Defibrillation in Models of Cardiac Muscle

The propagation of electrical activity in cardiac tissue can be modelled by reaction diffusion equations, where a tensor of diffusion coefficients represents anisotropy due to fibre orientation, and excitation is represented by high-order, stiff differential systems. The effects of external electrical stimulation, as in artificial pacemakers, or in defibrillators, requires bidomain models, in which intraand extracellular currents are treated separately. Simplified approaches are taken to this problem to illustrate two methods of defibrillation: by a single large pulse, that eliminates all propagating activity, and by a series of smaller amplitude perturbations, that drive out re-entrant sources of excitation.