Modeling the passive cardiac electrical conductivity during ischemia

A geometrical model of cardiac tissue was used to compute the bidomain conductivities. We simulated ischemic conditions by adapting the geometrical model to morphological and electrical changes reported in literature. The simulated changes included 1) expansion of capillaries 2) cell swelling and 3) the closure of gap junctions, which coincide with changes associated with the three phases of ischemia reported in the literature. Simulations were carried out in a finite element model describing 64 myocytes and the apparent conductivity was calculated by computing the amount of current is this piece of tissue due to an externally applied electric field. In the first case, capillary swelling led to a reduction in extracellular longitudinal conductivity by about 20%, which is in the range of reported literature values. Moderate cell swelling did not affect extracellular conductivity considerably. In order to match the reported drop in total tissue conductance in experimental studies during the third phase of ischemia, we simulated a ten fold increase in gap junction resistance. This ten fold increase correlates well with the reported changes in gap junction densities in literature. Keywords— Conductivity, Cardiac tissue, Bidomain, Ischemia, Cardiac modeling