Arterial / Arteriovenous Malformation

Arterial or arteriovenous malformation (AVM) is a high-flow congenital vascular anomaly with abnormal direct connection between arteries and veins through a tangle of dysplastic vessels (nidus), bypassing the capillary bed and producing significant left-to-right shunting. AVMs are present at birth but often quiescent until puberty, pregnancy, trauma, or partial treatment trigger progressive enlargement. Most are sporadic; familial syndromes include hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu, ENG/ACVRL1/SMAD4), capillary malformation–AVM syndrome (RASA1, EPHB4), and PTEN hamartoma tumor syndrome.

Clinical features include warm pulsatile soft tissue mass with palpable thrill and audible bruit, overlying skin discoloration (red-purple), pain, ulceration with pulsatile bleeding, gangrene from steal phenomenon, dilated venous outflow, hyperhidrosis, hyperthermia, limb hypertrophy, and high-output cardiac failure in extensive cases. Schobinger clinical staging classifies AVMs from stage I (quiescent) to stage IV (cardiac decompensation).

Imaging includes Doppler ultrasound (high-flow, low-resistance arterial waveforms with arterialized venous flow), MRI/MRA (no parenchymal mass, flow voids, enlarged feeding arteries and draining veins), CT angiography, and digital subtraction angiography (gold standard for therapy planning). Treatment is multidisciplinary and challenging; superselective embolization with ethanol, Onyx, n-butyl cyanoacrylate, or coils targets the nidus, often combined with surgical resection. Isolated embolization frequently leads to recruitment of new feeders and recurrence. Sirolimus may help symptomatic lesions or RASA1-related AVMs.