From the Guidelines
Pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH) differ primarily in their classification and underlying causes, with PAH being a specific type of PH characterized by pre-capillary PH and pulmonary vascular resistance >3 Wood units, as defined by the 2015 ESC/ERS guidelines 1. The distinction between PH and PAH is crucial, as PAH-specific therapies target specific pathways involved in PAH, but may not be appropriate or could be harmful in other forms of PH. Pulmonary hypertension is a broader term that encompasses all conditions causing elevated blood pressure in the pulmonary arteries, with a mean pulmonary arterial pressure ≥25 mmHg at rest as assessed by right heart catheterization 1. PAH, on the other hand, is a clinical condition characterized by pathological changes primarily in the small pulmonary arteries and arterioles, resulting from specific mechanisms including endothelial dysfunction, smooth muscle proliferation, and vascular remodeling 1. The other groups of pulmonary hypertension (Groups 2-5) include PH due to left heart disease, lung diseases/hypoxia, pulmonary artery obstructions, and unclear/multifactorial mechanisms, as outlined in the 2015 ESC/ERS guidelines 1. Accurate diagnosis through right heart catheterization and comprehensive evaluation is essential to distinguish between these conditions and guide appropriate management, as emphasized in the 2014 CHEST guideline 1. Key differences between PH and PAH include:
- Classification: PH is a broader term, while PAH is a specific type of PH (Group 1)
- Underlying causes: PAH is often idiopathic or associated with certain conditions, while PH can be caused by various factors, including left heart disease, lung diseases, and pulmonary artery obstructions
- Pathological changes: PAH is characterized by changes in the small pulmonary arteries and arterioles, while PH can involve various parts of the pulmonary vasculature
- Treatment: PAH-specific therapies target specific pathways involved in PAH, while PH treatment depends on the underlying cause and may involve different therapies.
From the Research
Definition and Classification
- Pulmonary hypertension (PH) is a broad term that encompasses a group of diseases characterized by high blood pressure in the pulmonary arteries 2, 3.
- Pulmonary arterial hypertension (PAH) is a subtype of PH, defined by a mean pulmonary artery pressure greater than 20 mm Hg, a pulmonary artery wedge pressure of 15 mm Hg or lower, and a pulmonary vascular resistance of 3 Wood units or greater 3.
- PH is classified into 5 clinical groups based on etiology, pathophysiology, and treatment, with PAH being one of the groups 2, 3.
Key Differences
- The main difference between PH and PAH is the specific location and nature of the high blood pressure: PH refers to high blood pressure in the pulmonary circulation, while PAH specifically refers to high blood pressure in the pulmonary arteries 2, 3.
- PAH is further divided into subgroups based on underlying etiology, including idiopathic PAH, heritable PAH, and PAH associated with other medical conditions 3.
Diagnosis and Treatment
- Diagnosis of PAH typically involves right heart catheterization, as well as other tests such as electrocardiography, chest radiography, and pulmonary function tests 2.
- Treatment of PAH usually involves targeted therapies, including phosphodiesterase type 5 inhibitors, soluble guanylate cyclase stimulators, endothelin receptor antagonists, prostacyclin analogues, and prostacyclin receptor agonists 2, 3, 4, 5, 6.
- Endothelin receptor antagonists, in particular, have been shown to improve exercise capacity, functional status, and clinical outcome in patients with PAH 4, 5, 6.