a hazard ratio of 19.7 (p < 0.0001). This marker had the highest sensitivity and negative predictive value for events.ConclusionsIn patients with preserved cardiac function, the incidence of indeterminate results of microvolt TWA is low, and a positive test result is associated with arrhythmic events. Microvolt TWA could be used for risk stratification in this low-risk population.