title: Usefulness of microvolt T-wave alternans to predict outcomes in patients with ischemic cardiomyopathy beyond one year.
abstract: Previous studies have demonstrated that microvolt T-wave alternans (MTWA) screening effectively risk-stratifies patients with ischemic cardiomyopathy. Whether the prognostic utility of MTWA diminishes over 3 years of follow-up remains unknown. In this study, a prospective cohort of 768 patients with ischemic cardiomyopathy (left ventricular ejection fraction <35%) and no previous sustained ventricular arrhythmia was developed, of whom 514 (67%) screened MTWA nonnegative (positive and indeterminate). The mean follow-up period was 18 +/- 11 months. The primary end point was all-cause mortality and appropriate implantable cardioverter-defibrillator shocks. Stratified Cox regression analyses (by implantable cardioverter-defibrillator status) estimated the predictive power of MTWA within each year of follow-up and determined whether this diminished over time. There were 99 deaths (MTWA negative: 21 [8.3%]; MTWA nonnegative: 78 [15.2%]) and 33 appropriate implantable cardioverter-defibrillator shocks (MTWA negative: 3 [4.0%]; MTWA nonnegative: 30 [9.5%]). After multivariate adjustment, a nonnegative MTWA test result was associated with a greater than twofold increased risk for events in each of the 3 years of follow-up (year 1: stratified hazard ratio 2.19, 95% confidence interval 1.10 to 4.34, p = 0.03; year 2: stratified hazard ratio 3.36, 95% confidence interval 1.28 to 8.83, p = 0.01; year 3: stratified hazard ratio 2.06, 95% confidence interval 0.81 to 5.22, p = 0.13). There were no significant interactions between the time periods (year 1 vs year 2: p = 0.47; year 1 vs year 3: p = 0.92). In conclusion, MTWA reliably and consistently predicts mortality and arrhythmic risk throughout the first 2 to 3 years of follow-up. Although these findings need further validation, they suggest that rescreening with MTWA may not need to be performed more frequently than once every 2 years.
authors.affiliation: Mid-America Heart Institute and University of Missouri, Kansas City, Missouri, USA. paul1chan@yahoo.com
authors.forename: Paul S
authors.initials: PS
authors.lastname: Chan
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Kereiakes
authors.forename: Cheryl
authors.initials: C
authors.lastname: Bartone
authors.forename: Theodore
authors.initials: T
authors.lastname: Chow
mesh_terms: D000368:Aged; D009202:Cardiomyopathies / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D017147:Defibrillators, Implantable; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D017202:Myocardial Ischemia / Q000150:complications*; D012044:Regression Analysis