A flexible, interactive finite difference system for modeling defibrillation shock fields

A system has been developed for modeling potential and current density in an arbitrary geometry using a finite difference approach and has been applied to the study of current flow from defibrillation electrodes in either homogeneous media or a physically accurate torso model. The torso models can be used to estimate the percent energy delivered to the heart from an implanted lead system and to identify regions of high or low gradient in the heart. Realistic torso models were generated from magnetic resonance imaging or computerized tomography scans which have been automatically tissue typed and converted to a conductivity array. Results demonstrate the pathways current follows through the thorax when using a lead system involving various endocardial and subcutaneous electrodes