Definition
The term “embolism” describes the medical phenomenon that carried material is transported via the blood vessel system to another part of the body, where it causes vascular occlusion. The displaced material can, for example, peel off an arteriosclerotic plaque (vascular calcification) or consist of blood clots that have formed in the left atrium. Behind the vascular occlusion there is then only limited blood flow and the tissue there is damaged.
Causes of embolism
The causes of an embolism are manifold. 90 percent of embolisms, however, come from the heart and occur, for example, in atrial fibrillation in the left atrium or in the ventricles if the heart has been damaged by a previous heart attack. It is also possible that the embolus forms on the heart valves, which happens for example when a heart valve malfunctions (vitium) or when the innermost layer of the heart wall becomes infected (endocarditis).
In about 10 percent of cases, the cause is to be found in the arterial vascular system: almost always, a piece of this calcifying material detaches from a site affected by vascular calcification (arteriosclerosis) and thus becomes an embolus. In rare cases, the cause is a so-called “paradoxical embolism“: through a hole in the wall of the vagina (open foramen ovale), which some people have without knowing it, an embolus that has detached itself from a venous thrombosis can enter the arterial vascular system and trigger an embolism. Other causes include cholesterol embolism, in which cholesterol deposited in the artery walls is detached, embolism from tumor tissue in cancer, or air or fat embolism (see below).
Thrombosis
A thrombosis is the formation of a blood clot in the vascular system. In most cases a thrombosis develops in venous vessels, mostly in the deep veins of the legs. The causes are changes in the vascular wall, slow blood flow and blood disorders.
However, thrombosis is also possible in the arterial blood vessel system. The difference between thrombosis and embolism is that in thrombosis a blood clot gradually forms at the site of the blood vessel, which is then also later affected by the vascular occlusion. (In embolism, the material that closes the vessel comes from another part of the body).
Arterial thrombosis is mostly caused by arteriosclerosis (hardening of the blood vessels) or by inflammatory changes in the arterial walls. More rare causes are diseases of the blood or blood clotting. Arterial thrombosis also occurs as a consequence of an embolism and thus increases the size of the occluded vessel section both in front of and behind the embolus.
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