Abstract 3514: Novel Electrode Design for Painless Internal Defibrillation also Allows for Successful External Defibrillation
Background: We previously showed that skeletal muscle activation, the source of ICD shock related pain, can be minimized during internal defibrillation using a novel “Faraday cage” electrode system that confines the shock field to cardiac tissue. That cage design, however, precluded external defibrillation. We now test a modified electrode cage system composed of closely spaced multiple conducting panels, which remain disconnected from each other except during internal shock delivery.
Methods: Eleven dogs were studied under general anesthesia. A single-coil integrated bipolar ICD lead was placed in the right ventricular apex, serving as internal shock cathode. Midline thoracotomy was performed and the multi-panel electrode cage was placed around the heart to serve as shock anode. The chest was closed and internal defibrillation threshold (IDFT) was determined. External defibrillation threshold (EDFT) was also determined, first while cage electrode panels were connected together, and then with panels disconnected. The cage was removed, and IDFT was then determined using a “dummy can” anode placed subcutaneously in the left chest, as internal control. The dummy can was removed, and EDFT was then determined as external control. During all internal shocks, the force of skeletal muscle contraction (FMC) was measured by strain gauges attached to the forelimbs, serving as surrogate measure of shock induced pain.
Results: IDFT using the electrode cage was higher than control configuration (23 ± 7 J vs. 16 ± 6 J, p < 0.02), while FMC at the IDFT was almost 10-fold less with the cage (1.3 ± 1.3 kg vs. 10.6 ± 2.2 kg, p < .0001). External defibrillation was impossible when cage panels were connected (EDFT > 360 J), while always possible with panels disconnected, although with higher energy than control (156 ± 68 J vs. 32 ± 24 J, p < .0001).
Conclusion: An electrode system based on a “switchable” Faraday cage concept may provide a nearly painless ICD system, while safely allowing for external defibrillation when necessary.