SIMULATED INTERNAL DEFIBRILLATION IN HUMANS USING AN ANATOMICALLY REALISTIC 3-DIMENSIONAL FINITE-ELEMENT MODEL OF THE THORAX

Introduction: Determination of the optimal electrode configuration dur ing implantabIe cardioverter defibrillator (ICD) implantation remains largely an empirical process. This study investigated the feasibility of using a finite element model of the thorax to predict clinical defi brillation metrics for internal defibrillation in humans. Computed def ibrillation metrics from simulations of three common electrode configu rations with a monophasic waveform were compared to pooled metrics for similar electrode and waveform configurations reported in humans. Met hods and Results: A three-dimensional finite element model was constru cted from CT cross-sections of a human thorax. Myocardial current dens ity distributions for three electrode configurations (epicardial patch es, right ventricular [RV] coil/superior vena cave [SVC] coil, RV coil /SVC coil/subcutaneous patch) and a truncated monophasic pulse with a 65% tilt were simulated, Assuming an inexcitability threshold of 25 mA /cm(2) (10 V/cm) and a 75% critical mass criterion for successful defi brillation, defibrillation metrics (interelectrode impedance, defibril lation threshold current, voltage, and energy) were calculated for eac h electrode simulation. Values of these metrics were within 1 SD of sa mple-size weighted means for the corresponding metrics determined for similar electrode configurations and waveforms reported in human clini cal studies. Simulated myocardial current density distributions sugges t that variations in current distribution and uniformity partially exp lain differences in defibrillation energy requirements between electro de configurations. Conclusion: Anatomically realistic three-dimensiona l finite element modeling can closely simulate internal defibrillation in humans. This may prove useful for characterizing patient-specific factors that influence clinically relevant properties of current densi ty distributions and defibrillation energy requirements of various ICD electrode configurations.