reported in a case with tetralogy of Fallot and pulmonary atresia when the aortic arch is right sided.85 A vascular course similar to the sling has been described involving the arterial duct.86 In this instance, the duct arose from the right pulmonary artery and coursed leftward through the space between the distal trachea and esophagus to connect to the descending aorta on the left side It is also suggested that an aberrant left subclavian artery can arise from the descending aorta and course through the space between the trachea and esophagus,1 but in this instance it is more likely that the artery is a collateral vessel rather than the left subclavian artery Clinical Manifestations Pulmonary arterial sling usually presents in the first year of life, although asymptomatic older children and adults have been reported.77 There is a slight male preponderance.77 The dominant clinical manifestations are due to obstruction of the airways and include stridor, wheeze, and cough Stridor is often expiratory but can be inspiratory or biphasic Less commonly, patients present with symptoms from esophageal compression, such as dysphagia and vomiting Rarely, the sling is found as an incidental lesion during cardiac or pulmonary investigations for other reasons Diagnostic Investigation The chest radiograph sometimes provides clues to the diagnosis (see Fig 47.20C) When present, abnormal branching of the airway can be appreciated in a well-taken frontal image The inverted T appearance of the tracheal bifurcation at a level lower than normal is an important sign Narrowing of long or short tracheal and bronchial segments can also be recognized The lungs may show various combinations of hyperinflation and/or atelectasis, according to the associated tracheobronchial narrowing and retention of secretions The pulmonary vascularity may be asymmetric, with the left lung or, less commonly, right lung showing less-prominent vascularity than its partner Barium esophagography is diagnostic.77 On the lateral view, the left pulmonary artery is seen as a round structure between the air-filled distal trachea and barium-filled esophagus, causing an anterior indentation in the esophagus Barium esophagography, nonetheless, should be avoided in critically ill neonates, especially if they are ventilator dependent.78 Echocardiography reveals continuation of the pulmonary trunk to the right, without origin of the normal left pulmonary artery, a feature that may suggest unilateral absence of the left pulmonary artery or aberrant origin of the left pulmonary artery from the ascending aorta The origin of the left pulmonary artery from the right pulmonary artery is appreciated when the pulmonary trunk is followed to the right (Fig 47.21) Echocardiography is always essential when assessing patients with a sling because associated congenital cardiac disease is common FIG 47.21 Echocardiographic images showing a left pulmonary arterial