An arteriovenous malformation is an abnormal group of blood vessels. Most arteriovenous malformations are made up of two different kinds of blood vessels – arteries and veins. Arteries are large blood vessels that carry blood from the heart to the body. Veins are large blood vessels that carry blood back from the body to the heart. Some arteriovenous malformations also include small blood vessels called capillaries.
Normally, blood travels from the heart through arteries to the tissues of the body. The blood then travels through capillaries to bring nutrients to the tissues. After passing through the tissue, the blood enters veins which carry it back to the heart.
In an arteriovenous malformation, the abnormal blood vessels are disorganized and blood travels directly from the arteries to the veins. Unlike normal blood vessels, the blood vessels in an arteriovenous malformation do not provide nutrients to the surrounding tissue.
Arteriovenous malformations can develop any where in the body although the most common locations are the brain, spinal cord, and liver.
The abnormal blood vessels in an arteriovenous malformations can bleed and damage the surrounding tissue. This can be especially dangerous if the arteriovenous malformation is located in the brain or spinal cord. Large arteriovenous malformations can also press against and damage the surrounding normal tissue. The symptoms depend on where in the body the arteriovenous malformation is located.