title: Optimal small-capacitor biphasic waveform for external defibrillation: influence of phase-1 tilt and phase-2 voltage.
abstract: BACKGROUND
  Biphasic waveforms have been reported to be more efficacious than monophasic waveforms for external defibrillation. This study examined the optimal phase-1 tilts and phase-2 leading-edge voltages with small capacitors (60 and 20 microF) for external defibrillation. We also assessed the ability of the "charge-burping" model to predict the optimal waveforms.
  
  
  RESULTS
  Two groups of studies were performed. In group 1, 9 biphasic waveforms from a combination of 3 phase-1 tilt values (30%, 50%, and 70%) and 3 phase-2 leading-edge voltage values (0.5, 1.0, and 1.5 times the phase-1 leading-edge voltage, V1) were tested. Phase-2 pulse width was held constant at 3 ms in all waveforms. Two separate 60- microF capacitors were used in each phase. The energy value that would produce a 50% likelihood of successful defibrillation (E50) decreased with increasing phase-1 tilt and increased with increasing phase-2 leading-edge voltage except for the 30% phase-1 tilt waveforms. In group 2, 9 waveforms were identical to the waveforms in group 1, except for a 20- microF capacitor for phase 2. E50 decreased with increasing phase-1 tilt. Phase-2 leading-edge voltage of 1.0 to 1.5 V1 appeared to minimize E50 for phase-1 tilt of 50% and 70% but worsened E50 for phase-1 tilt of 30%. There was a significant correlation between E50 and residual membrane voltage at the end of phase 2, as calculated by the charge-burping model in both groups (group 1, R2=0.47, P<0.001; group 2, R2=0.42, P<0.001).
  
  
  CONCLUSIONS
  The waveforms with 70% phase-1 tilt were more efficacious than those with 30% and 50%. The relationship of phase-2 leading-edge voltage to defibrillation efficacy depended on phase-2 capacitance. The charge-burping model predicted the optimal external biphasic waveform.
authors.affiliation: Department of Cardiology, Cleveland Clinic Foundation, Cleveland, Ohio, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamanouchi
authors.forename: J E
authors.initials: JE
authors.lastname: Brewer
authors.forename: K A
authors.initials: KA
authors.lastname: Mowrey
authors.forename: A M
authors.initials: AM
authors.lastname: Donohoo
authors.forename: B L
authors.initials: BL
authors.lastname: Wilkoff
authors.forename: P J
authors.initials: PJ
authors.lastname: Tchou
mesh_terms: D000818:Animals; D004553:Electric Conductivity; D004554:Electric Countershock / Q000295:instrumentation*; D008955:Models, Cardiovascular; D013552:Swine