title: Atrial defibrillation threshold in humans minutes after atrial fibrillation induction; "A stitch in time saves nine".
abstract: OBJECTIVE
  To assess the effects of atrial fibrillation duration on the defibrillation threshold in atrial fibrillation patients seconds or minutes after initiation of the arrhythmia.
  
  
  RESULTS
  Nineteen patients with recurrent symptomatic atrial fibrillation were evaluated. After programmed induction of atrial fibrillation, the defibrillation threshold was assessed after two sequential periods of arrhythmia in the same patient: an "ultrashort" period of 30 s duration and a "short" period, which lasted 10 min. After the specified period, internal cardioversion was attempted using a balloon-guided catheter that allows the delivery of biphasic shocks between one electrode array placed in the left pulmonary artery and a proximal electrode array on the lateral right atrial wall. The defibrillation threshold was assessed with energy steps of 0.5 J with a starting level of 0.5 J. Mean time from induction to successful defibrillation was 92+/-30 s after the "ultrashort" period of atrial fibrillation and 910+/-86 s after the short period. The defibrillation threshold was significantly greater after 10 min of atrial fibrillation than after 30 s of arrhythmia (2.32+/-0.61 J vs 1.31+/-0.66 J, P<0.001). Clinical data were not found to affect the defibrillation threshold.
  
  
  CONCLUSIONS
  Prolongation of atrial fibrillation over minutes in patients with paroxysmal arrhythmia increases the energy requirements for successful defibrillation.
authors.affiliation: Department of Cardiology, Heraklion University Hospital, P.O. Box 1352, Stavrakia, Heraklion-Crete, Greece.
authors.forename: P E
authors.initials: PE
authors.lastname: Vardas
authors.forename: E G
authors.initials: EG
authors.lastname: Manios
authors.forename: E M
authors.initials: EM
authors.lastname: Kanoupakis
authors.forename: D N
authors.initials: DN
authors.lastname: Dermitzaki
authors.forename: H E
authors.initials: HE
authors.lastname: Mavrakis
authors.forename: E M
authors.initials: EM
authors.lastname: Kallergis
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D004554:Electric Countershock; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged