Types of Coronary Artery Stents

Stents are used as scaffolding to prop open narrowed or weak coronary arteries. Coronary artery stents are less invasive than open heart surgery, but there is a 10 to 20 percent chance the procedure will need to be redone within a year, reports the National Heart, Lung and Blood Institute. Stents cause scar tissue to form, narrowing the artery again, a condition referred to as restenosis. Stent types differ by structure and function. They may be plastic or metal, coiled or slotted, bare or coated, self-expanding or not.

Coils, Mesh and Slotted Stents

• Coiled stents are more flexible but less strong.

  Coronary artery stents may exist as coils, slotted tubes or mesh. Slotted-tube stents are very strong stents that cover a high surface area. Coil stents are more flexible and can adapt to winding blood vessel routes, but the arteries tend to recoil. Mesh stents combine aspects of coil stents and slotted-tube stents and are the preferred choice, according to a 1999 article in the "Singapore Medical Journal."

Drug-eluting Stents

• Blood-thinners are necessary with the use of drug-eluting stents.

  The artery lining and scar tissue eventually grow over the stent, and re-narrowing makes further treatment necessary 10 to 15 percent of the time. Drug-eluting stents are coated with medications that help reduce the formation of scar tissue, but these drugs increase the risks of blood clots and heart attacks, reports The National Heart Foundation of Australia. If an unrelated surgery is expected in the future, it's good to go with a bare metal stent because it can be replaced at the same time.

Stent Grafts

• Fabric-covered grafts prevent weak areas from bulging.

  Another type of coronary artery stent is the stent graft or covered stent. Baylor College of Medicine reports that stent grafting is most useful for aneurysms. The fabric-covered stent prevents blood from flowing into a bulging or weakened area of the coronary artery. In some cases, stents may be covered with vascular tissue from the cephalic or ulnar artery. Stent grafts are a good choice for people too sick to undergo surgery, reports "Angioplasty.org," and many people would prefer such a minimally invasive procedure to open surgery any day.

Radioactive Stents

• Small doses of radiation can prevent scar tissue formation.

  Surgeons sometimes use radiation to inhibit the formation of scar tissue around coronary artery stents. Radioactive stents are constructed to emit small doses of radiation to the blood vessel wall to reduce restenosis. A study reviewed on "Medscape" has found that radioactive stents do reduce stenosis well within the stent itself, but not around the edges. Re-stenting is usually necessary after one year.

Bioactive Stents

• Stents may be covered with natural or synthetic substances.

  Bioactive stents are those that cause a reaction with your natural bodily processes, according to Patrick Driscoll of "MedMarket Diligence." These reactions are intended to lower the risk of restonosis. Scientists have experimented with a number of stent coatings from polyurethane to gold. Heparin-coated stents help to lower re-narrowing of the artery.

Biodegradable Stents

• Pateints with metal stents cannot have diagnostic MRIs.

  Scientists are also working to develop biodegradable stents--stents that dissolve over time. In 2006, the first absorbable metal stent was studied by Dr. Raimund Erbel of University Essen. The stent is constructed of a magnesium alloy that lasts for two months. The advantages of this type of stent include: long-term mechanical stent-strength isn't necessary; inflammatory reactions and scar tissue formation are much less likely to occur; and magnetic resonance imaging is possible after the stent has dissolved. Patients with permanent metal stents cannot have MRIs, and alternate imaging tools don't give as clear an image.