First performed in the mid-1980s, and approved by the U.S. Food and Drug Administration (FDA) in 1994, coronary artery stenting is a catheter-based procedure in which a stent (a small, expandable wire mesh tube) is permanently implanted in a diseased artery to hold it open.  Stents are delivered to blood vessels on catheters that are guided through the circulatory system until they reach the diseased artery.

Stents are more commonly used after a balloon angioplasty has been performed to treat coronary artery disease. Together, balloon angioplasty and coronary artery stenting are capable of reducing the degree of blockage in an artery by more than 90 percent. This has reduced the number of coronary artery bypass graft surgeries, which is a boon for patients.

Coronary stents are implanted as much as 90 percent of the time after a balloon angioplasty and/or atherectomy (a catheter-based procedure in which plaque is removed from an artery). Stents may also be used to restore normal blood flow in arteries that have been torn or otherwise damaged by previous catheter-based procedures (e.g., angioplasty or atherectomy). Finally, as coronary stent technology and experience have improved, they are being used in a wider patient population, including people who have already suffered a heart attack, the elderly and patients with complex coronary artery disease.

According to 2005 guidelines issued by the American Heart Association and American College of Cardiology, stents can be considered for use in patients who have significant disease of the left main and left anterior descending coronary arteries, the two largest coronary arteries. In addition, patients with diffuse triple-vessel disease or two-vessel disease with significant involvement of the left anterior descending coronary artery are also candidates for angioplasty and stenting. Previously, these patients were only candidates for bypass graft surgery. However, newer generation stents have been shown to be as effective as surgery in restoring blood supply in some patients. Patients with very serious coronary artery disease, or total blockage of major arteries, are still recommended for surgery.

Potential benefits to stenting include:

• Reduced chest pain, pressure or discomfort (angina)
  
  
• Less shortness of breath (dyspnea)
  
  
• Lower risk of heart attack after the procedure
  
  
• Less need for additional medical treatment with drugs
  
  
• Less pain from peripheral arterial disease (if stents were placed in a limb)
  
  
• Less risk of the artery re-closing (restenosis) compared to angioplasty
  
  
• Nearly no risk of abrupt vessel closures (which occur in about 2 to 10 percent of patients who have balloon procedures without stenting within the first 24 hours of the procedure). There is a reduced risk compared to angioplasty, but abrupt closure still occurs in about a very small percentage of patients. Additionally, there is a reduced risk of requiring emergency coronary bypass surgery compared to angioplasty.

The overall safety of coronary stenting has been shown in both male and female patients. Though studies have shown a statistically higher risk of heart attack or death in women one month after stent insertion, the rates tend to equal those of men at one year.

Stenting has also benefited individuals with diabetes, who have increased risk of atherosclerosis. In addition, up to two-thirds of diabetic individuals develop life-threatening heart or blood vessel disease. Stenting has compared favorably to balloon angioplasty in reducing the incidence of heart attack and need for repeat artery-widening procedures.

In addition to treating the coronary arteries, stents may be inserted in other arteries, such as those affected by plaque accumulation occurring as a result of peripheral arterial disease (PAD). Stenting in PAD, for example, can be used to support and hold open arteries in the kidney (renal arteries) or the iliac arteries that supply blood to the legs. Stents have also been approved for use in selected patients with atherosclerosis of the carotid arteries. Stents are used in these patients to open the artery and reduce the risk of stroke.

Special stents (stent-grafts) are also used to treat aneurysms, including abdominal aortic aneurysms. In a stent-graft procedure, the physician prevents blood from flowing through the aneurysm by placing one stent just above the aneurysm and a second stent just below the aneurysm. The two stents are connected by a patch of synthetic material (a graft), which provides a channel for blood to flow without entering the aneurysm.

Stents come in a variety of different materials, drug coatings, designs, lengths, diameters and flexibilities. Whether or not stenting can or should be done depends upon a number of factors, including:

• The size of the artery in question
• Where the blockage is located
• The extent of the blockage
• The extent of blockage in other arteries
• The strength of the heart muscle

Stents are designed to be permanently implanted into their host arteries. When they were first introduced, coronary stents were made from bare metal. These early generation stents greatly improved the success rate of balloon angioplasty, as measured by the restenosis rate. Restenosis occurs when the artery closes again after the procedure. The first bare-metal stents reduced the restenosis rate from about 50 percent to about 30-35 percent.

In 2003, however, the next generation of coronary stents was introduced. Called drug-eluting stents, these stents were coated with special drugs (e.g. sirolimus or paclitaxel) that further reduced the restenosis rate to less than 10 percent. These stents have since become the favored stent and are used in a majority of cases. They are also responsible for expanding the pool of patients who are candidates for angioplasty/stenting.

However, recent research has shown that drug-eluting coronary stents may have increased long-term risk of thrombosis, or blood clots, compared to bare metal stents. This appears to be the case among patients who discontinue clopidogrel therapy early. Clopidogrel, combined with aspirin, is standard therapy after stenting. These medications are anti-platelet medications that have been shown to reduce the risk of blood clots. However, some patients discontinue their clopidogrel early, which increases their risk of thrombosis. It is extremely important that patients continue to take their medications exactly as prescribed, for as long as prescribed. In some cases, patients may not be suited for a drug-eluting stent because of sensitivity to clopidogrel or if the physician feels there is a strong possibility they will discontinue therapy early.

Metal detectors have not been found to interfere with or detect the presence of stents.