Patent foramen ovale and stroke


 * Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
There is a lack of consensus about the association of patent foramen ovale and cryptogenic stroke. While some studies have demonstrated an increased incidence of patent foramen ovale (PFO) in younger patients with cryptogenic stroke others failed to show an association. Factors that might increase the occurrence of recurrent stroke in patients with patent foramen ovale are atrial septal aneurysm, bigger shunts and longer tunnels. Some systematic reviews done to compare medical versus percutaneous closure, found the rate of recurrent strokes with medical treatment to be greater than that with percutaneous closure. However, the results of these systematic reviews should be carefully interpreted, as the individual studies included in the review were very heterogeneous.

Association of cryptogenic stroke/transient ischemic attacks with patent foramen ovale

 * One in every four cases of ischemic stroke does not have an identifiable cause other than cryptogenic stroke which is a diagnosis of exclusion.


 * Cryptogenic stroke occurs more commonly in younger patients.


 * The association between the presence of a patent foramen ovale and cryptogenic stroke is controversial and inconsistent. While some studies have demonstrated an increased incidence of patent foramen ovale  (PFO) in younger patients with cryptogenic stroke others failed to show an association.

Patent foramen ovale and first stroke
Although, two prospective cohort studies namely, ‘ The Northern Manhattan Study’ (NOMAS) and 'Stroke Prevention: Assessment of Risk in a Community' (SPARC), found an increased incidence of first stroke in patients with patent foramen ovale, both these studies did not reach a statistical significance.

Patent foramen ovale and recurrent stroke

 * There exists a discrepancy between influence of patent foramen ovale (PFO) on recurrent stroke (after first episode of cryptogenic stroke).


 * Several factors have been found associated with a patent foramen ovale (PFO) that might increase the incidence of recurrent strokes namely, atrial septal aneurysm, (ASA) in association with PFO, bigger shunts and longer tunnels.


 * Nevertheless, some studies have found no association between PFO or abnormal septal morphology with recurrent strokes.


 * Studies are not able to establish a clear association of patent foramen ovale with recurrent strokes. A possible explanatation for these findings could be-
 * The studies didn’t control the nature of treatment after the index episode of stroke i.e. patients with one episode of cryptogenic stroke were given either medical (antiplatelet), percutaneous closure or no treatment depending on physician’s decision. Thus, a possibility could be that medical treatment might be highly effective and obscures the risk of patent foramen ovale.

Treatment options in patent foramen ovale with recurrent strokes

 * Medical

A metanalysis done by Almekhlafi et al. found that recurrent strokes were about half as likely on warfarin as compared with antiplatelet treatment.


 * Interventional or Surgical therapy includes:
 * Percutaneous device closure (commonest)
 * Suture closure
 * Radioablative therapy (under-development)
 * Open heart Surgery (uncommon)

Surgical closure of patent foramen ovale is uncommon these days especially after development of percutaneous device closure. Some systematic reviews done to compare medical versus percutaneous closure, found that the rate of recurrent strokes with medical treatment (5.2%) is greater than that with percutaneous closure (1.3%), ,. However, the results of these systematic reviews should be interpreted carefully, because there was lack of uniformity in the selection criteria, duration of follow up and end points in the individual studies that were used for the systematic review.