Rapid current switching with an endovascular electrode configuration significantly decreases implantable defibrillator thresholds

This study sought to demonstrate that defibrillation thresholds (DFTs) for electrical defibrillation of the heart could be reduced significantly with entirely endovascular electrode placements by switching current rapidly between electrode sets. A left ventricular (LV) electrode and custom defibrillator were built. A commercial defibrillation catheter was implanted in 9 swine with shocking coils in the right ventricle (RV) and superior vena cava (SVC). A pectoral (Can) electrode was implanted over the left pectoral muscle. The custom LV electrode was inserted into the middle cardiac vein. Defibrillation thresholds were determined for a control configuration (biphasic shock, RV^- → SVC⁺ + Can⁺), and for two experimental configurations. One configuration (2/2) split the current between two current paths (RV^- → SVC⁺ + Can⁺, LV^- → SVC⁺ + Can⁺) and another (3/3) distributed the current between three current paths (RV → SVC⁺ + Can⁺, SVC^- + Can^- → LV⁺, LV^- → RV⁺). DFT energy levels were more than 41.7% lower (p= 0.016) for the 2/2 configuration, and more than 42.7% lower (p=0.008) for the 3/3 configuration.