From there, they can travel to the brain and block blood flow, causing an ischemic stroke. Patent foramen ovale (PFO) is a hole between your heart's upper chambers.In addition, PFO closure could be helpful but also could be harmful (arrhythmogenic). Patent foramen ovale (PFO) or hole in the heart, affects millions of people and can cause a stroke. Stroke is the major potential complication of PFO. People who have a PFO are slightly more likely to have a stroke than people who do not. PFO's don't cause strokes. Blood clots can travel from the right atrium to the left atrium and out to blood vessels of the body. This patent foramen ovale (PFO) is a possible cause of ischemic stroke in selected patients, without any other cause of stroke. A patent foramen ovale is a small hole in the heart that may increase risk of stroke.