Comparison of microscopic and bidomain models of anisotropic conduction

The bidomain model is based on effective parameters to include the myocardial tissue properties into models of propagation of depolarization. In this study we examine whether these properties can be derived from histology by generating a geometrical model of cardiac tissue and computing the effective conductivity. We tested this hypothesis by generating a detailed model of cardiac tissue in which we simulated the propagation of depolarization directly, using the so-called microdomain approach. We compared both the the conduction across and along the fiber of the myocardium under both healthy and ischemic conditions. Under healthy conditions both the microdomain and bidomain approximation resulted in conduction velocities that were within 3% of each other. However under ischemic conditions the conduction velocity across the fiber approximated 20%, indicating that the effective conductivity tensors under those conditions are not a good approximation.