Pulmonary Embolism
What is a pulmonary embolism?
A pulmonary embolism (PE) is a blood clot that blocks one or more of the arteries in the lungs. Most clots start in the deep veins of the legs (deep vein thrombosis, DVT), break off and travel through the right side of the heart to the lungs. PE and DVT are together called venous thromboembolism (VTE).
A pulmonary embolism can range from small clots that cause mild symptoms to large clots that are life-threatening. It is treatable, and the outlook is much better when it is diagnosed and treated promptly.
How is it different from a heart attack?
A heart attack is a blockage in the arteries that supply the heart muscle. A pulmonary embolism is a blockage in the arteries of the lungs. The two can feel similar, with chest pain and breathlessness, which is why urgent assessment is needed.
Symptoms and when to get emergency help
Call 999 or go to A&E immediately if you have sudden breathlessness, chest pain, coughing up blood, or collapse, particularly if you also have a swollen, painful leg or have recently had surgery, a long period of immobility or a long journey.
Common symptoms
- sudden shortness of breath, which may be worse on exertion
- sharp chest pain that is worse when you breathe in
- a cough, sometimes with blood-stained phlegm
- a fast heart rate or palpitations
- feeling light-headed or fainting
Signs of a clot in the leg
A DVT often causes pain, swelling, warmth and redness in one calf or leg. Some people with a pulmonary embolism have no leg symptoms at all.
Mild or gradual symptoms
Small clots can cause milder, gradual breathlessness or reduced exercise tolerance that is easy to put down to being unfit. Unexplained new breathlessness should be assessed, particularly after a risk event.
Causes and risk factors
Blood clots form when the blood flows slowly, the vein wall is damaged, or the blood is more likely to clot than usual. Risk factors include:
- recent major surgery, especially hip or knee replacement
- being in hospital or immobile for a long period
- cancer and some cancer treatments
- a previous DVT or pulmonary embolism, or a family history of clots
- pregnancy and the weeks after birth
- oestrogen-containing contraceptives or hormone replacement therapy
- a leg fracture or plaster cast
- obesity, older age and some inherited or acquired clotting disorders
- long-haul travel combined with other risk factors
Provoked and unprovoked clots
A clot with a clear trigger, such as surgery, is called provoked. A clot with no obvious cause is called unprovoked, and this affects how long treatment continues.
How is it diagnosed?
Diagnosis combines your symptoms, risk factors and tests. Doctors often use a clinical scoring system, such as the Wells score, to estimate how likely a pulmonary embolism is before deciding which tests to do.
D-dimer blood test
D-dimer is a blood test that is raised when the body is breaking down clots. A normal result in someone at lower risk makes a pulmonary embolism unlikely, but a raised result is not specific and needs further tests, because many other conditions raise D-dimer.
CT pulmonary angiogram (CTPA)
This is the usual scan to confirm a pulmonary embolism. It uses X-rays and contrast dye to show clots in the lung arteries. A ventilation-perfusion (V/Q) scan may be used instead, for example in pregnancy or if you cannot have contrast dye.
ECG, chest X-ray and echocardiogram
An ECG and chest X-ray are used to look for other causes of chest pain and breathlessness. An ECG can be normal or show a fast heart rate, and sometimes signs of strain on the right side of the heart. An echocardiogram shows whether a large clot is putting strain on the right side of the heart, which helps decide how urgent and intensive treatment needs to be.
Treatment
Treatment starts as soon as a pulmonary embolism is suspected or confirmed, often before the scan result, if the risk is high.
Anticoagulant (blood-thinning) medicines
The mainstay of treatment is an anticoagulant, which stops the clot growing and lets the body break it down. NICE recommends a direct oral anticoagulant, such as apixaban or rivaroxaban, as first choice for most people; warfarin or injections are used in some situations. Treatment usually continues for at least 3 months, and is then reviewed.
How long does treatment last?
For a provoked clot with a clear, temporary cause, 3 months is often enough. For an unprovoked clot, or if the risk of another clot remains, longer treatment may be considered, balancing the risk of recurrence against the risk of bleeding.
Treatment for severe clots
A large pulmonary embolism that causes very low blood pressure or collapse is an emergency. Clot-dissolving drugs (thrombolysis) or, rarely, a procedure or surgery to remove the clot may be used in hospital.
Staying safe on anticoagulants
Take your medicine exactly as prescribed, tell every doctor, dentist and pharmacist that you take it, and seek advice about bleeding, a head injury or new medicines. Do not stop it without medical advice.
Recovery and long-term follow-up
Most people recover well. Breathlessness and tiredness can take weeks or months to improve, and some people have ongoing symptoms.
Ongoing breathlessness after a pulmonary embolism
A proportion of people still have breathlessness or reduced exercise capacity months after a pulmonary embolism. Reasons include lung scarring or deconditioning, anxiety, other heart or lung conditions, and, in a small minority, chronic thromboembolic disease where clots fail to clear. If you are still breathless 3 to 6 months after treatment, you should be assessed.
Chronic thromboembolic pulmonary hypertension (CTEPH)
In a small minority of people, unresolved clots narrow the lung arteries and raise the pressure in them, a condition called CTEPH. An echocardiogram is the usual first test, with a V/Q scan to look for unresolved clots. CTEPH is treatable, so it is important to recognise it.
Returning to activity
Gentle activity is encouraged as you feel able, and most people return to normal activities in stages. Ask your doctor about flying, exercise and returning to work.
Preventing another clot
- keep taking your anticoagulant for as long as advised
- move regularly and stay hydrated on long journeys
- keep to a healthy weight and stay active
- ask about clot prevention before surgery, hospital admission, or if your leg is in a plaster cast
- discuss oestrogen-containing contraception or hormone replacement therapy with your doctor if you have had a clot
- report new leg swelling or breathlessness promptly
Do I need tests for an underlying cause?
NICE advises against routine testing for inherited clotting disorders after a first clot, but it may be considered if you have a strong family history of clots. If a clot was unprovoked, your doctor will check your history and symptoms and arrange further tests only where they are indicated.
How a cardiologist can help
Most acute pulmonary embolisms are diagnosed and treated in hospital. A cardiologist can help afterwards if you have ongoing symptoms or concerns about your heart, including:
- persistent breathlessness, chest discomfort or reduced exercise capacity after a clot
- an echocardiogram to assess the heart and the pressure in the lung arteries
- an ECG, and heart rhythm monitoring if you have palpitations
- assessment of blood pressure and wider cardiovascular risk
- a second opinion on your results and follow-up plan
A consultation does not replace emergency care. If you have new, sudden breathlessness or chest pain, call 999.
Questions to ask your doctor
- Was my pulmonary embolism provoked or unprovoked, and what might have caused it?
- Which anticoagulant am I on, and how long should I take it?
- When will my treatment be reviewed?
- Do I need an echocardiogram or other follow-up tests?
- What symptoms should make me seek urgent help?
- When can I return to exercise, work and flying?
- What should I do about travel, surgery or dental treatment while on an anticoagulant?
- Do my contraception or hormone replacement therapy need to change?
- Do I need any tests to look for a cause?
- What should I do if I remain breathless after treatment?
Common questions
Can a pulmonary embolism go away on its own?
What is the difference between a DVT and a pulmonary embolism?
How long does recovery take?
Can I fly after a pulmonary embolism?
Can stress or anxiety cause these symptoms?
Can a pulmonary embolism cause pulmonary hypertension?
Guidelines and sources
- National Institute for Health and Care Excellence. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing (NG158). nice.org.uk/guidance/ng158
- Konstantinides SV, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism. European Heart Journal 2020;41:543–603. doi:10.1093/eurheartj/ehz405
- NHS. Pulmonary embolism. nhs.uk
Pulmonary embolism diagrams and visual aids
A blood clot blocking an artery in the lung (pulmonary embolism).
Image: Baedr-9439, Wikimedia Commons. CC0 (public domain).
How does the clot reach the lungs?
Most clots begin as a deep vein thrombosis in a leg or the pelvis. A piece breaks off, travels through the veins and the right side of the heart, and lodges in an artery of the lung, blocking blood flow to part of it. This is why leg swelling and pain, and sudden breathlessness or chest pain, need prompt medical attention.
If you have had a pulmonary embolism and still have breathlessness or chest symptoms, or want your heart assessed afterwards, you can book a video consultation or telephone consultation from anywhere in the UK, or a face to face consultation in Peterborough or Corby. For sudden breathlessness or chest pain, call 999.
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Medically reviewed by Dr Salam Salloum, Consultant Cardiologist. Last reviewed: . This page is for general information and does not replace personal medical advice.