A patent foramen ovale (PFO) has been shown to be highly prevalent in patients diagnosed with strokes of unknown cause, which are also called cryptogenic strokes (CSs). It has been a long-running controversy as to whether a PFO should be closed or not to prevent recurrent strokes in patients diagnosed with CS. A paradoxical embolism that is produced through a PFO is hypothesized to be a leading cause of CS, especially in younger patients with low risk factors for stroke. It remains controversial as to which anticoagulation therapy, defined as antithrombin or antiplatelet therapy, is better for patients with CS and a PFO. In addition, surgical and transcutaneous closure of a PFO has been proposed for the secondary prevention of stroke in patients with CS with PFO. Several randomized controlled trials have been conducted in recent years to test whether a PFO closure gives a significant benefit in the management of CS. Three earlier randomized controlled trials failed to show a statistically significant benefit for a PFO closure; thus, many investigators believed that a PFO was an incidental bystander in patients with CS. However, meta-analyses and more recent specific trials have eliminated several confounding factors and possible biases and have also emphasized the use of a shunt closure over medical therapy in patients with CS. Therefore, these latest studies (the CLOSE and REDUCE trials) can possibly change the treatment paradigm in the near future.
Keywords: Cryptogenic stroke; atrial septal aneurysm; paradoxical embolism; patent foramen ovale; transcatheter closure.