Rare lung & airway condition
Pulmonary arteriovenous malformations
Pulmonary AVMs are abnormal direct connections between lung arteries and veins that bypass the oxygenation and filtering functions of the lung - risking stroke and brain abscess - and most are caused by hereditary haemorrhagic telangiectasia (HHT).
Key points
The essentials at a glance.
What to look out for, how the diagnosis is confirmed, who looks after it, and the options that exist.
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01
Many are silent; clues include low oxygen levels, breathlessness, migraine and unexplained stroke or brain abscess at a young age.
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02
The lung capillary bed normally filters small clots and bacteria - an AVM lets them pass straight to the brain.
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03
Most pulmonary AVMs occur in HHT: ask about recurrent nosebleeds and family history.
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04
Embolisation - blocking the feeding artery via a catheter - is the standard, highly effective treatment.
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05
Lifelong follow-up, antibiotic prophylaxis before dental work, and screening of relatives (in HHT) are part of care.
Understanding it
What it is, and what happens next.
In plain English - what is going on, how specialists confirm it, and the routes to treatment in the UK.
A pulmonary AVM is a plumbing short-circuit: blood shunts from artery to vein without meeting the capillary network, so it emerges under-oxygenated and unfiltered. The unfiltered part is the menace - a fragment of clot or a mouthful of bacteria entering a leg vein can arrive intact in the brain, which is why paradoxical stroke or cerebral abscess in a young adult should always raise the question.
Screening (contrast echocardiography, then CT) is standard for anyone with HHT, and treatment thresholds are low because embolisation is safe and durable; care in centres experienced in HHT adds the wider surveillance the syndrome needs, simple but critical precautions - filters on intravenous lines, antibiotics before dental procedures - and family cascade screening. In many parts of the UK, routine NHS outpatient referrals for problems like this can take several months, whereas an initial appointment with a private consultant is typically available within around two weeks.
A quiet reminder
This guide is for information, not medical advice.
Your GP or specialist knows your history and can tell you which parts apply to you. If in doubt, speak to them.
Published 2026-09-27 · Next review 2027-09-27
Frequently asked
Common questions about Pulmonary arteriovenous malformations.
Quick, plain-English answers to what people ask us most.
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What are pulmonary arteriovenous malformations?
Pulmonary arteriovenous malformations (AVMs) are abnormal connections between arteries and veins in the lungs, bypassing the normal capillary network, which can allow blood to pass through the lungs without being properly oxygenated.
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What causes pulmonary AVMs?
Many are linked to an inherited condition called hereditary haemorrhagic telangiectasia (HHT), while others occur without this genetic link, developing from abnormal blood vessel formation.
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What are the symptoms?
Breathlessness, particularly with exertion, and reduced blood oxygen levels are common, though many smaller AVMs cause no symptoms; larger ones can occasionally cause more serious complications such as stroke or brain abscess.
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Are pulmonary AVMs dangerous?
Yes, they can be, as they allow blood clots or bacteria to bypass the lung's normal filtering function and potentially travel to the brain, causing serious complications like stroke, even when the AVM itself causes few respiratory symptoms.
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Is hereditary haemorrhagic telangiectasia linked to pulmonary AVMs hereditary?
Yes, HHT is an inherited condition in an autosomal dominant pattern, meaning each child of an affected parent has a 50% chance of inheriting it and potentially developing pulmonary AVMs.
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Can pulmonary AVMs be treated?
Yes, a minimally invasive procedure called embolisation, which blocks off the abnormal blood vessel connection, is highly effective and is the standard treatment for AVMs of significant size.
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How are pulmonary AVMs diagnosed?
CT imaging of the chest identifies the abnormal blood vessels, and screening is recommended for anyone diagnosed with HHT or with a family history, given the risk of AVMs developing without symptoms.
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How long does treatment take?
The embolisation procedure itself typically takes under an hour, performed under local anaesthetic with sedation, with most people going home the same day or after a short overnight stay.
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Pulmonary AVMs vs other causes of low blood oxygen — what's the difference?
Most causes of low blood oxygen relate to lung disease affecting how well oxygen crosses into the blood, while AVMs specifically create a direct bypass of the lung's oxygenating tissue; imaging helps identify this specific structural cause.
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When should I see a specialist, and how quickly can I be seen privately?
See a respiratory specialist if you have HHT or unexplained breathlessness with low oxygen levels. Private specialist assessment is typically available within about two weeks, faster than standard NHS pathways for this condition.