Computer simulation of defibrillating electric shocks: critical mass

Computer simulations of the propagation of depolarizing waves through the ventricular wall based on the Huygens principle are presented. Permanent troubles induced by unidirectional blocks are simulated. A critical size of a unidirectional block required in order to trigger a reentry for normal and ischemic tissues is calculated. The influence of anisotropic conduction on the initialization of reentries is also studied. It is shown that the reentry is favored when the unidirectional block is perpendicular to the direction of heart fibers. Electric shocks applied to the ventricle are simulated. Once a permanent trouble is initialized, an electric shock with a given percentage of depolarized cells is applied. The simulations show that in order to be sure that the reentry has been stopped, one must apply an electric shock with 100% depolarized cells. A very few nondepolarized cells are able to reinitialize several secondary reentries