Abstract 2903: Transvenous ICD Defibrillation Efficacy is Possible With a Completely Subcutaneous, Anterior-Posterior Shock Pathway
Introduction: An implantable cardioverter defibrillator (ICD) with sense and shock electrodes residing only in the subcutaneous or submuscular space provides potential advantages over traditional transvenous ICD systems. Without a shock-coil within the heart, such a device will likely require more energy to adequately defibrillate a population of patients. The purpose of this study was to identify non-transvenous defibrillation configurations that provide efficacy comparable to transvenous devices.
Methods: All patients received an active can emulator (ACE) in either a subpectoral pocket from an inframammary incision (IM), or a conventional subcutaneous pocket from an infraclavicular incision (IC). Patients received a 25-cm coil electrode implanted from a midaxillary incision on the left thorax and tunneled to the spine. All shocks were truncated exponential biphasic, with nominal tilt of 50% per phase but duration limited to 20 ms. Shocks in Groups A, B & C were delivered from a 270-μF capacitance, shocks in D & E with 160 μF. Groups C & E also were implanted with a 15-cm coil electrode along the left edge of the sternum and connected in parallel with the ACE electrode. VF was induced with a non-transvenous T-shock, non-transvenous 25-Hz burst or 50-Hz burst via an implanted EP catheter. Elapsed time from VF induction to shock was 20 sec. A modified 3-step binary search protocol was used to both characterize the defibrillation energy response curve and to determine the percentage of patients that can be successfully defibrillated with 2 tests 20-J below max output.
Results: Results for 136 patients completing the protocol are below:
Conclusions: Defibrillation efficacy comparable to a transvenous ICD was obtained with an anterior-posterior non-transvenous configuration with a capacitance of 160-μF and 70-J delivered energy maximum output. High efficacy with a conventional ICD pocket location is possible when a second subcutaneous coil is placed along the sternum.