Considering the correlations between inducible and constitutive NOS isoforms, PAH associated with congenital heart disease (CHD) showed elevated levels of both iNOS and eNOS in pulmonary vascular endothelial cells, but not in other cell types, i.e., pulmonary macrophages, airway epithelium, and alveolar lining cells [194]. Here, NOS2 is linked to congenital heart disease.