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]
Overview
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.
Classification
Clinical Classification
- PH 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 categorized 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)
- 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 |
| 1.3 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’ 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 |
WHO Functional Classification
The WHO functional classification is used for the assessment of the severity of PH in order to tailor the choice of therapy. Shown below is a table summarizing the different functional classes.[3]
| Class | Description |
| I |
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| II |
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| III |
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| IV |
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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 manifestation and some common histopathological features. Shown below is a table that summarizes the classification of PH based on histopathology findings.[4]
| Class | Histopathological findings[4] |
| Pulmonary arteriopathy | Constrictive lesions in pulmonary arteries:
Complex lesions in pulmonary arteries:
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| Pulmonary arteriopathy with venous-venular changes | Changes similar to pulmonary arteriopathy PLUS Changes in venules and veins |
| Pulmonary occlusive venopathy (with or without arteriopathy) |
Changes in venules and veins:
Changes in the capillaries:
Changes in the interstitium |
| Pulmonary microvasculopathy (with or without arteriopathy and/on venopathy) |
Changes in the capillaries:
Changes in the interstitium |
| Unclassified | Non specific changes |
References
- ↑ Hatano S, Strasser T. Primary Pulmonary Hypertension. Report on a WHO Meeting. October 15–17, 1973, Geneva: World Health Organization, 1975.
- ↑ 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.
- ↑ Rich S, Rubin LJ, Abenhail L, et al. Executive summary from the World Symposium on Primary Pulmonary Hypertension 1998, Evian, France, September 6-10, 1998. Geneva: The World Health Organization.
- ↑ 4.0 4.1 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.