Fig 2. Effects of microscopic heterogeneity on macroscopic conduction.

(a) Increasing degree of heterogeneity, as characterized by the obstacle width to strand width ratio, leads to slowing of macroscopic conduction (mean ± se; n = 13–68 monolayers; F(6,217) = 11.53. p < 0.0001; Asterisk indicates significant difference from homogenous case, p < 0.05; values represent average CV across each individual monolayer). (b). Shortening of action potential duration is observed at high obstacle-to-strand ratios (mean ± se; F(6, 217) = 42.7. p < 0.001). (c-e) Macroscopic activation maps becomes increasingly anisotropic as obstacle-to-strand ratio increases from 0 (c) to 1.5 (d) to 7.0 (e). Directional conduction velocities are as indicated. Average conduction velocities across these representative monolayers are 21.28 cm/s (c), 18.56 cm/s (d) and 16.79 cm/s (e). Scale bar = 5 mm; Activation isochrone lines at 8 ms spacing. (f) Quantified anisotropy of 1 indicates isotropic conduction while √2/2 indicates a diamond shape isochrone (mean ± sd; n = 10–15 monolayers; F(6,72) = 42.5. p < 0.001; * and # indicate significant difference from all lower obstacle-to-strand ratios, p < 0.05).