Patent foramen ovale (PFO) or hole in the heart, affects millions of people and can cause a stroke. Some studies have found that patent foramen ovales (PFOs) are more common in people with unexplained strokes and migraines with aura.PFOs can raise the risk for stroke. Patent foramen ovale (PFO) is a hole between the left and right atria (upper chambers) of the heart. This hole exists in everyone before birth. Patent foramen ovale (PFO) is significantly associated with cryptogenic stroke (CS). However, even in patients with CS, a PFO can be an incidental finding. Background and Purpose Patent foramen ovale (PFO) is significantly associated with cryptogenic stroke (CS). 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.