Abstracts are provided in the language submitted.

Introduction/Objective – Parasystole in an arrhythmia caused by the emergence of a second pacemaker, in addition to the sinoatrial (SA) node. This ectopic pacemaker can trigger early cardiac contractions in the atria or in the ventricles and they can lead to cardiomyopathies. Published models of parasystole suggest that the wave dynamics can be predicted from P, the ratio of the period of the ectopic pacemaker to that of the SA node, and the refractory period θ. These models do not model the excitable media which carries electronic impulses between the two pacemakers. Here, we built 1-dimensional and 2-dimensional models of parasystole using computational and experimental methods, respectively. Materials/Methods – We simulated wave propagation in 1D excitable media using a discrete cellular automaton as well as a system of continuous Fitzhugh-Nagumo differential equations. The experimental model is based on an all-optical non-contact system that allowed us to stimulate and record from bioengineered optogenetically-modified cardiac monolayers for long periods of time in a physiologically stable environment. To study parasystolic dynamics, we track the sequence N of numbers of normal SA node waves between consecutive ectopic beats. Results – Results from these three models are consistent: given the ratio P, the refractory period θ and a point X in space, there are only three unique values in N and they’re identical across the models. Conclusion/Implication – These results add another degree of complexity to parasystolic dynamics earlier described: the spatial structure and distance between the pacemakers also impacts the observable wave dynamics.

Khady Diagne