Pulmonary Hypertension: A Complete Overview

Pulmonary hypertension (PH) is a hemodynamic condition defined as a mean pulmonary arterial pressure (mPAP) greater than 20 mmHg, measured by right heart catheterization. The pulmonary arteries — which carry deoxygenated blood from the right heart to the lungs — become narrowed, thickened, stiff, or blocked, forcing the right ventricle to work against increasing resistance.

Over time, this relentless pressure overload causes the right ventricle to enlarge and eventually fail — a process called right heart failure or cor pulmonale. It is the ultimate cause of death in untreated or undertreated PH.

The Five WHO Groups of Pulmonary Hypertension

The term 'pulmonary hypertension' encompasses five fundamentally different diseases that share the same hemodynamic finding — high pulmonary pressure — but have different causes, mechanisms, and treatments.

Group 1 — PAH (Pulmonary Arterial Hypertension): Primary vascular disease of pulmonary arteries. Includes idiopathic PAH, heritable PAH, drug/toxin-induced, connective tissue disease (scleroderma, lupus), HIV, portal hypertension, congenital heart disease.

Group 2 — PH Due to Left Heart Disease: Most common form — secondary to left-sided cardiac conditions such as heart failure (HFrEF, HFpEF) and valvular heart disease. PAH drugs are generally contraindicated here.

Group 3 — PH Due to Lung Disease or Hypoxia: Secondary to COPD, interstitial lung disease (IPF), sleep apnea, or chronic high-altitude exposure. Treatment targets the underlying lung disease.

Group 4 — CTEPH (Chronic Thromboembolic PH): Chronic blood clots obstructing pulmonary arteries. The only potentially curable form — pulmonary endarterectomy is the treatment of choice when feasible.

Group 5 — PH with Unclear or Multifactorial Mechanisms: Rare conditions including sarcoidosis, sickle cell disease, and metabolic disorders.

Symptoms

PH symptoms are notoriously nonspecific in the early stages — often leading to an average diagnostic delay of 2–3 years.

Early symptoms: exertional dyspnea, unexplained fatigue, reduced exercise tolerance, lightheadedness with exertion, non-productive cough.

Advanced symptoms: syncope (fainting — a medical emergency in PH), chest pain, leg swelling (peripheral edema), abdominal distension (ascites), cyanosis, palpitations and arrhythmias.

WHO Functional Classification

• Class I: No symptoms with ordinary activity
• Class II: Comfortable at rest; ordinary activity causes symptoms
• Class III: Comfortable at rest; less than ordinary activity causes symptoms
• Class IV: Symptoms at rest; right heart failure signs likely present

Diagnosis

Diagnosing PH correctly requires a systematic workup including:

• Echocardiography: First-line screening tool — estimates pulmonary artery systolic pressure
• Right Heart Catheterization (RHC): The gold standard — the only test that directly measures mean pulmonary arterial pressure, pulmonary vascular resistance, and cardiac output
• CT Pulmonary Angiography & V/Q Scan: Detects chronic thromboembolic disease (Group 4)
• Biomarkers, Genetics & Connective Tissue Workup: NT-proBNP/BNP, ANA, BMPR2 genetic testing

Treatment of PAH (Group 1)

PAH treatment targets three approved mechanistic pathways — prostacyclin, endothelin, and nitric oxide — and now a fourth paradigm-shifting class: activin signaling inhibition.

• Endothelin Receptor Antagonists (ERAs): Ambrisentan, Macitentan, Bosentan (oral)
• PDE5 Inhibitors: Sildenafil (Revatio), Tadalafil (oral)
• Soluble Guanylate Cyclase Stimulator: Riociguat/Adempas (oral, also for CTEPH)
• Prostacyclins & Prostacyclin Agonists: Epoprostenol (IV), Treprostinil, Selexipag
• Activin Signaling Inhibitor: Sotatercept/Winrevair — FDA approved March 2024

Sotatercept: A Paradigm Shift in PAH

Sotatercept (Winrevair) was FDA-approved in March 2024 as the first disease-modifying therapy in PAH history. Unlike all previous drugs that worked by dilating pulmonary blood vessels, sotatercept directly targets the pathological cellular proliferation driving PAH. It is an activin receptor fusion protein that restores the balance between pro-proliferative and anti-proliferative signaling in pulmonary artery walls.

In the landmark STELLAR trial, sotatercept improved 6-minute walk distance by 40.8 meters vs. 1 meter on placebo, and reduced the risk of clinical worsening or death by 84%. The 2025 HYPERION trial (NEJM) confirmed its benefit in newly diagnosed high/intermediate-risk PAH patients.

Combination therapy is now the standard of care — guidelines recommend starting with an ERA + PDE5 inhibitor at diagnosis and adding prostacyclin pathway agents or sotatercept based on risk stratification.

Surgical & Advanced Interventions

• Pulmonary Endarterectomy (PEA): Surgical removal of chronic clot material — the only potential cure for CTEPH
• Balloon Pulmonary Angioplasty (BPA): Catheter-based dilation for inoperable CTEPH patients
• Lung or Heart-Lung Transplantation: Reserved for end-stage PAH failing maximal medical therapy
• Atrial Septostomy: Palliative procedure used as a bridge to transplant in refractory cases

PH must be managed at a specialized PH center. Studies consistently show better outcomes at high-volume, expert centers with multidisciplinary teams including pulmonologists, cardiologists, and rheumatologists experienced in PH.