To investigate the possibility that pulmonary vascular disease may be present at birth in children presenting with obstructed total anomalous pulmonary venous return in the neonatal period, pulmonary vascular structure was analysed in the lungs of six babies who died during the first week of life. Five babies had infradiaphragmatic total anomalous return and in one the pulmonary veins drained to the right atrium. In all cases mean percentage arterial medial thickness was greater than is normal at 5 hours. The most striking change occurred in the intra- and extrapulmonary veins. Within the lung, in all six cases mean percentage vein wall thickness was significantly increased and in two cases intimal proliferation occurred in preacinar veins. The extrapulmonary veins were generally small in all five cases of infradiaphragmatic total anomalous pulmonary venous return, microscopically were abnormally thick walled in four, and showed intimal proliferation in three cases. In two cases the descending vertical vein was severely narrowed or occluded. A prenatal increase in intrapulmonary arterial and venous muscularity may encourage episodic pulmonary hypertension in the immediate postoperative period. In the infradiaphragmatic type of anomaly, prenatal structural changes in the extrapulmonary veins may predispose to the later development of pulmonary vein stenosis despite a successful surgical repair.
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