Cross-species investigation of the mechanisms driving a period-doubling bifurcation in voltage and calcium dynamics of paced cardiac tissue

Much research has been devoted to investigating the initiation of cardiac arrhythmias by alternans, a period doubling bifurcation in the duration of cardiac action potentials which is strongly correlated with the onset of sudden cardiac death. Alternans results from a cellular level instability in the bidirectionally coupled voltage and calcium dynamics. Although the formation and maintenance of alternans has been studied extensively in animal models such as rabbit, rat, and zebrafish, surprisingly little attention has been given to the discrepancies observed across species. Even when the hearts of two species are anatomically similar, the electrophysiology can behave quite differently. In this talk I will present high spatiotemporal resolution optically mapped fluorescent recordings of transmembrane voltage and intracellular calcium transients from the surfaces of Langendorff-perfused whole hearts of a variety of species including rabbit, porcine, canine, cat, rat, zebrafish, alligator, and snake. I will discuss the variety of alternans observed in these species and the driving mechanisms. Furthermore, I will present a minimal cardiac cell model that reproduces the observed alternans dynamics when coupled in tissue.