Small random fiber angle variations as a mechanism for far-field stimulation of cardiac tissue

The mechanism by which an electric field stimulates cardiac tissue far from the stimulating electrode is not known. Current theories rely on the inherent heterogeneity of cardiac tissue as contributing to this phenomenon. This paper explores a possible mechanism for far-field stimulation in relation to fiber curvature. We incorporate a randomized fiber angle geometry into a two-dimensional active cardiac tissue model with unequal anisotropy ratios already exhibiting smooth, curving fibers. We simulate cross-field stimulation to initiate reentry in the tissue model, and compare the electric field thresholds at different S1-S2 intervals for tissue with randomized fiber angles and tissue with a smooth fiber geometry. The tissue with random fiber angles has a significantly lower threshold for reentry at certain intervals on the strength-interval curve. We conclude that a random fiber geometry may have an effect on the mechanism for far-field stimulation.