Global organization of dynamics in cultured cardiac monolayers

Gil Bub, Physiology, SUNY Downstate Medical Center

Cultured layers of cardiac cells display transitions between different spatiotemporal states as experimental conditions are varied. Monolayers display periodic target pattern waves, stable spiral waves, spirals that spontaneously initiate and terminate, multiple interacting wavefronts, and quiescence. Transitions between these states can be controlled by varying the connectivity and density of the preparation. In addition, experiments where connectivity is continuously varied by washing out pharmacological agents demonstrate that the system undergoes abrupt transitions between different spatiotemporal states. Simple cellular automaton models undergo the same transitions as local connectivity and density are continuously varied. Parameters that give rise to different spatiotemporal dynamics are organized in distinct zones in parameter space, leading to a global organization that should be applicable to the dynamics in a large class of excitable media. Similar m! echanisms may be responsible for transitions between healthy and unhealthy rhythms in intact hearts.