Computer simulation of defibrillations using subcutaneous implantable cardioverter-defibrillators

Implantable cardioverter-defibrillators (ICD) are routinely used for the primary and secondary prevention of sudden cardiac death due to ventricular tachycardias. A subcutaneous ICD (S-ICD) system has been recently developed with a lead just implanted under the skin instead of 1 or 2 transvenous leads traditionally implanted in a body. This may greatly reduce the complexity of the implantation procedure without or with less fluoroscopy, and avoid the complications due to transvenous leads. Although the safety and efficacy of the S-ICD has been evaluated in the clinical study, to date, a theoretical research has never been performed to study the conduction of the defibrillation currents in human bodies due to the defibrillation shocks of S-ICD systems. The conduction pattern of defibrillation currents may help improve the defibrillation effect through finding a better implantation site of the S-ICD generator or lead, and a better defibrillation protocol. As the defibrillation current or voltage in the body is impossible to be accurately measured due to the electrode polarization during the defibrillation shock, we performed the computer simulation to study the defibrillation effects of S-ICD systems in 4 suggested configurations. The defibrillation threshold (DFT) and myocardial damage for each configuration were estimated from the simulation results. The configuration with a left lateral pulse generator and an 8-cm coil electrode positioned at the left parasternal margin demonstrated the lowest DFT and minimum myocardial damage in the simulation. The simulation result of DFT is consistent with previous clinical studies, and the simulation method may serve as a tool to find an improved implantation configuration for an S-ICD system.