This is a prospective, single-arm study conducted in University Hospital of Split, Department of Cardiology. Patients treated with PFA for symptomatic paroxysmal atrial fibrillation will be asked to participate in the study. An implantable loop recorder (ILR) will be placed immediately after the PFA procedure for rhythm monitoring. Early recurrences will be subsequently divided into very early recurrences (up to 1 month post-procedure) and early recurrences (1-3 months post-procedure). Late recurrences will be defined as those 3 to 12 months post-procedure. Patients will be monitored routinely through follow up visits during which ILR will be interrogated and eventual symptoms will be assessed. Follow-up visits will be scheduled 1, 3, 6, 12 months post-procedure. Median follow-up will be 12 months. Data for the study will be obtained from a loop monitor to assess the arrhythmia burden during follow-up visits in the University Hospital of Split Arrhythmia Clinic.

This is a prospective, single-arm study conducted in the University Hospital of Split, Department of Cardiology. Patients treated with PFA for symptomatic paroxysmal atrial fibrillation will be asked to participate in the study. An implantable loop recorder (ILR) will be placed immediately after the PFA procedure for rhythm monitoring. Early recurrences will be subsequently divided into very early recurrences (up to 1-month post-procedure) and early recurrences (1-3 months post-procedure). Late recurrences will be defined as those 3 to 12 months post-procedure. Patients will be monitored routinely through follow-up visits during which ILR will be interrogated and eventual symptoms will be assessed. Follow-up visits will be scheduled 1, 3, 6, and 12 months post-procedure. The median follow-up will be 12 months. Data for the study will be obtained from a loop monitor to assess the arrhythmia burden during follow-up visits in the University Hospital of Split Arrhythmia Clinic.

For PVI, the "single-shot" multielectrode PFA catheter will be used. This catheter consists of 5 splines, with 4 electrodes per spline and 1 electrode available for intracardiac electrogram recording or 3-dimensional electroanatomic visualization. When used in conjunction with the PFA generator, an electric field is created that ablates tissue using irreversible electroporation. The catheter shape is changed through the manipulation of a slider mechanism on the handle of the catheter. The diameter of the catheter is measured in the fully deployed "flower" configuration and is available in 2 sizes (31 or 35 mm). Energy is delivered through all of the electrodes in a proprietary sequence.

All patients will be asked to provide written informed consent for their respective protocol before undergoing the study.

All procedures will be performed with conscious sedation and propofol bolus synchronized to sets of PFA applications. The procedures will be performed with uninterrupted oral anticoagulation, and left atrial thrombus will be excluded either through pre-procedure CT or intracardiac echocardiography (ICE) (AcuNav, Siemens, Munich, Germany) at the time of the procedure. Pre- and post-ablation diaphragm motion will be evaluated to observe changes in phrenic nerve function during the procedure. Esophageal temperature monitoring will not be utilized due to the nonthermal nature of PFA.

A single transseptal puncture will be performed with an 8.5-F sheath and exchanged for the 13-F PFA sheath in the left atrium, or a transseptal puncture will be performed directly with the PFA sheath. Intravenous heparin will be administered as boluses and continuous infusions to obtain an activated clotting time ≥300 s prior to ablation and throughout the procedure. A 0.035-inch, 180-cm extra-stiff, straight guidewire will be used to cannulate each vein over which the multielectrode PFA catheter will be deployed into the desired shape and advanced into position at the antrum of each vein. The antral level of catheter positioning will be monitored with ICE imaging and fluoroscopy. Patients with left common PV anatomy will receive therapy at the level of the common antrum with 2 sets of therapy delivered, 1 with the guidewire in a superior branch and 1 with the guidewire in an inferior branch.

Acute isolation of the treated vein will be determined by the mapping electrodes on each spline of the PFA catheter. Once all veins have been treated, a 3-dimensional electroanatomic voltage map will be created to confirm PV isolation and visualize the level of isolation of each lesion set. Entrance or exit block will be confirmed following a 20-min wait period after the last PFA application was delivered with a circular mapping catheter (Lasso, Biosense Webster, Irvine, California).

All patients will be implanted with an ILR (Medtronic Reveal LINQTM; Medtronic, Minneapolis, MN). After ablation procedure, the ILR will be inserted subcutaneously in the left fourth intercostal space. The procedure itself takes up to 15 minutes and local anesthetic will be administered prior to the implantation. The antiarrhythmic drugs, except beta-blocker, will be routinely discontinued.

Inclusion Criteria:

• Age >18
• Index PFA procedure after one failed or intolerant group I or III of the antiarrhythmic drug in patients with symptomatic paroxysmal AF (AF with self-terminating episodes lasting no longer than 7 continuous days)
• Willing and able to provide informed consent.

Exclusion Criteria:

• Any known contraindication to AF ablation or anticoagulation.
• History of previous left atrial ablation or surgical treatment.
• Secondary AF due to reversible or non-cardiac cause such as thyroid disease and electrolyte imbalance.
• Asymptomatic AF patients, persistent AF, permanent AF patients.
• History of clotting or bleeding disease or cryoglobulinemia.
• Pregnant or lactating.
• Other conditions that may make the patient a poor candidate for procedure such as mental illness, terminal illness, vulnerable patient population.

Patients with symptomatic paroxysmal atrial fibrillation after at least one failed or intolerant group I or III of antiarrhythmic drug that are eligible for PFA and are willing and able to provide informed consent.

All IPD that underlie results in a publication will be shared.

The data will become available immediately after the publication of the study.

The plan will be shared with other researchers who wish to replicate the study or study the protocol in detail.