Pulmonary hypertension

21 min read

What is pulmonary hypertension?

Pulmonary hypertension is raised blood pressure within the pulmonary arteries, which are the blood vessels that supply the lungs.

It's a serious medical condition that can damage the right side of the heart, making the heart less efficient at pumping blood around the body and getting oxygen to the muscles.

Symptoms of pulmonary hypertension include:

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symptoms of pulmonary hypertension

What happens in pulmonary hypertension

In a healthy person, blood travels through the pulmonary arteries from the right-hand side of the heart, picking up oxygen when it reaches the lungs.

Oxygen-rich blood from the lungs returns to the left-hand side of the heart, where it's pumped around the body to the muscles, where the oxygen is needed.

During exercise, the demand for oxygen increases, so the heart beats quicker and the pulmonary arteries usually widen to let more blood flow through to the lungs.

But if you have pulmonary hypertension, the walls of your pulmonary arteries are thick and stiff, making it difficult for them to expand to allow more blood through. Alternatively, your pulmonary arteries may be blocked by

blood clots
which can also hinder blood flow.

The reduced blood flow makes it difficult for the right-hand side of your heart to pump blood through the arteries, which means that this part of the heart has to work harder.

If the right-hand side of your heart has to continually work harder, it may gradually become weaker. This will make it less efficient at pumping blood and can lead to

heart failure

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causes of pulmonary hypertension

Diagnosing pulmonary hypertension

Correctly diagnosing pulmonary hypertension can sometimes take time because its symptoms are similar to many other heart and lung conditions.

But pulmonary hypertension can be a serious condition, so it's important you visit your doctor if you experience symptoms.

They'll ask about your symptoms and medical history. Tests, including an

(a type of ultrasound scan) and an electrodardiogram (tests the electrical rhythm of your heart) can be used to see how well your heart and pulmonary arteries are working.

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how pulmonary hypertension is diagnosed

Treating pulmonary hypertension

Pulmonary hypertension is a serious condition that usually gets progressively worse. Left untreated, it may cause heart failure, which can be fatal.

If pulmonary hypertension is caused by an existing condition, such as

heart disease
, lung disease or a blood clot, the underlying condition should be treated first. In some cases, this can prevent the pulmonary arteries being permanently damaged.

A number of medications can be used to treat PAH and other types of pulmonary hypertension. To start with,

anticoagulant medicines
and diuretics may be recommended. Later on, a number of more specialist medications may be prescribed.

Read more about

treating pulmonary hypertension


Symptoms of pulmonary hypertension, such as breathlessness, can significantly affect your quality of life as you may be unable to continue with your regular activities. Therefore, it's important treatment is started as soon as possible to improve your symptoms.

With the introduction of new medicines, people are now able to live longer with PAH. A study found about two-thirds of people lived for more than 5 years after their diagnosis.

Your outlook will depend on how quickly the condition is diagnosed, how advanced your symptoms are and whether you have another underlying health condition.

Pulmonary hypertension symptoms

Pulmonary hypertension is a potentially serious health condition that can lead to heart failure.

Symptoms of pulmonary hypertension include:

  • shortness of breath
  • fatigue (extreme tiredness)
  • dizziness
  • feeling faint
  • chest pain (angina)
  • a racing heartbeat (tachycardia)
  • leg swelling

Your symptoms may get worse when you exercise, which can limit your ability to take part in physical activities.

As pulmonary hypertension progresses, carrying out everyday activities may also become difficult. If your condition starts impact your everyday life, it can affect your quality of life and may lead to

. Visit your doctor if you feel depressed so they can recommend appropriate treatment.

If you have a type of pulmonary hypertension known as

pulmonary arterial hypertension
(PAH), you may not experience any symptoms until the condition is quite advanced.

Heart failure

Untreated pulmonary hypertension can lead to

heart failure
, where your heart struggles to pump enough blood around your body. As well as shortness of breath and tiredness, heart failure can also cause:

  • swelling in the legs, ankles and feet (
  • waking up in the middle of the night gasping for breath (paroxysmal nocturnal dyspnoea)
  • a persistent
  • nausea
    (feeling sick)
  • lack of appetite
  • weight loss
  • confusion or difficulty concentrating

Pulmonary hypertension causes

Pulmonary hypertension is caused by changes to the pulmonary arteries, which are blood vessels that carry blood from your heart to your lungs.

The walls of your pulmonary arteries can become stiff and thickened, or the blood vessels may get blocked by blood clots. This makes it difficult for your heart to pump blood through these arteries, which increases pressure inside them, leading to pulmonary hypertension.

There can be many different reasons for the changes to your arteries. The World Health Organization (WHO) has classified pulmonary hypertension into 5 different types, depending on the underlying cause. They are:

  • pulmonary arterial hypertension (PAH)
  • pulmonary hypertension associated with left heart disease
  • pulmonary hypertension associated with lung disease and hypoxia
  • pulmonary hypertension due to blood clots
  • pulmonary hypertension due to other causes

Pulmonary arterial hypertension (PAH)

Pulmonary arterial hypertension (PAH) is caused by problems with the smaller branches of the pulmonary arteries. In PAH, these changes are usually the main problem, rather than another condition.

As the pulmonary arteries are directly affected, they can be treated immediately, whereas in other types of pulmonary hypertension the underlying cause must be treated first.

PAH can be further divided into specific subtypes which are described below.

Idiopathic PAH

Idiopathic means the cause is unknown. If tests can't find an underlying reason for your condition, you may be diagnosed with idiopathic PAH. This is an extremely rare condition affecting only about 2 people in every million each year.

Inherited PAH

Some cases of PAH run in families. A particular genetic mutation (a change in one of the genes you inherit from your parents) is sometimes thought to cause PAH. There may be a family history of the condition in up to 10% of idiopathic PAH cases.

PAH associated with other conditions

Other conditions or treatments associated with PAH include:

  • connective tissue diseases that affect the structure or composition of your body tissue, such as
    (a disorder that causes hardening of the skin)
  • congenital heart problems
    , such as a hole in the heart
  • portal hypertension – a condition where blood pressure inside the liver is abnormally high, which causes veins to become swollen
  • HIV
    – about 1 in 200 people with HIV will develop PAH
  • certain medications or drugs – such as fenfluramine (a medication no longer available) and amphetamines, which are a type of illegal drug
  • thyroid gland disorder
  • sickle cell disease
    and related conditions
  • glycogen storage disorders (glycogen is a carbohydrate that produces short-term energy)

PAH can also be associated with rare conditions that affect your blood vessels such as:

  • pulmonary veno-occlusive disease – a condition that causes
    high blood pressure
    in the lungs
  • pulmonary capillary hemangiomatosis – where tiny blood vessels (capillaries) grow within the lungs, causing blockages

Persistent pulmonary hypertension of the newborn

It's estimated that persistent pulmonary hypertension affects around 2 in every 1,000 newborn babies.

Conditions that may also be associated with persistent pulmonary hypertension of the newborn include:

  • severe pulmonary hypoplasia – where your baby’s lungs are seriously underdeveloped
  • hypoglycaemia
    – an abnormally low level of glucose in the baby’s blood
  • sepsis
    – a life-threatening illness caused by a very severe infection
  • meconium aspiration syndrome – where a newborn baby breathes in a mixture of amniotic fluid (the fluid that surrounds the baby in the womb) and meconium (their first faeces), which can block their airways

Left heart disease

Pulmonary hypertension is sometimes associated with diseases that affect the left side of the heart (the side that pumps blood around the whole body apart from the lungs). The left side of the heart consists of:

  • the left atria (upper chamber)
  • the left ventricle (lower chamber)
  • the aortic and mitral valves – 1 way valves that allow blood to flow through the heart in the correct direction

As blood flows through the pulmonary arteries to the lungs and then to the left side of the heart, any problem could have a backwards effect on this circuit and affect the pulmonary arteries. This in turn could cause pulmonary hypertension.

Up to 60% of people with a condition that causes severe left ventricle dysfunction have pulmonary hypertension. Almost all people with a severe mitral valve condition, and nearly two-thirds of those with a severe aortic valve condition have pulmonary hypertension.

Lung disease and hypoxia

Pulmonary hypertension is also sometimes associated with lung diseases or hypoxia (a shortage of oxygen in the body). This includes:

  • chronic obstructive pulmonary disease
    (COPD) – a term that describes a number of lung diseases, such as emphysema, where people have trouble breathing; up to half of people with advanced COPD may also have pulmonary hypertension, although it's usually mild
  • interstitial lung disease – a group of lung disorders that cause scarring of the lung tissue, which makes it difficult to get enough oxygen into your body; about a third of people with interstitial lung disease may have pulmonary hypertension
  • sleep-disordered breathing – conditions that affect breathing while you're in deep sleep, such as
    obstructive sleep apnoea

These conditions can restrict the amount of oxygen able to get into your lungs and into your blood. A low level of oxygen in the blood causes the pulmonary arteries to constrict (get narrower). As these vessels are narrower, the blood is squeezed into a smaller space, which increases the blood pressure and results in pulmonary hypertension.

Blood clots

Pulmonary hypertension is sometimes the result of a blood clot that causes narrowing or a blockage in the pulmonary arteries or veins.

A blood clot that blocks one of the blood vessels that supply your lungs is known as a

pulmonary embolism
. After having a pulmonary embolism, up to 2 in 100 people may have pulmonary hypertension.

Other causes

Other, less common causes of pulmonary hypertension include:

  • sarcoidosis
    – a condition that causes inflammation of different organs, including the lungs and lymph nodes
  • histiocytosis X – a rare condition that causes scarring (granulomas) and air filled cysts, predominantly in the lungs
  • compression of the blood vessels in the lungs – for example, due to a tumour (growth)

Diagnosing pulmonary hypertension

Pulmonary hypertension can be difficult to diagnose because symptoms are often similar to other conditions that affect the heart or lungs.

This means there can sometimes be a long delay before a correct diagnosis is made.

However, as pulmonary hypertension can be serious, it's important you visit your doctor if you have symptoms such as breathlessness and fatigue (extreme tiredness). Your doctor will ask about:

  • your symptoms and how they affect your life
  • your family history (some types of pulmonary hypertension run in families)
  • whether you're currently taking any medication
  • whether you have any other medical conditions


You may have several tests, either to diagnose pulmonary hypertension, or to identify an underlying condition that may be causing it. The initial tests, described below, may be carried out by your doctor or a hospital specialist.


An echocardiogram is a type of

ultrasound scan
that can determine how well your heart is working.

It uses high-frequency sound waves to create an image of an area inside your body, such as your heart. The image can be used to estimate the pressure in your pulmonary arteries.


An electrocardiogram (ECG) records your heart's rhythm and electrical activity.

Small, metallic discs called electrodes are stuck to your arms, legs and chest and connected with wires to an ECG machine.

Every time your heart beats, it produces tiny electrical signals. The ECG machine traces these signals onto paper.

Chest X-ray


is an imaging technique that uses high-energy
to highlight abnormalities in bones and other types of tissue.

A chest X-ray can look for other causes of your symptoms, such as scarring in your lungs, which can also cause shortness of breath.

A chest X-ray can also check whether your heart is larger than normal. Pulmonary hypertension makes the right-hand side of your heart work harder, causing it to become enlarged.

Lung function tests

Lung function tests, also known as breathing tests, assess how well your lungs work.

The tests measure how quickly you're able to move air in and out of your lungs, how much air they can hold and how well they transfer oxygen into your blood and remove carbon dioxide from it.

During the tests, you'll be asked to breathe into a lung function machine. The data collected will help diagnose any underlying lung conditions.

Exercise tests

Exercise tests involve carrying out some form of exercise while checking your symptoms.

For example, you may be asked to walk on a treadmill or up and down a corridor for 6 minutes while your heart rate, blood pressure and oxygen levels are monitored. This can help determine whether there are any underlying causes of your symptoms.

Ventilation-perfusion scan

A ventilation-perfusion scan measures the amount of air and the blood flow in your lungs. This can be used to look for blood clots in your blood vessels that may be causing pulmonary hypertension.

Blood tests

A sample of blood may be taken and tested to rule out other possible conditions, such as thyroid and liver disease.

Confirming the diagnosis

The above tests may suggest pulmonary hypertension is present, but the diagnosis can only be confirmed by measuring your blood pressure in:

  • the right ventricle (lower chamber) of your heart, which pumps blood to your lungs
  • your pulmonary arteries, which carry blood from the right side of your heart to your lungs

Your blood pressure is measured using a procedure called right-heart catheterisation.

Right-heart catheterisation

In right-heart catheterisation, a thin flexible tube called a catheter is inserted into a vein in your neck, arm or groin. The catheter is then fed through into the right side of your heart and into your pulmonary arteries.

As well as measuring blood pressure, the catheter can be used to measure the:

  • amount of blood the right-hand side of your heart is pumping out to your lungs
  • pressure your heart must work against to get blood to your lungs (pulmonary vascular resistance)
  • amount of oxygen in the blood that returns to your heart

If the pressure in your pulmonary arteries is above a certain level, you'll be diagnosed with a particular type of pulmonary hypertension.

If the diagnostic tests described above reveal an underlying cause, you'll be diagnosed with a particular

type of pulmonary hypertension
. If no cause is found, you'll be diagnosed with idiopathic pulmonary arterial hypertension.

Classifying pulmonary hypertension

As part of your diagnosis, your condition will be classified depending on its severity. This will help determine the best treatment for you.

Pulmonary hypertension is classified into 4 types where:

  • ordinary physical activities do not cause any symptoms
  • ordinary physical activities cause symptoms, such as chest pain or fatigue, but you have no symptoms when resting
  • even slight physical activities, such as moving your arms, cause symptoms, but you have no symptoms when resting
  • you have symptoms when resting, which are increased with any type of physical activity

Pulmonary hypertension treatment

If you have pulmonary hypertension caused by another underlying condition, your treatment will focus on tackling it.

If the cause is identified and treated early, it may be possible to prevent permanent damage to your pulmonary arteries (the blood vessels that supply your lungs).

There are a number of medicines used to treat PAH and other types of pulmonary hypertension.

You'll probably be started on conventional therapy or background therapy (see below), before your treatment is changed or increased as necessary. Further treatment is called targeted therapy.

Background therapy

Background therapy includes:

These are explained in more detail below.

Anticoagulant medicines

PAH can increase your risk of developing venous thromboembolism, which is where a blood clot forms in a vein and breaks free.

The clot can become trapped in a blood vessel, blocking the vessel and the blood supply. If a blood clot blocks a blood vessel that supplies your lungs, it's known as a pulmonary embolism.

Anticoagulant medicines reduce the blood's ability to clot. Taking anticoagulants, such as

, may reduce your risk of developing venous thromboembolism.

Anticoagulants can cause side effects, such as increased bleeding, so you will need to be carefully monitored while taking them.


Diuretics are used to remove excess fluid from the body by increasing the production and flow of urine.

In pulmonary hypertension, diuretics may be used to treat fluid retention and swelling (oedema). This can occur if the condition starts to cause heart failure (where your heart struggles to pump blood around your body).

Diuretics used include:

  • furosemide
  • amiloride
  • spironolactone

Diuretics can cause side effects such as:

  • mild tummy upset
  • postural hypotension – where your blood pressure drops suddenly after moving, which can make you feel dizzy after you stand up
  • a dry mouth
  • rashes
  • headaches
  • confusion

Diuretics can also disrupt your levels of electrolytes (minerals in your blood, such as potassium) and affect your kidney function. Because of this, your kidneys and blood will be monitored while you're taking diuretics.


If you have low oxygen levels in your blood, you may need to be treated with oxygen. This involves inhaling air that contains a higher concentration of oxygen than normal. This will increase the amount of oxygen in your blood and should help improve your symptoms.


If pulmonary hypertension leads to heart failure, you may be treated with digoxin. Digoxin increases the strength of your heart muscle contractions and can slow down your heart rate.

Calcium channel blockers

Calcium channel blockers are medicines usually used to treat

high blood pressure
(hypertension) and angina (pain in the heart caused when the blood supply to the heart's muscles is restricted).

Calcium channel blockers work by relaxing your artery wall muscles. This widens your arteries and reduces your blood pressure.

Nifedipine and diltiazem are two possible calcium channel blockers that may be prescribed.

Calcium channel blockers may work for people with idiopathic PAH (where there is no known cause). However, the effect in other types of PAH is less clear.

You'll need a vasoreactivity test to find whether calcium channel blockers are suitable for you. This involves taking the medication and then checking whether the blood pressure in your pulmonary arteries has fallen. If it has, you may be prescribed calcium channel blockers.

Targeted therapy

If calcium channel blockers are not suitable for you, or are no longer effective, further treatments can be used. These are called targeted therapies and include the following medicines:

  • bosentan
  • ambrisentan
  • sildenafil
  • tadalafil
  • iloprost
  • epoprostenol

These are described below.


Bosentan tablets may help improve your symptoms and ability to exercise. 2 tablets are usually taken twice a day (in the morning and evening), although the dosage can sometimes vary.

You may need to spend a day in hospital when you start treatment. If your condition has not improved after 8-16 weeks, or if it has got worse, you may be given additional treatment as well as or instead of bosentan.

Bosentan can increase levels of some enzymes in the liver, which can cause liver damage. It may also cause anaemia in some people. As a result, your liver will need to be monitored once a month for as long as you're taking bosentan.

Fluid retention – for example, leg swelling - has been reported in up to 30% of patients using bosentan.

Bosentan will not be suitable for you if you:

  • already have a problem with your liver
  • are taking ciclosporin (a medicine that suppresses your immune system)
  • are pregnant

Women who could get pregnant must use contraception if they are taking bosentan. This type of medication can interact with hormonal contraception, such as the combined contraceptive pill, so it's better to use an alternative method, such as



Ambrisentan acts in exactly the same way as bosentan but only needs to be taken once a day. The side effects are also similar and monthly blood tests will be required to exclude liver abnormalities and anaemia.


Sildenafil tablets are usually taken 3 times a day to improve your ability to exercise.

You may need to spend a day in hospital when you start treatment, before returning home and carrying on taking the medicine. How long you can take sildenafil for will depend on your condition. If at any time your condition gets worse, you may be given additional treatment as well as or instead of sildenafil.

Sildenafil may not be suitable for you if you:

  • are also taking medicines or drugs that contain nitrates – organic nitrates are often used to treat angina and amyl nitrate is a recreational drug commonly known as 'poppers'
  • have a severe liver problem
  • have recently had a heart attack or stroke
  • have severe
    low blood pressure
  • have certain eye conditions


Tadalafil acts in exactly the same as sildenafil but only needs to be taken once a day. Its side effects are also similar to sildenafil.


Iloprost is inhaled through a nebuliser. This is a device that turns the liquid medicine into a mist you breathe in to your lungs. You may need to take iloprost 6-9 times a day. Each dose can take up to 10 minutes to inhale.

You'll need to stay in hospital for up to 3 days to be trained in using the nebuliser and to monitor your response. After this time, you should be able to return home and continue taking the medicine.

How long you need to take iloprost for will depend on your condition. You may need to continue taking it, possibly alongside other treatments, until your condition worsens and you need epoprostenol (see below).

Iloprost may not be suitable if:

  • you have a peptic ulcer
  • you have recently had a heart attack or stroke
  • your pulmonary hypertension is caused by pulmonary veno-occlusive disease (a rare condition that causes high blood pressure in the lungs)
  • your pulmonary hypertension is unstable, with advanced right heart failure


Epoprostenol (full name epoprostenol sodium) may be used if you do not respond to other treatments or if your condition is severe.

Epoprostenol needs to be given through an intravenous infusion, where a constant drip of medicine passes through a narrow tube into a vein in your arm or chest.

Treatment with epoprostenol will begin in hospital. It may take 1-2 weeks to find the correct dose for you. After this time it's possible, with special training and equipment, for you or your carer to learn how to administer the medicine yourself at home.

Once you've started taking epoprostenol you may not be able to stop. Coming off epoprostenol may cause your pulmonary hypertension to rapidly return, so you may need to take the medication for the rest of your life. This is why epoprostenol is considered last, after other treatments have not worked or your condition has got worse.

Epoprostenol may not be suitable for you if you have heart failure caused by a problem with the left side of your heart, or if you have or develop pulmonary oedema (fluid on the lungs).

Heart-lung transplant

A heart-lung transplant may be an option in cases of severe pulmonary hypertension. It's a major surgical procedure that involves transplanting healthy lungs or a heart and lungs from a donor into a recipient.

Read more about

heart-lung transplants

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.