Key Concepts
Introduction
Pulmonary hypertension (PH) is defined as a mean pulmonary artery pressure (mPAP) greater than 20 mmHg at rest, measured by right heart catheterization. The pathological process involves progressive remodeling of the pulmonary vasculature through three key mechanisms: vasoconstriction, vascular wall proliferation (intimal fibrosis and medial hypertrophy), and in-situ thrombosis. Endothelial dysfunction leads to an imbalance between vasodilators (nitric oxide, prostacyclin) and vasoconstrictors (endothelin-1, thromboxane A2). Plexiform lesions develop in advanced disease, representing disorganized endothelial cell proliferation that obliterates the vessel lumen. The increased pulmonary vascular resistance (PVR) forces the right ventricle to generate higher pressures, leading to RV hypertrophy, dilation, and eventually right heart failure (cor pulmonale). WHO classifies PH into 5 groups: Group 1 (pulmonary arterial hypertension/PAH), Group 2 (left heart disease), Group 3 (lung disease/hypoxia), Group 4 (chronic thromboembolic), and Group 5 (multifactorial/unclear mechanisms). On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan:...