Arteriovenous fistulae and malformations
Arteriovenous fistulae and malformations
D E FI N I T ION
Arteriovenous fistula: An abnormal communication between an artery and vein that
bypasses the capillary bed.
Arteriovenous malformations: Malformation with normal endothelium.
Haemangioma/Angioma: Malformation with endothelial hyperplasia.
AE T IOLOGY
Congenital: Divided into haemangiomas, (e.g strawberry naevi) and malformations (AVMs).
The latter is divided into low flow or high flow (e.g. hepatic or pulmonary AVM).
Hereditary: AVMs and haemangiomas are associated with many different hereditary
syndromes, e.g. Klippel–Trenaunay, Kasabach–Merritt, Sturge–Weber, von-Hippel–
Lindau and Hereditary Haemorrhagic Telangiectasia (Osler–Weber–Rendu syndrome).
Acquired: Trauma, tumours (e.g. glomus tumour, hypernephroma and sarcomas), infection,
inflammation (e.g. aorto-venocaval fistula) or iatrogenic (e.g. Brescia–Cimino fistula for
haemodialysis or portocaval shunt in portal hypertension).
E P IDEMIOLOGY
Cutaneous haemangiomas are very common, the others less so.
H ISTORY
Presentation is variable, depending on the site and size of the AVM and
symptoms may be due to local or systemic effects (see Complications).
Congenital cutaneous haemangiomas are often visible from or soon after birth.
Malformations usually grow with age, puberty or pregnancy.
Those within internal organs may only be detected once complications develop.
Other presentations include varicose veins, limb swelling or pain.
EXAMINA T I ON
Cutaneous haemangiomas (Campbell de Morgan spots) are usually
scarlet in colour, firm and cannot be emptied of blood on compression.
Internal AVMs may be revealed by an overlying bruit or palpable thrill, possibly with reduced
distal pulses and " pulse pressure.
Signs of complications (see Complications).
INVE S T I G A T IONS
Imaging of AVMs: Depends on the site of the lesion. Modalities used include duplex
scanning, CT or MRI scanning or invasive angiography.
SPECT scan: Quantification of AV shunting uses radiolabelled microspheres that are
introduced into an artery and are too large to pass through capillaries. Those passing
through AVMs are trapped in the lungs and quantified using a gamma camera.
MANAGEMENT
Conservative: Cutaneous haemangiomas usually undergo spontaneous regression at the
end of the first year of life. Internal organ AVMs may not necessitate treatment and can be
monitored.
Interventional radiology: In the case of internal AVMs or fistulae, embolization with metal
coils, tissue adhesive or particles can be performed.
Surgery: Often difficult, but excision (after pre-op embolization) may be possible in the case
of small and accessible AVMs.
Stereotactic radiosurgery: Useful on small AVMs, may take years for full effect.
COM P L IC A T I ONS
Cutaneous: Cosmetic disfigurement, ulceration, bleeding.
Organ-specific: E.g. brain AVMs can cause focal neurological deficits, seizures or stroke;
pulmonary AVMs can cause haemoptysis or parodoxical embolism.
Distal: Ischaemia of peripheral tissues.
Systemic: High-ouput cardiac failure in the case of large AVMs.
PROGNOSIS
Depends on site and aetiology. 90 % of haemangiomas regress by
5–10 years. 1–4 % annual risk of haemorrhage in cerebral AVMs.
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