Reentry in a model of myocardium with fractal uncoupling

An attempt was made to test the hypothesis that in a model of the myocardium, the greater the degree of heterogeneous cell-to-cell uncoupling, the greater the likelihood of reentry. The authors modeled a sheet of myocardium with a 128×128 grid of resistively coupled cells exhibiting modified FitzHugh-Nagumo kinetics. The diffusion coefficients, inversely related to coupling resistivity, were assigned to produce a mottled, fractal pattern using a recursive algorithm operating across size scales. Each fractal tissue was then subjected to the same type of periodic pacing at small areas and from different locations. In a series of experiments, a direct relationship was found between the degree of heterogeneous uncoupling and the propensity for reentry. In addition, it was noted that there must be a critical amount of geometric clumpiness for reentry to occur. Reentrant waves were found to wander locally rather than circulate about a stationary point