Patent Foramen Ovale (PFO)

What is a PFO?

A patent foramen ovale (PFO) is a defect in the septum (wall) between the two upper (atrial) chambers of the heart. Specifically, the defect is an incomplete closure of the atrial septum that results in the creation of a flap or a valve-like opening in the atrial septal wall (see illustration). A PFO is present in everyone before birth but seals shut in about 80% of people.

With each heart beat or when a person with this defect creates pressure inside his or her chest - such as when coughing, sneezing, or straining during a bowel movement - the flap can open, and blood can flow in either direction directly between the right and left atrium. When blood moves directly from the right atrium to the left atrium, this blood bypasses the filtering system of the lungs (the lungs actually do dissolve tiny blood clots). If debris is present in the blood, such as small blood clots, it now passes through the left atrium and can lodge in the brain, causing a stroke, or another organ, such as the heart, eyes, or kidneys.

What are the symptoms of a PFO?

Although present in about one in five adults, PFOs usually cause no symptoms at all. Far less than 1% has a stroke or other outcome that results in the need to have the PFO closed.

What causes a PFO?

A PFO is congenital, meaning it is a defect that is inborn or exists at birth. Stated another way, the defect is an abnormality, not a disease. The septum between the two atria of the heart developed normally before birth, but the flap did not seal completely after birth.

Heart defects in general

Sometimes a viral infection can cause heart defects to develop, other causes include genetic factors, certain other medical conditions (Down syndrome, for example), some prescription and nonprescription drugs, but 95% of the time a cause cannot be identified.

How is a PFO diagnosed?

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

PFO can only be detected by a specialized test. It does not cause a heart murmur. If a PFO is suspected, your doctor may order tests that can include:

Additional tests may be ordered as necessary.

How are PFOs treated?

If you or your child is diagnosed with a PFO, your primary care doctor will recommend that you meet with a congenital heart specialist (a doctor who has the training and equipment to determine the heart problem) who will order the necessary special tests, medical care and follow-up checkups. A careful assessment of the patient's stroke (if he or she has already experienced one) by a neurologist will first need to be done to determine the best course of action for the PFO.

The usual care for a patient who has had a stroke is the use of blood-thinning medications, such as aspirin or the prescription drugs warfarin (Coumadin) or clopidrogrel (Plavix). These drugs keep the blood cells from sticking together, reducing the risk of blood clot development that could lead to new TIAs or stroke.

However, there are risks and inconveniences associated with the long-term use of blood-thinning medications including:

An alternative for patients unable to take blood-thinning drugs or those who have a second stroke while on blood thinning drugs is nonsurgical (catheter based) closure of the hole. To learn more about this procedure, please see "How is a PFO Closed Using a Catheter-Based Procedure?".

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Reviewed on: 12/9/2008#11626


This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. For additional health information, please contact the Center for Consumer Health Information at the Cleveland Clinic (216) 444-3771 or toll-free (800) 223-2273 extension 43771. If you prefer, you may visit or This document was last reviewed on: 2/14/2017