Predictive value of microvolt T-wave alternans in patients with left ventricular dysfunction.

OBJECTIVES: The purpose of this study was to prospectively evaluate the utility of microvolt T-wave alternans (TWA) in predicting arrhythmia-free survival and total mortality in patients with left ventricular (LV) dysfunction.
BACKGROUND: Microvolt TWA has been proposed as a useful tool in identifying patients unlikely to benefit from prophylaxis with implantable cardioverter-defibrillator (ICD) prophylaxis.
METHODS: We evaluated 286 patients with an LV ejection fraction </=35% who underwent TWA and electrophysiologic testing (EPS) owing to nonsustained ventricular tachycardia and/or syncope. Positive and indeterminate TWA results were grouped as non-negative. The primary end point was arrhythmia-free survival; the secondary end point was all-cause mortality.
RESULTS: Patients were followed for a mean of 38 +/- 11 months. There was no significant difference between the TWA-negative (n = 90; 31%) and non-negative (n = 196; 69%) groups with respect to ICD implant rates (54% vs. 64%, respectively; p = 0.95) or etiology of cardiomyopathy (ischemic: 73% vs. 76%; p = 0.71). The Kaplan-Meier curves demonstrated improved arrhythmia-free survival in TWA-negative patients (81% vs. 66% at 2 years; p < 0.001), including in both ischemic (79% vs. 64% at 2 years; p = 0.004) and nonischemic (88% vs. 71% at 2 years; p = 0.015) subgroups. Total mortality was lower in the TWA-negative group (10% vs. 18% at 2 years; p = 0.04). The negative predictive value of TWA for (2-year) total mortality was 90%, and 83% for EPS.
CONCLUSION: Microvolt TWA predicts arrhythmia-free survival among patients with LV dysfunction. However, the event rate in the TWA-negative group suggests that TWA may not be capable of identifying a sufficiently low-risk subset in this population to obviate the need for ICD implantation.