title: A comparison of biphasic and monophasic shocks for external defibrillation. Physio-Control Biphasic Investigators.
abstract: OBJECTIVE
  The ability of a shock to defibrillate the heart depends on its waveform and energy. Past studies of biphasic truncated exponential (BTE) shocks for external defibrillation focused on low energy levels. This prospective, randomized, double-blind clinical trial compared the first-shock efficacies of 200-joule (J) BTE, 130-J BTE, and 200-J monophasic damped sine wave shocks.
  
  
  METHODS
  Ventricular fibrillation (VF) was induced in 115 patients during evaluation of implantable cardioverter-defibrillator function and 39 patients during electrophysiologic evaluation of ventricular arrhythmias. After 19 +/- 10 seconds of VF, a randomized transthoracic shock was administered. Mean first-shock success rates of the three groups were compared using a "Tukey-like" statistical test, adjusting for multiple comparisons. Blood pressures and arterial oxygen saturations were measured before VF induction and 30, 90, and 150 seconds after successful defibrillation.
  
  
  RESULTS
  First-shock success rates were 61/68 (90%) for 200-J monophasic, 39/39 (100%) for 200-J biphasic, and 39/47 (83%) for 130-J biphasic shocks. The 200-J biphasic shocks were simultaneously superior in first-shock efficacy to both 200-J monophasic and 130-J biphasic shocks (experimentwise error rate, alpha < 0.01). There was no significant difference between the efficacies of 200-J monophasic and 130-J biphasic shocks, nor was there any significant difference between the three groups in hemodynamic parameters after successful shocks.
  
  
  CONCLUSIONS
  Biphasic shocks of 200 J provide better first-shock defibrillation efficacy for short-duration VF than 200-J monophasic and 130-J biphasic shocks and thus may allow earlier termination of VF in cardiac arrest patients.
authors.affiliation: Arrhythmia Service, Scripps Memorial Hospital, La Jolla, California 92037, USA. epdoc@aol.com
authors.forename: S L
authors.initials: SL
authors.lastname: Higgins
authors.forename: J M
authors.initials: JM
authors.lastname: Herre
authors.forename: A E
authors.initials: AE
authors.lastname: Epstein
authors.forename: G S
authors.initials: GS
authors.lastname: Greer
authors.forename: P L
authors.initials: PL
authors.lastname: Friedman
authors.forename: M L
authors.initials: ML
authors.lastname: Gleva
authors.forename: J G
authors.initials: JG
authors.lastname: Porterfield
authors.forename: F W
authors.initials: FW
authors.lastname: Chapman
authors.forename: E S
authors.initials: ES
authors.lastname: Finkel
authors.forename: P W
authors.initials: PW
authors.lastname: Schmitt
authors.forename: R C
authors.initials: RC
authors.lastname: Nova
authors.forename: H L
authors.initials: HL
authors.lastname: Greene
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000628:therapy*; D001794:Blood Pressure; D017147:Defibrillators, Implantable / Q000592:standards*; D004554:Electric Countershock / Q000379:methods*; D017097:Electric Impedance; D006352:Heart Ventricles; D019220:High-Energy Shock Waves; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D016896:Treatment Outcome