T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: Prospective comparison with conventional risk markers

T Wave Alternans for Risk Stratification. Introduction: The current standar d for arrhythmic risk stratification is electrophysiologic CEP) testing, wh ich, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers, Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving ver y large numbers of patients, and in such studies, documentation of the occu rrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardiove rter defibrillator (ICD), and prospectively compared microvolt TWA with inv asive EP testing and other risk markers with respect to their ability to pr edict recurrence of ventricular tachyarrhythmias as documented by ICD elect rograms. Methods and Results: Ninety-five patients with a history of ventricular tac hyarrhythmias undergoing implantation of an ICD underwent EP testing, asses sment of TWA, as well as determination of LVEF, baroreflex sensitivity, sig nal-averaged EGG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface EGG. The endpoint of the study was first appropria te ICD therapy for electrogram-documented ventricular fibrillation or tachy cardia during follow-up. Kaplan-Meier survival analysis revealed that TWA ( P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk st ratifiers, EP testing was not statistically significant (P < 0.2). Multivar iate Cox regression analysis revealed that TWA was the only statistically s ignificant independent risk factor, Conclusions: Measurement of microvolt TWA compared favorably with both inva sive EP testing and other currently used noninvasive risk assessment method s in predicting recurrence of ventricular tachyarrhythmias in ICD recipient s. This study suggests that TWA might also be a powerful tool for risk stra tification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.