T-wave alternans in risk stratification of patients with nonischemic dilated cardiomyopathy: can it help to better select candidates for ICD implantation?

Background: Prophylactic implantable cardioverter-defibrillator (ICD) therapy reduces mortality in patients with heart failure (HF) and reduced left ventricular ejection fraction (LVEF), but the absolute risk reduction is relatively small. Thus, there is a strong need to identify reliable risk stratifiers, particularly among patients with nonischemic cardiomyopathy (NIDCM), in whom the search for risk predictors has been particularly frustrating. Objective: This study sought to review data regarding T-wave alternans (TWA) in patients with NIDCM and to discuss its potential role. Methods: We included in a meta-analysis clinical trials that enrolled ≥50 NICDM patients, had a follow-up of ≥1 year, and provided detailed data on NIDCM patients, in case of mixed population. Relative risks were derived from absolute numbers of events in abnormal (positive + indeterminate test whenever possible) TWA versus normal (negative) TWA group. Results: Eight studies with 1,456 patients (mean age 56 years, LVEF 30%, follow-up 25 months) were included. A negative TWA test occurred in 33%, and was indeterminate in 21% of the patients. The primary end point (VT+VF+sudden or all-cause death) occurred in 14.7% abnormal versus 3.8% normal TWA patients. The relative risk for the cumulative data was found to be 2.99 (95% confidence interval: 1.88 to 4.75). The negative predictive value was 96.2%. Conclusion: A normal TWA test identifies one-third of NIDCM patients who have a very good prognosis and are unlikely to significantly benefit from ICD therapy. A randomized clinical trial evaluating the utility of TWA in guiding therapy seems warranted, possibly a noninferiority trial of medical therapy only versus ICD in TWA-negative patients