A prosthetic or polyester graft is made out of a human-made (synthetic) polyester material. It is used to replace natural body tissues. Most grafts are in the shape of a tube to replace or repair blood vessels. The graft can be used as a stent to improve an artery, blood vessel, or other hollow structure in your body (such as the tube that carries urine) to hold it open. Polyester grafting is performed to bypass partial or complete blockages in arteries to improve the blood flow. Also, Polyester grafts are inserted in the blood vessels due to inadequate blood flow (ischemia) caused by atherosclerosis.