Anomalous origin of the left pulmonary artery from the ascending aorta in two children with pulmonary atresia, sub-aortic ventricular septal defect and right-sided major aorto-pulmonary collateral arteries.

We report two rare cases of an anomalous origin of the left pulmonary artery (AOLPA) from the ascending aorta, associated with pulmonary atresia, a ventricular septal defect and a left aortic arch. The cases are unusual because AOLPA is more commonly associated with a right aortic arch and it is more usual for the right pulmonary artery to originate anomalously from the ascending aorta. The pulmonary blood supply to the right lung in both patients was absent and provided instead by major aorto-pulmonary collateral arteries which were stenosed at multiple levels. The AOLPA in both patients originated from the postero-lateral aspect of the ascending aorta just distal to the sino-tubular junction. Only one patient showed the more common association of an unusual aortic arch branching pattern in the form of an anomalous right subclavian artery. Neither patient was in heart failure and the chest X-ray in both revealed differential pulmonary perfusion with prominent vascularity of the left lung. Cardiac catheterisation showed systemic pressures within the anomalous left pulmonary artery. Karyotyping revealed normal chromosomes, and fluorescent in-situ hybridisation done in one patient was negative for chromosome 22q11.2 microdeletion. Both patients have been managed conservatively.