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Little data is available comparing the efficacy of the Transvene, Endotak C 70 series, and the active CAN configuration on defibrillation success. In addition, the impact of the superior vena cava (SVC) electrode surface area and length on the active CAN system is unknown. Therefore, we compared the defibrillation efficacy of the Transvene and Endotak C 70 series lead systems with and without the active CAN in dogs. Defibrillation threshold (DFT) testing was randomly performed in 20 dogs. In protocol I (10 dogs), DFT energy was compared in three RV/SVC lead systems with an SVC electrode defibrillating surface area of 90 mm2 (Transvene-90), 160 mm2 (Transvene-160), 617 mm2 (Endotak), and an RV/CAN configuration. In protocol II (10 dogs), DFT comparison was performed in the Transvene-90/CAN, Transvene-160/CAN, Endotak/CAN, and RV/CAN configurations. In protocol I, increasing the SVC surface area from 90 to 160 mm2 and from 160 to 617 mm2 significantly lowered DFT energy. The Endotak and the RV/CAN systems provided the lowest DFT energy requirements. In protocol II, the Endotak/CAN system significantly lowered DFT energy compared to the other three lead configurations. In both protocols, the impedance decreased as the SVC surface area increased from 90 to 160 mm2. However, no significant reduction in DFT impedance occurred as the SVC surface area increased from the Transvene-160 to the Endotak lead. Increasing the SVC surface area from 90 to 617 mm2 in a two coil lead system lowered DFT energy to similar levels provided by the RV/CAN configuration. The addition of an SVC electrode with a surface area of 90 or 160 mm2 did not reduce DFT energy compared to the RV/CAN configuration. The Endotak/CAN system, however, provided the lowest DFT requirements.

In a study of 11 dogs, we assessed whether the defibrillation energy requirements of a single transvenous right ventricular electrode/defibrillator can system depended on the can size. We compared the defibrillation threshold obtained with 65% fixed-tilt biphasic shocks with 20, 40, and 80 ml surface area defibrillator cans. The energy was delivered between a right ventricular coil inserted through the jugular vein and the can placed in the subcutaneous tissue of the left superior chest wall. The testing order of each can size was randomly determined. Triplicate defibrillation thresholds were obtained with each can. Despite a higher impedance (20 ml 85 +/- 22 ohms vs 80 ml 71 +/- 16 ohms, p < 0.01), the 20 ml can resulted in a similar defibrillation threshold compared with the 80 ml (20 ml 7.6 +/- 2.8 J vs 80 ml 7.5 +/- 3.4 J) and the 40 ml cans (20 ml 7.6 +/- 2.8 J vs 7.5 +/- 3.4 J). In conclusion, with the unipolar lead system the can size does not appear to be a factor limiting defibrillation success. Even a can the size of a pacemaker does not appear to significantly affect the defibrillation efficacy of this lead system.