Pulmonary hypertension is defined as an elevation in pulmonary arterial pressures (mean pulmonary artery pressure [PAP] ≥25 mmHg or an estimated systolic PAP >36 mmHg). Advances in understanding the pathobiology over the last 2 decades have led to development of both primary therapy (diuretics, digoxin, anticoagulant and oxygen supplementation) and advanced therapy (endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and prostacyclins) initially directed at reversing the pulmonary vasoconstriction and more recently directed toward reversing endothelial cell dysfunction and smooth muscle cell proliferation.