Patent foramen ovale (PFO) or hole in the heart, affects millions of people and can cause a stroke. If clots remain in the blood and pass through the left chamber, they can lodge in the brain, heart, eyes or kidneys, causing a stroke.Some studies have found that patent foramen ovales (PFOs) are more common in people with unexplained strokes and migraines with aura. From there, the clot may travel to the brain, where it could block an artery and cause a stroke. Patent foramen ovale is commonly overrepresented in several disease states. Patent foramen ovale (PFO) is a hole between your heart's upper chambers. A patent foramen ovale is a small hole in the heart that may increase risk of stroke. Learn about how a PFO affect stroke risk.