Bipolar stimulation of a three-dimensional bidomain incorporating rotational anisotropy

A bidomain model of cardiac tissue was used to examine the effect of transmural fiber rotation during bipolar stimulation in three-dimensional (3-D) myocardium. A 3-D tissue block with unequal anisotropy and two types of fiber rotation (none and moderate) was stimulated along and across fibers via bipolar electrodes on the epicardial surface, and the resulting steady-state interstitial (/spl Phi//sub /spl epsiv//) and transmembrane (V/sub m/) potentials were computed. Results demonstrate that the presence of rotated fibers does not change the amount of tissue polarized by the point surface stimuli, but does cause changes in the orientation of /spl Phi//sub /spl epsiv//, and V/sub m/ in the depth of the tissue, away from the epicardium. Further analysis revealed a relationship between the Laplacian of /spl Phi//sub /spl epsiv//, regions of virtual electrodes, and fiber orientation that was dependent upon adequacy of spatial sampling and the interstitial anisotropy. These findings help to understand the role of fiber architecture during extracellular stimulation of cardiac muscle.