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A pulmonary embolism 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, causing vascular obstruction and impaired
Causes of pulmonary embolism
The most common sources of embolism are pelvic vein thromboses or proximal
leg deep venous thromboses (DVTs). Generally PE's are caused by a synergism
of several predisposing factors, roughly to be divided into genetic, acquired
and circumstantial causes:
- Factor V, Leiden type (3% of the population are heterozygous for FVL (G1691A).
- Prothrombin mutation (G20210A).
- Protein C deficiency.
- Protein S deficiency.
- Antithrombin III deficiency.
- High homocysteine levels due to MTHFR mutation.
- Plasminogen and fibrinolysis disorders.
- Antiphospholipid antibodies
- anticardiolipin antibodies and/or
- Lupus anticoagulant
- Renal disease (renal loss of antithrombin)
- Paroxysmal nocturnal hemoglobinuria
- Use of the oral contraceptive pill
- Immobilization, e.g. after-
Symptoms of pulmonary embolism
Signs of PE are (sudden)
shortness of breath (dyspnea), rapid breathing
rate (tachypnea), pleuritic chest pain,
cough, hemoptysis (coughing up
blood), and in severe cases, hypotension, loss of consciousness, and death.
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Diagnosis of pulmonary embolism
The diagnosis of pulmonary embolism (PE), suspected on the basis of
shortness of breath and chest pain, with or without an abnormal x-ray,
can be confirmed by a medical test called a "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). Recent research
has shown that in low suspicion of PE, a blood test (D dimer) might be
enough to exclude the possibility of PE as cause of someone's symptoms.
Instead of the V/Q scan spiral computed tomography (spiral CT) is increasingly
being used, especially when other lung disorders are part of the differential
Once 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,
liver enzymes, electrolytes).
If one of these is abnormal, further investigations might be warranted.
Treatment of pulmonary embolism
Treatment is via infusion of thrombolytic drugs (only in submassive
PE) and anticoagulation (heparin or low-molecular weight heparin, later
coumarins - generally for 6 months).
Prognosis of pulmonary embolism
Prognosis depends on the amount of lung that is affected and on the
co-existence of other debilitating conditions. Chronic embolization to
the lung can lead to pulmonary hypertension.
After a first PE, the search for secondary causes is usually brief. Only
when a second PE occurs, and especially when this happens while still
under anticoagulant therapy, a further search for underlying conditions
is undertaken. This will include testing (see above for full list) for
Factor V Leiden mutation, antiphospholipid antibodies, protein C and S
and antithrombin levels, and later prothrombin mutation, MTHFR mutation,
Factor VIII concentration and rarer inherited coagulation abnormalities.