What are the classifications of Pulmonary Hypertension (PH)?

From the Guidelines

Pulmonary hypertension is classified into five main groups based on etiology, pathophysiology, and treatment approaches, as outlined in the most recent guidelines 1. The classification system includes:

• Group 1: Pulmonary arterial hypertension (PAH), which includes idiopathic PAH, heritable forms, drug-induced PAH, and PAH associated with conditions like connective tissue diseases or congenital heart disease.
• Group 2: Pulmonary hypertension due to left heart disease, including left ventricular systolic or diastolic dysfunction and valvular disease.
• Group 3: Pulmonary hypertension due to lung diseases and/or hypoxia, such as COPD, interstitial lung disease, and sleep-disordered breathing.
• Group 4: Chronic thromboembolic pulmonary hypertension (CTEPH), resulting from persistent obstruction of pulmonary arteries following pulmonary embolism.
• Group 5: Pulmonary hypertension with unclear or multifactorial mechanisms, including hematologic disorders, systemic disorders, metabolic disorders, and other conditions. This classification system guides diagnostic workup and treatment decisions, as each group has distinct underlying mechanisms requiring different therapeutic approaches, as supported by the guidelines 1 and earlier studies 1. Key considerations in managing these groups include:
• Group 1 may benefit from pulmonary vasodilators like phosphodiesterase-5 inhibitors or endothelin receptor antagonists.
• Group 2 focuses on treating the underlying cardiac condition.
• Group 4 may require surgical intervention. The most recent guidelines 1 provide the foundation for these classifications and treatment approaches, emphasizing the importance of a comprehensive clinical classification of pulmonary hypertension for effective management.

From the Research

Classifications of Pulmonary Hypertension (PH)

The classifications of Pulmonary Hypertension (PH) are as follows:

• Pulmonary arterial hypertension (PAH) 2, 3, 4
• PH due to left-sided heart disease 2, 3, 5
• PH due to chronic lung disease and/or hypoxia 2, 3, 5
• Chronic thromboembolic PH (CTEPH) 2, 3, 5
• PH with an unclear and/or multifactorial mechanisms 2, 3

Characteristics of Each Classification

Some key characteristics of each classification include:

• PAH: pre-capillary PH, defined by a normal pulmonary artery wedge pressure (PAWP) ≤ 15 mmHg, due to remodelling of the small pulmonary arteries (<500 μm) 3
• PH due to left-sided heart disease: post-capillary PH, defined by an increased pulmonary artery wedge pressure (PAWP) >15 mmHg 3
• PH due to chronic lung disease and/or hypoxia: associated with lung diseases or hypoxia, or both 5
• CTEPH: due to chronic thromboembolic occlusion of pulmonary vasculature 5
• PH with an unclear and/or multifactorial mechanisms: includes haematological, systemic, or metabolic disorders 5

Diagnostic Approaches

Diagnostic approaches for PH include:

• Electrocardiography 2
• Chest radiography 2
• Pulmonary function tests 2
• Transthoracic echocardiography to estimate the probability of PH 2
• Right-sided heart catheterization for accurate diagnosis and classification 2, 6
• Ventilation-perfusion scan to exclude CTEPH 2