131-05: Comparison of Defibrillation Thresholds in Swine for Transvenous, Subcutaneous and Substernal Electrode Configurations

Purpose: Transvenous (TV) ICD systems represent the device-based standard of care for treatment of arrhythmia, yet TV lead implantation is often not possible or desired. Subcutaneous (SQ) ICDs have emerged as a non-TV option, but energy requirements for defibrillation through the chest wall have resulted in larger, heavier SQ ICDs with high defibrillation thresholds (DFTs). Described here are the results of research evaluating the DFT of a novel substernal-lateral electrode vector, as compared to both TV and SQ DFTs. Method: Each animal was implanted with three leads: a 5.7 cm coil implanted in the right ventricle, an 8 cm coil tunneled SQ and positioned parasternally (right side) and an 8 cm coil in the substernal (SS) space at or adjacent the sternal midline via minimally invasive subxiphoid access. An active can emulator (ACE) was placed in a pocket on the left lateral thorax at the level of the heart. DFT testing was performed using a step-up, step-down DFT search protocol, with DFTs calculated via logistic regression. Results: DFT testing was completed in n = 11 pigs (39.3 ± 9.5 kg). Average DFTs (see graph) in Joules (J) were 15 ± 6 J (TV), 22 ± 6 J (SS) and 121 ± 76 J (SQ). Average shock impedances were 38.9 ± 3.3 Ω (TV), 37.7 ± 5.4 Ω (SS) and 43.2 ± 8.8 Ω (SQ).