title: Triphasic waveforms are superior to biphasic waveforms for transthoracic defibrillation: experimental studies.
abstract: OBJECTIVE
  Our objective was to evaluate the efficacy of triphasic waveforms for transthoracic defibrillation in a swine model.
  
  
  BACKGROUND
  Triphasic shocks have been found to cause less post-shock dysfunction than biphasic shocks in chick embryo studies.
  
  
  METHODS
  After 30 s of electrically induced ventricular fibrillation (VF), each pig in part I (n = 32) received truncated exponential biphasic (7.2/7.2 ms) and triphasic (4.8/4.8/4.8 ms) transthoracic shocks. Each pig in part II (n = 14) received biphasic (5/5 ms) and triphasic shocks (5/5/5 ms). Three selected energy levels (50, 100, and 150 J) were tested for parts I and II. Pigs in part III (n = 13) received biphasic (5/5 ms) and triphasic (5/5/5 ms) shocks at a higher energy (200 and 300 J). Although the individual pulse durations of these shocks were equal, the energy of each pulse varied. Nine pigs in part I also received shocks where each individual pulse contained equal energy but was of a different duration (biphasic 3.3/11.1 ms; triphasic 2.0/3.2/9.2 ms).
  
  
  RESULTS
  Triphasic shocks of equal duration pulses achieved higher success than biphasic shocks at delivered low energies: <40 J: 38 +/- 5% triphasic vs. 19 +/- 4% biphasic (p < 0.01); 40 to <50 J: 66 +/- 7% vs. 42 +/- 7% (p < 0.01); and 50 to <65 J: 78 +/- 4% vs. 54 +/- 5% (p < 0.05). Shocks of equal energy but different duration pulses achieved relatively poor success for both triphasic and biphasic waveforms. Shock-induced ventricular tachycardia (VT) and asystole occurred less often after triphasic shocks.
  
  
  CONCLUSIONS
  Triphasic transthoracic shocks composed of equal duration pulses were superior to biphasic shocks for VF termination at low energies and caused less VT and asystole.
authors.affiliation: Cardiovascular Center, College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: R S
authors.initials: RS
authors.lastname: Ramabadran
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Boddicker
authors.forename: Imran
authors.initials: I
authors.lastname: Bawaney
authors.forename: Loyd R
authors.initials: LR
authors.lastname: Davies
authors.forename: M Bridget
authors.initials: MB
authors.lastname: Zimmerman
authors.forename: Scott
authors.initials: S
authors.lastname: Wuthrich
authors.forename: Janice L
authors.initials: JL
authors.lastname: Jones
authors.forename: Richard E
authors.initials: RE
authors.lastname: Kerber
mesh_terms: D000818:Animals; D004554:Electric Countershock / Q000379:methods*; D004594:Electrophysiology; D023421:Models, Animal; D013552:Swine; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy*