Coronary angioplasty. Coloured X-ray angiogram of a balloon catheter and stent (orange) inflating within a coronary artery of a heart. They are being used to treat stenosis (narrowing) of the artery. The flexible catheter used to place them there is seen running across from far left. The inflation of the balloon catheter is expanding the artery and restoring normal blood flow. The stent is a hollow tube mesh, expanded by the balloon catheter, that stays in the artery and supports it after the balloon catheter has been withdrawn. Arterial stenosis may arise from arterial disease. X-ray angiography injects a radio-opaque contrast medium to highlight blood vessels on X-rays.