Growth and development of pulmonary circulation in pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries.

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Abstract
In 11 necropsy specimens of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries, central pulmonary arteries were present in all cases, supplied by collateral arteries which anastomosed with a lobar pulmonary artery or, less commonly, with a central pulmonary artery. These normally connected pulmonary arteries frequently perfused only a minority of bronchopulmonary segments. The remaining segments were connected to collateral arteries which, within the lung, were continuous with vessels which had the structure of normally connected vessels and branched with the pre- and intra-acinar airways in a normal manner to perfuse the alveolar capillary bed. These collateral arteries and the intrapulmonary vessels with which they anastomosed had no connection, macroscopically or microscopically, with the central pulmonary arteries or their branches within the lung. Irrespective of the type of proximal connection, the segmental pulmonary arteries were generally abnormally small. Stenoses occurred in 58.8% of collateral arteries, usually as a thick-walled narrowed muscular section between the aorta and lung. Microscopically quantitative morphometric analysis showed that within the respiratory unit the pulmonary circulation failed to grow normally in all save the youngest patient dying at 12 days of age. The structural changes were usually consistent with a reduction in pulmonary blood flow; only 3 cases contained any segments of lung showing structural evidence of pulmonary hypertension. These anatomical and histological findings are discussed in relation to the embryology, nomenclature and natural history of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries. The structural findings provide a rational basis for the clinical management of this condition.