title: Clinical utility of microvolt T-wave alternans testing in identifying patients at high or low risk of sudden cardiac death.
abstract: BACKGROUND
  Previous studies have demonstrated that microvolt T-wave alternans (MTWA) testing is a robust predictor of ventricular tachyarrhythmias and sudden cardiac death (SCD) in at-risk patients. However, recent studies have suggested that MTWA testing is not as good a predictor of "appropriate" implantable cardioverter-defibrillator (ICD) therapy as it is a predictor of SCD in patients without ICDs.
  
  
  OBJECTIVE
  To evaluate the utility of MTWA testing for SCD risk stratification in patients without ICDs.
  
  
  METHODS
  Patient-level data were obtained from 5 prospective studies of MTWA testing in patients with no history of ventricular arrhythmia or SCD. In these studies, ICDs were implanted in only a minority of patients and patients with ICDs were excluded from the analysis. We conducted a pooled analysis and examined the 2-year risk for SCD based on the MTWA test result.
  
  
  RESULTS
  The pooled cohort included 2883 patients. MTWA testing was positive in 856 (30%), negative in 1627 (56%), and indeterminate in 400 (14%) patients. Among patients with a left ventricular ejection fraction (LVEF) of ≤35%, annual SCD event rates were 4.0%, 0.9%, and 4.6% among groups with MTWA positive, negative, and indeterminate test results. The SCD rate was significantly lower among patients with a negative MTWA test result than in patients with either positive or indeterminate MTWA test results (P <.001 for both comparisons). In patients with an LVEF of >35%, annual SCD event rates were 3.0%, 0.3%, and 0.3% among the groups with MTWA positive, negative, and indeterminate test results. The SCD rate associated with a positive MTWA test result was significantly higher than that associated with either negative (P <.001) or indeterminate MTWA test results (P = .003).
  
  
  CONCLUSIONS
  In patients without ICDs, MTWA testing is a powerful predictor of SCD. Among patients with an LVEF of ≤35%, a negative MTWA test result is associated with a low risk for SCD. Conversely, among patients with an LVEF of >35%, a positive MTWA test result identifies patients at significantly heightened SCD risk. These findings may have important implications for refining primary prevention ICD treatment algorithms.
authors.affiliation: Cardiology Division, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Faisal M
authors.initials: FM
authors.lastname: Merchant
authors.forename: Takanori
authors.initials: T
authors.lastname: Ikeda
authors.forename: Roberto F E
authors.initials: RF
authors.lastname: Pedretti
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Salerno-Uriarte
authors.forename: Theodore
authors.initials: T
authors.lastname: Chow
authors.forename: Paul S
authors.initials: PS
authors.lastname: Chan
authors.forename: Cheryl
authors.initials: C
authors.lastname: Bartone
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Hohnloser
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cohen
authors.forename: Antonis A
authors.initials: AA
authors.lastname: Armoundas
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000401:mortality; D016757:Death, Sudden, Cardiac / Q000453:epidemiology* / Q000517:prevention & control*; D018572:Disease-Free Survival; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D018570:Risk Assessment; D013318:Stroke Volume; D017180:Tachycardia, Ventricular / Q000517:prevention & control / Q000628:therapy