Pulmonary Embolism

A pulmonary embolism is a blockage in one of the blood vessels (arteries) that carry blood through the lungs. The blockage is almost always a blood clot, although fat, air, or other material can rarely be responsible.

Most clots form first in a deep vein, usually in the leg or pelvis, a condition called deep vein thrombosis. Part of the clot can then break away, travel through the heart, and become stuck in the lungs. Because the lungs are where blood picks up oxygen, a large or multiple clots can quickly become dangerous, which is why a pulmonary embolism is treated as a medical emergency.

Common symptoms include sudden shortness of breath, sharp chest pain that often gets worse when you breathe in or cough, a fast or irregular heartbeat, feeling faint or dizzy, and coughing up blood. Signs of a clot in the leg, such as pain, swelling, warmth, or redness in the calf, may come first.

A pulmonary embolism can be life-threatening. Call your local emergency number or go to an emergency department straight away if you have sudden breathlessness, chest or upper back pain, a rapid heartbeat, you cough up blood, or you collapse or lose consciousness. Do not wait to see if symptoms settle.

Anything that slows blood flow or makes blood more likely to clot increases the risk. This includes long periods of immobility, such as recovering from surgery, a serious illness, or a long flight or car journey; recent major surgery, especially of the hip or knee; pregnancy and the weeks after birth; some cancers and their treatments; and certain medicines such as the combined contraceptive pill or hormone therapy.

Other factors include being over 60, being very overweight, smoking, a previous clot, and inherited conditions that make the blood clot more easily. Often several factors combine to trigger a clot.

Because symptoms overlap with many other conditions, diagnosis is made in hospital using a combination of tests. A blood test called a D-dimer can help show whether a clot is likely. Imaging is then used to look directly at the lung arteries, most often a CT pulmonary angiogram, which uses a special dye and a CT scanner to highlight any blockage.

Other tests may include a ventilation-perfusion (V/Q) scan, an ultrasound of the leg veins to look for deep vein thrombosis, an electrocardiogram (ECG) to check the heart, and blood tests to assess how the heart and lungs are coping. Doctors also use scoring tools to judge how likely a clot is before deciding which tests to order.

The main treatment is anticoagulant medicine, often called a blood thinner. These do not dissolve the existing clot, but they stop it growing and prevent new clots while the body breaks the clot down naturally. Treatment usually starts quickly, and most people continue an anticoagulant for at least three months; some need it for longer depending on the cause.

For a large clot causing a serious drop in blood pressure, doctors may use clot-busting medicine (thrombolysis) or, in rare cases, a procedure or surgery to remove the clot. Oxygen and other supportive care may be given in hospital. The right plan depends on the size of the clot, your symptoms, and your overall health.

In hospital, the risk of clots is lowered with measures such as early movement after surgery, compression stockings, and sometimes blood-thinning injections. For long journeys, it helps to move around regularly, do simple leg exercises, drink plenty of water, and wear compression socks if advised. Stopping smoking and keeping to a healthy weight also reduce the risk.

With prompt treatment, many people recover well. Some are left with breathlessness or, less commonly, longer-term raised pressure in the lung arteries. Because a clot can return, it is important to take medicines as prescribed, attend follow-up appointments, and seek urgent care if symptoms come back.