Mitral isthmus ablation - radiofrequency, pulsed-field ablation or both? acute and long-term outcomes
D Gerontitis, D Katsaras, V Tsonona, P Charalampopoulos, K Kouvelas, D Samara, E Christoforatou, P IoannidisAbstract
Background
Pulmonary vein isolation (PVI) remains the cornerstone of ablation in atrial fibrillation (AF). Additional substrate ablation is often performed in persistent AF to improve outcomes. Mitral isthmus (MI) ablation is often used for substrate modification in persistent AF and for treatment perimitral atrial flutter (AFL). Posterior MI ablation is frequently challenging and requires epicardial ablation within the coronary sinus (CS). Radiofrequency (RF) ablation has been the main energy source used, although after the emergence of pulsed-field ablation (PFA), there are reports of its use in MI ablation.
Purpose
Describe our experience and outcomes of MI ablation in patients with perimitral AFL or persistent AF using RF, PFA or hybrid approach to achieve MI block.
Methods
We performed retrospective analysis in patients who underwent MI ablation for perimitral AFL or for substrate modification in persistent AF. The patients underwent ablation using RF, PFA or both. RF was delivered with irrigated contact force (CF) sensing ablation catheter at 30-40W, minimum CF of 15grams until elimination of the local endocardial electrogram (EGM). PFA was delivered with pentaspline PFA catheter at flower configuration on the MI with two applications per lesion. Additional epicardial RF ablation was performed when block could not be achieved in posterior MI ablation. Acute success and long term freedom from atrial arrhythmias were assessed.
Results
Eighty patients (84 MI ablation lines) with perimitral AFL or persistent AF were studied retrospectively. Forty-seven (59%) patients had atrial tachycardia and 41 (51%) had previous left atrial ablation. Seventy-four posterior MI and 10 anterior MI were performed in total. PFA only was used in 8 (9%), RF only in 51 (61%) and both in 25 (30%) of the isthmuses. Acute MI block was achieved in all isthmuses performed, after a minimum wait period of 20 minutes. Epicardial RF ablation was required in 31 (42%) of the posterior MI performed. Median follow-up was 15 months (IQR, 9 – 21.25). Freedom from atrial arrhythmias was observed in 54 (67.5%) patients following the index procedure. 8 patients (10%) had a "redo" procedure (2 for left atrial appendage closure and 6 due to recurrent atrial arrhythmia). Recurrence of MI conduction was observed in 2/10 (20%) MI lines, both of which were performed with PFA. There was no recurrence in the RF performed isthmuses. No acute complications were observed.
Conclusion
Mitral isthmus ablation can be performed safely with both PFA and RF as energy source. To our experience PFA was associated with frequent acute recurrence of MI conduction requiring delivery of additional ablation. In the redo cases, two MI conduction recurrences were seen, both with PFA. Epicardial RF ablation within the CS is necessary in substantial number of cases.