Coexistence of multiple spiral waves with independent frequencies in a heterogeneous excitable medium

We studied the interactions and coexistence of stable spiral waves with independent frequencies in a heterogeneous excitable medium, using numerical simulations of a spatial system based on the FitzHugh-Nagumo cell model. When the heterogeneity of the medium exceeded a critical value, a transition took place from a single dominant spiral wave to a coexistence of multiple spiral waves with independent frequencies and n:n-1 wave conduction blocks. In this case, multiple spiral waves could coexist because they are "insulated" from each other by chaotic regions.