Pulmonary Embolism: Difference between revisions

'''Pulmonary embolism''' ('''PE''') is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream (embolism). Usually this is due to embolism of a thrombus (blood clot) from the |deep veins in the legs, a process termed venous thromboembolism. A small proportion is due to the embolization of air, fat, talc in drugs of intravenous drug abusers or amniotic fluid. The obstruction of the blood flow through the lungs and the resultant pressure on the right ventricle of the heart leads to the symptoms and signs of PE. The risk of PE is increased in various situations, such as cancer or prolonged bed rest.<cite>Goldhaber</cite>

Symptoms of pulmonary embolism include difficulty breathing, chest pain on inspiration, and palpitations. Clinical signs include low blood oxygen saturation and cyanosis, rapid breathing, and a rapid heart rate. Severe cases of PE can lead to collapse, abnormally low blood pressure, and sudden death.<cite>Goldhaber</cite>

Diagnosis is based on these clinical findings in combination with laboratory tests (such as the D-dimer test) and imaging studies, usually CT pulmonary angiography. Treatment is typically with anticoagulant medication, including heparin and warfarin. Severe cases may require thrombolysis with drugs such as tissue plasminogen activator (tPA) or may require surgical intervention via pulmonary thrombectomy.<cite>Goldhaber</cite>

Symptoms of PE are sudden-onset dyspnea (shortness of breath), tachypnea (rapid breathing), chest pain of a "pleuritic" nature (worsened by breathing), cough and hemoptysis (coughing up blood). More severe cases can include signs such as cyanosis (blue discoloration, usually of the lips and fingers), collapse, and circulatory instability due to decreased blood flow through the lungs and into the left side of the heart. About 15% of all cases of sudden death are attributable to PE.<cite>Goldhaber</cite>

On physical examination, the lungs are usually normal. Occasionally, a pleural friction rub may be audible over the affected area of the lung (mostly in PE with infarct) . A pleural effusion is sometimes present that is transudative, detectable by decreased percussion note, audible breath sounds and vocal resonance. Strain on the right ventricle may be detected as a left parasternal heave, a loud pulmonary component of the second heart sound, and raised jugular venous pressure.<cite>Goldhaber</cite> A low-grade fever may be present, particularly if there is associated pulmonary hemorrhage or infarction.<cite>Stein</cite>

More rarely, inability of the right ventricle to remove fluid from the tissues leads to fluid accumulation in the legs (peripheral edema), congestion of the liver with mild jaundice and tenderness, and ascites (fluid in the abdominal cavity).{{citation needed | date=November 2010}}

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), cancer (also procoagulant)

** 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)

** Cancer]] (due to secretion of pro-coagulants)