Introduction
Patent foramen ovale (PFO) is a normal embryological opening between the left and right atria of the heart that usually closes shortly after birth. However, in around 25% of the adult population, the opening fails to seal completely, leaving a PFO. While PFO is generally clinically silent, it has been implicated as a potential cause of cryptogenic stroke and migraine headaches. PFO closure devices are minimally invasive medical devices used to close an abnormal opening in the heart called a patent foramen ovale (PFO). This article discusses the need for PFO closure, available devices, procedure details and outcomes.

Need for Closure of PFO
PFO is generally clinically silent throughout life however it is associated with increased risk of cryptogenic stroke, migraines and other complications in some individuals. Closure of PFO is usually considered in patients who have had a stroke that cannot be explained by other causes (cryptogenic stroke). Studies have shown that almost half of cryptogenic strokes may be caused by a PFO with right-to-left shunting of blood clots from the venous circulation to the arterial circulation bypassing the lungs. PFO closure aims to prevent recurrence of stroke by closing the pathway for blood clots to bypass the lungs. It is also considered for patients with frequent severe migraine headaches that are refractory to medical management as PFO allows passage of vasoactive molecules that may trigger migraines.

Available PFO Closure Devices
Several self-expanding, generally nitinol-based devices have been developed for percutaneous closure of PFO. The most commonly used devices include:

Amplatzer PFO Occluder: One of the first generation devices, it is a self-expanding Nitinol mesh disc device available in various sizes. It has two retention disks, one on each side of the septum connected by a central connecting waist.

Figulla Flex II PFO Occluder: Similar to Amplatzer device, it has a double disc design with connecting waist. Discs are made of braided Nitinol wire mesh.

HELEX Septal Occluder: Dome shaped nitinol mesh device consisting of two retention disks with a connecting central waist.

Cera PFO Occluder: self-expanding nitinol mesh disc device with two retention disks and connecting waist made of polyester mesh to allow tissue ingrowth.

The devices vary in terms of design, retention disk size and shape, waist length etc. Selection depends on the PFO anatomy. Newer devices aim to improve safety, efficacy and long term durability.

PFO Closure Procedure
Patent Foramen Ovale (PFO) Closure Devices closure is generally performed as an outpatient or short stay procedure under conscious sedation or local anesthesia. Access is obtained via the femoral or jugular vein. Transesophageal echocardiography (TEE) or intracardiac echocardiography (ICE) is used to visualize the defect during the procedure. The delivery sheath containing the compressed PFO device is advanced into position across the PFO defect under fluoroscopic and echocardiographic guidance. The device is then deployed with release of the retention disks on either side of the septum to close the opening.

Immediate closure and positioning is confirmed with echo and bubble study. Antiplatelet or anticoagulant therapy may be prescribed post procedure for a period based on device used and risk profile. Patients can usually return to routine work within a couple of days. Follow up echos are done periodically to assess for adequate closure and device position over time.

Outcomes of PFO closure
Multiple randomized controlled trials have evaluated outcomes of PFO closure versus medical management alone for cryptogenic stroke. While all have demonstrated safety of the procedure, efficacy results have been mixed.

The CLOSE trial showed significant reduction in recurrent cryptogenic stroke or TIAs with PFO closure compared to medical management alone over 5 years (HR 0.37). Similarly, the RESPECT trial showed a trend favoring closure though statistical significance was not reached.

Other trials like PC Trial, REDUCE and CLOSE did not show statistically significant difference in primary endpoint of stroke recurrence between groups. However, most showed superiority of closure for prevention of recurrent brain lesions detected on MRI.

With regard to migraine, theMIGRAINE trial showed significant reduction in number of monthly migraine headaches with PFO closure versus sham at 6 months which persisted to 3 years.

Overall, current evidence suggests PFO closure may be reasonable for recurrent cryptogenic strokes but benefits are modest. More definitive benefits are seen for refractory migraine headaches. Safety has been well established across studies. Proper patient selection based on individual risk profile is important for optimal outcomes. Longer term results on efficacy and safety are still awaited from ongoing studies.

Conclusion
PFO closure devices aim to address the risk of recurrent cryptogenic strokes or refractory migraines attributable to PFO anatomy. While the procedure itself is safe, efficacy outcomes vary based on individual trials. Modest yet potentially significant reductions in stroke recurrence as well as considerable benefits for migraine prevention have been demonstrated. With evolving device technologies and improved patient selection, PFO closure continues to establish its role as an important treatment strategy. However, clear benefits still need validation from ongoing long term outcomes.

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