Introduction: Pulsed field ablation (PFA) has emerged in routine clinical practice as a new promising technology in catheter-based treatment of atrial fibrillation (AF). The ease of PFA technology enables more extensive ablation in shorter time. On one hand, extensive ablation is advocated to decrease the AF recurrence in persistent patients, on the other hand it is an important predictor of developing left atrial stiff syndrome with a reported incidence rate of 3.7 - 8.2 % in persistent patients during the era of radiofrequency ablation.

Goals of the study: The main hypothesis is that the LA function (strain) will tend to decline after extensive PFA. It will be assessed using transthoracic echocardiography (TTE) and magnetic resonance (MRI).

Secondary endpoint analysis will include the evaluation of the distribution of late gadolinium enhancement (LGE) after ablation compared to baseline scans, evaluation of heart failure biomarkers after ablation, and description of the rate of AF recurrence.

Methods: This project is a prospective, nonrandomised, two-centre (University Hospital Kralovske Vinohrady and University Hospital Motol) observational study including 50 non-paroxysmal AF patients with indication for catheter ablation. Before the ablation, all patients will undergo LGE MRI and TTE (after cardioversion if AF present). The ablation procedure will be performed using pulsed field technology and will include pulmonary vein isolation, posterior wall ablation and mitral isthmus ablation. Patients will be followed for 6 months. 3 months after the ablation, LGE MRI will be performed. TTE examinations will be carried out on the day after the ablation, at 3 and at 6 months. Heart failure biomarkers (N-terminal proatrial natriuretic peptide, fibroblast growth factor 23, and galectin 3) levels will be analysed at baseline, and 3 and 6 months after the procedure. ECG Holter monitoring will be performed at 3- and 6-months visits.

Inclusion Criteria:

• Non-paroxysmal AF with an indication for catheter ablation
• Age above 18
• Signed informed consent

Exclusion Criteria:

• Contraindication to MRI
• BMI > 35 kg/m2
• Contraindication to amiodarone
• Left atrial size > 60 mm
• History of any LA ablation
• Significant valvular disease (mitral regurgitation ¾ or greater, moderate or severe aortic stenosis)
• Severe pulmonary hypertension
• Pregnancy

Patients scheduled for AF ablation procedures