title: Double-pulse defibrillation using pulse separation based on the fibrillation cycle length.
abstract: BACKGROUND
  We investigated a method of defibrillation in which two shocks were delivered to the same electrodes with a separation based on the cycle length of the fibrillation event (FCL).
  
  
  RESULTS
  In pentobarbital anesthetized dogs, a computerized system determined the FCL from the fibrillation event, computed the desired double-pulse (DP) shock separation, and immediately delivered the DP shocks. In group 1, energy for 50% success at defibrillation (E50) was measured using separations from 55% to 95% of the FCL and remeasured after administration of flecainide, clofilium, or vehicle to change the FCL. Both drugs increased FCL by approximately 25%. Plots of E50 versus %FCL aligned before and after drug showed that the optimum pulse separation followed the FCL. In group 2, E50s were measured for 55% to 185% FCL separations in clofilium or vehicle-treated animals. The optimum DP E50 was at 85% FCL and was not significantly different from the single-shock E50. In group 3, no differences were found when comparing the probability of success versus total energy relationships for single and optimum DP shocks. Group 4 compared E50s for single and DP shocks using a single-catheter configuration and three-electrode configurations (catheter-subdermal patch). E50s for single and DP shocks were equal using the single-catheter configuration but DP shocks required approximately 20% more energy in the three-electrode configurations.
  
  
  CONCLUSIONS
  In single-pathway lead configurations, two shocks with 85% FCL separation can be reliably combined to defibrillate using the same total energy as a larger single shock. Since the energy is unchanged but the total duration is doubled, DP shock currents are reduced by 20% to 30%.
authors: Department of Electrophysiology Research, Lilly Research Laboratory Division, Eli Lilly and Company, Indianapolis, Indiana.
authors: R J
authors: RJ
authors: Sweeney
authors: R M
authors: RM
authors: Gill
authors: P R
authors: PR
authors: Reid
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D017147:Defibrillators, Implantable; D004285:Dogs; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D008297:Male; D014693:Ventricular Fibrillation / Q000503:physiopathology* / Q000628:therapy*
chemical_list: D000889:Anti-Arrhythmia Agents