Efficacy of T-Wave Alternans for the Prediction of Lethal Arrhythmic Events after Myocardial Infarction

Background and Objectives:The prevention of sudden death in patients with a myocardial infarction (MI) remains the therapeutic target. T-wave alternans is as a heart rate dependent measure of repolarization, which correlates with ventricular arrhythmia vulnerability. The goals of this study were to clarify whether microvolt-level T-wave alternans (mTWA) can predict lethal arrhythmic events, and compare their role with other risk indices in predicting lethal events following a MI. Subjects and Methods:The mTWA was analyzed in 78 MI patients, using a power-spectral method during bicycle exercise testing. Additionally, the left ventricular ejection fraction (EF), late potentials (LP) and heart rate variability were also measured. Results:The mTWA was positive in 16 patients (21%), negative in 36 (46%) and indeterminate in 21 (33%). Lethal arrhythmic events developed in 7 patients (3 sudden deaths, 3 ventricular tachycardia and 1 ventricular fibrillation), during a mean follow-up of 12±3 months. The event rate was significantly higher in patients with a positive mTWA (relative risk 12.0, 95% CI 1.2 to 118.1, p=0.01) or lower EF (<40%)(relative risk 11.0, CI 1.9 to 65.0, p=0.002). The mTWA test exhibited the highest sensitivity, relative risk and negative predictive value, but the lowest specificity; positive predictive values were observed compared with the EF or a combination of the two indices. Conclusion: mTWA was closely related to the occurrence of lethal arrhythmic events in patients with a MI. Therefore, mTWA with a lower EF could be a useful screening test for the prediction of potentially lethal arrhythmic events following a MI. (Korean Circulation J 2005;35:597-604)