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Figure 1 Snapshots of re-entrant activation during ventricular fibrillation (VF) episodes in control (A), acute (B) and chronic amiodarone (C) animals. Each colored pixel is an electrode site at which dV/dt <0.5 V/s sometime during the 5-ms interval represented by each frame. The black numbers show the time in milliseconds from the onset of the analysis interval for the corresponding frame 15 s after VF induction. Different colored pixels indicate distinct isolated wavefronts with re-entrant circuits shown in red. The arrows indicate the direction of wavefront movements. The re-entrant wavefronts rotate counterclockwise in A and C and clockwise in B. The core perimeter in A is smaller than in B or C. The wavefronts are more fragmented and complex in A than in B or C.