Suppression of fibrillation consisting of stable rotors by periodic pacing

Abstract

Recent experimental studies have shown that a sequence of low-energy electrical far-field pulses is able to terminate fibrillation with substantially lower per-pulse energy than a single high-energy electric shock (see S. Luther et al. Nature 475 (7355), 235-239). During this low-energy antifibrillation pacing (LEAP) procedure only tissue near sufficiently large conduction heterogeneities, such as large coronary arteries, is activated. In order to understand the mechanism behind LEAP, We have carried out a statistical study of resetting a medium filled by one or more stable spirals ("rotors") in a two-dimensional electrophysiological model of cardiac tissue perforated by blood vessels to the resting state ("defibrillation"). We found the highest success probabilities for this defibrillation for underdrive pacing with periods 10 - 20 percent larger than the dominant period of the stable rotors in the unperturbed dynamics. If a sufficiently large number pulses is applied and an optimal pacing period chosen, the energy per pulse required for successful defibrillation is about 75 - 80 percent lower than the energy needed for single-shock defibrillation. Optimal conditions to control and suppress fibrillation based on stable rotors, hence, are similar to the ones in found for the case of an electrophysiological model displaying spatiotemporal chaos ("electrical turbulence") in an earlier study (see P. Buran et al. Chaos 27, 113110 (2017)). The optimal pacing period is found to increase with increasing strength of the electrical field strength used in the model. The success probability also increases strongly until the fourth or fifth pulse administered, which is strongly correlated to an observed increase of the fraction of re-excitable tissue with each subsequent pulse. Monitoring the fraction of excitable tissue in the model as key quantity of the excitable medium, moreover, enabled us to successfully predict the optimal pacing period for defibrillation.