Pulmonary Embolism

pulmonary embolism

Venous thromboembolism
Pulmonary embolism (PE) is part of a group of problems together known as venous thromboembolism (VTE). A deep vein thrombosis (DVT) is the usual cause of a PE. A DVT occurs in a vein in the leg. DVT is also part of VTE.

What is a pulmonary embolism?

A PE is a blockage in one of the arteries (blood vessels) in the lungs - usually due to a blood clot. A PE can be in an artery in the centre of the lung or one near the edge of the lung. The clot can be large or small and there can be more than one clot.

What causes a pulmonary embolism?

The usual cause - a DVT

In almost all cases, the cause is a blood clot (thrombus) that has originally formed in a deep vein (known as a DVT). This clot travels through the circulation and eventually gets stuck in one of the blood vessels in the lung.

Other causes

  • Fatty material from the marrow of a broken bone (if a large, long bone is broken - such as the femur (thigh bone).
  • Foreign material from an impure injection - for example, with drug misuse.
  • Amniotic fluid from a pregnancy or childbirth (rare).
  • A large air bubble in a vein (rare).
  • A small piece of tumour (cancer) that has broken off from a larger tumor in the body.

Who gets a pulmonary embolism?

Nearly all cases of PE are caused by a DVT. So, people more likely to get a PE are those prone to DVTs. Some important risk factors are immobility, other serious illnesses and major surgery (especially gynaecological surgery, and operations on the pelvis and legs). The risk of developing a DVT or PE in hospital can be greatly reduced by early mobilisation and medicine to help prevent a DVT or PE in those at particular risk.

What are the symptoms of a pulmonary embolism?

The symptoms will depend on how large or small the clot is, and on how well the person's lungs can cope with the clot.

A small PE may cause:

  • No symptoms at all (common).
  • Breathlessness - this can vary in degree from very mild to obvious shortness of breath.
  • Chest pain which is pleuritic, meaning sharp pain felt when breathing in.
  • Coughing up blood (this is known as haemoptysis).
  • A mild fever.
  • A fast heart rate.

A massive PE or multiple emboli (lots of clots) may cause:

  • Severe breathlessness.
  • Chest pain - with a large PE the pain may be felt in the centre of the chest behind the breastbone.
  • Feeling faint, feeling unwell, or a collapse.
  • Rarely, in extreme cases, a massive PE can cause cardiac arrest, where the heart stops pumping due to the clot.

How is a pulmonary embolism diagnosed?

The diagnosis is often suspected on the basis of symptoms and your medical history. Various tests may be used to help confirm the diagnosis. These may include one or more of the following:

  • Ultrasound of the leg
    • A type of ultrasound called a duplex Doppler is used to show blood flow in the leg veins, and any blockage to blood flow.
  • Blood test for D-dimer
    • This detects fragments of breakdown products of a blood clot.
  • Ultrasound of the heart (echocardiography)
    • This test is useful for people who may have a massive PE, as it can show up large clots in the lung and/or their effect on the heart.
  • Isotope scan and CTPA scan
    • These are specialised scans which look at the circulation in the lung. They are useful, because they can show quite accurately whether or not a PE is present.
    • The isotope scan is also called a V/Q scan or ventilation/perfusion scan. The CTPA scan is a type of CT scan looking at the lung arteries - the full name is computed tomographic pulmonary angiography scan.

General tests

  • An ECG (heart trace) is often done.
  • Blood tests to look for signs of a heart attack, infection or inflammation.
  • A chest X-ray to look for pneumonia or other chest conditions.

What is the treatment for a pulmonary embolism?

Anticoagulant treatment

Anticoagulation is often called thinning the blood. It alters certain chemicals in the blood to stop clots forming so easily. It doesn't dissolve the clot either. Anticoagulation prevents a PE from getting larger, and prevents any new clots from forming. Anticoagulation treatment is usually started immediately (as soon as a PE is suspected) in order to prevent the clot worsening, while waiting for test results.

Anticoagulation medication comes in two forms: injections and tablets

The injectable form is heparin (or similar injections called low molecular weight heparins (LMWH)).  A new drug called fondaparinux sodium can be given by injection in some circumstances, either to prevent VTE or treat a PE or DVT.

The tablets or syrup are called warfarin. They all belong to the group known as oral anticoagulants.

Anticoagulant treatment is continued until three months after a PE in most cases. Sometimes longer treatment is advised, especially if there is a high risk of a further embolism.

Supportive treatment

Oxygen to reduce breathlessness.
In some cases, IV fluids are given to support the circulation.

Additional treatments

Clot-dissolving injection (thrombolysis). This is medication given to help dissolve the blood clot. Alteplase is the medication usually used; streptokinase or urokinase are alternatives.
Filters. These can be used to stop any more blood clots from reaching the lung. The filter is placed in a large vein called the inferior vena cava (IVC). The filter is inserted via a thin tube, which is put into a large vein and then fed along the vein into the correct position.

Surgery (embolectomy). In some cases, it may be possible to remove the embolus surgically. This is called embolectomy. This is a major operation because it involves surgery inside the chest, close to the heart. It requires a specialist hospital and surgical team. It is generally considered as a last resort for very ill patients.

Treating the clot through a catheter (tube). This type of treatment is called catheter embolectomy or catheter fragmentation of the clot. This is highly specialised treatment and so is only available at certain hospitals.

What are the complications of a pulmonary embolism?

  • Collapse - This can cause a cardiac arrest where the heart stops, and may be fatal.
  • Complications due to treatment. The anticoagulant treatment can have side-effects. The main one is bleeding elsewhere in the body - for example, from a stomach ulcer.

What is the outlook (prognosis) for a pulmonary embolism?

This depends on the type of PE and on whether there are any other medical problems. If a PE is treated promptly, the outlook is good, and most people can make a full recovery. The outlook is less good if there is an existing serious illness which helped to cause the embolism - for example, advanced cancer. A massive PE is more difficult to treat and is life-threatening.

How can a pulmonary embolism be prevented?

This involves preventing a DVT. People having major surgery should be assessed for their DVT risk, and people at high risk of DVT may need preventative (prophylactic) doses of heparin or a similar drug before and after surgery. Other preventative measures are also possible while in hospital.

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