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What is patent foramen ovale?

Patent foramen ovale (PFO), a hole in the heart that can be present at birth, is a common structural heart defect. It occurs in about 25 percent of all newborns, but most people do not experience problems because of it.


Often a PFO is not diagnosed until a child or adult with this defect has a transient ischemic attack (TIA) or a stroke. TIAs produce stroke-like symptoms that last less than 24 hours. Symptoms of PFO include any of the following TIA or stroke symptoms:

  • Sudden numbness or weakness in the face, arm or leg (especially on one side of the body)
  • Difficulty speaking or understanding words or simple sentences
  • Sudden blurred vision or decreased vision in one or both eyes
  • Difficulty swallowing
  • Dizziness, loss of balance or coordination
  • Brief loss of consciousness
  • Sudden paralysis in one part of the body
  • Severe migraines


The actual cause of a PFO is unknown, but it occurs when the small flap-like opening in the tissue (septum) that separates the two upper (atrial) chambers of the heart prior to birth fails to seal afterward. Since a fetus’ lungs cannot breathe until they are exposed to air, the hole lets blood bypass its lungs. After birth, when the newborn starts to breathe, normally the foramen ovale closes, and later seals completely in approximately 75 percent of people. If it remains open, it is called a patent (open) foramen ovale. Most people with a PFO do not have trouble with it, even though blood leaks from the right atrium to the left.

This condition may become problematic if a blood clot forms. A very small blood clot (venous thrombus) will be filtered by capillaries in the lungs and not cause a problem, but a larger clot in the brain could be serious. PFOs don’t actually cause strokes, but the hole in the heart might enable a larger clot to travel.


A PFO can be detected with an echocardiogram, which creates an image of the heart by using ultrasound. If the hole still cannot be seen, a cardiologist can perform a “bubble test,” in which a saline solution (saltwater) is injected into your body. The doctor observes the heart on an echocardiogram monitor, and if there is a PFO, will see bubbles traveling from one side of the heart to the other.