What Causes Pulmonary Hypertension? Common Causes & Risks

The causes of pulmonary hypertension fall into five groups: disease of the lung arteries themselves, left-sided heart disease, chronic lung disease or low oxygen, old blood clots that block the lung arteries, and a mixed group of other conditions. Left heart disease is by far the most common cause, followed by lung diseases such as COPD. Rarer causes include genetic changes, scleroderma, certain drugs like methamphetamine, liver cirrhosis and HIV.

Pulmonary hypertension (PH) is not one disease. It is a measurement: the average pressure in the pulmonary arteries is above 20 mmHg at rest, measured during a right heart catheterization. Many different problems can push that number up, and the cause decides almost everything that follows, from which tests you need to which treatments can help.

This guide walks through each cause in plain language, shows which ones are common and which are rare, and explains how doctors work out which one applies to you.

How Pulmonary Hypertension Develops

Your right ventricle pumps blood into the lungs through a low-pressure, wide-open network of vessels. In a healthy adult, mean pulmonary artery pressure sits around 14 mmHg, roughly a sixth of the pressure in the arteries of your arm. (Our guide to pulmonary vs. systemic circulation explains why the two circuits run at such different pressures.)

Pressure in the lungs rises for one of three basic reasons:

• The vessels narrow. The artery walls thicken, stiffen or tighten, so the same amount of blood meets more resistance. Doctors measure this as pulmonary vascular resistance (PVR).
• Blood backs up from the left side of the heart. If the left heart can’t empty well, pressure travels backward into the lung veins and then the arteries. This shows up as a raised wedge pressure (PCWP).
• Something physically blocks the vessels. Scarred-over blood clots, tumors or outside compression cut down the number of open channels.

Think of a garden hose. You can raise the pressure by squeezing the hose (narrowing), kinking the far end (backup), or stuffing debris inside it (blockage). Each cause of PH works through one or more of these routes. Whatever the route, the right ventricle has to work harder, and over years it can thicken, stretch and eventually fail.

For the full breakdown of pressure numbers, see high pulmonary artery pressure explained.

The 5 Groups of Causes of Pulmonary Hypertension

Doctors sort the causes of pulmonary hypertension into five groups using a classification last updated at the 7th World Symposium on Pulmonary Hypertension in 2024. The groups matter because each one is treated differently. A drug that helps one group can be useless, or even harmful, in another.

Group	What’s going wrong	Common examples	How common	Can treating the cause help?
1. Pulmonary arterial hypertension (PAH)	Disease of the small lung arteries themselves	Idiopathic, inherited, scleroderma, methamphetamine, HIV, cirrhosis	Rare (about 4 per 100,000 people)	Sometimes; mostly needs PAH-specific drugs
2. Left heart disease	Blood backs up from a weak or stiff left heart or leaky/narrow valves	Heart failure, mitral or aortic valve disease	Most common (about 65–80%)	Yes, fixing the heart problem often lowers lung pressure
3. Lung disease or low oxygen	Low oxygen makes lung arteries clamp down; scarring destroys vessels	COPD, pulmonary fibrosis, sleep apnea, high altitude	Second most common	Partly; oxygen and treating the lung disease help
4. Pulmonary artery blockage	Old clots turn into scar tissue inside the arteries	CTEPH after pulmonary embolism, rare tumors	Uncommon	Yes, surgery can cure some patients
5. Unclear or multiple mechanisms	Several overlapping processes	Sickle cell disease, sarcoidosis, kidney failure	Uncommon	Depends on the condition

If you want a deeper look at how the system is built, our overview of the groups of pulmonary hypertension covers the history and subgroups.

Group 1: Pulmonary arterial hypertension (PAH)

In PAH, the problem starts inside the small arteries of the lungs. The inner lining overgrows, the muscle layer thickens, and tiny vessels close off. The left heart and the lungs themselves are usually normal. PAH is rare, but it is the form most people mean when they talk about pulmonary hypertension as a standalone disease. Read more in Group 1 pulmonary arterial hypertension explained.

Recognized causes of PAH include:

• Idiopathic PAH. No cause is found despite a full workup. It is a diagnosis of exclusion.
• Heritable PAH. A changed gene, most often BMPR2, is passed down in families. Experts now count 12 genes with strong evidence. Many people who carry a variant never develop the disease, so a second trigger likely plays a role.
• Drugs and toxins. Substances with a definite link include methamphetamine, the old diet pills fenfluramine and dexfenfluramine, benfluorex, aminorex, the cancer drugs dasatinib, carfilzomib and mitomycin C, and toxic rapeseed oil. Cocaine, amphetamines and several other medicines have a possible link.
• Connective tissue disease. Systemic sclerosis (scleroderma) carries the highest risk, followed by mixed connective tissue disease and lupus. People with scleroderma are often screened every year for this reason.
• Liver disease with portal hypertension. This is called portopulmonary hypertension and is checked before liver transplant.
• HIV infection, now less common in the US thanks to modern antiviral treatment.
• Congenital heart disease, such as a large hole between the heart chambers that floods the lungs with extra blood for years.
• Schistosomiasis, a parasitic infection that is a leading cause of PAH in parts of Africa, South America and Asia.

For a detailed look at each of these, see our article on the causes of pulmonary arterial hypertension.

Group 2: Left heart disease (the most common cause)

About 65 to 80% of people with PH have it because of a problem on the left side of the heart. When the left ventricle is weak, stiff, or working against a faulty valve, pressure builds up in the left atrium. That pressure spills backward into the lung veins and then the lung arteries.

Main causes include:

• Heart failure with preserved ejection fraction (HFpEF), the “stiff heart” often linked to age, obesity, high blood pressure, diabetes and atrial fibrillation
• Heart failure with reduced ejection fraction (HFrEF), often after a heart attack
• Mitral valve disease (leaky or narrowed valve)
• Aortic valve disease, especially aortic stenosis
• Specific cardiomyopathies such as amyloid and hypertrophic cardiomyopathy

Roughly half of people with left heart disease develop some degree of PH. In most, the lung vessels are healthy and pressure falls when the heart condition is treated. In some, long-standing backup pressure remodels the lung arteries too. Our full guide to Group 2 pulmonary hypertension explains the difference.

Group 3: Lung disease and low oxygen

Your lung arteries have a built-in reflex: when a patch of lung gets too little oxygen, the arteries supplying it tighten so blood goes to better-ventilated areas. That’s useful for a small pneumonia. But when the whole lung is short of oxygen for months or years, the arteries stay clamped and eventually thicken. This process, called hypoxic pulmonary vasoconstriction, is the main driver of Group 3 PH.

Causes include:

• COPD and emphysema, the most common lung cause worldwide
• Interstitial lung disease and pulmonary fibrosis, which also destroy vessels as the lung scars
• Combined pulmonary fibrosis and emphysema
• Obstructive sleep apnea and obesity hypoventilation syndrome
• Severe chest wall or neuromuscular problems that limit breathing
• Living at high altitude (generally above about 8,000 feet) without lung disease

Most people with COPD or fibrosis who develop PH have mild-to-moderate pressures. Severe PH is less common, affecting roughly 1 to 5% of people with COPD. Learn more in our Group 3 pulmonary hypertension guide.

Group 4: Blocked pulmonary arteries (CTEPH)

Most blood clots in the lungs dissolve with blood thinners over weeks to months. In a small number of people, the clot doesn’t fully clear. It turns into tough scar tissue stuck to the artery wall, a condition called chronic thromboembolic pulmonary hypertension (CTEPH).

Studies that followed pulmonary embolism survivors suggest about 2 to 4% go on to develop CTEPH within two years. A surprising fact: many people with CTEPH never had a diagnosed clot. Up to half have no known history of pulmonary embolism, because the original clots caused few or no symptoms. If you’ve wondered whether that’s possible, see how long you can have a pulmonary embolism without knowing.

Risk factors for CTEPH include a large or repeated pulmonary embolism, antiphospholipid syndrome, a removed spleen, cancer, and certain inflammatory bowel conditions. Group 4 also covers rare blockages such as pulmonary artery sarcoma and other tumors.

CTEPH matters because it is the one form of PH that can often be cured. Surgery to remove the scar tissue (pulmonary endarterectomy) or balloon angioplasty can bring pressures back toward normal.

Group 5: Unclear or multiple mechanisms

This group collects conditions that raise lung pressure through several overlapping routes at once:

• Blood disorders: sickle cell disease, thalassemia and other chronic hemolytic anemias, and myeloproliferative disorders such as polycythemia vera
• 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, where scar tissue in the chest squeezes the vessels
• Complex congenital heart disease and tumor microemboli

See our Group 5 pulmonary hypertension page for more detail on each.

Risk Factors That Raise Your Chances

A cause is the condition that directly drives the pressure up. A risk factor is something that makes that more likely. According to the National Heart, Lung, and Blood Institute and the CDC, the main risk factors are:

• Older age. PH affects about 1% of people worldwide, but up to 10% of those over 65, mostly because heart and lung disease become more common with age.
• Female sex. PAH and PH linked to HFpEF are both more common in women.
• Race. US surveillance data show higher rates in non-Hispanic Black adults.
• Family history of PAH or of blood clots.
• Obesity, through sleep apnea, hypoventilation and stiff-heart failure.
• Smoking, mainly by causing COPD and heart disease.
• Stimulant use, especially methamphetamine and cocaine.
• Certain genetic conditions, such as Down syndrome and Gaucher disease.
• Asbestos exposure and some parasitic infections.

Reversible vs. Long-Term Causes

This is the question most patients actually want answered, and most articles skip it. Whether PH can improve depends heavily on the cause.

Often improves when the cause is treated	Usually long-term, but manageable
CTEPH treated with surgery or balloon angioplasty	Idiopathic and heritable PAH
Valve disease fixed by repair or replacement	Scleroderma-associated PAH
Untreated sleep apnea started on CPAP	PH from advanced pulmonary fibrosis
Heart failure that responds to treatment	Long-standing congenital heart disease with Eisenmenger syndrome
High-altitude PH after moving lower	Sickle cell disease-related PH
Some drug-related PAH after stopping the drug	PH with several overlapping causes

Even “long-term” forms have far better treatment options than a decade ago. Our article on whether a cure for pulmonary hypertension is possible looks at this honestly, and how pulmonary hypertension is treated covers the options by group.

Can You Have More Than One Cause?

Yes, and it’s common. Up to 60 to 85% of people in modern PAH registries also have heart or lung conditions. A 70-year-old with COPD may also have a stiff left heart and old clots. A person with scleroderma can have PAH, lung scarring and heart involvement all at once. In these cases, doctors classify PH by the cause they believe is doing the most damage, while treating the others too.

How Doctors Find the Cause

Finding the cause is a step-by-step process. Doctors start with simple tests and move to specialized ones only if needed:

1. History and exam. Your doctor asks about breathlessness, swelling, fainting, past clots, autoimmune symptoms, drug use, family history and snoring.
2. Basic tests. ECG, chest X-ray, oxygen level, and blood tests including BNP or NT-proBNP.
3. Echocardiogram. This ultrasound estimates lung pressure and checks the left heart and valves, which spots Group 2 causes quickly.
4. Lung tests. Breathing tests, a diffusion test (DLCO), chest CT, and a sleep study if apnea is suspected.
5. V/Q lung scan. The best screening test for CTEPH. A normal scan essentially rules it out.
6. Targeted blood work. HIV, hepatitis, thyroid, autoimmune antibodies, and a urine drug screen.
7. Right heart catheterization. The only test that confirms PH and separates pre-capillary from post-capillary causes.

The full workup is explained in how pulmonary hypertension is diagnosed and how pulmonary hypertension is measured.

Common Myths About What Causes Pulmonary Hypertension

• “It’s the same as high blood pressure.” No. Regular hypertension affects the arteries of your body. PH affects only the lung circulation, though systemic high blood pressure can cause PH indirectly by straining the left heart. See hypertension vs. pulmonary hypertension.
• “It’s always genetic.” Heritable PAH makes up only about 3% of PAH cases, and PAH itself is a small slice of all PH.
• “Only older people get it.” Idiopathic PAH often strikes adults in their 30s to 50s, and children can be affected too.
• “Mild symptoms mean mild disease.” Early PH symptoms are vague, and diagnosis is often delayed by two years or more.

When to See a Doctor

Book an appointment if you notice shortness of breath that’s getting worse with everyday activity, unexplained tiredness, ankle or belly swelling, chest pressure during exertion, or lightheadedness when climbing stairs. These symptoms deserve a check sooner if you have any of the conditions above, such as heart failure, COPD, scleroderma, a past blood clot, liver disease, or a family history of PAH. The Mayo Clinic notes that symptoms often build slowly over months or years.

If you need a specialist, you can find a pulmonologist near you in our doctor directory.

Call 911 right away if you have chest pain, fainting, coughing up blood, sudden severe shortness of breath, or bluish lips. These can signal a pulmonary embolism or right heart failure and need emergency care.

Key Takeaways

• Pulmonary hypertension means mean lung artery pressure above 20 mmHg at rest. It has many causes, grouped into five categories.
• Left heart disease (Group 2) is the most common cause, followed by lung disease and low oxygen (Group 3). Together they account for 90 to 95% of cases.
• PAH (Group 1) is rare and can be idiopathic, inherited, drug-related, or linked to scleroderma, liver disease, HIV or congenital heart disease.
• CTEPH (Group 4) follows unresolved blood clots and is the form most likely to be cured.
• Many people have more than one contributing cause.
• Pinning down the cause, ideally at a PH center, is the single most important step toward the right treatment.

Frequently Asked Questions

What is the most common cause of pulmonary hypertension?

Left-sided heart disease, mainly heart failure and mitral or aortic valve disease, is the most common cause. It accounts for roughly two-thirds or more of all cases. Chronic lung disease, especially COPD, is second.

What are the early warning signs of pulmonary hypertension?

The earliest sign is usually shortness of breath during activity that used to feel easy. Fatigue, lightheadedness, chest pressure and ankle swelling often follow. Because these symptoms overlap with many conditions, PH is frequently diagnosed late.

Can anxiety or stress cause pulmonary hypertension?

No. Anxiety can make you feel breathless and raise your heart rate for a short time, but it does not cause lasting pulmonary hypertension. If you have ongoing breathlessness, it’s worth getting checked rather than assuming it’s stress.

Can sleep apnea cause pulmonary hypertension?

Yes. Repeated drops in oxygen during sleep make the lung arteries tighten. Sleep apnea alone usually causes mild PH, which often improves with CPAP. It can add to PH from other causes, such as obesity or heart failure.

Can a blood clot cause pulmonary hypertension years later?

Yes. In about 2 to 4% of people who survive a pulmonary embolism, the clot leaves behind scar tissue that slowly raises lung pressure. This is CTEPH. It’s why doctors recommend follow-up if breathlessness persists three months or more after a clot.

Is pulmonary hypertension hereditary?

Only sometimes. Heritable PAH, usually from a BMPR2 gene change, can run in families, but it accounts for a small share of cases. Most people get PH from heart, lung or clot-related conditions that are not inherited in a simple way.

Can pulmonary hypertension be prevented?

Not always, but you can lower your risk. Controlling blood pressure, not smoking, avoiding stimulants like methamphetamine, treating sleep apnea, managing heart and lung disease, and following up after a blood clot all help. People in high-risk groups, such as those with scleroderma, may benefit from regular screening.

References

1. Kovacs G, Bartolome S, Denton CP, et al. Definition, classification and diagnosis of pulmonary hypertension. Eur Respir J. 2024;64(4):2401324.
2. Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43:3618–3731.
3. National Heart, Lung, and Blood Institute. Pulmonary hypertension: causes and risk factors.
4. Centers for Disease Control and Prevention. About pulmonary hypertension.
5. Mayo Clinic. Pulmonary hypertension: symptoms and causes.
6. Hoeper MM, Humbert M, Souza R, et al. A global view of pulmonary hypertension. Lancet Respir Med. 2016;4:306–322.
7. Ende-Verhaar YM, Cannegieter SC, Vonk Noordegraaf A, et al. Incidence of chronic thromboembolic pulmonary hypertension after acute pulmonary embolism: a contemporary view of the published literature. Eur Respir J. 2017;49:1601792.

This article is for general education and is not a substitute for advice from your doctor.