Ventricular Conduction System Modeling for Electrophysiological Simulation of the Porcine Heart

Depolarization sequences triggering mechanical contraction of the heart are largely determined by the cardiac conduction system $(CS)$. Many biophysical models of cardiac electrophysiology still have poor representations of the $CS$. This work proposes a semiautomatic method for the generation of an anatomically-realistic porcine $CS$ that reproduces ventricular activation properties in swine computational models. Personalized swine biventricular models were built from magnetic resonance images. Electrical propagation was described by the monodomain model. The $CS$ was defined from manually-determined anatomic landmarks using geodesic paths and a fractal tree algorithm. Two $CS$ distributions were defined, one restricted to the subendocardium and another one by performing a subendo-to-intramyocardium projection based on histological porcine data. Depolarization patterns as well as left ventricular transmural and inter-ventricular delays were assessed to describe ventricular activation by the two $CS$ distributions. The electrical excitations calculated using the two $CS$ distributions were in good agreement with reported activation patterns. The pig-specific subendo-intramyocardial $CS$ led to improved reproduction of experimental activation delays in ventricular endocardium and epicardium.