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CLINICAL RESEARCH: HEART RHYTHM DISORDERS

Predictive Value of Microvolt T-Wave Alternans in Patients With Left Ventricular Dysfunction

Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, New York

Manuscript received December 29, 2006; revised manuscript received February 5, 2007, accepted February 13, 2007.

^_* Reprint requests and correspondence: Dr. Sei Iwai, Division of Cardiology, Cornell University Medical Center, 525 East 68th Street, Starr 409, New York, New York 10021. (Email: sei2002{at}med.cornell.edu).

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.

Abbreviations and Acronyms   EF = ejection fraction   EPS = electrophysiology study   ICD = implantable cardioverter-defibrillator   LV = left ventricle/ventricular   LVEF = left ventricular ejection fraction   NPV = negative predictive value   NYHA = New York Heart Association   TWA = T-wave alternans   VT = ventricular tachycardia

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