An arteriovenous malformation (AVM) is a tangle of blood vessels that irregularly connects arteries and veins, disrupting blood flow and oxygen circulation. Arteries move oxygen-rich blood from the heart to the brain and other organs. Veins drain the oxygen-depleted blood back to the lungs and heart.
When an AVM disrupts this critical process, the surrounding tissues might not get enough oxygen. Also, because the tangled blood vessels in an AVM do not form properly, they can weaken and rupture. If an AVM in the brain ruptures, it can cause bleeding in the brain, stroke or brain damage. Bleeding in the brain also is called hemorrhage.
AVM's can happen anywhere in the body.