Mechanisms of defibrillation by standing waves in the bidomain ventricular tissue with voltage applied in an external bath

Standing waves of depolarisation produced by periodic low-voltage driving eliminate propagation activity in the heart, thus providing a defibrillating effect. The phenomenon cannot be reproduced by mono- or bidomain models of cardiac tissue, where voltage perturbations decay exponentially with a space constant λ1≈1 mm. Extension of the bidomain model taking into account effects of the external bathing medium allows simulation of the standing waves which eliminate spiral wave activity in the tissue. Mechanisms of such a defibrillating effect can be explained by the existence of an additional, unusually long space constant, λ2≈20 mm, in the bidomain model with a bath, which emerges due to redistribution of the applied voltage by the external conductive medium.