A narrowed or blocked coronary artery can compromise the blood supply to the heart muscle. A supportive tube or stent passed into each affected artery can restore the blood supply. The stent has a heparin coating to stop blood clots from forming. Since they were first performed in 1987, intracoronary stents have cut the re-blockage rate, from one in three patients who have had coronary angioplasty to fewer than one in ten in cases where a stent was used with angioplasty.