"The primary objective of the study is to evaluate whether the incidence of symptomatic or asymptomatic atrial fibrillation, atrial flutter, and atrial tachycardia within 30 days after percutaneous closure of idiopathic patent foramen ovale is reduced in the beta-blocker treatment group compared to the non-treatment group.

The secondary objective is to assess the safety and performance of the Cocoon Patent Foramen Ovale Occluder and collect real-world data on patient outcomes.

Patients will be randomly assigned in a 1:1 ratio to either the beta-blocker treatment group or the non-treatment group. Randomization will be performed using a 1:1 allocation ratio with stratification based on (1) PFO device size and (2) sex, employing a block randomization method (mixed block sizes of 4 or 6). This process will be conducted independently through an interactive web response system.

The beta-blockers used in this study are extended-release beta-blockers, specifically bisoprolol or nebivolol. The choice between bisoprolol and nebivolol will be determined at the discretion of the investigators, with the initial dose set at the minimum dose for each drug (1.25 mg once daily). During the study period, adjustments to the beta-blocker dose, including maintenance or modification, will be made based on the investigators' clinical judgment, taking into account the patient's heart rate, blood pressure, and medication adherence. All reasons for dose adjustments will be documented in detail."

Inclusion Criteria:

1. Age 19 years or older
2. Patients scheduled to undergo Patent Foramen Ovale closure using the Cocoon Patent Foramen Ovale Occluder
3. Individuals who have provided informed consent for study participation

Exclusion Criteria:

1. History of paroxysmal, persistent, or permanent atrial arrhythmia
2. Atrial arrhythmia confirmed by a 14-day Holter ECG using the AT Patch before PFO closure
3. Patients with uncontrolled asthma or chronic obstructive pulmonary disease (COPD)
4. Patients with high-degree atrioventricular (AV) block
5. History of heart failure, severe valvular disease, or left ventricular dysfunction (ejection fraction <50%)
6. Patients for whom initiating or discontinuing beta-blocker therapy is deemed impossible by the investigator
7. Patients who, as assessed by the investigator, cannot be followed up for one year after enrollment
8. Patients with hypersensitivity or contraindications to any proposed drug therapy or device component
9. Patients with an expected life expectancy of less than one year
10. Patients currently participating in another investigational drug or device study