title: Kinetics of atrial repolarization alternans in a free-behaving ovine model.
abstract: Kinetics of Atrial Repolarization Alternans.
  
  
  BACKGROUND
  Repolarization alternans (Re-ALT), a beat-to-beat alternation in action potential repolarization, promotes dispersion of repolarization, wavebreaks, and reentry. Recently, Re-ALT has been shown to play an important role in the transition from rapid pacing to atrial fibrillation (AF) in humans. The detailed kinetics of atrial Re-ALT, however, has not been reported so far. We developed a chronic free-behaving ovine pacing model to study the kinetics of atrial Re-ALT as a function of pacing rate.
  
  
  METHODS
  Thirteen sheep were chronically implanted with 2 pacemakers for the recording of broadband right atrial unipolar electrograms and delivery of rapid pacing protocols. Beat-to-beat differences in the atrial T-wave apex amplitude as a measure of Re-ALT and activation time were analyzed at incremental pacing rates until the effective refractory period (ERP) defined as stable 2:1 capture.
  
  
  RESULTS
  Atrial Re-ALT appeared intermittently but without periodicity, and increased in amplitude as a function of pacing rate until ERP. Intermittent 2:1 atrial capture was observed at pacing cycle lengths 40 ms above ERP, and increased in duration as a function of pacing rate. Episodes of rapid pacing-induced AF were rare, and were preceded by Re-ALT or complex oscillations of atrial repolarization, but without intermittent capture.
  
  
  CONCLUSIONS
  We show in vivo that atrial Re-ALT developed and increased in magnitude with rate until stable 2:1 capture. In rare instances where capture failure did not occur, Re-ALT and complex oscillations of repolarization surged and preceded AF initiation. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1003-1012, September 2012).
authors.affiliation: Applied Signal Processing Group, Swiss Federal Institute of Technology, Lausanne, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Jousset
authors.forename: Joanna
authors.initials: J
authors.lastname: Tenkorang
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Vesin
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pascale
authors.forename: Patrick
authors.initials: P
authors.lastname: Ruchat
authors.forename: Anne Garderes
authors.initials: AG
authors.lastname: Rollin
authors.forename: Martin
authors.initials: M
authors.lastname: Fromer
authors.forename: Sanjiv M
authors.initials: SM
authors.lastname: Narayan
authors.forename: Etienne
authors.initials: E
authors.lastname: Pruvot
mesh_terms: D000200:Action Potentials; D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D006325:Heart Atria / Q000503:physiopathology*; D007700:Kinetics; D008297:Male; D023421:Models, Animal; D012032:Refractory Period, Electrophysiological; D012756:Sheep