Blockage of an artery by an embolus. Blood clots that have broken off from a larger clot located elsewhere in the circulation are the most common type of embolus. Pulmonary embolism is usually the result of a fragment breaking off from a deep vein thrombosis and being carried via the heart to block an artery supplying the lungs; this is a common cause of sudden death. Blood clots may form on the heart lining after a myocardial infarction, or in the atria in atrial fibrillation, and then travel to the brain, resulting in a cerebral embolism, which is an important cause of stroke. Air embolism, in which a small artery is blocked by an air bubble, is rare. Fat embolism, in which vessels are blocked by fat globules, is a possible complication of a major fracture of a limb. Symptoms of an embolism depend on the site of the embolus. Pulmonary embolism can lead to breathlessness and chest pains. If the embolus lodges in the brain, a stroke may occur, affecting speech, vision, or movement. If an embolism blocks an artery to the leg, the limb will become painful and turn white or blue. Untreated, gangrene may develop. In serious cases of fat embolism, heart and breathing rates rise dramatically, and there is restlessness, confusion, and drowsiness. Embolectomy (surgery to remove the blockage) may be possible. If surgery is not possible, thrombolytic and anticoagulant drugs may be given.


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