MECHANISM OF CARDIAC DEFIBRILLATION - A DIFFERENT POINT-OF-VIEW

Many studies have investigated the mechanism of defibrillation by direct recordings of cardiac activations before and after successful and unsuccessful defibrillation shocks. We reviewed these experimental studies and found that in the vast majority of cases 1) shocks slightly weaker than necessary to defibrillate stop ventricular fibrillation activation fronts but give rise to new activation fronts that reinitiate ventricular fibrillation, and 2) these new activation fronts arise as a result of a complex interaction of the shock electric field and tissue refractoriness. These experimental results support the upper limit of vulnerability hypothesis of defibrillation.