Sunday, November 12, 2006 4:15pm - 4:30pm. 2003 Microvolt T-Wave Alternans Identifies ICD Benefit in Ischemic Cardiomyopathy Patients

Paul S Chan, University of Michigan, Ann Arbor, MI
Theodore Chow, Ohio Heart and Vascular Center, Cincinnati, OH

Keywords:	Implantable cardioverter defibrillator, Arrhythmias, Ischemic heart disease, Cardiomyopathies
Disclosure Block:	P.S. Chan, None; D.J. Kereiakes, None; C. Bartone, None; T. Booth, None; E.J. Schloss, None; T. Waller, None; E. Chung, None; S. Menon, None; B.K. Nallamothu, None; T. Chow, Medtronic, St. Judes, Modest,2. Research Grant (includes principal investigator, collaborator or consultant and pending grants as well as grants already received).
Abstract:	Objective: To assess if implantable cardioverter-defibrillators (ICDs) have different mortality benefits among patients with ischemic cardiomyopathy who screen microvolt T-wave alternans (MTWA) negative and non-negative (positive and indeterminate). Background: MTWA has been proposed as an effective tool for risk stratification. However, no studies have examined whether ICD benefit differs by MTWA group. Methods: We developed a prospective cohort of 768 patients with ischemic cardiomyopathy (LVEF<35%) and no prior sustained ventricular arrhythmia, of which 392 (51%) received ICDs. Mean follow up was 27+12 months. Propensity scores for ICD implantation based on the three variables (EPS testing, QRS duration >120ms, and abnormal Holter) most likely to influence defibrillator implantation were developed for each MTWA cohort. Multivariable Cox analyses which controlled for propensity score, demographics, clinical variables, and medication usage evaluated the degree to which ICDs decreased mortality risk for each MTWA group. Results: We identified 514 (67%) patients with a non-negative MTWA test. C-statistics for the propensity scores showed good discrimination [C=0.81 (MTWA non-negative); C=0.78 (MTWA negative)]. After multivariable adjustment, ICDs were associated with lower all-cause mortality in MTWA non-negative patients [hazard ratio (HR)=0.45 (95% CI: 0.27, 0.76); p=0.003] but not in MTWA negative patients [HR=0.85 (0.33, 2.20); p=0.73] (p-value for interaction=0.04), with the mortality benefit in MTWA non-negative patients largely mediated through arrhythmic mortality reduction [HR=0.30 (0.13, 0.68); p=0.004]. The number needed to treat with an ICD for 2 years to save one life was 9 among MTWA non-negative patients and 76 among MTWA negative patients. Conclusion: In patients with ischemic cardiomyopathy and no prior history of ventricular arrhythmia, mortality reduction with ICD implantation differs by MTWA status, with implications for risk stratification and health policy.