Pulmonary arteriovenous malformations.

Pulmonary arteriovenous malformations (PAVMs) are abnormal vascular structures that most often connect a pulmonary artery to a pulmonary vein, bypassing the normal pulmonary capillary bed and resulting in an intrapulmonary right-to-left shunt. As a consequence, patients with PAVM can have hypoxemia and paradoxical embolization complications, including stroke and brain abscess. PAVMs may be single or multiple, unilateral or bilateral, and simple or complex. Most PAVMs are hereditary and occur in hereditary hemorrhagic telangiectasia, an autosomal dominant vascular disorder, and screening for PAVM is indicated in this subgroup. PAVMs may also be idiopathic, occur as a result of trauma and infection, or be secondary to hepatopulmonary syndrome and bidirectional cavopulmonary shunting. Diagnostic testing involves identifying an intrapulmonary shunt, with the most sensitive test being transthoracic contrast echocardiography. Chest CT scan is useful in characterizing PAVM in patients with positive intrapulmonary shunting. Transcatheter embolotherapy is the treatment of choice for PAVM. Lifelong follow-up is important because recanalization and collateralization may occur after embolization therapy. Surgical resection is rarely necessary and reserved for patients who are not candidates for embolization. Antibiotic prophylaxis for procedures with a risk of bacteremia (eg, dental procedures) is recommended in all patients with PAVM because of the risk of cerebral abscess.