Coronary angioplasty. Coloured X-ray angiogram of a stent (orange) within and supporting a coronary artery of a heart. It was placed there during a coronary angioplasty to treat stenosis (narrowing) of the artery. The flexible catheter used to place it and a balloon catheter (not seen), is seen running down from upper left. The inflation of the balloon catheter expanded the artery and restored normal blood flow. The stent was expanded by the balloon catheter and remains after its withdrawal. Arterial stenosis may arise from arterial disease. X-ray angiography injects a radio-opaque contrast medium to highlight blood vessels on X-rays.