Chest Radiography
The lower trachea is deviated to the left and may appear compressed on its right side. Hyperinflation of the right lung may be seen because of impingement on and compression of the right main stem bronchus. The left lung also may appear hyperinflated because of obstruction at the level of the carina and the left main stem bronchus. In patients with severe obstruction, atelectasis of a single lung or single lobe may be observed. The lateral view may reveal a density anterior to the esophagus and posterior to the trachea just above the carina. This is the left pulmonary artery viewed on end.
Barium Swallow
The barium swallow is the diagnostic procedure of choice. An anterior indentation of the esophagus on the lateral projection is diagnostic of pulmonary artery sling. The esophagus is usually displaced to the right in the frontal projection and demonstrates an oblique impression immediately posterior to the carina.
Echocardiography
In the usual coronal-plane suprasternal-notch images, absence of normal bifurcation of the main pulmonary artery into right and left pulmonary arteries is visible. The left pulmonary artery appears to be absent. However, examination of the right pulmonary artery reveals the left pulmonary artery arising from its posterior surface. The left pulmonary artery can be followed posterior to the trachea and anterior to the esophagus. It passes anterior to the descending aorta and enters the hilum of the left lung. Echocardiography also reveals any associated congenital heart defects.
Magnetic Resonance Imaging and Computed Tomography Scanning
Magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA), computed tomography (CT) scanning, or a combination of these imaging modalities can be helpful in delineating the details of the anatomy, [4] as well as in three-dimensional reconstruction of the anatomy of the sling as it relates to the airway anatomy.
Bronchoscopy
Bronchoscopy is generally not recommended in patients with pulmonary artery sling. If performed, tracheal compression is noted, and accompanying tracheomalacia, tracheal stenosis, or both is common. [5] Some recommend bronchoscopic evaluation of selected surgical candidates because surgical reconstruction of the trachea or bronchi may be necessary if the airway compromise is severe.
Cardiac Catheterization and Angiography
The diagnosis can usually be noninvasively established. Pulmonary artery angiography may be advisable to delineate anatomic details prior to surgical correction. [6, 7] This permits diagnosis of variations in right and left pulmonary artery anatomy that may not be apparent from noninvasive studies and that can alter the surgical approach. Origin and course of the anomalous left pulmonary artery is best revealed by contrast injection into the main pulmonary artery filming in an oblique view with steep cranial angulation of 60º -70º.
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Slide tracheoplasty and left PA sling repair. Procedure performed by Giles Peek MD, FRCS, CTh, FFICM, The Children’s Hospital at Montefiore, Bronx, NY. Video courtesy of Montefiore.
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Aberrant left pulmonary artery or pulmonary artery sling.
