Arteriovenous malformation or AVM is a congenital disorder of the veins and arteries that make up the vascular system . The cause of this disorder is unknown, but is not generally thought to be hereditary, unless in the context of a specific hereditary syndrome. more...
Arteries and veins are part of the human cardiovascular system. Normally, the arteries in the vascular system carry oxygen-rich blood at a relatively high pressure. Structurally, arteries divide and sub-divide repeatedly, eventually forming a sponge-like capillary bed. Blood moves through the capillaries, giving up oxygen and taking up waste products from the surrounding cells. Capillaries successively join together, one upon the other, to form the veins that carry blood away at a relatively low pressure. The heart acts to pump blood from the low pressure veins to the high pressure arteries.
If the capillary bed is thought of as a sponge, then an AVM is the rough equivalent of jamming a tangle of flexible soda straws from artery to vein through that sponge. On arteriorgram films AVM formation often resemble a tangle of spaghetti noodles. This tangle of blood vessels forms a relatively direct connection between high pressure arteries and low pressure veins.
The result is a collection of blood vessels with abnormal connections and without capillaries. This collection, often called a nidus, can be extremely fragile and prone to bleeding. AVMs can occur in various parts of the body including the brain (see cerebral arteriovenous malformation), spleen, lung, kidney and liver. AVMs may occur in isolation or as a part of another disease (e.g. von Hippel-Lindau disease or Rendu-Osler-Weber syndrome).
This bleeding can be devasting, particularly in the brain. They can cause severe and often fatal strokes. If detected before the stroke occurs, usually the arteries feeding blood into the nidus can be closed off, ensuring the safety of the patient.
This condition affected the character of Nate in the US TV series Six Feet Under.
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