Stents are usually used when a blood vessel gets blocked by plaque. Plaque is a material made up of cholesterol and other chemicals that sticks to the inner side of the vessel’s walls. In the process of stent placement, a catheter is inserted into the blocked coronary artery by the doctor.   This allows the doctor to open the obstruction with balloon angioplasty. After that, they put a stent in the artery to keep it open.   A stent is