Impact of additional pulsed field ablation in unsuccessful radiofrequency linear lesions -including the assessment of the LA wall thickness at the gap locations-

Performing linear ablation such as roof line, floor line in the posterior part of the LA, and posterior mitral isthmus (MI) line in addition to PVI is one of the strategies for treating persistent atrial fibrillation. However, remnant conduction or reconnection in the lines is linked with atrial arrhythmia recurrence, either AF or AT. Radiofrequency ablation (RFA) is often unsuccessful achieving durable linear ablation. It is not yet well known whether using pulsed field ablation (PFA) would be superior in achieving complete linear lesions in human.

We sought to evaluate the wall thickness of the LA along the position of linear lesion and gaps in cases where linear lesion creation using RFA failed, and to evaluate the effectiveness of PFA on them.

We studied 21 patients that underwent redo procedures due to atrial arrhythmia recurrence. All of them underwent PFA (using a pentaspline PFA catheter) ablation lines due to previous unsuccessful RF ablation, either due to remnant conduction in the line or to reconnection of the line. Lines of block were evaluated based on activation mapping and differential pacing maneuvers close to the lines. Furthermore, regarding dome-transection lines, the linear lesions created by RFA, and the positions of their gaps were projected onto the 3D reconstructed image from CT taken before procedure, and the wall thickness at positions along them was evaluated postoperatively.

We conducted 20 dome-posterior lines and 6 posterolateral mitral isthmus lines using PFA after several times unsuccessful linear lesions by RFA.

Dome-posterior line bidirectional block based on activation mapping and differential pacing maneuvers was achieved in all cases (20/20, 100%) after PFA. Posterior MI line bidirectional block based on activation mapping and differential pacing maneuvers was achieved in 5 out of 6 patients (83.3%). In one case additional Et-VOM was needed to achieve MI block.

6 patients have experienced AT/AF recurrence after PFA. Three of them underwent redo procedure, but no reconnection of these linear lesions treated with PFA was observed.

Regarding the assessment of LA wall thickness, the mean LA wall thickness at positions along the gap location was thicker compared to the mean LA wall thickness at positions along the linear lesion created by RFA (2.49±0.43mm vs 1.91±0.41mm; 95%CI 0.48-0.68; p<0.001).

PFA treatment seems promising to back-up RF failed linear lesions. Furthermore, when creating a linear lesion using RFA, it may be better to ablate while avoiding locations with thick walls based on a prior evaluation of wall thickness. If the wall thickness at the target location is thick overall, it may be better to create a linear lesion using PFA instead of RFA. However, we cannot exclude that it is in fact the combination of the 2 energies that was successful in those resistant cases.

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