Patent Foramen Ovale (PFO)
Patent foramen ovale (PFO) overview
A patent foramen ovale (PFO) is a small flap-like opening between the two upper chambers of the heart, the right and left atria. Before birth, this opening lets blood bypass the lungs. It normally seals shortly after birth, but in about 1 in 4 adults it stays slightly open. It is sometimes called a hole in the heart, but it is better described as a flap valve that is not fully sealed.
For most people a PFO is harmless and is never noticed. It is often found by chance on a heart scan done for another reason. A PFO is different from an atrial septal defect (ASD), which is a true hole in the wall between the atria, and is more likely to need treatment.
How can a PFO matter?
Normally, the pressure in the left atrium is higher than in the right, so the flap stays shut. When the pressure on the right rises, for example when you cough, strain or lift, the flap can open briefly. A small clot or bubble from a vein can then, rarely, cross into the left side of the heart and travel to the brain. This is called a paradoxical embolism. It is one reason a PFO has been linked to some strokes, to migraine with aura and to decompression illness in divers.
PFO symptoms and signs
A PFO does not usually cause symptoms. It is a finding rather than an illness. When health problems are linked to it, they are the following:
Conditions linked with a PFO
- Stroke or transient ischaemic attack (TIA): sudden weakness, numbness, speech or vision problems, particularly in a younger person where no other cause is found.
- Migraine with aura: visual disturbance or tingling before a headache. Many people with migraine have a PFO, but the link is not fully understood.
- Decompression illness in divers: joint pain, rash, dizziness or neurological symptoms after diving.
- Breathlessness or low oxygen when upright: this is rare and is called platypnoea-orthodeoxia.
When there are no symptoms
If you have a PFO and no symptoms, it is normal and needs no action. Your doctor will check that there is no other heart problem, and will reassure you.
Causes and risk factors of PFO
A PFO is a normal part of foetal development that has not closed. It is not caused by lifestyle, and nothing you did before or after birth made it happen. It can run in families.
Factors that raise the chance of a clot crossing a PFO
- a clot in the leg or pelvic veins (deep vein thrombosis)
- long periods of immobility, such as a long flight or bed rest
- pregnancy and the weeks after delivery
- an inherited tendency to clotting
- a large PFO, or a PFO with an atrial septal aneurysm (a floppy bulge in the septum)
- activities that raise chest pressure, such as heavy straining, or scuba diving
Is a PFO always the cause of a stroke?
No. A PFO is common, so finding one in someone who has had a stroke does not prove it caused it. Doctors weigh the features of the PFO and the stroke, and look for other causes such as an irregular heart rhythm, narrowing of the neck arteries, high blood pressure or clotting disorders.
When to see a doctor about PFO
If you have sudden weakness of the face, arm or leg, slurred speech, loss of vision or a sudden severe headache, call 999. Do not wait, even if the symptoms settle.
Arrange an assessment if you:
- have had a stroke or TIA and want to know if your heart is involved
- have been told you have a PFO and have migraine with aura, or a history of clots
- are a diver, or plan to dive, and have been told you have a PFO
- feel breathless or unwell when upright and sitting up, with no clear cause
- have a family history of stroke at a young age
How a PFO is diagnosed
A PFO is usually found with an echocardiogram and confirmed with a bubble echo.
1. Bubble echo (contrast echocardiogram)
A small amount of agitated saline (salt water with tiny bubbles) is injected into a vein while the heart is scanned. If bubbles pass from the right to the left side within a few heartbeats, a PFO or other shunt is likely. The test is quick, uses no radiation and is done without sedation.
2. Transoesophageal echocardiogram (TOE)
If more detail is needed, for example before closure, a probe is passed down the gullet under sedation to give a closer view of the septum, its size and any aneurysm.
3. Looking for other causes
After a stroke or TIA, tests may include brain and neck artery imaging, heart rhythm monitoring (to look for atrial fibrillation), blood tests and a check for clots in the legs. A scoring system called the RoPE score helps estimate the chance that a PFO was related to the stroke.
PFO treatment options
Most people with a PFO need no treatment. When treatment is needed, the choice depends on why the PFO is being considered.
1. Observation and reassurance
A PFO found by chance, with no stroke or clot history, needs no treatment or restrictions, other than advice for divers.
2. Medicines
After a stroke or TIA, an antiplatelet medicine such as aspirin or clopidogrel is usually used. If a clot in a vein has been found, an anticoagulant may be needed. Blood pressure and cholesterol are treated as for any stroke prevention.
3. Closing the PFO
Closure is done through a vein in the groin using a small device that seals the flap, under local anaesthetic or sedation. Trials such as CLOSE, REDUCE and RESPECT found that closure reduces the risk of another stroke in carefully selected patients, generally aged 18 to 60 with a stroke of no other cause and a high-risk PFO. Possible complications include a rhythm problem called atrial fibrillation, which affects a small minority, up to about 1 in 20 people and is usually short-lived, as well as bleeding, device problems and, rarely, a heart perforation. Closure is decided by a team that includes a stroke specialist and a cardiologist.
4. Migraine and diving
Closing a PFO is not currently recommended to treat migraine alone. Divers with a PFO should seek advice from a diving medicine specialist about diving, and may be advised to avoid provocative dives or have the PFO closed.
Living with a PFO
Most people live completely normal lives with a PFO.
Everyday life
- Exercise, flying, pregnancy and childbirth are generally safe if you have no related problems.
- On long journeys, keep moving and drink water to lower the risk of leg clots.
- Tell your doctors you have a PFO if you are having surgery or are on a long period of bed rest.
- Keep blood pressure, cholesterol and weight healthy, and do not smoke.
Diving and driving
If you dive, speak to a diving medicine specialist. A PFO alone does not stop you driving. If you have had a stroke or TIA, the DVLA rules for stroke apply; see DVLA cardiac assessment for related advice.
PFO prognosis and outlook
The outlook for a PFO found by chance is excellent. It does not shorten life and rarely causes problems.
After a stroke, the risk of another one depends on the cause. In people whose stroke is linked to a PFO, closure and medicines lower that risk. Follow-up usually includes a check of the closure device with an echocardiogram, as well as continued medicines for a period as advised.
PFO key facts
- A PFO is a flap-like opening between the upper chambers, present in about 1 in 4 people.
- It is usually harmless and does not need treatment.
- A bubble echo is the main test.
- It is linked with some strokes, migraine with aura and decompression illness.
- Closure is considered only in selected patients after a stroke with no other cause.
Guidelines and sources
This page follows NICE guidance on percutaneous closure of patent foramen ovale to prevent recurrent cerebral embolic events (originally IPG472, December 2013, now numbered HTG325), the SCAI Guidelines for the Management of Patent Foramen Ovale (2022), the CLOSE, REDUCE and RESPECT trials (all published in the New England Journal of Medicine, 2017) and NHS patient information.
PFO questions and answers
Is a PFO dangerous?
Usually not. It is common and most people never know they have it.
Can a PFO cause a stroke?
Rarely. A clot can cross a PFO to the brain, but a PFO is only one of several possible causes, and doctors look for others first.
Does a PFO cause migraine?
Migraine with aura is more common in people with a PFO, but closing it is not a recommended treatment for migraine.
Can I scuba dive with a PFO?
It depends on your circumstances. A PFO may increase the risk of decompression illness, so please get advice from a diving medicine specialist.
Will a PFO close by itself?
In adults it usually does not, but it rarely needs to.
Can I fly or exercise with a PFO?
Yes, in almost everyone. Stay active and hydrated on long flights.
Can I have a PFO assessment privately?
Yes. A consultation, echocardiogram and bubble echo can be arranged, and any further tests or procedures coordinated with a stroke team.
Questions to ask your cardiologist about PFO
- How large is my PFO, and is there an atrial septal aneurysm?
- Is it likely to be related to my stroke, TIA or migraine?
- Have other causes been checked, including heart rhythm monitoring?
- Would closure benefit me, and what are the risks?
- Which medicines should I take, and for how long?
- Do I need any restrictions for diving, travel or exercise?
- What follow-up tests will I need?
PFO diagrams and visual aids
Patent foramen ovale diagram
Image: Manco Capac, Patent foramen ovale, Wikimedia Commons. Licensed under CC BY-SA 3.0.
How a PFO works
Simplified diagram of a PFO with the flap closed (left) and opening briefly with straining (right).
Before birth, a small flap-like opening between the upper chambers lets blood bypass the lungs. After birth it normally seals. In about 1 in 4 adults it stays loosely closed, and may open briefly when the pressure in the right side of the heart rises, for example when coughing or straining.
When is closure considered?
Most people with a PFO need no treatment. Closure may be considered after an unexplained stroke or TIA in selected patients.
The decision is made individually by a cardiologist together with a stroke specialist, after other causes of stroke have been looked for.
If you have been told you have a PFO, or have had a stroke or TIA and are unsure what your heart scan means. You can book a video consultation or telephone consultation from anywhere in the UK, or a face to face consultation in Peterborough or Corby. A bubble echo and echocardiogram can be arranged if needed.
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Medically reviewed by Dr Salam Salloum, Consultant Cardiologist. Last reviewed: . This page is for general information and does not replace personal medical advice.