Pulmonary embolism

A pulmonary embolism (thromboembolism) occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death. Treatment is with anticoagulant medication, such as warfarin.

Diagnosis

Confirming PE

The gold standard for diagnosing pulmonary embolism (PE) is still pulmonary angiography. In most of the cases, however, when PE is suspected on the basis of shortness of breath and chest pain, the following scans may confirm the presence of an embolus:

Related Topics:
Gold standard - Pulmonary angiography

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• "Ventilation-perfusion scan" (or V/Q scan), which shows that some areas of the lung are being ventilated but not perfused with blood (due to obstruction by a clot). It is a type of scintigraphy.
• Increasingly, the V/Q scan is being replaced with computed tomography with radiocontrast, effectively a pulmonary angiogram done under CT. Advantages are clinical equivalence, better access for patients and the possibility of picking up other lung disorders from the differential diagnosis in case there is no pulmonary embolism.

In low/moderate suspicion of PE, a normal D-dimer level (shown in a blood test) is enough to exclude the possibility of PE (Bounameaux et al 1994).

Related Topics:
D-dimer - Blood test

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

An electrocardiogram will show signs of right heart strain in cases of large PEs - the classic signs are a large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In massive PE, dysfunction of the right side of the heart can be seen on echocardiography, an indication that the pulmonary artery is severely obstructed and the heart is unable to match the pressure. In the United States, many physicians see this as an adequate indication for thrombolysis (see below).

Related Topics:
Echocardiography - Pulmonary artery - United States - Thrombolysis

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The presence of deep venous thrombosis is in itself enough to warrant anticoagulation, without requiring the V/Q or spiral CT scans, and leg ultrasound can be used as a surrogate. This may be valid approach in pregnancy, in which the other modalities would increase the risk of birth defects in the unborn child. However, a negative scan does not rule out PE, and low-radiation dose scanning may be required if the mother is deemed at high risk of having pulmonary embolism.

Related Topics:
Deep venous thrombosis - Ultrasound

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Further analysis

When a PE is being suspected, a number of blood tests are also done, in order to exclude important secondary causes of PE. This includes a full blood count, clotting status (PT, APTT, TT), and some screening tests (Erythrocyte sedimentation rate, renal function, liver enzymes, electrolytes). If one of these is abnormal, further investigations might be warranted.

Related Topics:
Blood test - Full blood count - Clotting status - PT - APTT - Erythrocyte sedimentation rate - Renal function - Liver enzyme - Electrolyte

~ ~ ~ ~ ~ ~ ~ ~ ~ ~