Example responses to premature S2 stimulus in virtual tissue with heterogeneity on spatial scale of 10 mm, ΔgKmax of 0.003 mS mm-2, and diffusion coefficient set to 0.1 mm2 ms-1. Blue lines outline regions with prolonged repolarisation.. (a) S2 at 230 ms and induction of re-entry. (b) S2 at 250 ms, wavebreaks are indicated with a star. (c) S2 at 265 ms and delayed propagation with no wavebreak. In (a-c) snapshots 50, 100 and 150 ms after the S2 stimulus are included, with propagation from bottom to top of the figure. Isochrones at intervals of 5 ms are shown, and colour coding indicates the progress of the wavefront. Movies of the simulations shown in this figure are available as additional files Figure 5a Figure 5b, and Figure 5c.