The investigators hypothesized that PeAF-by-LAWT, a personalized protocol that uses a contact-force catheter, a multichannel radiofrequency (RF) generator, and integrated LAWT information to adapt the ablation index (AI) target to the subjacent LAWT, is safe, while showing at least the same efficacy and better efficiency than the CLOSE protocol for persistent AF ablation.

Pulmonary vein isolation (PVI) remains the cornerstone of all catheter-based treatment strategies in atrial fibrillation (AF). Currently, PVI is recommended (class IA indication) after one failed or intolerant class I or III antiarrhythmic drug (AAD) to improve symptoms, either in paroxysmal (PaAF) or persistent AF (PeAF). However, PVI can be also considered as first-line treatment to achieve rhythm control, particularly in cases when tachycardia-induced cardiomyopathy is suspected, a circumstance likely more related to a higher AF burden or PeAF.

PVI has been proven to be effective in treating PeAF, although long-term ablation outcomes have been significantly less satisfactory than in PaAF. In a recent metaanalysis, PVI in PeAF achieved an arrhythmia-free survival at 12 months of 66.7%, with > 80% of the patients off AAD. Other ablation strategies combining PVI plus additional substrate ablation (linear ablation and/or complex fractionated atrial electrogram ablation) have been unable to demonstrate better outcomes than PVI-alone.

On the other hand, recent advances both in technology and ablation protocols have resulted in greatly improved outcomes after PVI. The introduction of contact force-sensing catheters, novel estimates of lesion size [ablation index (AI) or lesion size index, and the fact of ensuring lesion contiguity (≤ 6 mm inter-lesion distance) have markedly improved arrhythmia-free survival after PVI, particularly in PaAF.

The CLOSE clinical study analyzed the utility of ablation index (AI), a novel formula developed to assess real-time effect of RF delivery and improve the rates of PVI, with 91.3% of the patients free from AF/AT/atrial flutter (AFL) at 12 months follow-up. The CLOSE protocol targeted an interlesion distance (ILD) of 6 mm and AI ≥ 400 at the posterior wall and ≥550 at the anterior wall. Recently, Hussein et al. demonstrated that the use of AI-guided PVI alone performed with radiofrequency energy in a point-by-point wide area circumferential ablation (WACA) pattern according to CLOSE protocol achieves good clinical outcomes in persistent AF patients at 12 months follow-up. Finally, a more recent, personalized PVI strategy, aiming for contiguous lesions with AI titration according to the local left atrial wall thickness (LAWT) as per multidetector cardiac tomography (MDCT), has demonstrated to achieve an arrhythmia-free survival > 95% at 12 months in PaAF.

Up to date, there are no randomized studies for persistent AF ablation comparing the outcomes of PVI-alone procedures performed with a personalized ablation protocol that uses the information of left atrial wall thickness (LAWT), compared with the CLOSE protocol.

The investigators hypothesized that PeAF-by-LAWT, a personalized protocol that uses a contact-force catheter, a multichannel radiofrequency (RF) generator, and integrated LAWT information to adapt the ablation index (AI) target to the subjacent LAWT, is safe, while showing at least the same efficacy and better efficiency than the CLOSE protocol for persistent AF ablation.

This is a two-arm, single-blind, single-center, randomized controlled trial. The study will be conducted in a tertiary hospital with an electrophysiology team of qualified investigators with proven experience in performing atrial fibrillation ablation.](streamdown:incomplete-link)

Inclusion Criteria:

• Age > 18 years.
• Indication for persistent atrial fibrillation ablation.
• Signed informed consent

Exclusion Criteria:

• Age < 18 years.
• Pregnancy.
• Previous AF redo procedure.
• Impossibility to perform a pre-procedural CT scan.
• Concomitant investigation treatments.
• Medical, geographical and social factors that make study participation impractical, and inability to give written informed consent. Patient's refusal to participate in the study.