A Simple Cardiac Model Exhibiting Stationary Discordant Alternans

The term alternans refers to a period-doubling bifurcation that occurs in rapidly-paced cardiac cells: although all stimuli are equally spaced, short and long action potentials alternate with one another. Cardiac waves that propagate in extended tissue often su er phase reversals at various locations, a phenomenon that is known as discordant alternans. Even simulations cannot capture the full complexity of this phenomenon with realistic cardiac models in three-dimensional geometry. Significant insight into the phenomenon has been gained from the study of simple cardiac models propagating in just one dimension, and this is the context of the present paper.