title: The effects of biphasic and conventional monophasic defibrillation on postresuscitation myocardial function.
abstract: OBJECTIVE
  The purpose of this study was to compare the effects of biphasic defibrillation waveforms and conventional monophasic defibrillation waveforms on the success of initial defibrillation, postresuscitation myocardial function and duration of survival after prolonged ventricular fibrillation (VF).
  
  
  BACKGROUND
  We have recently demonstrated that the severity of postresuscitation myocardial dysfunction was closely related to the magnitude of the electrical energy of the delivered defibrillation shock. In the present study, the effects of fixed 150-J low-energy biphasic waveform shocks were compared with conventional monophasic waveform shocks after prolonged VF.
  
  
  METHODS
  Twenty anesthetized, mechanically ventilated domestic pigs were investigated. VF was induced with an AC current delivered to the right ventricular endocardium. After either 4 or 7 min of untreated ventricular fibrillation (VF), the animals were randomized for attempted defibrillation with up to three 150-J biphasic waveform shocks or conventional sequence of 200-, 300- or 360-J monophasic waveform shocks. If VF was not reversed, a 1-min interval of precordial compression preceded a second sequence of up to three shocks. The protocol was repeated until spontaneous circulation was restored or for a total of 15 min.
  
  
  RESULTS
  Monophasic waveform defibrillation after 4 or 7 min of untreated VF resuscitated eight of 10 pigs. All 10 pigs treated with biphasic waveform defibrillation were successfully resuscitated. Transesophageal echo-Doppler, arterial pressure and heart rate measurements demonstrated significantly less impairment of cardiovascular function after biphasic defibrillation.
  
  
  CONCLUSIONS
  Lower-energy biphasic waveform shocks were as effective as conventional higher energy monophasic waveform shocks for restoration of spontaneous circulation after 4 and 7 min of untreated VF. Significantly better postresuscitation myocardial function was observed after biphasic waveform defibrillation.
authors.affiliation: The Institute of Critical Care Medicine, Palm Springs, California 92262-5309, USA.
authors.forename: W
authors.initials: W
authors.lastname: Tang
authors.forename: M H
authors.initials: MH
authors.lastname: Weil
authors.forename: S
authors.initials: S
authors.lastname: Sun
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: H P
authors.initials: HP
authors.lastname: Povoas
authors.forename: A M
authors.initials: AM
authors.lastname: Pernat
authors.forename: J
authors.initials: J
authors.lastname: Bisera
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D006321:Heart / Q000503:physiopathology*; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy; D006439:Hemodynamics; D011897:Random Allocation; D012151:Resuscitation / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy