Finite element computer modeling of transthoracic atrial defibrillation.

Placement of external electrodes can significantly affect the success rate of transthoracic atrial defibrillation, but studies have not led to agreement on optimal electrode placements. This study aims to (1) develop an anatomically realistic, finite element model of the human torso for external atrial defibrillation, (2) investigate model parameters of skeletal muscle conductivity and anisotropy and the presence of subcutaneous fat, and (3) investigate clinical defibrillation parameters of electrode size, shape, and location. The model predicts atrial defibrillation threshold (ADFT) energy by requiring a voltage gradient of 5 V/cm over at least 95% of atrial myocardium. The model compares favorably with a clinical study of 301 patients that reported an anterior-posterior electrode position required approximately 20% less energy than an anterior-anterior position. Results indicate that a change in electrode size has a different effect for different electrode placements. This study finds that variation in electrode placement by only a few centimeters can change ADFTs by up to 51%. This is the first computer model of transthoracic atrial defibrillation to our knowledge. Our computer model is not limited to a few empirically selected electrode placements as in clinical studies and can test any location, size, and number of electrode placements.