Angioplasty (also known as Percutaneous Coronary Intervention, or PCI) is the technique of mechanically widening narrowed or obstructed arteries. An empty and collapsed balloon, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size. The balloon forces expansion of the inner white blood cell/clot plaque deposits and the surrounding muscular wall, opening up the blood vessel for improved flow, and the balloon is then deflated and withdrawn. A stent (metal scaffold) is then placed at the site of the narrowing to keep the artery open.