Patent Foramen Ovale and Ischemic Stroke

Patent foramen ovale (PFO) is a common congenital cardiac finding. The foramen ovale allows for unidirectional blood flow from the right atria to the left atria while in utero, and while it typically closes after birth, persistence of the foramen ovale is seen in ~ 25% of healthy adults. It is, therefore, a very frequent incidental finding. PFO has been implicated as a potential source of ischemic stroke via paradoxical embolization, in which a clot from the systemic venous system travels to the right atrium and passes through the PFO in order to reach the left side of the heart and the systemic arterial circulation. The association between stroke and PFO is most robust for younger patients (≤ 60 years) with otherwise unexplained (cryptogenic) stroke; in this population, percutaneous PFO closure reduces the risk of recurrent stroke. . However, in cases where a specific alternative stroke etiology is identified, this is much more likely to be the cause of the stroke than the PFO, and closure is rarely indicated.

A.

Trials of PFO closure in cryptogenic ischemic stroke included only patients 60 years old or younger. In older patients, the association of PFO and stroke is much weaker, likely due to the much higher prevalence of traditional stroke mechanisms in this population such that the PFO is most often an “innocent bystander.” Given this, PFO closure in older patients is not recommended.
B.

Confirmation of acute ischemic stroke on imaging is critical before considering PFO closure. In younger patients, symptoms suggestive of transient ischemic attack commonly are due to nonvascular mechanisms, such as migraine and seizure. Chronic infarctions are not infrequently found on imaging and are not an indication for PFO closure as the underlying stroke mechanisms in these cases are typically obscure, the risk of recurrence uncertain, and such patients are not eligible for inclusion in trials showing benefit for PFO closure.
C.

A comprehensive evaluation to determine stroke mechanism is critical for all younger patients with ischemic stroke. This is outlined in Chapter 45 . If an alternative mechanism is identified, PFO closure should not be pursued. The absolute risk of recurrent stroke associated with PFO is very low, so closure is not emergent, leaving time to complete a careful, thorough workup. The Risk of Paradoxical Embolization (ROPE) score is a simple scoring system that can be used to estimate the likelihood that stroke was related to PFO in the individual patient; it also can be used to predict the risk of recurrent stroke.
D.

The clinical trials that demonstrated the efficacy of PFO closure focused on patients with embolic appearing infarcts, typically excluding those with small deep infarcts thought to be due to lacunar disease. Subgroup analysis of one trial that separately analyzed those with cortical compared with small deep infarcts (presumed to be nonlacunar by the enrolling investigator) suggested no benefit in the latter group.
E.

In the context of underlying thrombophilia that requires anticoagulation, it is unclear whether PFO closure conveys added benefit. Closure certainly does not preclude the need for anticoagulation, as it does not mitigate the risk of deep vein thrombosis or pulmonary embolism. While patients with thrombophilia were largely excluded from PFO closure trials, subgroup analysis of one trial revealed no additional benefit of closure in patients treated with anticoagulation. In another trial that randomized patients between closure and anticoagulation, there was no significant difference in these treatments, raising the possibility that closure likely conveys little or no added benefit.
F.

A larger PFO or an associated atrial septal aneurysm may be associated with an increased risk of recurrent stroke, with the benefit of closure magnified in such patients. In patients lacking any of these high-risk features, the benefit of closure is less clear, but may be considered.
G.

Percutaneous PFO closure is performed with a small device deployed into the PFO via cardiac catheterization. Open surgical repair is generally only performed if cardiac surgery is required for a different issue.