Pulmonary embolism (PE) is a blockage of the pulmonary artery (or one of its branches), usually when a venous thrombus (blood clot from a vein), becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. This process is termed thromboembolism.
Symptoms may include difficulty breathing, pain in the chest during breathing, and in more severe cases collapse, circulatory instability and sudden death. Treatment, usually, is with anticoagulant medication, such as heparin and warfarin, and rarely (in severe cases) with thrombolysis or surgery. In other, rarer forms of pulmonary embolism, material other than a blood clot is responsible; this may include fat or bone (usually in association with significant trauma), air (often when diving), clumped tumor cells, and amniotic fluid (affecting mothers during childbirth).
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Symptoms of PE are sudden-onset dyspnea (shortness of breath), tachypnea (rapid breathing), chest pain of "pleuritic" nature (worsened by breathing), cough, hemoptysis (coughing up blood), and may aid in the diagnosis. More severe cases can include signs such as pleural rub, cyanosis (blue discoloration, usually of the lips and fingers), collapse, and circulatory instability. About 15% of all cases of sudden death are attributable to PE.
Risk factors
The most common sources of embolism are proximal leg deep venous thrombosis (DVTs) or pelvic vein thromboses. Any risk factor for DVT also increases the risk that the venous clot will dislodge and migrate to the lung circulation, which happens in up to 15% of all DVTs. The conditions are generally regarded as a continuum termed venous thromboembolism (VTE).
The development of thrombosis is classically due to a group of causes named Virchow's triad (alterations in blood flow, factors in the vessel wall and factors affecting the properties of the blood). Often, more than one risk factor is present.
- Alterations in blood flow: immobilization (after surgery, injury or long-distance air travel), pregnancy (also procoagulant), obesity (also procoagulant)
- Factors in the vessel wall: of limited direct relevance in VTE
- Factors affecting the properties of the blood (procoagulant state):
- Estrogen-containing hormonal contraception
- Genetic thrombophilia (factor V Leiden, prothrombin mutation G20210A, protein C deficiency, protein S deficiency, antithrombin deficiency, hyperhomocysteinemia and plasminogen/fibrinolysis disorders).
- Acquired thrombophilia (antiphospholipid syndrome, nephrotic syndrome, paroxysmal nocturnal hemoglobinuria)
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