The efficacy of pulsed-field ablation to achieve bidirectional block on mitral isthmus

Feasibility and safety in achieving an acute mitral isthmus (MI) line with pulsed-field ablation (PFA) in patients with atrial fibrillation (AF) have not been extensively evaluated. This study aimed 1) to evaluate the overall efficacy of PFA in achieving complete block across the MI and 2) to assess how often empirical, anatomically-guided ablation leads to a complete bidirectional block (BDB) on MI.

Patients with non-paroxysmal AF were studied. The procedure consisted of a pulmonary vein isolation (PVI), ablation of the left atrial posterior wall, and a MI line between the left inferior PV or the left atrial appendage (LAA) and the mitral annulus. The presence of a BDB across the MI was checked by pacing from the LAA and from the distal coronary sinus. If a BDB was not present, additional PF applications were performed to achieve it.

80 patients (age: 65.9 ± 7.1 years, 70% males) were enrolled. Complete BDB on the MI (overall efficacy) was achieved in 77 (97.3%) patients with a mean of 13.1 ± 6.2 applications per patient. After the first set of PF applications, BDB on the MI (first-pass block) was present in 36 (45.0%) patients. During the first lesion set, there was a trend towards a higher probability of a BDB in patients initially in sinus rhythm compared to those in whom the first series was applied during AF/AT (55.6% vs 36.4%, p=0.08).

Although PFA is highly effective at achieving a MI block, an empirical-only ablation without electrophysiological testing maneuvers is insufficient.