In a CA, each cell has a finite number of states, which are updated based on its neighbours and its own state the previous time step. In CA models of cardiac dynamics, the cells are either active, refractory or excitable. The length of time each cell spends in each state, as well as the size of the neighbourhood and the threshold for activation, are all adjustable parameters. A similar model is formally described here . This applet works best with with Netscape .
Spirals have different characteristics for different parameters.
Control-click in the window to bring up a graph that shows the period of the spiral. Inactive cells have a small chance of becoming active in this example. This activity can cause unidirectional propagation and spiral waves. A target wave is initiated every 100 timesteps from the top left corner. You can start a target wave if you click in the applet, and you can get a spiral wave by clicking in the wake of the periodic wave.