Skip to main content

Health condition

Patent foramen ovale, stroke risk, and when closure is worth discussing.

A small opening between the heart's upper chambers, present in around 1 in 4 people - usually harmless, occasionally relevant after a stroke of unknown cause.

Jump to treatment
A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Checked against NICE, British Cardiovascular Society and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK guidance on cryptogenic stroke assessment and percutaneous PFO closure.

Key facts

Patent foramen ovale at a glance.

The essentials, in plain English - what it is, how common it is, and how it's assessed in the UK today.

  • What it is

    A small flap-like opening between the right and left atria that normally seals after birth but stays open in around 1 in 4 people.

  • How common

    Present in roughly 25% of the general population - most people never know they have one.

  • Usual presentation

    The vast majority are silent and are only found by chance during an echocardiogram done for another reason.

  • Main clinical link

    Cryptogenic stroke - a stroke with no obvious cause - particularly in adults under 60.

  • First-line test

    Transthoracic echocardiography with a bubble (agitated saline contrast) study.

  • Closure decision

    Made jointly by cardiology and stroke medicine, and only for carefully selected patients after cryptogenic stroke.

Why this guide matters

Common, usually harmless - occasionally the missing piece.

A PFO sits in an unusual place in medicine - almost always irrelevant, but sometimes the answer to a stroke that otherwise makes no sense. The three points below shape everything else on this page.

  • Finding a PFO is not a diagnosis on its own

    A quarter of the population has one - the finding only matters once it is weighed against your actual medical history and symptoms.

  • Cryptogenic stroke changes the conversation

    A stroke with no clear cause, particularly under 60, is the main scenario where a PFO becomes clinically relevant and worth investigating properly.

  • Closure is selective, not routine

    Percutaneous closure helps specific, carefully chosen patients - it is not offered to everyone with a PFO, and trial evidence guides who qualifies.

How the diagnosis is made

From an unexplained event to a clear answer.

The steps a UK cardiologist or stroke physician will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    Clinical context and history

    A doctor looks at why the PFO is being considered - an incidental finding, a cryptogenic stroke work-up, migraine with aura, or unexplained decompression illness in a diver.

  2. 02

    Assessing

    Stroke or TIA work-up first

    After a stroke or TIA, standard causes - atrial fibrillation, carotid disease, small vessel disease - are ruled out before a PFO is considered relevant.

  3. 03

    Confirming

    Bubble study echocardiogram

    Transthoracic echocardiography with agitated saline contrast is the first-line screening test - it shows bubbles crossing from the right to the left atrium.

  4. 04

    Confirming

    Transoesophageal echocardiogram

    A more detailed probe-down-the-throat scan (TOE) if the transthoracic study is unclear or more anatomical detail is needed before a closure decision.

  5. 05

    Confirming

    Risk-scoring the PFO

    Features such as a large shunt, an atrial septal aneurysm or a long tunnel raise the likelihood that the PFO, rather than chance, explains the stroke.

  6. 06

    Deciding

    Joint cardiology and stroke review

    A specialist multidisciplinary discussion weighs age, PFO features and stroke pattern to decide whether closure, medication, or neither is right.

  7. 07

    Deciding

    Shared decision on next steps

    The plan - watchful waiting, antiplatelet or anticoagulant therapy, or catheter-based closure - is agreed with the patient, not imposed on them.

Typical timeline: from stroke work-up to a settled plan in a few weeks.

Symptoms

What a PFO actually looks like in practice.

Almost always nothing at all. And the small number of situations where it becomes worth investigating.

  • No symptoms at all

    The overwhelming majority of people with a PFO have no symptoms whatsoever and never find out they have one.

  • Incidental echo finding

    Often spotted by chance during an echocardiogram done for an unrelated heart concern.

  • Cryptogenic stroke or TIA

    A stroke or mini-stroke with no clear cause, especially in someone under 60 without the usual risk factors.

  • Migraine with aura

    An association with migraine that includes visual or sensory aura exists, though whether the PFO causes the migraine is still debated.

  • Unexplained breathlessness on exertion

    Rarely, a large shunt can cause low oxygen levels and breathlessness, particularly on standing or exercising - platypnoea-orthodeoxia syndrome.

  • Decompression illness in divers

    Divers who develop unexplained decompression illness, especially with neurological symptoms, are sometimes found to have a PFO.

  • Paradoxical embolism

    A clot forming in the leg veins can, in theory, cross the PFO and travel to the brain or another artery instead of being filtered by the lungs.

  • Found during unrelated imaging

    Sometimes identified on a CT or MRI scan done for a completely different reason, prompting a cardiology opinion.

Treatment

How a PFO is managed in the UK.

No treatment for most, medication for some, and catheter-based closure for a carefully selected group after cryptogenic stroke.

  • No treatment needed

    For an incidental PFO with no relevant stroke or symptom history, reassurance and no intervention is the right answer for most people.

  • Antiplatelet therapy

    Aspirin or clopidogrel may be used as an alternative to closure, or alongside it, depending on individual stroke risk.

  • Anticoagulant therapy

    Warfarin or a DOAC is considered when another clotting risk exists, or when closure is not suitable or declined.

  • Percutaneous PFO closure

    A catheter-based device closes the defect from inside the heart - considered for selected patients with cryptogenic stroke and high-risk PFO features.

  • Joint cardiology-stroke assessment

    A specialist multidisciplinary review weighs trial evidence, PFO anatomy and stroke pattern before any closure decision is made.

  • Diving-specific discussion

    For divers with unexplained decompression illness, a specialist conversation covers PFO testing, closure, and adjusted diving practice.

  • Migraine management as usual

    Standard migraine treatment is still the first approach - PFO closure is not currently recommended purely to treat migraine.

  • Structured follow-up

    Patients who have a PFO closure or start long-term medication are followed up to check the device or therapy is working as expected.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, cardiologist or stroke physician knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Percutaneous closure of patent foramen ovale for the secondary prevention of recurrent paradoxical embolism (interventional procedures guidance).

  • British Cardiovascular Society. Position statement on patent foramen ovale and cryptogenic stroke.

  • European Society of Cardiology (ESC). Guidelines on the management of adult congenital heart disease.

  • British Heart Foundation. Patient information on patent foramen ovale.

Red flags

When to seek urgent help.

A PFO itself is rarely an emergency. These situations are - and none of them should wait for a routine appointment.

  • Sudden stroke symptoms

    Facial droop, arm weakness or slurred speech (FAST) is a medical emergency regardless of PFO status - call 999 immediately.

  • Recurrent stroke or TIA

    A further stroke or TIA after a PFO diagnosis needs urgent specialist reassessment of the closure or medication plan.

  • New breathlessness with low oxygen

    Sudden breathlessness that worsens on sitting or standing upright can signal a large right-to-left shunt and needs prompt cardiology review.

  • Decompression illness after a dive

    Neurological symptoms, joint pain or skin changes after diving are a diving-medicine emergency - seek immediate assessment, ideally at a hyperbaric centre.

  • Signs of a deep vein thrombosis

    A hot, swollen, painful calf raises the risk of a paradoxical embolism through a PFO and needs same-day medical assessment.

  • Bleeding on anticoagulants

    Unusual bruising, blood in urine or stool, or a head injury while on warfarin or a DOAC needs urgent medical attention.

  • Chest pain or palpitations after closure

    New chest pain, irregular heartbeat or breathlessness in the weeks after a closure procedure should be assessed promptly by the implanting team.

  • Suspected device-related complication

    Rare but serious complications after closure, including device erosion or new atrial fibrillation, need specialist cardiology input without delay.

Living with it

For most people, life goes on unchanged.

Four things that matter if you have been told you have a PFO - reassurance where it is due, awareness of stroke signs, tailored diving advice, and follow-up if you have had treatment.

A quiet reminder

A PFO is a finding, not a sentence.

For the vast majority, it changes nothing about how you live, work, exercise or plan your future.

  1. 01 Reassurance

    Most PFOs need nothing at all

    If yours was found by chance and you have no relevant history, it usually needs no treatment and no restriction on daily life.

  2. 02 Awareness

    Know the signs of stroke

    Learning FAST (Face, Arms, Speech, Time) matters for everyone, but especially if a PFO has been part of your story.

  3. 03 Diving

    Get specific diving advice

    If you dive and have a known PFO, a diving-medicine specialist can advise on safer practices or whether closure is worth discussing.

  4. 04 Follow-up

    Keep review appointments

    If you have had a closure device fitted or started long-term medication, attending follow-up checks confirms everything is working as intended.

Frequently asked

Everything we get asked about PFO.

Quick answers on diagnosis, stroke risk, closure and the migraine link.

  • What is a patent foramen ovale?

    It is a small flap-like opening between the right and left upper chambers of the heart that everyone has before birth. In around 25% of people it does not fully seal afterwards, usually without causing any problems.

  • Is a PFO dangerous?

    For most people, no - it is a normal variant found incidentally and needs no treatment. It becomes clinically relevant mainly when a cryptogenic stroke has happened, or in divers with unexplained decompression illness.

  • How is a PFO diagnosed?

    The first-line test is a transthoracic echocardiogram with a bubble (agitated saline contrast) study, which shows bubbles crossing from the right side of the heart to the left. A transoesophageal echocardiogram gives more detail if needed.

  • Does a PFO cause strokes?

    It can contribute to a small number of strokes through paradoxical embolism, where a clot passes from the vein circulation to the artery circulation via the PFO instead of being filtered by the lungs. This is mainly considered after a cryptogenic stroke, especially in younger adults.

  • Should my PFO be closed?

    Closure is only considered for selected patients who have had a cryptogenic stroke and high-risk PFO features, decided jointly by cardiology and stroke medicine. It is not routinely offered for an incidental finding or for migraine alone.

  • Is there a link between PFO and migraine?

    An association between PFO and migraine with aura exists, but whether the PFO actually causes the migraine is still debated. PFO closure is not currently recommended purely to treat migraine.

Related content

Keep reading.