FIG. 9.

(a) Bifurcation diagram of deterministic system when Ca cycling and voltage are negatively coupled $(\gamma =-55\mathrm{ms})$. The map shows a typical period doubling bifurcation at higher pacing rates. (b) Bifurcation diagram for the stochastic map model with uniform initial conditions $x_{ij}(0)=1$ and spatial coupling $l=2$. To the right are snapshots of three independent simulation runs at $T=400\mathrm{ms}$, showing distinct steady state patterns after 1000 beats. (c) Bifurcation diagram for the case of random initial conditions and spatial coupling $l=2$. Snapshots of three independent runs at $T=520\mathrm{ms}$ also evolve to distinct steady state patterns. Vertical dashed lines indicate the pacing rate at which snapshots are taken.