Collateral arteries in pulmonary atresia with ventricular septal defect. A precarious blood supply.

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Abstract
In pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries lung growth and survival depend on the size and continued patency of the collateral arteries. Arterial structure was examined in 13 collaterals, taken from the necropsy specimens of 7 children, 6 of whom died during the first 7 mo. of life. Serial reconstruction was made of 2 collaterals, from the aorta to the intrapulmonary vessels; the other collaterals were examined by taking sections at intervals along the same course. The collateral arteries arose from the aorta as elastic vessels with a wide lumen or as muscular arteries when they were stenosed. Nearly all vessels rapidly resembled muscular systemic arteries, the external and lumen diameter becoming smaller. All collateral arteries but 1 showed areas of intimal proliferation which varied in the extent to which they surrounded and encroached on the lumen. Four collaterals contained large intimal cushions which severely narrowed or occluded the lumen. At the anastomosis of collateral and intrapulmonary artery intimal cushions were seen in all collaterals examined and the extent to which the structures reduced lumen diameter varied. The structure of collaterals is compared with that of growing systemic arteries and the ductus arteriosus; emphasis is given to the different types of intimal change. The clinical relevance of the findings is discussed.