Pulmonary atresia can be congenital or acquired.
The VSD is of the malalignment type and there might be other types of VSD seen. Collateral vessels could come from the descending aorta or the brachiocephalic arteries. Collateral vessels may feed one side of the lungs, both sides or cross to the opposite side. Collaterals are typically from the thoracic aorta and less common from the subclavian artery and rarely from the descending aorta directly or left carotid artery. Embryologically, the lungs are supplied by primitive blood vessels from the descending aorta and in patients with pulmonary atresia these vessels may persist as collaterals.