Patent Foramen Ovale (PFO) and Long COVID have become an area of growing research interest. While COVID-19 does not cause a PFO, researchers are investigating whether an existing PFO could contribute to unexplained breathlessness or low oxygen levels in a small number of people after infection. Most people never know they have one and it usually causes no symptoms. Researchers are investigating whether, in a small number of people, a PFO could contribute to unexplained breathlessness or low oxygen levels after COVID-19 by allowing some blood to bypass the lungs. However, there is currently no evidence that PFO explains most cases of Long COVID, and closure is only recommended in carefully selected situations.
Last evidence review: July 2026
Key Takeaways
- Around one in four adults has a PFO.
- Most PFOs never cause symptoms.
- COVID does not cause a PFO.
- In a small number of people, a PFO may contribute to low oxygen levels or breathlessness.
- A bubble echocardiogram is the most common way to diagnose a PFO.
- PFO closure is not a routine treatment for Long COVID.
After recovering from COVID-19, some people continue to experience unexplained breathlessness, dizziness or drops in oxygen levels despite having reassuring heart scans and lung tests. Occasionally, further investigations reveal something completely unexpected: a patent foramen ovale (PFO).
This often comes as a surprise. How can a hole in the heart suddenly appear after COVID?
The answer is that it usually hasn’t.
Most people with a PFO have had it since birth and never know it’s there. In fact, around one in four adults has a PFO without ever developing symptoms. COVID doesn’t create a PFO, but in some situations it may make an existing one more noticeable by changing the way blood flows through the heart and lungs.
That doesn’t mean a PFO explains Long COVID. For most people, it doesn’t. However, in a small number of carefully selected patients, it may contribute to unexplained breathlessness or low oxygen levels. Understanding that difference is important because it helps explain why some people are investigated further while many others are not.
Why Are Researchers Interested in PFO After COVID?
COVID affects far more than the lungs alone. It can temporarily increase pressure within the blood vessels of the lungs, alter blood flow and affect how efficiently oxygen moves into the bloodstream. In most people, these changes gradually improve as they recover.
For someone with a PFO, however, those temporary changes may occasionally allow a little more blood to pass through the opening instead of travelling to the lungs first. Because that blood bypasses the lungs, it also bypasses the opportunity to collect oxygen.
This is the key idea. The PFO isn’t new. The blood is simply taking a route that has always been there but rarely mattered before.
Researchers believe this may help explain why a small number of people develop unexplained breathlessness or oxygen desaturation after COVID despite otherwise reassuring investigations. Even so, this appears to represent only a small subgroup of patients, and much more research is needed to understand exactly when a PFO becomes clinically important.
What Is a Patent Foramen Ovale (PFO) and Long COVID?
This is where many people understandably become confused. Discovering a PFO after COVID can feel like finally finding the answer. But because around 25% of healthy adults also have a PFO, finding one does not automatically mean it is causing symptoms.
Think of it like discovering an old side road while investigating a traffic jam. The road has always been there. The important question isn’t whether it exists, but whether traffic is actually using it.
That’s exactly what doctors try to determine. They look for evidence that blood is genuinely passing through the PFO in a way that could reduce oxygen levels or increase the risk of complications. Only then does it become relevant to treatment decisions.
What Is a Patent Foramen Ovale (PFO)?
A Patent Foramen Ovale is a small flap-like opening between the two upper chambers of the heart (called the atria). Everyone has this opening before birth, it allows blood to bypass the lungs while a baby is in the womb. Normally, it closes soon after birth.
In some people, though, it stays open. That’s called a PFO. Most people with a PFO never know they have one, and it usually causes no problems at all. However, in certain situations, it can allow a small amount of blood to pass the “wrong way” through the heart from the right side to the left without going through the lungs first. This is sometimes referred to as a right-to-left shunt.
In rare cases, this can increase the risk of small blood clots travelling through the bloodstream (a phenomenon called a paradoxical embolism), which in turn has been linked with some strokes or episodes of unexplained breathlessness.
How COVID-19 Might Make PFO Symptoms More Noticeable
COVID-19 affects both the lungs and the cardiovascular system, and in some cases, it can unmask or worsen problems that were previously silent, including underlying cardiac or vascular issues.
Some case reports and studies have found that:
- Increased strain on the heart and lungs during or after COVID-19 can make the pressure in the right side of the heart rise temporarily. This pressure shift can cause a PFO to open more easily, allowing blood to move through it when it normally wouldn’t.
- A few patients recovering from COVID-19 have experienced unexplained low oxygen levels (hypoxaemia) or shortness of breath during activity (exertional dyspnoea), which later turned out to be linked to an undiagnosed PFO. In those cases, closing the PFO helped restore normal oxygen levels.
- In people who were severely ill with COVID-19 and needed ventilation, studies have shown that mechanical pressure in the lungs can sometimes push blood through an existing PFO, reducing oxygenation efficiency.
It’s important to stress that this is still an emerging area of research, and not everyone with Long Covid or fatigue has a PFO-related problem.But understanding this link can help guide sensible next steps if symptoms don’t add up.
How Common Is a PFO?
A PFO is very common present in roughly one in five adults (16–25%). Most people will never know it’s there. However, in people with existing cardiovascular stress or certain post-COVID symptoms, it might become more noticeable.
Some studies of post-COVID patients have noted ongoing fatigue, palpitations, or shortness of breath, and while there can be many causes, in a few cases, a previously unnoticed PFO was contributing to these issues.
How a PFO Is Diagnosed
If your doctor suspects a PFO might be playing a role in your symptoms, they may arrange a few simple, non-invasive tests:
- Echocardiogram (heart ultrasound): This visualises the structure of the heart and can often spot a PFO.
- Bubble study: A small amount of saline (salt water) is mixed with air and injected during an echocardiogram to check whether tiny bubbles cross from the right to the left side of the heart.
- Oxygen monitoring and exercise tests: These can help detect drops in oxygen levels during movement, which may suggest a shunt (abnormal blood flow) through a PFO.
Your GP can refer you for these investigations if needed, usually to a cardiologist.
Management and Treatment Options
If a PFO is discovered, the next step depends entirely on whether it’s actually causing symptoms or complications. Many people don’t require any treatment at all.
For those who do have persistent problems such as unexplained low oxygen levels, stroke of unknown cause, or severe exertional breathlessness closure may be considered.
There are two main approaches:
- Percutaneous closure: A small, minimally invasive procedure where a thin tube (catheter) is passed through a vein to place a tiny device that seals the opening.
- Surgical closure: Much less common, and usually done only if a person is already having heart surgery for another reason.
A cardiologist would help decide if either approach is suitable, based on test results, overall health, and symptom history.
Managing Post-COVID Fatigue and Circulation Symptoms
Even if your symptoms are not directly caused by a PFO, these general principles can help support cardiovascular recovery after COVID-19:
- Start gently: Build up activity slowly especially if you suffer of PEM and rest before you feel exhausted.
- Monitor symptoms: Keep an eye on heart rate, oxygen levels, and how you feel during exertion.
- Stay hydrated and nourished: Dehydration can worsen fatigue and circulation symptoms.
- Check in with your GP: Especially if symptoms such as shortness of breath, dizziness, or palpitations persist or worsen.
FAQs
What is a Patent Foramen Ovale (PFO)?
A PFO is a small opening between the upper chambers of the heart that does not fully close after birth. It is common and usually harmless.
Can COVID cause a PFO?
COVID does not cause a PFO, but it may make an existing PFO more noticeable by affecting heart and lung function.
Can a PFO cause shortness of breath after COVID?
In some cases, yes. A PFO can allow blood to bypass the lungs, which may reduce oxygen levels and contribute to breathlessness during activity.
How is a PFO diagnosed?
A PFO is usually diagnosed using an echocardiogram, often with a bubble study to detect abnormal blood flow between the heart chambers.
Do all PFOs need treatment?
No. Most PFOs do not require treatment unless they are clearly linked to symptoms or complications such as stroke or low oxygen levels.
Is PFO closure a major procedure?
Most closures are done using a minimally invasive catheter procedure rather than open surgery, but suitability depends on individual cases.
Disclaimer
This article is for information only and does not constitute medical advice. It should not be used to diagnose or treat any health condition. Always consult a GP or qualified healthcare professional if you have concerns about your heart health, recovery after COVID-19, or possible PFO-related symptoms.