Inclusion Criteria:
1. Diagnosis of PFO, defined as visualization of microbubbles per TEE in the left atrium within three cardiac cycles from the right atrial opacification demonstrating right-to-left shunting at rest and/or during Valsalva release
2. Cryptogenic stroke within the last 270 days; stroke is defined as acute focal neurological deficit, presumed to be due to focal ischemia, and confirmed by MRI or CT to be a new, neuroanatomically relevant cerebral infarct
Exclusion Criteria:
1. Age \<18 years and age \>60 years
2. Greater than 50% lumen diameter stenosis of intracranial or extracranial vessels
3. Intracardiac thrombus or tumor
4. Acute or recent (within 6 months) myocardial infarction (MI) or unstable angina
5. Left ventricular aneurysm or akinesis
6. Mitral valve stenosis (mitral valve area less than 1.5cm2) or severe mitral regurgitation
7. Aortic valve stenosis (gradient \>40 mmHg) or severe aortic valve regurgitation
8. Mitral or aortic valve vegetation or prosthesis
9. Left ventricular ejection fraction \<35%
10. Other identifiable cause of stroke, including but not limited to aortic arch plaques (protruding \>4 mm into the lumen), large artery atherosclerotic disease, an established cardioembolic source, small-vessel occlusive disease, or arterial dissection
11. Evidence of a hypercoagulable disorder requiring anticoagulation therapy; this determination will be based on the evaluation of: anticardiolipin antibody (Ab) of the IgG or IgM type, Lupus anticoagulant, B2-glycoprotein-1 Ab, and fasting plasma homocysteine
12. Another source of right-to-left shunts identified at baseline, including an atrial septal defect and/or fenestrated septum
13. Any history of atrial fibrillation/atrial flutter (chronic or intermittent)
14. Active endocarditis or other untreated infections
15. Chronic kidney disease stage 4 or higher or end-stage renal failure requiring dialysis (eGFR less than 30)
16. Severe liver disease (ALT 3X ULN) or documented cirrhosis
17. Lung disease requiring continuous home oxygen
18. Uncontrolled hypertension, defined as sustained elevated blood pressure \>160/90 mm Hg on medication
19. Uncontrolled diabetes mellitus, defined as HbA1c greater than 9 (based on most recent test which must have been collected within the last year)
20. Anatomical or physiological structures that do not permit TEE
21. Anticipated need for treatment of structural cardiac defects other than PFO
22. Concomitant cardiac anomalies requiring an operative procedure
23. Hemorrhagic diseases (e.g., coagulopathy, tendency to hemolysis)
24. Hypersensitivity to contrast medium or nickel
25. Contraindication to aspirin or clopidogrel
26. The required sheaths cannot be passed through the relevant vessels for access to the PFO
27. Vulnerable patient (e.g., incarcerated or cognitively challenged adults); see Section 7.2.1
28. Subject is unable or unwilling to provide informed consent
29. Subject is unable to comply with the protocol
30. Any other clinical reasons for which the patient would not be an appropriate candidate for the study, as determined by the site investigators
