A 41-year-old man had undergone pulmonary vein isolation and linear ablation at the roof and mitral isthmus (MI) for persistent atrial fibrillation. He subsequently experienced atrial tachycardia (AT). The activation map during the AT revealed macro-re-entrant AT with impulse propagation in a clockwise direction around the mitral annulus and left atrial appendage (LAA), and through the scar tissue bundle at the MI (Figure). We cannulated the vein of Marshall (VOM) using a 2-Fr octapolar electrode catheter. The post-pacing intervals at multiple points along the VOM were equal to the tachycardia cycle length. The fractionated potentials at the left pulmonary vein–LAA (LPV–LAA) ridge expanded to a duration of 110 ms and preceded the electrogram at the main spike of the distal VOM. Accordingly, radiofrequency ablation was applied at the LPV–LAA ridge (Figure), which successfully terminated the AT. Bidirectional block across the MI, distal VOM, and LPV–LAA ridge was confirmed by post-ablation. When a conduction gap is apparent at the MI lesion, as seen in this case, and radiofrequency ablation at the MI does not produce a complete bidirectional block, we suggest applying radiofrequency ablation to the LPV–LAA ridge area.
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