title: New approach to biphasic waveforms for internal defibrillation: fully discharging capacitors.
abstract: BACKGROUND
  The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform.
  
  
  RESULTS
  Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 microF) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 microF, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23+/-2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of < or =40 microF had the same E50 (6.7+/-1.7 J to 7.3+/-3.9 J) as the single-capacitor truncated waveform (7.3+/-3.7 J), whereas waveforms with phase-2 capacitors of > or =60 microF had an extremely high E50 (14.5+/-10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of > or =60 microF additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344+/-65 V to 407+/-50 V vs 339+/-83 V).
  
  
  CONCLUSIONS
  Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors.
authors.affiliation: Cleveland Clinic Foundation, Ohio 44195, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamanouchi
authors.forename: M G
authors.initials: MG
authors.lastname: Fishler
authors.forename: K A
authors.initials: KA
authors.lastname: Mowrey
authors.forename: B L
authors.initials: BL
authors.lastname: Wilkoff
authors.forename: T N
authors.initials: TN
authors.lastname: Mazgalev
authors.forename: P J
authors.initials: PJ
authors.lastname: Tchou
mesh_terms: D000818:Animals; D017147:Defibrillators, Implantable; D004553:Electric Conductivity; D004554:Electric Countershock / Q000379:methods*; D004867:Equipment Design; D013552:Swine; D014693:Ventricular Fibrillation / Q000628:therapy*