Unilateral lung hypoperfusion with normal ventilation on pulmonary scintigraphy caused by pulmonary artery sling

Anomalous origin of the left pulmonary artery, arising from the right pulmonary artery and coursing between the trachea and the esophagus to reach the left hilum, represents a rare vascular abnormality. It has been termed pulmonary artery sling because of its effect on the airway; it generally manifests itself in infancy and is accompanied by severe respiratory symptoms. A young adult patient had an asymptomatic pulmonary artery sling found subsequent to ventilation-perfusion scintigraphy, which showed uniformly decreased perfusion to the left lung with normal ventilation.