Simulated Internal Defibrillation in Humans Using an Anatomically Realistic Three-Dimensional Finite Element Model of the Thorax |
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| Authors: | THOMAS F KINST MS MICHAEL O SWEENEY MD JOHN L LEHR PHD SOLOMON R EISENBERG ScD |
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| Institution: | Department of Biomedical Engineering, Boston University;;Department of Medicine, Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School;;Department of Clinical Engineering, Brigham and Women's Hospital, Boston, Massachusetts |
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| Abstract: | Finite Element Modeling of Defibrillation. Introduction: Determination of the optima) electrode configuration during implantable 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 defibrillation metrics for internal defibrillation in humans. Computed defibrillation metrics from simulations of three common electrode configurations with a monophasic waveform were compared to pooled metrics for similar electrode and waveform configurations reported in humans. Methods and Results: A three-dimensional finite element model was constructed from CT cross-sections of a human thorax. Myocardial current density distributions for three electrode configurations (epicardial patches, right ventricular RV] coil/superior vena cava 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/cm2 (10 V/cm) and a 75% critical mass criterion for successful defibrillation, defibrillation metrics (interelectrode impedance, defibrillation threshold current, voltage, and energy) were calculated for each electrode simulation. Values of these metrics were within 1 SD of sample-size weighted means for the corresponding metrics determined for similar electrode configurations and waveforms reported in human clinical studies. Simulated myocardial current density distributions suggest that variations in current distribution and uniformity partially explain differences in defibrillation energy requirements between electrode configurations. Conclusion: Anatomically realistic three-dimensional 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 density distributions and defibrillation energy requirements of various ICD electrode configurations. |
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| Keywords: | implantable defibrillator defibrillation modeling defibrillation metrics computer models catheter electrode |
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