Y. Yamanouchi et al., Optimal small-capacitor biphasic waveform for external defibrillation - Influence of phase-1 tilt and phase-2 voltage, CIRCULATION, 98(22), 1998, pp. 2487-2493
Citations number
23
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-Biphasic waveforms have been reported to be more efficacious tha
n monophasic waveforms for external defibrillation. This study examined the
optimal phase-1 tilts and phase-2 leading-edge voltages with small capacit
ors (60 and 20 mu F) for external defibrillation. We also assessed the abil
ity of the "charge-burping" model to predict the optimal waveforms.
Methods and Results-Two groups of studies were performed. In group 1,9 biph
asic waveforms from a combination of 3 phase-1 tilt values (30%, 50%, and 7
0%) and 3 phase-2 leading-edge voltage values (0.5, 1.0, and 1.5 times the
phase-1 leading-edge voltage, V-1) were tested. Phase-2 pulse width was hel
d constant at 3 ms in all waveforms. Two separate 60-mu F capacitors were u
sed in each phase. The energy value that would produce a 50% likelihood of
successful defibrillation (E-50) 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 wavef
orms in group 1, except for a 20-mu F capacitor for phase 2. E-50 decreased
with increasing phase-1 tilt. Phase-2 leading-edge voltage of 1.0 to 1.5 V
-1 appeared to minimize E-50 for phase-1 tilt of 50% and 70% but worsened E
-50 for phase-1 tilt of 30%. There was a significant correlation between E-
50 and residual membrane voltage at the end of phase 2, as calculated by th
e charge-burping model in both groups (group 1, R-2=0.47, P<0.001; group 2,
R-2=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-burpin
g model predicted the optimal external biphasic waveform.