An arteriovenous fistula (AVF) is an abnormal connection between an artery and a vein. It can occur anywhere in the body, including the brain.
Normally, blood flows from arteries through capillaries and back to your heart in veins. When an AVF is present, a short circuit exists and blood flows directly from an artery into a vein, bypassing the capillaries. If the volume of diverted blood flow is large enough, it may precipitate heart failure or the tissues downstream may be compromised due to lack of oxygen.
An interventional radiologist treats an AVF by excluding it from the circulation. This may be achieved by sealing off the artery with a special device called a covered stent or by occluding the artery with various agents such as coils.