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Pulmonary embolism (PE) is a blockage of the lung's main artery or one of its branches by a substance that has traveled from elsewhere in the body through the bloodstream (embolism). PE results from a deep vein thrombosis (commonly a blood clot in a leg) that breaks off and migrates to the lung, a process termed ''venous thromboembolism'' (VTE). A small proportion of cases is caused by the embolization of air, fat, or talc in drugs of intravenous drug abusers or amniotic fluid. The risk of PE is increased in various situations, such as cancer or prolonged bed rest. The obstruction of the blood flow through the lungs by a PE results in increased pressure on the right ventricle of the heart, since it is the chamber that pumps blood to the lungs, and leads to the symptoms and signs of a PE. Symptoms of a 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.〔 Diagnosis is based on these clinical findings in combination with imaging studies, usually CT pulmonary angiography. If suspicion of a pulmonary embolus is lower, a negative result from a D-dimer test can be used to rule out a pulmonary embolus. Treatment is typically with anticoagulant medication, including heparin and warfarin. Severe cases may require thrombolysis using medication such as tissue plasminogen activator (tPA), or may require surgical intervention via pulmonary thrombectomy.〔 Pulmonary embolisms occur in more than 600,000 people in the United States each year and results in between 50,000〔 and 200,000 deaths per year. ==Signs and symptoms== Symptoms of pulmonary embolism are typically sudden in onset and may include one or many of the following: 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 because of 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.〔 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 exudative, 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/or raised jugular venous pressure.〔 A low-grade fever may be present, particularly if there is associated pulmonary hemorrhage or infarction. As smaller pulmonary emboli tend to lodge in more peripheral areas without collateral circulation they are more likely to cause lung infarction and small effusions (both of which are painful), but not hypoxia, dyspnea or hemodynamic instability such as tachycardia. Larger PEs, which tend to lodge centrally, typically cause dyspnea, hypoxia, hypotension, tachycardia and syncope, but are often painless because there is no lung infarction due to collateral circulation. The classic presentation for PE with pleuritic pain, dyspnea and tachycardia is likely caused by a large fragmented embolism causing both large and small PEs. Thus, small PEs are often missed because they cause pleuritic pain alone without any other findings and large PEs often missed because they are painless and mimic other conditions often causing ECG changes and small rises in troponin and BNP levels.〔Pregerson DB, Quick Essentials: Emergency Medicine, 4th edition. EMresource.org〕 PEs are sometimes described as massive, submassive and nonmassive depending on the clinical signs and symptoms. Although the exact definitions of these are unclear, an accepted definition of massive PE is one in which there is hemodynamic instability such as sustained hypotension, bradycardia or pulselessness. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pulmonary embolism」の詳細全文を読む スポンサード リンク
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