DOUBLE-PULSE DEFIBRILLATION USING PULSE SEPARATION BASED ON THE FIBRILLATION CYCLE LENGTH

Introduction: We investigated a method of defibrillation in which two shocks were delivered to the same electrodes with a separation based o n the cycle length of the fibrillation event (FCL). Methods and Result s: In pentobarbital anesthetized dogs, a computerized system determine d the FCL from the fibrillation event, computed the desired double-pul se (DP) shock separation, and immediately delivered the DP shocks. In group 1, energy for 50% success at defibrillation (E50) was measured u sing separations from 55% to 95% of the FCL and remeasured after admin istration of flecainide, clofilium, or vehicle to change the FCL. Both drugs increased FCL by approximate to 25%. Plots of E50 versus %FCL a ligned before and after drug showed that the optimum pulse separation followed the FCL. In group 2, E50s were measured for 55% to 185% FCL s eparations in clofilium or vehicle-treated animals. The optimum DP E50 was at 85% FCL and was not significantly different from the single-sh ock E50. In group 3, no differences were found when comparing the prob ability of success versus total energy relationships for single and op timum DP shocks. Group 4 compared E50s for single and DP shocks using a single-catheter configuration and three-electrode configurations (ca theter-subdermal patch). E50s for single and DP shocks were equal usin g the single-catheter configuration but DP shocks required approximate to 20% more energy in the three-electrode configurations. Conclusion: In single-pathway lead configurations, two shocks with 85% FCL separa tion can be reliably combined to defibrillate using the same total ene rgy as a larger single shock. Since the energy is unchanged but the to tal duration is doubled, DP shock currents are reduced by 20% to 30%.