title: Detection of T-wave beat-by-beat variations prior to ventricular arrhythmias onset in ICD-stored intracardiac electrograms: the Endocardial T-Wave Alternans Study (ETWAS).
abstract: BACKGROUND
  The aim of the Endocardial T-Wave Alternans Study was to prospectively assess the presence of T-wave alternans (TWA) or beat-to-beat repolarization changes on implantable cardioverter-defibrillator (ICD)-stored electrograms (EGMs) immediately preceding the onset of spontaneous ventricular tachycardia (VT) or fibrillation (VF).
  
  
  METHODS
  Thirty-seven VT/VF episodes were compared to 116 baseline reference EGMs from the same 57 patients. A Bayesian model was used to estimate the T-wave waveform in each cardiac beat and a set of 10 parameters was selected to segment each detected T wave. Beat-by-beat differences in each T-wave parameter were computed using the absolute value of the difference between each beat and the following one. Fisher criterion was used for determining the most discriminant T-wave parameters, then top-M ranked parameters yielding a normalized cumulative Fisher score > 95% were selected, and analysis was applied on these selected parameters. Simulated TWA EGMs were used to validate the algorithm.
  
  
  RESULTS
  In the simulation study, TWA was detectable even in the case of the smallest simulated alternans of 25 μV. In 13 of the 37 episodes (35%) occurring in nine of 16 patients, significant larger beat-to-beat variations before arrhythmia onset were detected compared to their respective references (median one positive episode per patient). Parameters including the T-wave apex amplitude seem the more discriminant parameters.
  
  
  CONCLUSIONS
  Detection of beat-by-beat repolarization variations in ICD-stored EGMs is feasible in a significant subset of cases and may be used for predicting the onset of ventricular arrhythmias.
authors: Federation of Cardiology, University Hospital Rangueil, Toulouse, France.
authors: Philippe
authors: P
authors: Maury
authors: Chao
authors: C
authors: Lin
authors: Jean-Luc
authors: JL
authors: Pasquié
authors: Frank
authors: F
authors: Raczka
authors: Lionel
authors: L
authors: Beck
authors: Jérôme
authors: J
authors: Taieb
authors: Corinne
authors: C
authors: Mailhes
authors: Jean-Yves
authors: JY
authors: Tourneret
authors: Anne
authors: A
authors: Rollin
authors: Alexandre
authors: A
authors: Duparc
authors: Pierre
authors: P
authors: Mondoly
authors: Pierre
authors: P
authors: Winum
authors: Philippe
authors: P
authors: Rolland
authors: Francis
authors: F
authors: Castanié
authors: Benoit
authors: B
authors: Hallier
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D017147:Defibrillators, Implantable; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000002:abnormalities; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000628:therapy*
keywords: T-wave alternans; implantable cardioverter defibrillator; intracardiac electrogram; sudden death; ventricular tachycardia