title: Biphasic versus monophasic shock for external cardioversion of atrial flutter: a prospective, randomized trial.
abstract: BACKGROUND
  External cardioversion is effective to terminate persistent atrial flutter. Biphasic shocks have been shown to be superior to monophasic shocks for ventricular defibrillation and atrial fibrillation cardioversion. The purpose of this trial was to compare the efficacy of rectilinear biphasic versus standard damped sine wave monophasic shocks in symptomatic patients with typical atrial flutter.
  
  
  METHODS
  135 consecutive patients were screened, 95 (70 males, mean age 62 +/- 13 years) were included. Patients were randomly assigned to a monophasic or biphasic cardioversion protocol. Forty-seven patients randomized to the monophasic protocol received sequential shocks of 100, 150, 200, 300 and 360 J. Forty-eight patients with the biphasic protocol received 50, 75, 100, 150 or 200 J.
  
  
  RESULTS
  First-shock efficacy with 50-Joule, biphasic shocks (23/48 patients, 48%) was significantly greater than with the 100-Joule, monophasic waveform (13/47 patients, 28%, p = 0.04). The cumulative second-shock efficacy with the 50- and 75-Joule, biphasic waveform (39/48 patients, 81%) was significantly greater than with the 100- and 150-Joule, monophasic waveform (25/47 patients, 53%, p < 0.05). The cumulative efficacy for the higher energy levels showed naturally no significant difference between the two groups. The amount of the mean delivered energy was significantly lower in the biphasic group (76 +/- 39 J) compared to the monophasic one (177 +/- 78 J, p < 0.05).
  
  
  CONCLUSIONS
  For transthoracic cardioversion of typical atrial flutter, biphasic shocks have greater efficacy and the mean delivered current is lower than for monophasic shocks. Therefore, biphasic cardioversion with lower starting energies should be recommended.
authors.affiliation: Department of Cardiology, University Heart Center Hamburg, Hamburg, Germany. k.mortensen@uke.uni-hamburg.de
authors.forename: Kai
authors.initials: K
authors.lastname: Mortensen
authors.forename: Tim
authors.initials: T
authors.lastname: Risius
authors.forename: Tjark F
authors.initials: TF
authors.lastname: Schwemer
authors.forename: Muhammet Ali
authors.initials: MA
authors.lastname: Aydin
authors.forename: Ralf
authors.initials: R
authors.lastname: Köster
authors.forename: Hanno U
authors.initials: HU
authors.lastname: Klemm
authors.forename: Boris
authors.initials: B
authors.lastname: Lutomsky
authors.forename: Thomas
authors.initials: T
authors.lastname: Meinertz
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Ventura
authors.forename: Stephan
authors.initials: S
authors.lastname: Willems
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000628:therapy*; D004554:Electric Countershock / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016896:Treatment Outcome