10265-84 Impact of the Defibrillating Surface Area of an Additional Superior Vena Cava Electrode on the Unipolar Right Ventricular Coil/Defibrillator Can System

We assessed the hypothesis that the surface area of an additional superior vena cava (SVC) defibrillation electrode may impact on the defibrillation efficacy of a right ventricular (RV) coil/CAN system. In ten dogs we randomly compared the energy requirements for defibrillation (DFT) using the RV/CAN configuration and three triple lead systems employing an additional lead in the SVC with a defibrillating surface area of 90mm2, 160mm2 and 617mm2 respectively. Biphasic shocks with 65% fixed tilt were used for defibrillation. Triplicate defibrillation thresholds were determined with each lead system. With every electrode system the RV coil was used as cathode. Energy (J), peak voltage (VI and impedance at defibrillation threshold are shown below:RV/CAN90mm2160mm2617mm2DFT(J)8.6±3.38.1±2.68.2±2.54.9±1.9*Voltage(V)373±73365±58367±65284±53*Impedance74±2453±13+48±11+52±10+*617mm2 vs RV/CAN p<0.01+90mm2 160mm2, 617mm2 vs RV/CAN p<0.01These results indicate that the surface area of an additional SVC defibrillating electrode may be critical to improving the energy requirement for defibrillation achieved with a single lead right ventricular coil/defibrillator can system