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A pulmonary arteriovenous malformation (PAVM) is a direct abnormal communication between a pulmonary artery and a pulmonary vein, bypassing the capillary bed. This results in a right-to-left shunt, potentially causing hypoxemia, paradoxical embolism, and stroke.

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![The structure of the normal capillary bed and the PAVM.

Lu W, Dai H, Li Y, Meng X. Neurological and cardiopulmonary manifestations of pulmonary arteriovenous malformations. Frontiers in Medicine. 2024;11. doi:https://doi.org/10.3389/fmed.2024.1449496](attachment:f6186306-122c-4ad9-8aba-298a3401f81a:fmed-11-1449496-g001.jpg)

The structure of the normal capillary bed and the PAVM.

Lu W, Dai H, Li Y, Meng X. Neurological and cardiopulmonary manifestations of pulmonary arteriovenous malformations. Frontiers in Medicine. 2024;11. doi:https://doi.org/10.3389/fmed.2024.1449496

Etiology

Etiology	Details
Congenital (majority)	– Hereditary haemorrhagic telangiectasia (HHT) ”Osler–Weber–Rendu syndrome”
Acquired (rare)	- Trauma or surgery (iatrogenic)

Infection (e.g., actinomycosis)
Hepatic cirrhosis | | Sporadic | ~10–15%, often solitary and asymptomatic |

Epidemiology

~70–90% of PAVMs are associated with HHT
Females > males
Symptoms usually appear in 2nd–4th decade of life

Pathophysiology

Loss of normal capillary filtration → right-to-left shunt
Risk of hypoxemia, brain abscess, stroke, and paradoxical emboli
Increased load on systemic circulation

Clinical Features

Symptom	Cause
Dyspnea, hypoxemia	Due to right-to-left shunt
Cyanosis, clubbing	Chronic hypoxia
Hemoptysis, hemothorax	Rupture of malformation
Neurologic complications	Stroke, TIA, brain abscess (paradoxical emboli)
Epistaxis, telangiectasias	Suggest underlying HHT

Hereditary haemorrhagic telangiectasia (HHT)

Key Signs	Notes
Epistaxis	Recurrent nosebleeds
Telangiectasia	Mucocutaneous: lips, tongue, hands
AVMs in lung, liver, brain	Screening required in family members
Genetics	AD inheritance; mutations in ENG, ACVRL1, SMAD4