Create comprehensive postgraduate (MD/DM/DNB Internal Medicine) notes on Pulmonary Hypertension (PH) based primarily on Harrison’s Principles of Internal Medicine (22nd Edition), supplemented with the latest ESC/ERS Pulmonary Hypertension Guidelines (2022/2025 updates where applicable). The notes should be detailed, clinically oriented, and suitable for postgraduate examinations and superspecialty Cover the following sections in depth: 1. Definition * Historical and current hemodynamic definition * Normal pulmonary circulation * Normal pulmonary artery pressure, PAWP, PVR, and cardiac output * Changes from previous definitions 2. Epidemiology * Global prevalence and incidence * Age and sex distribution * Major etiologies worldwide and in India * Prognosis and survival 3. Etiology * Detailed WHO Clinical Classification (Groups 1–5) * Causes under each group * Risk factors * Genetic mutations (BMPR2, ALK1, ENG, EIF2AK4, etc.) 4. Pulmonary Circulation Physiology * Anatomy * Pulmonary vascular resistance * Right ventricular–pulmonary artery coupling * Pulmonary vascular compliance 5. Pathophysiology * Endothelial dysfunction * Nitric oxide pathway * Prostacyclin pathway * Endothelin pathway * Vascular remodeling * Plexiform lesions * In-situ thrombosis * Inflammation * Right ventricular adaptation and failure * Flowcharts explaining disease progression 6. Hemodynamic Classification * Pre-capillary PH * Isolated post-capillary PH * Combined pre- and post-capillary PH * Definitions using mPAP, PAWP, PVR, and DPG * Clinical examples 7. WHO Clinical Classification (Groups 1–5) * Detailed explanation * Examples * Characteristic hemodynamics * Characteristic pathology * Common investigations 8. Clinical Features * Symptoms * Physical examination * WHO Functional Class * Signs of right heart failure * Red flag features 9. Diagnostic Approach * Stepwise diagnostic algorithm * Clinical suspicion * ECG * Chest X-ray * Echocardiography * Pulmonary function tests * HRCT chest * CT pulmonary angiography * V/Q scan * Cardiac MRI * Blood investigations * Biomarkers * Right heart catheterization * Vasoreactivity testing * Interpretation of hemodynamic data * Diagnostic flowchart 10. Investigations * Findings in each investigation * Advantages * Limitations * Diagnostic accuracy * Interpretation 11. Risk Stratification * ESC/ERS risk model * WHO Functional Class * BNP/NT-proBNP * Six-minute walk test * CPET * Echocardiographic markers * Hemodynamic markers 12. Treatment * General measures * Supportive therapy * Oxygen * Diuretics * Digoxin * Anticoagulation * Iron therapy * Vaccination * Pregnancy considerations * Rehabilitation 13. PAH-Specific Therapy * Endothelin receptor antagonists * PDE-5 inhibitors * Soluble guanylate cyclase stimulators * Prostacyclin analogues * Prostacyclin receptor agonists * Calcium channel blockers * Drug indications * Contraindications * Adverse effects * Combination therapy * Initial and sequential treatment algorithms 14. Management According to WHO Groups * Group 1 * Group 2 * Group 3 * Group 4 (including pulmonary endarterectomy and balloon pulmonary angioplasty) * Group 5 15. Special Situations * Pregnancy * Congenital heart disease * Connective tissue disease-associated PAH * Portopulmonary hypertension * HIV-associated PAH * CTEPH 16. Complications * Right ventricular failure * Arrhythmias * Hemoptysis * Syncope * Sudden cardiac death 17. Prognosis * Prognostic factors * REVEAL score * Survival predictors 18. Important Tables * WHO Groups * Pre- vs Post-capillary PH * Investigation comparison * Drug comparison * Vasodilator classes * Hemodynamic definitions * Functional classes 19. Flowcharts * Diagnostic approach * Pathophysiology * Treatment algorithm * Right heart catheterization interpretation * Management by WHO group 20. High-Yield Exam Pearls * Harrison’s key points * Frequently asked MD/DNB/DM examination questions * Recent guideline updates * Common viva questions * Clinical pearls * Mnemonics Output requirements: * Use clear headings and subheadings. * Include detailed explanations, flowcharts, tables, and summary boxes. * Emphasize important examination points * Highlight differences between Harrison’s concepts and the latest ESC/ERS guidelines where relevant.