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.

Keywords: Sudden death, Risk stratification, Heart failure, T-wave alternans, Nonischemic cardiomyopathy