Figure 4.

Genesis of re-entry in the PV region. (a–i) snapshots of wave-front propagation following a short-coupled ectopic S2 applied to a site in the LSPV (shown with an asterisk). Arrows indicate the directions of wave-front propagation. Thick solid black lines indicate conduction block areas. The wave from the LSPV is blocked towards the IPA owing to a combination of large heterogeneity and anisotropy in the border area (see circle in figure 2b). The wave therefore propagates down into the LIPV and from there into the IPA and the rest of the PV region, eventually re-entering the now-recovered LSPV after approximately 95 ms.