Anode / Cathode Make and Break Phenomena in aModel of De brillation 1

The goal of this simulation study is to examine, in a sheet of myocardium, the contribution of anode and cathode break phenomena in terminating a spiral wave reentry by the de brillation shock. The tissue is represented as a homogeneous bidomain with unequal anisotropy ratios. Two case studies are presented in this article: tissue that can electroporate at high levels of transmembrane potential, and model tissue that does not support electroporation. In both cases the spiral wave is initiated via crosseld stimulation of the bidomain sheet. The extracellular de brillation shock is delivered via two small electrodes located at opposite tissue boundaries. Modi cations in the active membrane kinetics enable the delivery of high-strength de brillation shocks. Numerical solutions are obtained using an e cient semi-implicit predictor-corrector scheme that allows to execute the simulations within reasonable time. The simulation results demonstrate that anode and/or cathode break excitations contribute signi cantly to the activity during and after the shock. For a successful de brillation shock, the virtual electrodes and the break excitations restrict the spiral wave and render the tissue refractory so it cannot further maintain the reentry. The results also indicate that electroporation alters the anode/cathode break phenomena, the major impact being on the timing of the cathode-break excitations. Thus, electroporation results in di erent patterns of transmembrane potential distribution after the shock. This di erence in patterns may or may not result in change of the outcome of the shock.