Evaluation of the STARFlex® Septal Closure System in Patients With a Stroke or TIA Due to the Possible Passage of a Clot of Unknown Origin Through a Patent Foramen Ovale (PFO)

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.