Determining the level of complexity required to model transvenous defibrillation fields

The objective of this study is to determine the level of complexity needed to model transvenous defibrillation fields in the heart. A physiologically realistic 3D finite element model is constructed from 90 transverse magnetic resonance images of the human thorax. Two models are developed: 1) a realistic torso and 2) a spherical torso surrounding the great vessels and heart. The defibrillation threshold (DFT) is calculated based on a potential gradient of 5 V/cm throughout 95% of the ventricular myocardium during a shock. Comparison of the realistic and spherical models shows that the DFT is altered by 21%, 18%, and 8% for RV-SVC, RV-CAN, and RV-SVC/CAN electrode configurations, respectively. These results indicate that for configurations producing more uniform defibrillation fields between the electrodes (RV-SVC/CAN), the complexity of the model can be greatly reduced by excluding the tissue structures external to the heart. The significance of this study is that realistic representation of the human thorax is needed in order to accurately predict DFTs