A new defibrillation mechanism: Termination of reentrant waves by propagating action potentials induced by nearby heterogeneities

Introduction. Recently, there has been a major effort to develop new, low-energy defibrillation methods that would be less damaging and less traumatic for the patient, and would save battery energy. However, these methods have not been entirely successful, due in part to an incomplete understanding of all the mechanisms present that may help or hinder the process of terminating the rotating waves present during fibrillation. Here we describe new mechanisms whereby a far-field electric field pulse terminates unpinned waves that are rotating in the vicinity of a blood vessel, plaque deposit or other heterogeneity in the gap junction conductivity. Methods. We ran a series of two-dimensional computer simulations of a spiral wave rotating in the vicinity of a non-conducting obstacle. Application of a low-energy electric field pulse caused a semicircular action potential wave to be launched from the heterogeneity which then interacted with the rotating wave. Results and Conclusions: We found, that, when this interaction is combined with, importantly, the presence of nearby non-conductive boundaries, termination of the rotating waves can occur via a number of new mechanisms, overa wide range of timings of the electric field pulse, and for a number of different initial locations of the rotating wave. The mechanisms only require the rotating wave to be nearby, but not necessarily pinned to the heterogeneity, and thus extends the effectiveness of the electric field pulses used in low-energy defibrillation. Consideration of these mechanisms together with those already discovered could result in the development of improved, low-energy defibrillation protocols.