Embolism

An embolism is the lodging of an embolus, a piece of material that travels through the bloodstream, inside a blood vessel, partially or completely blocking the flow of blood through it. The material forming the embolus can be a blood clot, a globule of fat, a bubble of air or other gas, amniotic fluid, or foreign material introduced into the circulation. Arterial embolism occurs in the systemic circulation and can starve tissue of blood, producing a stroke when the blockage lodges in an artery supplying the brain. Venous embolism usually forms in a systemic vein and travels through the heart before lodging in the lungs as a pulmonary embolism, often as a complication of deep vein thrombosis, while a rarer paradoxical embolism crosses from the venous side into the arterial system through a structural defect such as a patent foramen ovale. Embolism is usually a pathological event caused by illness or injury, though physicians can deliberately create one therapeutically, called embolization, to stop bleeding or to cut off blood supply to a tumor.