Spiral waves in excitable media with negative restitution - art. no. 041912

We study numerically the dynamics of spiral waves in an excitable medium wi th negative restitution. For our study we use two models of the excitable m edium: a cellular automaton and a reaction-diffusion model. There are no si gnificant effects of negative restitution as long as the slope of the resti tution curve is less steep than -1. In media with slopes steeper than -1, t he dynamics of spiral waves can change significantly: (1) the average resti tution time jumps to a value where the slope of the restitution curve is ab out -1; (2) spiral waves can break up into turbulent patterns. We discuss a possible connection between such instabilities and fibrillation in atrial tissue.