title: Prognostic significance of electrical alternans versus signal averaged electrocardiography in predicting the outcome of electrophysiological testing and arrhythmia-free survival.
abstract: OBJECTIVE
  To investigate the accuracy of signal averaged electrocardiography (SAECG) and measurement of microvolt level T wave alternans as predictors of susceptibility to ventricular arrhythmias.
  
  
  METHODS
  Analysis of new data from a previously published prospective investigation.
  
  
  METHODS
  Electrophysiology laboratory of a major referral hospital.
  
  
  METHODS
  43 patients, not on class I or class III antiarrhythmic drug treatment, undergoing invasive electrophysiological testing had SAECG and T wave alternans measurements. The SAECG was considered positive in the presence of one (SAECG-I) or two (SAECG-II) of three standard criteria. T wave alternans was considered positive if the alternans ratio exceeded 3.0.
  
  
  METHODS
  Inducibility of sustained ventricular tachycardia or fibrillation during electrophysiological testing, and 20 month arrhythmia-free survival.
  
  
  RESULTS
  The accuracy of T wave alternans in predicting the outcome of electrophysiological testing was 84% (p < 0.0001). Neither SAECG-I (accuracy 60%; p < 0.29) nor SAECG-II (accuracy 71%; p < 0.10) was a statistically significant predictor of electrophysiological testing. SAECG, T wave alternans, electrophysiological testing, and follow up data were available in 36 patients while not on class I or III antiarrhythmic agents. The accuracy of T wave alternans in predicting the outcome of arrhythmia-free survival was 86% (p < 0.030). Neither SAECG-I (accuracy 65%; p < 0.21) nor SAECG-II (accuracy 71%; p < 0.48) was a statistically significant predictor of arrhythmia-free survival.
  
  
  CONCLUSIONS
  T wave alternans was a highly significant predictor of the outcome of electrophysiological testing and arrhythmia-free survival, while SAECG was not a statistically significant predictor. Although these results need to be confirmed in prospective clinical studies, they suggest that T wave alternans may serve as a non-invasive probe for screening high risk populations for malignant ventricular arrhythmias.
authors.affiliation: Harvard University-Massachusetts Institute of Technology, Division of Health Sciences and Technology, Cambridge, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Armoundas
authors.forename: D S
authors.initials: DS
authors.lastname: Rosenbaum
authors.forename: J N
authors.initials: JN
authors.lastname: Ruskin
authors.forename: H
authors.initials: H
authors.lastname: Garan
authors.forename: R J
authors.initials: RJ
authors.lastname: Cohen
mesh_terms: D001145:Arrhythmias, Cardiac / Q000175:diagnosis*; D016009:Chi-Square Distribution; D004198:Disease Susceptibility; D018572:Disease-Free Survival; D004562:Electrocardiography; D004594:Electrophysiology; D006801:Humans; D011237:Predictive Value of Tests; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted