Researchers used an electrophysiological computer model of the heart's electrical circuits to examine the effect of the applied voltage field in multiple fibrillation-defibrillation scenarios. They discovered far less energy is needed than is currently used in state-of-the-art defibrillation techniques. The authors applied an adjoint optimization method and discovered adjusting the duration and the smooth variation in time of the voltage supplied by defibrillation devices is a more efficient mechanism that reduces the energy needed to stop fibrillation by three orders of magnitude.