HOW DOES AN ELECTRIC-FIELD DEFIBRILLATE CARDIAC-MUSCLE

Cardiac fibrillation is caused by an irregular wave propagation. Fibri llation can be eliminated by a strong electric field (5 kV, 20 A, 2 ms ec). The mechanism of this phenomenon (defibrillation) is not known. T he principal difficulty, as shown in experiments and confirmed by clas sical cable theory, is that the changes in transmembrane potential, e, induced by electric field, decay exponentially with distance from the electrodes. We study wave suppression by an electric field in generic excitable media. In excitable media consisting of separate cells (sim ilar to biological tissues), we have found a suppression of rotating w aves and defibrillation induced by strong electric field, contrary to what happens in continuous media. We show that the spatially periodic component of e which arises in cellular media is responsible for defib rillation. We have found that (i) it does not decay with distance; (ii ) it can excite quiescent cells and terminate excitation in excited ce lls; (iii) the coupling between cardiac cells is a crucial parameter a ffecting the amplitude of the spatially periodic component of e, and t he efficiency of defibrillation. New experiments on cardiac muscle are proposed.