A stent is a tiny tube placed into an artery, blood vessel, or other duct (such as one that carries urine) to hold the structure open.

When a stent is placed into the body, the procedure is called stenting. There are different kinds of stents. Most are made of a metal or plastic mesh-like material. However, stent grafts are made of fabric. They are used in larger arteries.

Other types of stents are listed below.

An intraluminal coronary artery stent is a small, self-expanding, metal mesh tube that is placed inside a coronary artery after balloon angioplasty to prevent the artery from re-closing.

A drug-eluting stent is coated with a medicine that helps further prevent the arteries from re-closing. Like other coronary stents, it is left permanently in the artery.

Most of the time, stents are used to treat conditions that result when arteries become narrow or blocked. The devices are also used to unblock and keep open other tube-shaped structures in the body, including the ureters (the tubes that drain urine from the kidneys to the bladder) and bronchi (the small windpipes in the lungs).

Stents are commonly used to treat coronary heart disease (CHD). If you have coronary artery disease that does not cause symptoms, you can be treated with either medicine or angioplasty with stenting. Recent studies show that medicine and angioplasty with stenting have equal benefits. Angioplasty with stenting does not help you live longer, but it can reduce angina or other symptoms of coronary artery disease.

Angioplasty with stenting, however, can be a life-saving procedure if you are having a heart attack

Other reasons to use stents include:

• Keeping open a blocked or damage ureter
• Treatment of aneurysms, including thoracic aortic aneurysms
• Unblocking a large artery, such as the carotid artery (carotid endarterectomy)
• To keep bile flowing in blocked bile ducts (biliary stricture)
• Helping you breathe if you have a blockage in the airways

Risks of stents and stent placement may include:

• Allergic reaction to stent material
• Allergic reaction to the drug used in a drug-eluting stent
• Blood clot
• Clogging of the inside of the stent (in-stent restenosis)
• Rupture of the duct or vessel when the stent is inserted

Drug-eluting stents may not be recommended for patients who had recent heart surgery, or women who are nursing or pregnant. Patients who receive a drug-eluting stent may need blood thinning drugs for at least several months.

The safety of drug-eluting stents -- and how well they work -- has not been studied in persons with a blockage in a heart bypass graft, who are having a heart attack, or who have had radiation treatment inside a blood vessel.

Boden WE, O'rourke RA, Teo KK, et al. Optimal Medical Therapy with or without PCI for Stable Coronary Disease. N Engl J Med. 2007 Mar 26; [Epub ahead of print].

Winslow RD, Sharma SK, Kim MC. Restenosis and drug-eluting stents. Mt Sinai J Med. 2005 Mar;72(2):81-9.

Moreno R, Fernandez C, Hernandez R, Alfonso F, Angiolillo DJ, Sabate M, et.al. Drug-eluting stent thrombosis: results from a pooled analysis including 10 randomized studies. J Am Coll Cardiol. 2005 Mar 15;45(6):954-9.