Figure 3.

Rotor modification by DC shock applied to sustained VT in the absence and presence of RC. A: Failure of cardioversion by low-intensity shock in the absence of RC through repining of PS. Top, action potential trace; middle, phase maps before and after 25-V DC shock application. Black and white circles, PSs of clockwise and counterclockwise rotation, respectively. *Site of action potential recording. Bottom, trajectory of PSs plotted on space-time axes. A part of the trajectory in the left panel (immediately before and after DC shock application) is expanded in the right panel to show generation, mutual annihilation (#), and repining of PSs. B: Success of cardioversion by low-intensity DC shock in the presence of RC through unpinning of PS. Left, action potential trace (top) and phase maps (bottom) before (a) and after application of a 25-V DC shock (b– e). The shock application generated new PSs (black and white circles, clockwise and counterclockwise rotation, respectively). Trajectory of the PSs is illustrated in the right bottom panel. PS8 was pushed out of the observation area after meandering. PS1–PS3, PS4–PS7, and PS5–PS6 dissipated by mutual annihilation within 100 ms. PS2 survived and drifted in the periphery of the RC region (unpinning), and collided with the atrioventricular groove. *Site of action potential recording. Right, trajectory of PSs 1–3 plotted on space-time axes. Blue columns indicate the RC region. Abbreviations as in Figure 2.