Study on the Safety and Effectiveness of a Biodegradable Patent Foramen Ovale Occluder System

Inclusion Criteria: * Aged between 18 and 65 years. * Presence of a patent foramen ovale (PFO) confirmed by transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE). * Presence of a moderate-to-large right-to-left shunt (RLS) at rest or during the Valsalva maneuver, as confirmed by agitated saline contrast echocardiography (also known as bubble study). * Clinically diagnosed with a PFO-associated ischemic stroke or transient ischemic attack (TIA). Exclusion Criteria: * An alternative, clearly identified cause of ischemic stroke or TIA (other than PFO) is determined by the investigator. * Large territory cerebral infarction within 4 weeks prior to the planned procedure. * Atherosclerotic stenosis (\>50%) of the carotid or vertebral arteries, as confirmed by CT angiography or vascular ultrasound per investigator assessment. * Presence of intracardiac thrombus or vegetation as confirmed by echocardiography. * Left ventricular ejection fraction (LVEF) \< 35%. * Atrial fibrillation or atrial flutter. * Left ventricular aneurysm or severe regional wall motion abnormality. * Significant valvular stenosis or regurgitation, or history of valvular replacement or repair surgery. * Pulmonary hypertension or a PFO constituting a special conduit (e.g., right-to-left shunt due to elevated right heart pressures). * Other confirmed causes of right-to-left shunt, such as atrial septal defect (ASD) or pulmonary arteriovenous fistula. * Complex PFO anatomy (e.g., multi-t…