Comparison of pulmonary vein and left atrial posterior wall isolation durability and clinical outcome between radiofrequency and pulse field ablation in patients with persistent and longstanding persistent atrial fibrillation.

Patients with persistent and longstanding persistent atrial fibrillation will be randomized to control and investigational group.

In control group they will receive pulmonary vein and posterior wall ("box lesion") isolation with point by point radiofrequency ablation utilizing the CLOSE protocol with predetermined interlesion distance of up to 6 mm and predetermined ablation index/lesion size index.

In investigational group they will receive pulmonary vein and posterior wall ("box lesion" and additional ablations inside the "box") isolation with point by point pulse field ablation with a predetermined interlesion distance of up to 6 mm and predetermined energy delivery settings.

30 minutes after the last ablation point a high-density mapping of the left atrium will be performed.

Preprocedurally all patients will undergo computer tomography angiography of the left atrium, which will be processed resulting in a three dimensional anatomy reconstruction that will be utilized during the procedures in conjunction with the three dimensional mapping system. Also, left atrial wall thickness will be determined and displayed on the three dimensional anatomy reconstruction.

Before and after radiofrequency and pulse field ablation a five minute bipolar and unipolar intracardiac electrogram recording will be performed at at least two predetermined locations according to wall thickness (at the thinest and at the thickest part of the wall) for later analysis of changes due to different modes of ablation with correlation to lesion durability at a three month re-mapping procedure.

Collection of full blood before and 24 and 48 hours after the procedure to analyse activation of inflammation, coagulation, and also nevral tissue injury and endotelial injury due to ablation. Deviation of markers from the baseline value before the procedure will serve as a measure of activation. Markers analysed: troponin (ng/ml), D dimer (mg/l fibrinogen equivalent units), protein S100 (ng/ml), protein NSE (ng/ml), NT proBNP (pg/ml), high sensitivity CRP (mg/l), interleukin (IL) 6 (pg/ml), procalcitonin (ng/ml), fibrinogen (g/l), P selectin /pg/ml).

Postprocedurally pateints will undergo a remapping procedure three months later to determine pulmonary vein and left atrial posterior wall isolation durability.

Pateints will be followed up with clinical checkup and 1-7 day ECG holters at 3, 6, 12 months.

Inclusion Criteria:

• atrial fibrillation recorded with 12-lead ECG, holter ECG or implantable device on two occasions at least one week apart

Exclusion Criteria:

• history of previous catheter ablation, history of previous heart surgery, life expectancy less than one year, any lifethreatening severe acute condition, acute deep venous thrombosis, presence of intracardiac masses or thrombi.