An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels connecting arteries and veins in the brain or other parts of the body. Normally, arteries carry oxygenated blood away from the heart to various tissues, and veins carry deoxygenated blood back to the heart. In an AVM, the typical network of capillaries between arteries and veins is missing, and the direct connection between arteries and veins can result in abnormal blood flow and pressure.