Patent foramen ovale: the known and the to be known.

The patent foramen ovale (PFO) is a normal interatrial communication during fetal life that persists after birth in approximately 1 of every 4 adults. PFO is a potential route for embolic transit from the systemic venous circulation to the brain. Though there is compelling circumstantial evidence implicating PFO, the precise role of PFO in the pathogenesis of cryptogenic stroke is not yet established. Several randomized trials of transcatheter PFO closure versus medical management are ongoing. Results of these trials may improve our ability to select the best treatment for individual patients. Further well-designed studies are necessary to address several unresolved issues related to PFO stroke and PFO migraine pathophysiology, and to identify the patients who would most likely benefit from PFO closure. The purpose of this review is to summarize contemporary understanding, discuss current treatments, and explore some of the knowledge gaps pertaining to the clinical significance of PFO.