Occurs due to the failure of formation of the sixth aortic arch. Blood to the left lung arises from an aberrant left pulmonary artery that arises from the right pulmonary artery. The vessel passes between the trachea and oesophagus and causes narrowing of the trachea in a caudal direction. Associated with other anomalies (e.g. patent ductus arteriosus).
● Bronchial obstruction causes lung emphysema (right lung, middle lobe, lower lobes, left upper lobe)
● Anterior indentation on the oesophagus, just above the level of the carina
Pulmonary sling: The key view is the lateral where red arrow points to aberrant left pulmonary artery interposed between the esophagus and trachea.