Pulmonary Sling and Double Aortic Arch

Pulmonary Sling 

• Pulmonary sling occurs because of failure of formation of Left 6th aortic arch so there is absence of Left pulmonary artery
• The blood to the Left lung comes from an aberrant Left pulmonary artery which arises from Right pulmonary artery and crosses between esophagus and trachea
• Bronchial cyst may produce same finding on esophagus/trachea

Pulmonary sling: The key view is the lateral where red arrow points to aberrant
left pulmonary artery interposed between the esophagus and trachea.

Pulmonary sling: Again note the aberrant left pulmonary artery interposed between the esophagus and trachea on multiple barium swallows.

Double Aortic Arch

• Double aortic arch is most common vascular ring
• Caused by persistence of Right and Left IV branchial arches
• Rarely associated with Congenital Heart Disease
• Symptoms (of tracheal compression or difficulty swallowing) may begin at birth
• Right arch is higher, left arch is lower producing reverse S on esophagram in AP
• Right arch supplies Right common carotid and Right subclavian arteries
• Left arch supplies Left common carotid and Left subclavian arteries
• On lateral, arches are posterior to esophagus and anterior to trachea  

Double Aortic Arch. Frontal chest shows impression on right-side of barium-filled esophagus from higher right-sided arch and below it an impression on the left-side of the esophagus from left-sided arch. Lateral film shows anterior displacement of both trachea and esophagus.

• Anterior impression on the trachea alone may be caused by isolated anomalous innominate artery (arises from arch more distal than normal) or anomalous Left common carotid (originates more proximal than normal)