Fig. 7

Two representative simulation results of 100 × 100 Zhang model cells. In a, there were multiple regions where phase-4 slope became locally maximum, and the leading pacemaker site emerged in one of the regions with locally maximum phase-4 slope. In b, the leading pacemaker site dissociated from the region of maximum phase-4 slope. The dissociation is explained by a more depolarized MDP at the leading pacemaker site shown in the inset. The left panel indicates entire action potential waveforms and the right panel shows expanded action potential waveforms. The red trace illustrates the action potential trajectory of the leading pacemaker site (open circles on activation map); the blue trace illustrates the action potential trajectory of the cell with the maximum phase-4 slope (open triangle on phase-4 slope map)