Background Pulmonary arterial hypertension (PAH) is a major complication of congenital heart disease (CHD),causing increasing morbidity and mortality with age.Sustained increase in the pulmonary arterial pressure (PAP) may result in progressive pulmonary vascular remodeling and eventually lead to irreversible changes including extensive intimal injury, obliteration, adventitial fibrosis and smooth muscle cell proliferation.In recent years, insight into thepathogenesis of PAH has resulted in the development of therapeutic strategies for PAH including endothelin receptor antagonists, prostacyclin analogs and phosphodiesterase-5 inhibitors.Endothelin has a key role in the pathobiology of PAH, exerting vasoconstrictor and mitogenic effects by binding to two distinct receptor isoforms in the pulmonary vascular smooth muscle cells.Bosentan, an orally active dual endothelin receptor antagonist, has been shown to improve exercise capacity, hemodynamics in patients with idiopathic, chronic thromboembolic, and connective tissue disease-associated PAH.However the data of efficacy and safety of bosentan in patients with CHD and PAH are limited.