Of all the nonsurgical treatments that have been used in an effort o improve angioplasty, implantable stents have had the greatest success. Coronary stents are implantable, expandable metal devices placed, by way of a catheter, permanently at a site of obstruction, clot, or occlusion.. Stents maintain the diameter of the artery by mechanically supporting the diseased site. Recent studies have concluded that the rate of restenosis in patients who receive coronary stents after angioplasty is approximately 30% lower than in those who do not receive stents. The use of arterial stents after angioplasty procedures still has certain drawbacks. Not only are they permanent implants that may result in unforeseen long-term adverse effects, but they cannot be used in coronary arteries that are tortuous, narrow, or small. In addition, restenosis may still occur, often requiring even more aggressive procedures to restore arterial blood flow.