title: A comparison of rectilinear and truncated exponential biphasic waveforms in elective cardioversion of atrial fibrillation: a prospective randomized controlled trial.
abstract: BACKGROUND
  Several different biphasic waveforms are used clinically, but few studies have compared their efficacy. The two main waveforms are the biphasic rectilinear (BR) and biphasic truncated exponential (BTE) waveforms, both of which have important differences, particularly at the extremes of transthoracic impedance.
  
  
  OBJECTIVE
  To compare the efficacy of two commonly used defibrillation waveforms in the elective cardioversion of atrial fibrillation.
  
  
  METHODS
  In a prospective randomized controlled study, sequential adult patients undergoing elective cardioversion for AF were recruited. Patients were randomized to receive synchronized defibrillation using either a BR or BTE waveform, both using a 50J, 100J, 150J, 200J, 200J selected energy escalating protocol. Failure to cardiovert after the fifth shock was classed as failed defibrillation. The power of this study was 80% with 5% significance level to detect a difference of 20% or greater between groups. Survival analysis was used to compare the total energy delivered to achieve successful cardioversion between groups.
  
  
  RESULTS
  A total of 202 patients were recruited, of which data are complete for 199 (100 BR; 99 BTE). Median number of shocks to achieve cardioversion was 2 for the BR waveform and 3 for the BTE waveform (P = 0.059). In the BR waveform group, 95/100 (95.0%) achieved sinus rhythm. In the BTE waveform group, 90/99 (90.9%) achieved sinus rhythm and this group required on average 117.1J more energy to achieve the outcome compared to the BR waveform group (P = 0.838).
  
  
  CONCLUSIONS
  BR and BTE waveforms show similar high efficacy in the elective cardioversion of atrial fibrillation.
authors: Department of Anaesthetics, University Hospital Southampton NHS Foundation Trust, Southampton SO16 6YD, UK. charlesdeakin@doctors.org.uk
authors: Charles D
authors: CD
authors: Deakin
authors: Stephanie
authors: S
authors: Connelly
authors: Rupert
authors: R
authors: Wharton
authors: Ho Ming
authors: HM
authors: Yuen
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology / Q000628:therapy*; D002307:Cardiography, Impedance / Q000379:methods*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D016037:Single-Blind Method; D016896:Treatment Outcome