Pulmonary hypertension classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Richard Channick, M.D.; Assistant Editor(s)-in-Chief: Ralph Matar; Lisa Prior, Ann Slater, R.N.; Rim Halaby, M.D. [2]; José Eduardo Riceto Loyola Junior, M.D.[3]


Pulmonary hypertension may be classified according to the mechanism leading to its development into 5 groups: pulmonary arterial hypertension, pulmonary hypertension due to left heart disease, pulmonary hypertension due to chronic lung diseases and/or hypoxia, and pulmonary hypertension due to embolic disease, and miscellaneous causes.


  • Pulmonary hypertension was first classified into primary and secondary in 1973 during the World Health Organization (WHO) meeting on PH in Geneva, Switzerland.[1]
  • Pulmonary hypertension can be classified following different methods such as using the WHO clinical criteria, the hemodynamic findings, and the histopathological findings. The most common method of classification is using the disease mechanism, established by the World Health Organization, which is discussed below in detail.

WHO - Clinical Classification

  • Pulmonary hypertension was first classified into primary and secondary in 1973 during the World Health Organization (WHO) meeting on PH in Geneva, Switzerland.[1]
  • The classification of the disease has been progressively updated since then and the latest version was defined in 2018, during the 6th World Symposium on Pulmonary Hypertension.
  • It is currently used by the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the labeling of new drugs approved for the treatment of pulmonary hypertension.
  • The latest classification method categorizes pulmonary hypertension into 5 groups:
    • Group I - Pulmonary arterial hypertension
    • Group II - Pulmonary hypertension due to left heart disease
    • Group III - Pulmonary hypertension due to chronic lung diseases and/or hypoxia
    • Group IV - Pulmonary hypertension due to embolic disease
    • Group V - Miscellaneous causes (e.g., sarcoidosis, lymphatic obstruction)

WHO Classification

Shown below is a table with the detailed classification of pulmonary hypertension.[2]

Abbreviations: BMPR, bone morphogenic protein receptor type II; CAV1, caveolin-1; ENG, endoglin; HIV, human immunodeficiency virus.

Group 1. Pulmonary arterial hypertension (PAH)
1.1. Idiopathic PAH
1.2. Heritable PAH

1.2.1 BMPR2
1.2.2 ALK-1, ENG, SMAD9, CAV1, KCNK3
1.2.3 Unknown

1.3 Drug and toxin-induced

Definite (an epidemic or large multicenter epidemiological studies demonstrating an association between a drug and PAH)

Likely (a single case-control study demonstrating an association or a multiple-case series)

Possible (drugs with similar mechanisms of action as those in the definite or likely category but which have not yet been studied)

Unlikely (one in which a drug has been studied in epidemiological studies and an association with PAH has not been demonstrated)

1.4 Associated with:

1.4.1 Connective tissue disease
1.4.2 HIV infection
1.4.3 Portal hypertension
1.4.4 Congenital heart diseases
1.4.5 Schistosomiasis

1’ Pulmonary veno-occlusive disease (PVOD) and/or pulmonary capillary hemangiomatosis (PCH)
1’’ Persistent pulmonary hypertension of the newborn (PPHN)
Group 2. Pulmonary hypertension due to left heart disease
2.1 Left ventricular systolic dysfunction
2.2 Left ventricular diastolic dysfunction
2.3 Valvular disease
2.4 Congenital/acquired left heart inflow/outflow tract obstruction and congenital cardiomyopathies
Group 3. Pulmonary hypertension due to lung diseases and/or hypoxia
3.1 Chronic obstructive pulmonary disease
3.2 Interstitial lung disease
3.3 Other pulmonary diseases with mixed restrictive and obstructive pattern
3.4 Sleep-disordered breathing
3.5 Alveolar hypoventilation disorders
3.6 Chronic exposure to high altitude
3.7 Developmental lung diseases
Group 4. Chronic thromboembolic pulmonary hypertension (CTEPH)
Group 5. Pulmonary hypertension with unclear multifactorial mechanisms
5.1 Hematologic disorders: chronic hemolytic anemia, myeloproliferative disorders, splenectomy
5.2 Systemic disorders: sarcoidosis, pulmonary histiocytosis, lymphangioleiomyomatosis
5.3 Metabolic disorders: glycogen storage disease, Gaucher disease, thyroid disorders
5.4 Others: tumor obstruction, fibrosing mediastinitis, chronic renal failure, segmental PH

Classification Based on Hemodynamical Findings

Abbreviations: PAP: Pulmonary artery pressure; PWP: pulmonary wedge pressure

Type of pulmonary hypertension Possible clinical class Mean PAP PWP
Pre-capillary Class I
Class III
Class IV
Class V
≥ 25 mmHg ≤ 15 mmHg
Post-capillary Class II ≥ 25 mmHg > 15 mmHg

Classification Based on Histopathological Findings

PH is a pathological condition present in different disease states that share similar clinical manifestations and some common histopathological features. Shown below is a table that summarizes the classification of PH based on histopathology findings.[3]

Class Histopathological findings[3]
Pulmonary arteriopathy Constrictive lesions in pulmonary arteries:
  • Medial hypertrophy
  • Intimal thickening
  • Adventitial thickening

Complex lesions in pulmonary arteries:

  • Plexiform lesions
  • Dilatation lesions
  • Arteritis
Pulmonary arteriopathy with venous-venular changes Changes similar to pulmonary arteriopathy
Changes in venules and veins
Pulmonary occlusive venopathy
(with or without arteriopathy)
Changes in venules and veins:
  • Diffuse fibrotic occlusion
  • Intimal thickening
  • Medial thickening
  • Adventitial thickening

Changes in the capillaries:

  • Dilatation
  • Congestion

Changes in the interstitium

Pulmonary microvasculopathy
(with or without arteriopathy and/on venopathy)
Changes in the capillaries:
  • Localized capillary proliferation

Changes in the interstitium

Unclassified Non specific changes


  1. 1.0 1.1 Hatano S, Strasser T. Primary Pulmonary Hypertension. Report on a WHO Meeting. October 15–17, 1973, Geneva: World Health Organization, 1975.
  2. Simonneau G, Gatzoulis MA, Adatia I, Celermajer D, Denton C, Ghofrani A; et al. (2013). "Updated clinical classification of pulmonary hypertension". J Am Coll Cardiol. 62 (25 Suppl): D34–41. doi:10.1016/j.jacc.2013.10.029. PMID 24355639.
  3. 3.0 3.1 Pietra GG, Capron F, Stewart S, Leone O, Humbert M, Robbins IM; et al. (2004). "Pathologic assessment of vasculopathies in pulmonary hypertension". J Am Coll Cardiol. 43 (12 Suppl S): 25S–32S. doi:10.1016/j.jacc.2004.02.033. PMID 15194175.

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