Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare progressive disease of the pulmonary vasculature characterized by increased pulmonary vascular resistance and elevated right ventricular afterload, leading to right heart failure and death if untreated. PAH involves complex pathophysiology including endothelial dysfunction, vasoconstriction (abnormal nitric oxide and prostacyclin signaling), thrombosis, and vascular remodeling with progressive reduction of cross-sectional area available for blood flow. Idiopathic PAH (IPAH) has no identifiable cause but involves genetic predisposition (BMPR2, ALK1, ENG mutations). Secondary PAH occurs with connective tissue diseases (particularly scleroderma), chronic lung disease, liver disease, chronic hypoxia, and HIV. Patients experience dyspnea, chest pain, fatigue, and syncope. Without treatment, median survival from diagnosis is approximately 2.8 years; with modern combination therapies, outcomes have improved dramatically.