title: Microvolt T-wave alternans identifies patients with ischemic cardiomyopathy who benefit from implantable cardioverter-defibrillator therapy.
abstract: OBJECTIVE
  This study sought to assess whether implantable cardioverter-defibrillators (ICDs) have different mortality benefits among patients with ischemic cardiomyopathy who screen negative and non-negative (positive and indeterminate) for microvolt T-wave alternans (MTWA).
  
  
  BACKGROUND
  Microvolt T-wave alternans has been proposed as an effective tool for risk stratification. However, no studies have examined whether ICD benefits differ by MTWA group.
  
  
  METHODS
  We developed a prospective cohort of 768 patients with ischemic cardiomyopathy (left ventricular ejection fraction < or =35%) and no prior sustained ventricular arrhythmia, of which 392 (51%) received ICDs. The mean follow-up time was 27 +/- 12 months. Propensity scores for ICD implantation based on the variables most likely to influence defibrillator implantation were developed for each MTWA cohort. Multivariable Cox analyses that controlled for propensity score, demographics, and clinical variables 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 result. After multivariable adjustment, ICDs were associated with lower all-cause mortality in MTWA-non-negative patients (hazard ratio [HR] 0.45, 95% confidence interval [CI] 0.27 to 0.76, p = 0.003) but not in MTWA-negative patients (HR 0.85, 95% CI 0.33 to 2.20, p = 0.73) (for interaction, p = 0.04), with the mortality benefit in MTWA-non-negative patients largely mediated through arrhythmic mortality reduction (HR 0.30, 95% CI 0.13 to 0.68, p = 0.004). The number needed to treat with an ICD for 2 years to save 1 life was 9 among MTWA-non-negative patients and 76 among MTWA-negative patients.
  
  
  CONCLUSIONS
  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.
authors.affiliation: The Lindner Clinical Trial Center at the Christ Hospital and the Ohio Heart and Vascular Center, Cincinnati, Ohio, USA.
authors.forename: Theodore
authors.initials: T
authors.lastname: Chow
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Kereiakes
authors.forename: Cheryl
authors.initials: C
authors.lastname: Bartone
authors.forename: Terri
authors.initials: T
authors.lastname: Booth
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Schloss
authors.forename: Theodore
authors.initials: T
authors.lastname: Waller
authors.forename: Eugene
authors.initials: E
authors.lastname: Chung
authors.forename: Santosh
authors.initials: S
authors.lastname: Menon
authors.forename: Brahmajee K
authors.initials: BK
authors.lastname: Nallamothu
authors.forename: Paul S
authors.initials: PS
authors.lastname: Chan
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac; D009202:Cardiomyopathies / Q000175:diagnosis* / Q000209:etiology / Q000628:therapy*; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications / Q000628:therapy; D011446:Prospective Studies