New technique to achieve total mitral isthmus block: Targeting masked epicardial conductions.

BACKGROUND

Achieving mitral isthmus (MI) block remains a challenge. Epicardial conduction (EC) could play a key role in peri-mitral atrial tachycardia recurrence.

OBJECTIVE

The aims of this study were to evaluate the prevalence of masked EC in patients with MI block and to assess the feasibility of targeting EC by radiofrequency ablation.

METHODS

50 consecutive patients who underwent ablation for persistent atrial fibrillation with successful pulmonary vein isolation, roof line block, and MI block were included. After completion of MI block using a systematic strategy comprising up to 3 consecutive steps, patients underwent pacing from the left lateral ridge (LLR) up to the roof to unmask EC. Isolation by radiofrequency ablation of EC was evaluated in patients with masked EC. Presence of conduction block across the ablation line was confirmed using standard pacing maneuvers from the left atrial appendage and along the mitral line in all 50 patients.

RESULTS

Pacing from the LLR up to the roof unmasked EC in 16 of 50 patients (32%). Among these patients, additional ablation was performed to isolate EC with a success rate of 81.3% (13/16). Overall total isthmus block was observed in 47/50 patients (94%). No complications were reported.

CONCLUSION

After MI block, an additional pacing maneuver from the LLR up to the roof unmasked EC in 32% of patients. Targeting these conductions achieved total MI block in 94% of patients.