Unilateral ventilation-perfusion mismatch on pulmonary scintigraphy caused by anomalous origin of a pulmonary artery from the innominate artery

A ventilation-perfusion mismatch on pulmonary scintigraphy is usually secondary to a pulmonary vascular problem, such as thromboembolism, tumor compression, or congenital artery defects or to shunt procedures performed to treat congenital heart disease. The authors present a rare case of anomalous origin of the left pulmonary artery from the innominate artery, left pulmonary hypoplasia, and a right aortic arch. A Tc-99m MAA perfusion scan revealed unilateral absence of pulmonary perfusion. In the Xe-133 ventilation study, both lungs were visualized.