Figure 5: Left Atrial Roof-Dependent Reentry in a Patient with Prior Mitral Valve Repair and Maze Procedure.

Electroanatomical mapping demonstrates reentry around the right pulmonary vein with a gap in a prior ablation line in the inferior posterior wall. Bipolar electrograms in the gap demonstrated an amplitude of <0.05 mV (circled star and electrogram in inset). This zone was considered the ‘practical isthmus’, a more efficient target for ablation than a linear lesion across the left atrial roof. PA = posterior-anterior; RAO = right anterior oblique.