title: [Biphasic low-energy internal cardioversion in atrial fibrillation induced during electrophysiologic study].
abstract: BACKGROUND
  Atrial fibrillation is observed in 10% of electrophysiological studies. Previous studies have shown the efficacy of biphasic low energy internal cardioversion to restore sinus rhythm. We studied the efficacy and safety of low-energy internal cardioversion and the biphasic curve, in sustained atrial fibrillation (>15 min) during electrophysiologic procedures.
  
  
  METHODS
  From January 1997 to August 1998, 320 patients underwent an electrophysiological study. An internal cardioversion was done on those patients who developed sustained atrial fibrillation. We delivered biphasic shocks between electrodes-catheters positioned in the right atrium and the coronary sinus. Increasing energy was applied until restoration of sinus rhythm or a maximum of 10 joules were achieved with no result. A right ventricle electrode was used to synchronize the V wave and for temporary pacing.
  
  
  RESULTS
  Thirty one episodes of sustained atrial fibrillation were observed in 26 patients (1,23 episodes/patient) and a mean of 2,58 internal cardioversions were applied per every patient. Sinus rhythm was restored in twenty three patients. The mean energy delivered was 4.1 joules. The mean time for the recovery was 3,200 ms. Temporary pacing was used in 16% of the patients for up to 1 minute. No AV blocks were observed.
  
  
  CONCLUSIONS
  Internal cardioversion successfully restored sinus rhythm in 88.5% of the patients who presented sustained atrial fibrillation (88.5%). Temporary pacing was necessary for the treatment of postsinus shock pauses.
authors.affiliation: Departamento de Enfermedades Cardiovasculares, Laboratorio de Electrofisiología Cardíaca, Pontificia Universidad Católica, Santiago, Chile. elecfisi@med.puc.cl
authors.forename: C F
authors.initials: CF
authors.lastname: Karmelic
authors.forename: A M
authors.initials: AM
authors.lastname: Cambón
authors.forename: R
authors.initials: R
authors.lastname: González
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods* / Q000706:statistics & numerical data; D004554:Electric Countershock / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged