Drifting dynamics of dense and sparse spiral waves in heterogeneous excitable media.

Spiral wave is shown to drift in heterogeneous excitable media, yet the dynamics remains incompletely understood. In this study, we investigated the effects of heterogeneities in excitable media on the drifting behaviors of dense and sparse spiral waves. Dense spiral waves occur in media of normal excitability and sparse spiral waves in media of low excitability. We numerically simulated the spiral wave drifting in a reaction-diffusion system with the Barkley kinetics and showed that dense and sparse spiral waves drifted differently under the same heterogeneous medium. To understand the drifting behaviors, we developed a kinematic model to describe the tip properties of the spiral waves under different conditions and showed that the kinematic model could well recapitulate the results observed in the reaction-diffusion system.