Figure 5 Axial contrast CT showing the left pulmonary artery (LPA, curved arrow) arising from the right pulmonary artery (RPA, straight arrow) encircling the distal trachea which is very narrow (*). The LPA path is retro-tracheal between the trachea and oesophagus. RV= right ventricle, RPA = right pulmonary artery and LAP = left pulmonary artery