An angiography is a medical procedure used to look at the blood vessels in your chest. A small, thin tube called a catheter is inserted into an artery in your arm and threaded through your body to the arteries in your chest. Once the catheter is in place, a special dye is injected into the artery. The dye makes the arteries show up on x-ray images. The x-ray images are used to figure out if there are any blockages in the arteries.