Left superior pulmonary artery sling.

A pulmonary artery sling is formed when the left pulmonary artery originates from the right pulmonary artery and encircles the distal trachea, coursing between the trachea and esophagus to reach the hilum of the left lung. Pulmonary artery slings are often associated with distal tracheal narrowing, due to either intrinsic stenosis or secondary compression by the anomaly itself. We report a very rare case in which the left superior pulmonary artery originated from the right pulmonary artery and then acted as a sling, the left inferior pulmonary artery originated from the pulmonary trunk.