Pulmonary Arteriovenous Malformation

Pulmonary arteriovenous malformation (PAVM) is an abnormal vascular communication between pulmonary artery and pulmonary vein without intervening capillary bed, producing right-to-left intrapulmonary shunt. Approximately 80% of PAVMs are associated with hereditary hemorrhagic telangiectasia (HHT, Osler-Weber-Rendu syndrome, autosomal dominant; ENG, ACVRL1, SMAD4 mutations). The remaining 20% are sporadic. Most PAVMs are simple (one feeding artery, one draining vein), located in lower lobes, and may be solitary or multiple.

Clinical features depend on size and shunt fraction. Asymptomatic PAVMs are common; symptomatic patients present with exertional dyspnea, hypoxemia worsening upright (orthodeoxia) and improved supine, platypnea (dyspnea improved supine), cyanosis, clubbing, and bruit on auscultation over the chest. Devastating complications result from paradoxical embolization: ischemic stroke, transient ischemic attack, brain abscess (most distinctive complication), spinal cord infarction, and migraine aura. Pulmonary hemorrhage and hemothorax may occur with rupture.

Diagnosis: contrast (bubble) echocardiography is highly sensitive screening test (delayed appearance of bubbles in left heart >3 cardiac cycles after right heart). High-resolution CT confirms PAVM location, size, and feeding vessels. Digital subtraction pulmonary angiography is gold standard and used during embolization. Treatment of choice is transcatheter coil or vascular plug embolization of feeding artery (>3 mm feeding artery is treatment threshold), with success rate >90%. Surgical resection is reserved for failed embolization. Antibiotic prophylaxis before dental and surgical procedures prevents brain abscess. HHT screening evaluates other organ AVMs (liver, brain, spine).