Boundary-layer analysis of a spiral wave core

The size of a circular spiral wave core is predicted on the basis of a boundary layer analysis of a spiral wave tip. Dependencies of a spiral core radius on medium parameters are found analytically and numerically for the FitzHugh-Nagumo and Beeler-Reuter models of excitable media. It is shown that the core radius is determined by all currents which are active during a wavefront formation associated with the diffusion fluxes coupling neighboring elements of excitable media. This analysis provides new information about reentrant cardiac arrhythmias.