Possibilities and impossibilities in the evaluation of pulmonary vascular disease in congenital heart defects.

In congenital heart defects with left to right shunting, the increased pulmonary blood flow and pulmonary hypertension leads to structural and functional changes in the pulmonary vasculature. These changes, known as pulmonary plexogenic arteriopathy, include increased muscularization, altered vasoconstrictive and impaired vasodilatatory responses in the arterial tree, and extensive extracellular matrix modulation (including increased collagen deposition and gradual occlusion of the small pulmonary arteries by intimal proliferation and fibrosis). These alterations will result in decreased compliance by the pulmonary vessels and, thus, a stiffening of the arterial wall.