The primary objective of the study is to determine whether the STARFlex® septal closure system will safely and effectively prevent a recurrent embolic stroke/transient ischemic attack (TIA) and mortality in patients with a PFO and to demonstrate superiority of the STARFlex® device compared to best medical therapy.

Major Inclusion Criteria:

• Age 18-60 years inclusive.
• Positive contrast valsalva bubble study by trans-esophageal echocardiogram (TEE) for patent foramen ovale (PFO), with or without atrial septal aneurysm.
• Stroke or clinically definite TIA (contact study coordinator).
• Be able to comply with follow up over two years.
• Be competent to, or have a legal guardian competent to, provide informed consent following full disclosure of risks and benefits of both treatment arms by a study investigator.
• Venous access capable of accepting a 10F minimum vascular sheath.
• Have, or be willing to, discontinue hormonal based contraceptive use prior to enrollment and for the term of the study.
• Has cardiac anatomy based on enrollment echocardiogram that will allow for placement of the implant if randomized to the implant arm.
• Note: Additional inclusion criteria may apply. Contact study coordinator or principal investigator for details.

Post-randomization - device patients only

• The size of the PFO (measured by indentation with a soft balloon) must be amenable to selection of a STARFlex device.

Major Exclusion Criteria:

• Carotid artery stenosis > 50%.
• Intracranial stenosis > 50% appropriate to symptoms.
• Complex aortic arch atheroma with high risk features for embolism
• Aortic arch, carotid or vertebral artery dissection.
• Mitral or aortic valve stenosis, vegetation, or calcification > 5 mm mitral annular calcification (MAC) thickness.
• Active pregnancy.
• Active infections (contact study coordinator).
• Active infective endocarditis or bacteremia.
• Prosthetic heart valves in any location.
• Anterior MI within 3 months of neurological event.
• Chronic atrial fibrillation
• Thrombus in, or occluded, venous access route.
• Contraindication to heparin, aspirin, clopidogrel, or warfarin, or a known medical condition that requires continuous warfarin.
• Patient enrolled in another investigation study where clinical endpoint interference may occur.
• Permanent pacemaker or inferior vena cava (IVC) filter.
• Serum creatinine > 2.0 mg/dL
• Patients with known vasculitis or neurologic disorder.
• Baseline modified Rankin score of 3 or more.
• Hypercoagulopathies requiring long-term warfarin.
• Note: Additional exclusion criteria may apply.