Pulmonary vascular disease with congenital heart lesions: pathologic features and causes.

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Abstract
Pulmonary vascular disease [in humans], a serious complication of many congenital heart lesions, has 3 major components: increased muscularity of small pulmonary arteries; intimal hyperplasia, scarring and thrombosis; and reduced numbers of intraacinar arteries. The muscularity is due to increased stress on the vessel wall and is reversible. The intimal changes may be due to endothelial damage, causing an imbalance between prostacyclin and thromboxane A2 production and leading to local platelet aggregation. This may stimulate migration and division of myointimal cells, which thicken the intima and lead to scarring and thrombosis. Extensive intimal changes are probably irreversible, but the possibility of preventing them by use of agents that inhibit platelet aggregation needs to be considered. The mechanism of a decrease in the numbers of intraacinar arteries is unexplained. The potential for growth of new vessels after corrective surgery of the cardiac defect is an important factor in restoring pulmonary vascular resistance to normal. Apparently this growth potential is reduced after 2 yr of age and early surgical relief of pulmonary vascular stresses is recommended.