Pharmacotherapy of Pulmonary Hypertension

Introduction & haemodynamics

• Definition — pulmonary hypertension (PH) = mean pulmonary arterial pressure (mPAP) > 20 mmHg at rest by right heart catheterization (RHC); the historic >25 mmHg threshold was lowered (2019, 6th World Symposium). Normal mPAP ≈ 14 ± 3 mmHg.
• Pulmonary arterial hypertension (PAH) — the WHO Group 1 subset — a primary small-pulmonary-artery vasculopathy and the principal target of targeted drug therapy; full haemodynamic definition: mPAP ≥ 20 mmHg + PCWP ≤ 15 mmHg + PVR > 3 Wood units (pre-capillary).
• Core relationship — PAP = CO × PVR; because PVR ∝ 1/r⁴ (Poiseuille), a 16% fall in arteriolar radius doubles PVR — small remodeling produces large pressure rise.
• Prognosis — idiopathic PAH is progressive and fatal — untreated median survival ≈ 2.8 years, extended to ≈ 9 years with modern therapy. RV failure is the major cause of death.
• Therapy is palliative — improves symptoms, function, haemodynamics and survival but does not cure the underlying vasculopathy.