Figure 3. Activation sequence and distribution of the safety factor in evolving waves.

Excitation waves were generated in an isotropic tissue stimulated with a 3×0.1 mm electrode (white colored) at the center of the tissue in order to observe the effect of increased load present at the ends of the electrode. The end of the electrode results in an increased load for the cells at the ends of the electrode thus creating a non-uniformity of the source-sink relationship along the length of the electrode. Activation maps are represented by isochrones (black lines, numbers indicate the instant of activation in ms) and the safety factor is color-coded in all panels. Bottom panels are zooms of top panels. A and D: control conditions; B and E: reduced excitability (50% reduction of the maximum sodium conductance (g_Na)); and C and F: reduced tissue conductivity (75% tissue conductivity reduction). Tissue boundaries were not shown for the sake of clarity.