Coronary Stents: What They Are and What They Do

"Around 2 million coronary stents are implanted each year in the U.S., in about 1 million procedures," says Giora Weisz, MD, medical director of interventional cardiology at NewYork-Presbyterian Hospital Hudson Valley Hospital and an associate professor of medicine at Columbia University Vagelos College of Physicians and Surgeons. 

Coronary stents are implanted via Percutaneous Coronary Intervention (PCI). But what is PCI?

PCI, a minimally invasive procedure, treats blockage in coronary arteries by opening up narrowed or blocked sections of an artery, thereby increasing or restoring blood flow.

According to the American Heart Association, PCI uses balloon angioplasty, often followed by implantation of a stent to treat conditions where blood flow to the heart muscle has been reduced or cut off. The stent props open the artery, which decreases the chance of another blockage.

A stent is a small wire mesh tube that holds a narrowed blood vessel open to dilate the artery. "Stents are metal scaffolds that are used to treat blockages and can be placed in a variety of vessels in the body," Rajiv Gulati, MD, chair of the Division of Interventional Cardiology in the Department of Cardiovascular Medicine at the Mayo Clinic, explains. 

He adds, "They are used in the aorta (usually to seal aneurysms), in peripheral arteries (leg vessels, for example), and coronary arteries." Physicians who implant stents are called interventional cardiologists. 

"Depending on their subspecialty training and expertise," Gulati explains, "interventional cardiologists may perform other procedures, including implanting stents in other locations like peripheral arteries, valve replacement (most commonly transcatheter aortic valve replacement), mitral valve repair and more."

"The decision whether to treat a blockage with a stent depends on the degree and location of the narrowing," Weisz says. "Stents are selected based on their diameter and length, to best fit the narrowed segment."

Three reasons why a stent is indicated:

1. Opening a coronary artery blockage during a heart attack or in patients with unstable angina (which occurs while at rest).
2. Opening additional coronary artery blockages identified during the heart attack (non-culprit lesions) to prevent future episodes.
3. Opening a coronary artery narrowing or blockage to improve blood flow to the heart to treat stable angina that has not been adequately managed with anti-anginal medication. Stable angina is chest pain that usually happens due to a trigger, like stress or exercise, and is predictable.

According to Gulati, "Stents can re-narrow or close off completely due to scar tissue growth over several months or years, although with modern stents this is unusual." 

"If this happens, another stent may need to be implanted or a balloon used to re-open the stent, or coronary artery bypass surgery to bypass the narrowing or blockage. Very rarely, stents can suddenly block with a blood clot, which could result in a major heart attack, but this is very rare with modern medications."

Coronary stents have gotten better in recent years. "The technology of stents is ever-changing and improving," Gulati says. "The stents we have today are made of better metal alloys, enabling the combination of better flexibility and strength, and are covered with a specific medication to prevent the formation of internal scars, thus providing long-term durability."

Sometimes, knowing whether stent implantation or bypass surgery is the best treatment for coronary artery blockage may be challenging. "This decision is made by the cardiologist based on the number and location of the blockages," Weisz explains. "In general, the more blockages, the higher the benefit of bypass surgery."

However, the location of the blockages is also a consideration, he adds. "Some spots are regarded as widow makers, and surgery may be a better choice."

"Most of the time it's quite clear which is the preferred treatment for certain situations," Gulati says. "For example, stents are used for heart attack while coronary artery bypass surgery is more for severe blockages in all the major coronary arteries in patients with diabetes, particularly if they are younger or without other life-limiting illnesses."

Weisz says the physician also considers the "overall risk to the patient in each alternative procedure and individual suitability. In borderline situations, we use the heart team consisting of an interventional cardiologist and a heart surgeon to decide what to recommend to the patient and their family." 

According to Gulati, when a situation "can be addressed by either stents or coronary artery bypass surgery, patient values and preferences may be the most important deciding factor." For example, patients may opt for stents vs. bypass due to the more rapid recovery period or because they want to avoid major surgery.

Gulati and Weisz emphasize that the final decision should be up to the patient. "Careful discussions with the patient, loved ones, cardiologist and cardiac surgeon are important to help with these decisions," Gulati says.

Implanting stents is one way to treat coronary artery disease. Medications and lifestyle modifications are also effective. For example, antiplatelet medicines like aspirin and Plavix prevent blood clots from forming in the stents. 

Cholesterol-lowering medication (statins) reduces the chance of developing new blockages in other coronary artery locations. In addition, controlling blood pressure and diabetes can reduce the likelihood of future coronary blockages and heart attacks, Gulati says.

Lifestyle modifications include tobacco cessation, diet, exercise, mental health, healthy sleep, maintaining a healthy weight, and healthy levels of blood lipids, blood glucose and blood pressure.