In some instances, the cardiologist will place a delicate metal device inside the artery to help it remain patent (open) after he completes the angioplasty (balloon) procedure. The stent is a metal coil or mesh structure that is permanently placed in the affected coronary artery. It provides a rigid structure to give the blood vessel shape and keep it open so blood may flow to the cardiac muscle tissue it serves. Because the stent is larger than balloon catheters, the artery must be dilated with a balloon before placement. In addition, the size of the stent limits its use to only larger coronary arteries.