Acute Feasibility Investigation of a New S-ICD Electrode

This is an early-stage feasibility study. This study seeks to characterize the performance of the new electrode shock configuration with the S-ICD

Background: The subcutaneous implantable cardioverter-defibrillator (S-ICD, EMBLEM®, Boston Scientific Corp) delivers 80 J shocks from an 8 cm left-parasternal coil (LPC) to a 59 cc left lateral pulse generator (PG). A system that defibrillates with lower energy could significantly reduce PG size. Computer modeling and animal studies suggest a 2nd shock coil either parallel (P) to LPC or transverse (T) from xiphoid to PG pocket would significantly reduce shock impedance and defibrillation threshold (DFT). Objective: Acutely test defibrillation efficacy of P and T configurations in patients receiving an S-ICD. Methods: Testing was performed in patients receiving a conventional S-ICD system (C) for standard indications. Patients at risk for conversion failure, stroke or infection were excluded. A 65 J success with the conventional S-ICD was required prior to investigational testing. A second electrode was temporarily inserted from the xiphoid incision using the same introducer and sheath tools and connected to the PG with an investigational Y-adapter (Model 3598, Boston Scientific). Phase 1 (n=11) tested only P at a starting energy of 50 J with subsequent tests at 65 or 30 J then 40 or 20 J depending upon outcome. Phase 2 (n=21) tested both P and T in random order, starting at 30 J then either 40 or 20 J.