Abnormal formation of blood vessels that shunt arterial blood directly into veins without passing through the CAPILLARIES. They usually are crooked, dilated, and with thick vessel walls. A common type is the congenital arteriovenous fistula. The lack of blood flow and oxygen in the capillaries can lead to tissue damage in the affected areas.

Synonyms: Arteriovenous Malformation, Arteriovenous Malformations, Malformation, Arteriovenous, Malformations, Arteriovenous