This is a prospective, randomized clinical trial evaluating the efficacy and safety of two techniques for repeat catheter ablation in patients with recurrent atrial fibrillation (AF): thermal energy ablation (radiofrequency) and non-thermal electroporation (pulsed field ablation), both guided by 3D imaging systems.

Patients undergoing repeat AF ablation will be randomly assigned to receive either thermal or electroporation ablation, performed according to standard hospital protocols. No additional invasive procedures are required. Following the ablation, participants will attend follow-up visits at 3, 6, and 12 months, including medical history review, physical examination, 12-lead ECG, and 24-hour Holter monitoring. Unscheduled ECG assessments will also be available if arrhythmia symptoms occur.

All study-related procedures are non-invasive and align with routine post-ablation care. Risks are limited to those typically associated with standard AF ablation procedures.

The main benefit of participation is close, structured follow-up by experienced electrophysiologists, allowing for early detection of arrhythmia recurrence and timely medical intervention when necessary.

Participant confidentiality and data protection will be ensured in accordance with GDPR regulations.

Background Atrial fibrillation (AF) is one of the most common cardiac arrhythmias, with a lifetime risk of approximately 30% in individuals over 55 years of age. A primary treatment option for AF is pulmonary vein isolation (PVI), which targets the anatomical substrate of the arrhythmia. PVI can be achieved using thermal energy-either radiofrequency (RF) ablation or cryoablation-or with the newer, non-thermal method of pulsed field ablation (PFA). PFA delivers sequences of electrical pulses that cause selective electroporation of cardiomyocyte membranes, resulting in cell death while sparing adjacent non-cardiac tissues.

Despite these therapies, AF recurs in 30-50% of patients within the first year after ablation, regardless of the energy source used. The standard management for recurrence involves repeat ablation (re-PVI), targeting pulmonary vein reconnections and atrial substrate identified by electroanatomical mapping.

Randomized controlled trials comparing thermal modalities (RF vs. cryoablation) in first-time PVI have demonstrated similar safety and efficacy. Registry data and a single randomized trial suggest that PFA offers improved safety and comparable efficacy in initial PVI. However, no prospective randomized trial has evaluated the role of PFA in re-PVI.

Re-PVI procedures are technically more complex than index PVI, requiring high-resolution electroanatomical mapping of the left atrium to identify reconnection sites, followed by targeted ablation. While RF remains the established standard, growing evidence suggests that PFA may offer advantages due to its distinct mechanism of action, potentially overcoming thermal resistance from prior ablation. Retrospective data from our institution indicate that PFA may reduce procedure times and improve long-term success compared with RF, though these findings require confirmation in a controlled trial.

Study Overview This dual-center, prospective, randomized trial will compare the feasibility, safety, and efficacy of PFA versus RF ablation for re-PVI in patients with recurrent AF.

Study Design and Procedures Eligible patients admitted for clinically indicated repeat AF ablation at either the University Clinical Hospital in Wrocław (Department of Cardiology) or the University Clinical Hospital in Poznań (Department of Intensive Cardiac Therapy and Internal Medicine) will be invited to participate.

After providing informed consent, participants will be randomized in a 1:1 ratio to undergo either RF ablation or PFA. All procedures will include high-resolution electroanatomical mapping of the left atrium, followed by energy delivery according to the assigned modality. Post-ablation remapping will be performed to confirm acute procedural success.

Follow-up visits will take place at 3, 6, and 12 months, including medical history review, physical examination, 12-lead ECG, and 24-hour Holter monitoring. Additional visits and ECG assessments will be available if symptoms occur.

Data collected will include patient demographics, comorbidities, left atrial anatomy (by echocardiography), procedural characteristics (duration, fluoroscopy time, number and location of applications, acute isolation success, complications), and follow-up outcomes (late complications, arrhythmia recurrence, repeat ablation).

Study Locations Clinical Department of Cardiology, Jan Mikulicz-Radecki University Clinical Hospital, Wrocław, Poland Department of Intensive Cardiac Therapy and Internal Medicine, University Clinical Hospital, Poznań, Poland

Risks and Inconveniences Risks are consistent with standard AF ablation and are not increased by study participation. Potential complications include vascular access site events (bleeding, hematoma, arteriovenous fistula), stroke, or tamponade. No additional invasive procedures will be performed beyond routine ablation and follow-up. Participants must attend at least three scheduled outpatient visits.

Participant Characteristics Age: 18-85 years Gender: All Health status: Patients with AF recurrence after prior thermal PVI undergoing clinically indicated re-ablation Planned enrollment: Up to 250 participants

Inclusion Criteria:

Documented recurrence of AF or atypical atrial flutter after prior PVI Eligibility for re-PVI

Exclusion Criteria:

Left ventricular ejection fraction < 30% Left atrial volume index (LAVI) > 72 mL/m² Untreated hyperthyroidism Hypertrophic cardiomyopathy Severe valvular heart disease