title: Relative efficacy of monophasic and biphasic waveforms for transthoracic defibrillation after short and long durations of ventricular fibrillation.
abstract: BACKGROUND
  Recently, interest has arisen in using biphasic waveforms for external defibrillation. Little work has been done, however, in measuring transthoracic defibrillation efficacy after long periods of ventricular fibrillation. In protocol 1, we compared the efficacy of a quasi-sinusoidal biphasic waveform (QSBW), a truncated exponential biphasic waveform (TEBW), and a critically damped sinusoidal monophasic waveform (CDSMW) after 15 seconds of fibrillation. In protocol 2, we compared the efficacy of the more efficacious biphasic waveform from protocol 1, QSBW, with CDSMW after 15 seconds and 5 minutes of fibrillation.
  
  
  RESULTS
  In protocol 1, 50% success levels, ED50, were measured after 15 seconds of fibrillation for the 3 waveforms in 6 dogs. In protocol 2, defibrillation thresholds were measured for QSBW and CDSMW after 15 seconds of fibrillation and after 3 minutes of unsupported fibrillation followed by 2 minutes of fibrillation with femoral-femoral cross-circulation. In protocol 1, QSBW had a lower ED50, 16.0+/-4.9 J, than TEBW, 20.3+/-4.4 J, or CDSMW, 27.4+/-6.0 J. In protocol 2, QSBW had a lower defibrillation threshold after 15 seconds, 38+/-10 J, and after 5 minutes, 41.5+/-5 J, than CDSMW after 15 seconds, 54+/-19 J, and 5 minutes, 80+/-30 J, of fibrillation. The defibrillation threshold remained statistically the same for QSBW for the 2 fibrillation durations but rose significantly for CDSMW.
  
  
  CONCLUSIONS
  In this animal model of sudden death and resuscitation, these 2 biphasic waveforms are more efficacious than the CDSMW at short durations of fibrillation. Furthermore, the QSBW is even more efficacious than the CDSMW at longer durations of fibrillation.
authors.affiliation: Division of Cardiovascular Diseases, Department of Medicine, University of Alabama at Birmingham, AL, USA. gpw@crml.uab.edu
authors.forename: G P
authors.initials: GP
authors.lastname: Walcott
authors.forename: S B
authors.initials: SB
authors.lastname: Melnick
authors.forename: F W
authors.initials: FW
authors.lastname: Chapman
authors.forename: J L
authors.initials: JL
authors.lastname: Jones
authors.forename: W M
authors.initials: WM
authors.lastname: Smith
authors.forename: R E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000818:Animals; D004285:Dogs; D004554:Electric Countershock; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000628:therapy*