Spiral waves in monodomain reaction-diffusion model

A monodomain reaction-diffusion system is implemented to simulate spiral waves.

Matlab implementation of a monodomain reaction-diffusion model in 2-D. The model equations are a variant of the Fitzhugh-Nagumo equations modified to simulate the cardiac action potential. The progression of the two normalized state variables, membrane voltage (v) and recovery (r), is computed across a 128 x 128 spatial domain and across time. This function simulates spiral waves, which are hypothesized to underlie reentrant tachycardia. The spiral waves can be initiated by two different cardiac pacing methods:

(1) two-point stimulation where a point stimulus is delivered in the center of the domain followed by another point stimulus on the partially refractory wake of the first wave of excitation.

(2) cross-field stimulation where a stimulus is applied to the left domain boundary causing a plane wave. As this wave travels across the domain, a second stimulus is applied to the bottom boundary of the domain.

This function accepts only one input argument, StimProtocol, which can be either the numerical values '1' (for two-point stimulation) or '2' (for cross-field stimulation). As the simulation runs, the activation
state of the individual units comprising the domain is mapped to color and plotted in a figure window. A count of time steps is displayed at the top of the plot along with the values of v and r for the upper left
element of the domain.

Model equations are solved using a finite difference method for spatial derivatives and explicit Euler integration for time derivatives. Newman boundary conditions are assumed. Model parameters are taken from two journal articles: [1] Rogers JM et al. "A collocation-Galerkin finite element model of cardiac action potential propagation". IEEE TBME;41:743-757 (1994). [2] Pertsov AM et al. "Spiral waves of excitation underlie reentrant activity in isolated cardiac muscle". Circulation Research;72:631-650(1993).

Following the simulated spiral waves, a movie (AVI) is generated and the user is given the option to save the movie to disk. One simulation takes about 160 seconds on a 2.33 GHz Intel Dual Core 64-bit laptop with 3.3 GB of RAM.