Left pulmonary artery sling complex: Computed tomography and hypothesis of embryogenesis

Background. We retrospectively reviewed cases of left pulmonary artery (LPA) sling complex with computed tomography to explore its possible meaning in embryogenesis. Methods. Eighteen children (6 girls and 12 boys aged 5 days to 17.5 years; mean, 1.5 years) were identified as having LPA sling during the period of October 1996 to March 2006. Another 2,364 cardiac computed tomography scans that had no LPA sling were included as control. The associated bronchopulmonary and vascular anomalies were identified. Chi-square tests were used to compare the probabilities of coexistence of these anomalies, with or without LPA sling. Results. All patients with LPA sling presented with tracheal stenosis (100%), and there was a high incidence of combined right tracheal bronchus (22%), underdeveloped right lung (22%), persistent left superior vena cava (22%), and left patent ductus arteriosus (39%). These associated anomalies were more highly associated with subjects who had LPA sling than with those who did not (p < 0.01). Conclusions. Owing to the spatial coexistence of LPA sling with the associated anomalies in the embryonic foregut mesoderm, we propose that a "space available" hypothesis in the local environment appears to be important in the embryogenesis of an LPA sling complex.