What a pulmonary embolism is
A pulmonary embolism is a blood clot that travels to the lungs, usually from the veins of the legs. Small clots can be incidental findings on a CT scan and often cause few or no symptoms. Larger or multiple clots cause breathlessness, chest pain and, in some cases, coughing up blood. Small clots have little effect on the heart, but a larger clot or a greater burden of clots strains the heart muscle and in severe cases causes heart failure.
Symptoms that are easily missed
It may cause sudden breathlessness, chest pain or collapse, but sometimes the symptoms are mild and easily missed.
Who is at risk
Recent surgery, long periods of immobility, cancer, hormone treatments and long haul travel all raise the risk.
- Surgery. Most clots develop during recovery from surgery. The risk depends on the type of surgery and on patient factors such as advanced age, obesity and the medicines a patient is taking.
- Immobility. Any prolonged period of immobility, in a vehicle or in bed, of more than three to four hours can lead to clot formation.
- Cancer. Certain cancers, such as pancreatic, breast and blood cancers, put patients at very high risk of forming clots.
- Hormone treatment. Oestrogen-containing treatments, such as hormone replacement therapy and the combined contraceptive pill, raise the risk of clot formation.
How it is diagnosed
A CT scan confirms the diagnosis. A blood test (D-dimer) can guide us on how likely a clot is, but it is not diagnostic. A CT pulmonary angiogram, a CT scan of the blood vessels of the lung, is now the most common way to diagnose clots in the lung. A detailed ultrasound of the legs looks for clots in the veins that drain the legs.
How it is treated
Treatment with blood thinners is highly effective. Treatment depends on factors such as the location and size of the clots, and in most cases blood thinners (anticoagulants) are enough: they prevent further clots from forming while the original clots are broken down by the body. For the most severe clots, stronger treatments to dissolve or remove the clot are needed. Mechanical removal of the clot by an interventional radiologist may be necessary, and for those who cannot have that procedure, more powerful clot-dissolving medicines (thrombolytics) can be considered.
Recovery and prevention
Some patients remain breathless months later and need further assessment. In most cases the breathlessness resolves within days to weeks, but in a small group it persists because of a high clot burden; treatment may then involve surgical removal of the clots or specific medicines that relieve the strain on the heart.
For most people, simple measures such as moving about at least every two hours, staying hydrated and avoiding alcohol are enough to prevent clots on long flights. For those at higher risk of clots, a preventive anticoagulant injection before a long-haul flight can be considered.
Related reading
Lung and Respiratory Conditions: A Patient Guide · Deep Vein Thrombosis (DVT) · The Aeden Physicians
Frequently Asked Questions
What are the symptoms of a pulmonary embolism?
A pulmonary embolism is a blood clot that travels to the lungs, usually from the veins of the legs. It may cause sudden breathlessness, chest pain or collapse, but sometimes the symptoms are mild and easily missed.
What raises the risk of a pulmonary embolism?
Recent surgery, long periods of immobility, cancer, hormone treatments and long haul travel all raise the risk. Oestrogen-containing treatments and certain cancers, such as pancreatic, breast and blood cancers, carry a particularly high risk.
How is a pulmonary embolism treated?
In most cases blood thinners (anticoagulants) are enough: they prevent further clots from forming while the body breaks down the original clot. For the most severe clots, mechanical removal or clot-dissolving medicines are used.