There are five types of pulmonary hypertension, known as WHO Groups 1 to 5. Each group is defined by what is causing the high pressure in the lung arteries: disease of the arteries themselves (Group 1), left-sided heart disease (Group 2), lung disease or low oxygen (Group 3), blocked pulmonary arteries, usually from old blood clots (Group 4), or a mix of other conditions (Group 5).
Knowing the types of pulmonary hypertension matters because the group decides the treatment. A medicine that helps one group can be useless, or even harmful, in another. This guide explains each group in plain English, how doctors work out which one you have, and what changed in the latest classification from the 7th World Symposium on Pulmonary Hypertension in 2024.
What Is Pulmonary Hypertension?
Pulmonary hypertension (PH) is high blood pressure in the arteries that carry blood from the right side of the heart to the lungs. It is a different problem from the everyday high blood pressure measured with an arm cuff. If you want the full comparison, see our guide on hypertension vs pulmonary hypertension.
The lung circulation is normally a low-pressure system. Mean pulmonary artery pressure (mPAP) at rest usually sits around 14 mm Hg, and 20 mm Hg is the upper limit of normal. Since the 2022 ESC/ERS guidelines, and confirmed at the 2024 World Symposium, PH is diagnosed when mPAP is above 20 mm Hg at rest, measured by right heart catheterization. You can read more about these numbers in our explainer on high pulmonary artery pressure.
When the pressure stays high, the right ventricle has to push harder with every beat. Over months to years it thickens, stretches and can eventually fail. That is why symptoms such as breathlessness, tiredness and ankle swelling tend to creep up slowly. The National Heart, Lung, and Blood Institute estimates that about 1% of people worldwide have PH, and the figure is higher in people over 65.
Types of Pulmonary Hypertension at a Glance
The table below sums up all five groups. The “how common” column is a rough guide; exact shares vary between studies and countries.
| WHO group | Name | Where the problem starts | Common causes | How common | Main treatment focus |
|---|---|---|---|---|---|
| Group 1 | Pulmonary arterial hypertension (PAH) | Walls of the small lung arteries | Idiopathic, inherited genes, scleroderma/lupus, drugs (e.g. methamphetamine), HIV, liver disease, congenital heart defects | Rare | PAH-specific medicines |
| Group 2 | PH from left heart disease | Left side of the heart (pressure backs up) | Heart failure (especially with preserved ejection fraction), mitral or aortic valve disease | Most common | Treat the heart condition |
| Group 3 | PH from lung disease and/or hypoxia | Lung tissue and low oxygen | COPD, interstitial lung disease, sleep apnea, hypoventilation, high altitude | Second most common | Treat lung disease, oxygen |
| Group 4 | PH from pulmonary artery obstructions | Larger lung arteries blocked by scar or tumor | Chronic thromboembolic PH (CTEPH) after blood clots; rarely tumors or artery narrowing | Uncommon | Surgery, balloon angioplasty, blood thinners |
| Group 5 | PH with unclear and/or multifactorial mechanisms | Several places at once | Sickle cell disease, sarcoidosis, chronic kidney failure, myeloproliferative disorders, fibrosing mediastinitis | Uncommon | Treat the underlying disease |
Group 1: Pulmonary Arterial Hypertension (PAH)
In Group 1 pulmonary arterial hypertension, the disease is inside the walls of the small lung arteries. The cells lining these vessels grow abnormally, the muscle layer thickens, and the channel for blood narrows. Think of a garden hose slowly furring up from the inside. The heart and lungs may be otherwise healthy.
PAH is rare. In Europe it affects roughly 50 adults per million, and it is diagnosed more often in women. Group 1 is split into subgroups:
- Idiopathic PAH – no cause is found. The 2024 classification brought back a special subgroup, long-term responders to calcium channel blockers, for the small number of people whose arteries relax during a vasoreactivity test. Our article on CCB therapy for pulmonary hypertension explains why this test matters.
- Heritable PAH – caused by gene changes, most often in BMPR2, that can run in families.
- Drug- and toxin-associated PAH – linked to substances such as methamphetamine, certain old diet drugs (fenfluramine, aminorex), dasatinib and, as added in 2024, the cancer drugs mitomycin-C and carfilzomib.
- PAH associated with other conditions – connective tissue diseases (especially scleroderma), HIV, portal hypertension from liver disease, congenital heart disease and schistosomiasis.
- PAH with venous or capillary involvement (PVOD/PCH) and persistent pulmonary hypertension of the newborn.
Group 1 is the type with the most targeted drug options. These include endothelin receptor antagonists, PDE-5 inhibitors, soluble guanylate cyclase stimulators, prostacyclin-pathway drugs and, since 2024, the activin-signaling inhibitor sotatercept. Most people start on a combination. For the full picture, see how pulmonary arterial hypertension is treated and our breakdown of the causes of pulmonary arterial hypertension.
Group 2: Pulmonary Hypertension Due to Left Heart Disease
Group 2 pulmonary hypertension is by far the most common type. Reviews estimate it accounts for most PH cases, and the NHLBI names it the leading type in the United States.
The problem starts on the left side of the heart. If the left ventricle is stiff or weak, or a left-sided valve leaks or narrows, blood backs up into the lung veins. That back-pressure travels upstream into the lung arteries, like traffic backing up from a blocked exit. Doctors call this post-capillary PH because the pressure rise starts beyond the tiny lung capillaries. The wedge pressure that reflects it is explained in our guide to pulmonary capillary wedge pressure.
Common causes include:
- Heart failure with preserved ejection fraction (HFpEF), very common in older adults with high blood pressure, obesity, diabetes or atrial fibrillation
- Heart failure with reduced or mildly reduced ejection fraction
- Specific cardiomyopathies, such as cardiac amyloidosis, hypertrophic cardiomyopathy, Fabry disease and Chagas disease (listed separately since 2024)
- Mitral or aortic valve disease
Treatment targets the heart: heart failure medicines, diuretics to clear fluid, and valve repair or replacement. PAH drugs are generally not recommended in Group 2 because they have not been shown to help and can worsen fluid in the lungs.
Group 3: Pulmonary Hypertension Due to Lung Disease and/or Hypoxia
Group 3 pulmonary hypertension develops when chronic lung disease or long-term low oxygen damages the lung circulation. When oxygen levels fall, lung arteries tighten to redirect blood toward better-ventilated areas, a reflex covered in our article on hypoxia and pulmonary vasoconstriction. Useful in the short term, this reflex raises pressure when it never switches off. Scarring and emphysema also destroy small vessels outright.
The 2024 classification now sorts Group 3 by the underlying disease, because outcomes differ between them:
- COPD and/or emphysema
- Interstitial lung disease, including pulmonary fibrosis
- Combined pulmonary fibrosis and emphysema
- Other lung diseases and non-lung restrictive problems, such as obesity hypoventilation
- Hypoxia without lung disease, for example living at high altitude
- Developmental lung disorders
Treatment focuses on the lung disease, oxygen when levels are low, treating sleep apnea and pulmonary rehabilitation. Inhaled treprostinil is approved in the US for PH linked to interstitial lung disease. In COPD, however, PAH-type drugs have not proved helpful and one trial was stopped early over safety concerns, which is one more reason the correct group matters.
Group 4: Pulmonary Hypertension Due to Pulmonary Artery Obstructions
Group 4 PH happens when the larger lung arteries are physically blocked. The main form is chronic thromboembolic pulmonary hypertension (CTEPH). After a pulmonary embolism, most clots dissolve with blood thinners. In a small share of survivors, often estimated at around 3 in 100, the clot turns into firm scar tissue stuck to the artery wall, leaving the vessel narrowed or blocked. Rarer causes in this group include tumors such as angiosarcoma, inflammation of the arteries, parasites (hydatid cysts) and congenital narrowing.
Group 4 stands out because it is the type most likely to be potentially curable. Options include:
- Pulmonary endarterectomy – open surgery at a specialist center to peel the scar out of the arteries.
- Balloon pulmonary angioplasty – a catheter procedure to stretch narrowed arteries when surgery is not possible.
- Medicines – lifelong blood thinners, plus a PH drug such as riociguat for disease that cannot be removed or remains after surgery.
Anyone with breathlessness that persists three months or more after a pulmonary embolism should ask about a V/Q scan to check for CTEPH. Our article on whether pulmonary hypertension can be cured covers this in more depth.
Group 5: Pulmonary Hypertension With Unclear or Multiple Causes
Group 5 pulmonary hypertension collects conditions that raise lung pressure through several mechanisms at once, or through pathways nobody fully understands yet. Examples include:
- Blood disorders – sickle cell disease and other chronic hemolytic anemias, myeloproliferative disorders
- Systemic disorders – sarcoidosis, pulmonary Langerhans cell histiocytosis, neurofibromatosis type 1
- Metabolic disorders – glycogen storage disease, Gaucher disease
- Chronic kidney failure, with or without dialysis
- Fibrosing mediastinitis, pulmonary tumor thrombotic microangiopathy and complex congenital heart disease
Treatment is aimed at the underlying condition. PAH drugs are used only case by case, usually at a specialist center.
Pre-Capillary vs Post-Capillary: How Doctors Assign Your Group
Most articles list the groups but skip how a doctor actually places you in one. The key test is right heart catheterization, which measures three numbers. Our guide to how pulmonary hypertension is measured walks through the procedure.
| Hemodynamic pattern | mPAP | Wedge pressure (PAWP) | PVR | Usual groups |
|---|---|---|---|---|
| Pre-capillary PH | > 20 mm Hg | ≤ 15 mm Hg | > 2 Wood units | 1, 3, 4, some 5 |
| Isolated post-capillary PH | > 20 mm Hg | > 15 mm Hg | ≤ 2 Wood units | 2, some 5 |
| Combined post- and pre-capillary PH | > 20 mm Hg | > 15 mm Hg | > 2 Wood units | 2 (more advanced), some 5 |
PVR (pulmonary vascular resistance) shows how hard the lung arteries resist flow; normal values are covered in our article on normal pulmonary vascular resistance. A high wedge pressure points to the left heart. A normal wedge with high resistance points to disease in the lung arteries or lungs.
The numbers alone do not finish the job. Doctors combine them with an echocardiogram, lung function tests, a CT scan, a V/Q scan for old clots, blood tests and sleep studies. The step-by-step process is in our guide to how pulmonary hypertension is diagnosed.
Can you have more than one type?
Yes, and it is common. Someone with COPD may also have heart failure, giving a Group 2 and Group 3 overlap. A large Ontario study found that, after Group 2 alone, the next most frequent pattern in adults was Groups 2 and 3 together. In these cases, doctors usually classify by the condition that best explains the pressure and treat every contributor.
What Changed in the 2024 Classification?
The 7th World Symposium on Pulmonary Hypertension, held in Barcelona in 2024, kept the five-group structure but made several updates (see the symposium proceedings):
- Definition confirmed – PH is mPAP above 20 mm Hg; pre-capillary PH needs PVR above 2 Wood units.
- Group 1 – “long-term responders to calcium channel blockers” returned as a subgroup of idiopathic PAH, and mitomycin-C and carfilzomib were added to drugs with a definite PAH link.
- Group 2 – new subgroups separate HFpEF, HFrEF and specific cardiomyopathies.
- Group 3 – subgroups now follow the actual lung disease (COPD, ILD, combined fibrosis and emphysema) rather than broad patterns.
- Exercise PH – recognized again as an abnormal rise in pressure during exercise.
You may still see older names, such as “primary pulmonary hypertension” for idiopathic PAH, or a cutoff of 25 mm Hg in older articles. Those are out of date.
Why Your PH Group Matters
- Treatment – PAH drugs help Group 1 and inoperable Group 4, but not Group 2, and generally not COPD-related Group 3.
- Curability – some Group 4 patients can be cured with surgery; most other types are managed long term.
- Outlook – survival depends heavily on the group and the underlying disease. See how long you can live with pulmonary hypertension and how serious pulmonary hypertension is.
- Family screening – heritable PAH may justify genetic counseling for relatives.
A general overview of options across groups is in our guide to how pulmonary hypertension is treated.
Key Takeaways
- Pulmonary hypertension means mean lung artery pressure above 20 mm Hg, confirmed by right heart catheterization.
- There are five WHO groups, defined by cause: arteries (1), left heart (2), lungs/low oxygen (3), artery blockages (4) and mixed causes (5).
- Group 2 is the most common; Group 1 (PAH) is rare but has the most targeted drugs.
- Group 4 (CTEPH) can sometimes be cured with surgery or balloon angioplasty.
- Wedge pressure and vascular resistance help separate pre-capillary from post-capillary PH.
- Many people have more than one contributing cause, and the right group guides safe treatment.
When to See a Doctor
Make an appointment if you notice:
- Shortness of breath with everyday activity that is getting worse
- Tiredness that limits your normal routine
- Swelling in your ankles, legs or belly
- Chest discomfort or a racing heartbeat during exertion
- Breathlessness that lingers months after a pulmonary embolism
- New symptoms if you have scleroderma, liver disease, HIV, sickle cell disease or a family history of PAH
Ask whether you should be referred to a pulmonologist or PH center. You can find a pulmonologist near you in our directory.
Call 911 if you faint, have sudden severe chest pain, cannot catch your breath at rest, cough up blood, or notice lips or fingertips turning blue.
Frequently Asked Questions
What are the 5 types of pulmonary hypertension?
The five WHO groups are: Group 1, pulmonary arterial hypertension; Group 2, PH from left heart disease; Group 3, PH from lung disease or low oxygen; Group 4, PH from pulmonary artery obstructions such as CTEPH; and Group 5, PH with unclear or multiple causes.
What is the most common type of pulmonary hypertension?
Group 2, caused by left-sided heart disease such as heart failure or valve disease, is the most common type. Group 3, linked to lung diseases like COPD and pulmonary fibrosis, is second.
Which type of pulmonary hypertension is the most serious?
All types are serious. Untreated Group 1 PAH can progress quickly, while Group 2 and Group 3 PH signal more advanced heart or lung disease and carry a worse outlook than those diseases alone. Your prognosis depends on your group, the underlying condition and how early treatment starts.
What is the difference between PH and PAH?
PH is the umbrella term for high pressure in the lung arteries from any cause. PAH is one specific type, Group 1, where the disease starts in the walls of the small lung arteries themselves.
Which type of pulmonary hypertension can be cured?
Group 4 CTEPH is the type most often cured, through pulmonary endarterectomy surgery. Some Group 1 cases caused by drugs can improve after stopping the drug, and some Group 2 cases improve after valve repair. Most other cases are managed rather than cured.
Is pulmonary hypertension genetic?
Only some cases. Heritable PAH, part of Group 1, is linked to gene changes such as BMPR2 and can run in families. Most PH, especially Groups 2 and 3, is caused by other diseases rather than inherited genes.
Can you have pulmonary hypertension from more than one group?
Yes. Overlap is common, especially Groups 2 and 3 in people who have both heart failure and COPD. Doctors treat each contributing condition.
References
- Kovacs G, Bartolome S, Denton CP, et al. Definition, classification and diagnosis of pulmonary hypertension (7th World Symposium on Pulmonary Hypertension). Eur Respir J. 2024;64(4):2401324.
- Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43(38):3618–3731.
- Humbert M, Galiè N, Rubin LJ, et al. The Seventh World Symposium on Pulmonary Hypertension: our journey to Barcelona. Eur Respir J. 2024. WSPH proceedings.
- Wijeratne DT, Lajkosz K, Brogly SB, et al. Increasing incidence and prevalence of World Health Organization Groups 1 to 4 pulmonary hypertension: a population-based cohort study in Ontario, Canada. Circ Cardiovasc Qual Outcomes. 2018;11(2):e003973.
- National Heart, Lung, and Blood Institute. What Is Pulmonary Hypertension?
- Cleveland Clinic. Pulmonary Hypertension.
- American Thoracic Society. Pulmonary Hypertension patient fact sheet.
This article is for general education and is not a substitute for advice from your doctor.
Shirley Setia is a medical student who writes and updates our guides to pulmonary embolism and pulmonary hypertension. Her articles are reviewed by a doctor on our team before publication.
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