Coronary artery stent. Model of a coronary artery stent being implanted into an artery. The artery may have become narrowed due to atherosclerosis, the deposition of fatty plaques of atheroma in the artery. This restricts blood supply to the heart muscle and can cause a heart attack. The stainless steel stent has been expanded by a balloon (not seen) attached to the wire-like catheter so it holds the artery open. Stents are also used to keep the blood flowing through transplanted veins after heart bypass surgery, and to treat acute vessel closure following arterial surgery (angioplasty).