Discussion: The first description [1] of pulmonary artery sling was of an infant who died of respiratory obstruction. Death from airway obstruction has been observed as early as 2 days of life and is common before age 6 months in untreated patients.[2]

The abnormality probably develops early in embryonic life when the lungs are a single mass. Left and right pulmonary arteries form on each side of this common pulmonary mass and make contact with their respective sixth aortic arches. This progression fails to occur on the left in PAS. At this early stage, the lungs are a single mass and have a common vascular supply. Consequently, the left half of the lung mass retains a vascular connection with the right.

The soft tracheal rings of the neonate are compressed by the pulmonary artery, often causing obstructive emphysema or atelectasis of the right lung. Associated tracheobronchial malformations are common, particularly bronchus suis (i.e. tracheal origin of the right upper lobe bronchus) and complete tracheal rings.

The surgeon should be forewarned of such a tracheobronchial variant so as not to mistake a bronchus suis for a tracheal bifurcation. Preoperative identification of tracheal stenosis is essential as simple correction of the aberrant vessel without correction of the tracheal rings is of no value in such cases.[3] Intermediate results of primary one-stage repair with tracheal resection and left pulmonary artery re-implantation or translocation in early childhood have been promising.[4]

Associated cardiac anomalies include persistent left superior vena cava (20%), atrial septal defect (20%), ventricular septal defect (10%), and patent ductus arteriosus (25%).[5]

References:
1. Glavaevecke H, Doehle H. Uber eine seltene angeborene Anomalie der
Pulmonalarterie. MMW 987; 44:950-951.

2. Gumbiner C, Mullins C, McNamara D. Pulmonary artery sling. Am J Cardiol
1980; 45:311-315.

3. Sailer R, Zimmerman T, Bowing B et al. Pulmonary artery sling associated
with tracheobronchial malformations. Arch Otolaryng – Head and Neck Surgery
1992; 118(8):864-867.

4. Kessler RM, Wernly JA, Katz RW, Berman W Jr. Pulmonary artery sling with
severe tracheobronchial stenosis: repair in infancy by tracheal resection and
pulmonary artery reimplantation. J Cardiac Surg 1992; 7(1):5-8.

5. Amplatz K, Moller JH. Radiology of congenital heart disease St. Louis:
Mosby-Year Book, Inc., 1993: 1039-1044.

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