Figure 7. Phase-2 reentry due to dynamical instabilities (Modified from Maoz et al (Maoz et al., 2009)).

A. Phase-2 reentry in a homogeneous 1D cable (I_to distribution in C). On the first beat shown, the action potential is long and exhibits spike-and-dome morphology for all cells. On the second and third beats, the action potential is short with no dome. On the fourth beat (close-up in B), however, the action potential becomes spatially heterogeneous, cells close to the pacing site (*) exhibit spike-and-dome morphology and distal cells lose the dome, leading to an anterograde phase-2 reentry (arrow). D. Phase-2 reentry in a heterogeneous cable (I_to distribution in F). In the small I_to region, the action potential morphology is always stable, but in the large I_to region, the action potential morphology is unstable, forming retrograde phase-2 reentry on the third beat (Close-up in E).