Pathophysiological and metabolic manifestations of pulmonary vascular disease in children.

In children with congenital heart disease pulmonary vascular disease can be fatal for a variety of reasons. Even before the classical changes of advanced pulmonary vascular obstructive disease have developed, a marked increase in pulmonary vascular smooth muscle can be fatal due to pulmonary hypertensive crises. After the Fontan procedure, a modest increase in muscularity can jeopardise the outcome since there is no subpulmonary ventricle to support the pulmonary circulation. Following heart transplantation, a slight increase in muscularity can cause failure of the donor right ventricle unless that heart is already hypertrophied as in the domino procedure. In all children with pulmonary hypertension, either persistent pulmonary hypertension of the newborn or secondary to congenital heart disease the pulmonary vasculature fails to remodel normally after birth. Newborn vessels are characterized by the immaturity of the smooth muscle cells and the paucity of connective tissue. In the hypertensive lung smooth muscle differentiation and connective tissue deposition is accelerated. In children with congenital heart disease intimal changes follow. In these children the potential reversibility of disease following intracardiac repair is determined by the type of pathological change present at the time of repair. However, pulmonary hypertensive crises can occur in young children with potentially reversible disease. Operability is not synonymous with the potential reversibility of pathological lesions. Correlations between structural findings at lung biopsy and haemodynamic findings at cardiac catheterization have improved the accuracy with which the natural and unnatural history of pulmonary vascular disease can be predicted, but is still inadequate because we do not understand the functional implications of the changes.(ABSTRACT TRUNCATED AT 250 WORDS)