A stent is a metal or plastic tube inserted into an abnormally narrowed or closed conduit (such as an artery or duct) in the body. It serves to keep the conduit open and maintain flow. 

Stents are most often used to treat conditions that result when arteries narrow or become blocked. They are also used to unblock and keep open other tube-shaped structures in the body, such as the ureters (the tubes that drain urine from the kidneys to the bladder) and bronchi (the small windpipes in the lungs).

The implantation of a stent for the treatment of coronary artery disease is a common procedure. An intraluminal coronary artery stent is a small, self-expanding, metal mesh tube that is placed within a coronary artery after balloon angioplasty to prevent the artery from reclosing (restenosis).

A drug-eluting stent is coated with medication (sirolimus or paclitaxel) to help prevent reclosure of the coronary arteries. Like other coronary stents, it is left permanently in the artery, and slowly releases a drug that prevents the build-up of tissue that leads to restenosis.

There are many uses for stents. A few include:

• Keeping the ureters open if they are blocked or damaged
• Coronary atherosclerotic disease (CAD)
• Unblocking large arteries throughout the body
• To keep bile flowing in the bile ducts if they are blocked
• Maintaining are flow in the bronchi if they are obstructed (for example, by a tumor)

• In-stent restenosis (the risk is higher in patients receiving non-drug-eluting stents)
• Blood clot
• Allergic reaction to stainless steel or other stent material
• Allergic reaction to the drug used in a drug-eluting stent
• Rupture of the duct or vessel during insertion

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

The safety and effectiveness of a drug-eluting stent have not been studied in patients who have a blockage in a heart bypass graft, who are actually having a heart attack, or who had previous intravascular radiation treatment.

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.