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, impaired gas exchange, shortness of breath (dyspnea), rapid breathing rate (tachypnea), pleuritic chest pain, cough, hemoptysis, and in severe cases, hypotension, loss of consciousness, and death.
Many patients who have a pulmonary embolism have an underlying inherited predisposition that remains clinically silent until a stressor such as surgery, trauma, obesity, use of birth control pills, pregnancy, cancer, or immobilization occurs. The most frequent of these predispositions is a variant coagulation factor (Factor V Leiden) which occurs in about 3% of the population. Other hypercoagulable states are seen in protein C deficiency, protein S deficiency, antithrombin III deficiency, and various plasminogen disorders.
The most common sources of embolism are pelvic vein thromboses or proximal leg deep venous thromboses (DVTs).
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.
Treatment is via infusion of thrombolytic drugs and anticoagulation. Prognosis depends on the amount of lung that is affected and on the co-existence of other debilitating conditions.
