Prognostic utility of microvolt T-wave alternans in risk stratification of patients with ischemic cardiomyopathy

OBJECTIVES The purpose of this study was to assess if microvolt T-wave alternans (MTWA) is an independent predictor of mortality in patients with ischemic cardiomyopathy. BACKGROUND Microvolt T-wave alternans has been proposed as an effective tool for identifying high-risk patients with ischemic cardiomyopathy who are likely to benefit from implantable cardioverter-defibrillator (ICD) therapy. However, earlier studies have been limited in their ability to control for baseline differences between MTWA-negative and -non-negative (positive and indeterminate) patients. METHODS We enrolled 768 consecutive patients with ischemic cardiomyopathy (left ventricular ejection fraction <= 35%) and no prior history of ventricular arrhythmia. All patients underwent baseline MTWA testing and were classified as MTWA negative or non-negative. Multivariable Cox regression analyses, stratified by ICD status, were used to determine the association between MTWA testing and mortality after adjusting for demographic, clinical, and treatment differences between MTWA-negative and -non-negativc patients. RESULTS We identified 514 (67%) patients with a non-negative MTWA test. After multivariable adjustment, a non-negative MTWA test was associated with a significantly higher risk for all-cause (stratified hazard ratio [HR] = 2.24 [95% confidence interval 1.34 to 3.75]; p = 0.002) and arrhythmic mortality (stratified HR = 2.29 [1.00 to 5.24]; p = 0.049) but not for nonarrhythmic mortality (stratified HR = 1.77 [0.84 to 3.741; p = 0.13). In subgroup analyses, a non-negative MTWA test was also associated with a higher risk for all-cause mortality in patients with ejection fractions <= 30% (stratified HR = 2.10 [1.18 to 3.73]; p = 0.01) and after excluding those with indeterminate MTWA tests (stratified HR = 2.08 [1.18 to 3.66]; p = 0.01). CONCLUSIONS Microvolt T-wave alternans is a strong and independent predictor of all-cause and arrhythmic mortality in patients with ischemic cardiomyopathy.