Summary
First performed in the mid–1980s, and approved by the U.S. Food and Drug Administration (FDA) in 1994, stenting is a catheter-based procedure in which a small, expandable wire mesh tube (stent) is implanted into a diseased artery as a scaffold to hold it open. Stents can be placed in arteries and veins throughout the body. Coronary stents are designed to be placed into the coronary arteries that lie on the surface of the heart and supply the heart with oxygen-fresh blood. Coronary artery stents have made it possible for physicians to treat diseased coronary arteries with less trauma to the patient than coronary artery bypass graft surgery. As a result of advancing stent design, more patients with more complex disease are candidates for stenting, which reduces the number of surgeries.
Coronary artery stenting is almost always performed in conjunction with other catheter-based procedures, such as balloon angioplasty or atherectomy. These procedures are used to partially reduce the narrowing caused by atherosclerosis. In particular, stenting has been an important advance in balloon angioplasty. Before the introduction of stents, as many as half of all coronary arteries opened with a balloon-tipped catheter narrowed once again after the procedure (restenosis). With today's advanced stents, the restenosis rate has dropped to below 10 percent in some cases. In addition, stents have reduced the risk of sudden, or acute, closure of a coronary artery after angioplasty from 2 to 10 percent to less than 1 percent. Because of the stent's effectiveness, they are now used in the vast majority of balloon angioplasty cases and researchers are continually finding new applications for them.
By its nature, a stent is designed to be a permanent implant. In cases of complex or diffuse disease, multiple or even overlapping stents can be used. Until recently, most stents were made from bare metal. In 2003, however, a new generation of stents was introduced. These stents, called drug-eluting stents, are covered with special drugs that reduced the restenosis rate to its current low rate. Today, drug-eluting stents comprise the majority of stents in clinical use for coronary artery disease. However, new research has indicated that drug-eluting stents may raise the risk of blood clots in certain patients, especially those who discontinue their medications early.
Stents are not affected by metal detectors or most mBalloon angioplasty and stenting are procedures to increase blood flow through a narrowed artery.echanical equipment. The success of a stenting procedure can be compromised by risk factors such as smoking or high cholesterol levels, which could lead to new blockages in the coronary arteries. People receiving stents are strongly encouraged to learn and practice healthy lifestyle behaviors for good heart
About stenting
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.
A heart attack happens every 29 seconds and is usually due to coronary artery disease (CAD).
Atherectomy involves using a bladed device to cut or grind away hardened plaque in arteries.
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:
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Reduced chest pain, pressure or discomfort (angina)
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Less shortness of breath (dyspnea)
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Lower risk of heart attack after the procedure
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Less need for additional medical treatment with drugs
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Less pain from peripheral arterial disease (if stents were placed in a limb)
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Less risk of the artery re-closing (restenosis) compared to angioplasty
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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.
Before and during the stenting procedure
Before stenting, patients will discuss their medical history with their physician and disclose any medications being taken. Certain medications may need to be discontinued or reduced at some point prior to the procedure. Aspirin may be recommended in order to help reduce the chance of blood clots forming at the stent site. Because local anesthesia is used, patients will be asked to refrain from eating and drinking after midnight before the procedure (patients with diabetes should consult with their physician regarding food and insulin intake).
The stenting procedure takes place in a catheterization laboratory, which is usually cool and softly lit. To the patient, the “cath lab” may resemble an operating room with its many monitoring devices, video displays and x-ray cameras.
The patient will lie down on a table under an x-ray camera. He or she will be given a mild sedative and remain awake but relaxed for the duration of the procedure. Once the patient is comfortable, heart monitoring begins, an intravenous line (I.V.) is established and the area where the sheath is to be inserted may be shaved, is sterilely prepped, and is locally anesthetized. The majority of stent procedures are performed via the femoral artery in the groin. However, the brachial artery in the arm or the radial artery in the wrist can be utilized as well.
The injection of the local anesthesia may result in a brief period of minor discomfort. This is normal and should be no cause for concern. An anticoagulant is then administered through the I.V. to prevent blood clot formation within the artery during the procedure. In selected stent procedures, the use of additional anticoagulants (e.g., intravenous antiplatelet drugs) has been shown to lower complication rates dramatically and possibly reduce restenosis. Statin drugs may also be recommended before stenting.
When the coronary arteries are being treated, the guiding catheter is advanced through the sheath to the heart and positioned near the origin of the coronary artery. The physician will inject dye (contrast medium) through the catheter. The dye can be seen on a special x-ray (fluoroscope) and serves as a road map for the procedure.
Angioplasty with Collapsed Stent
The physician and other attending medical staff may ask the patient to perform tasks such as coughing, turning the head, taking a deep breath or not speaking for a while. Throughout the procedure, heart rate will be monitored.
A guide wire is then passed through the catheter into the coronary artery and to the narrowing of the coronary artery. In most cases, the physician then performs a balloon angioplasty.
The stent is next carried to the site on a balloon-tipped catheter. The balloon is inflated for several seconds to several minutes, expanding the stent, which adheres to the wall of the artery. The balloon catheter is removed while the stent remains permanently fixed to the artery. Approximately four to six weeks after the stent is inserted, it will become completely covered by a thin layer of arterial tissue. The length of time this takes depends on the type of stent that is used. For example, bare metal stents may take a few weeks while drug eluting stents appear to take several months, which is felt to be a possible cause of late thrombosis.
After the stenting procedure
Once the procedure is completed, the patient will be transferred to a cardiac recovery room. He or she may feel groggy from the sedative. The catheter insertion site may be bruised and sore.
If the groin area was used as the point of catheter insertion, the patient will be instructed to lie in bed with legs out straight. The physician may choose to use one of two techniques for removing the sheath that was placed at the initiation of the procedure. The traditional technique is to wait until the effects of the anticoagulant have passed (four to six hours) and then to apply pressure while removing the sheath from the femoral artery. Another technique allows the sheath to be removed immediately after the procedure through the use of hemostatic devices that seal or stitch the femoral artery.
If the wrist or arm was used as the point of catheter insertion, the patient does not need to stay in bed. Throughout the post-procedure monitoring, the point of catheter entrance will be checked for bleeding, swelling or inflammation. Vital signs will be continuously monitored during this observation period. Usually, the patient will stay overnight for further observation.
During the first day or two after stenting, patients should drink plenty of fluids to prevent dehydration and help flush from the body the dye that was used during the procedure. Patients are also advised to avoid driving, bathing or smoking during this time.
Patients are given instructions from the medical staff regarding:
* Exercise and exertion. Patients are reminded to refrain from lifting heavy objects and engaging in strenuous exercise or sexual activity for 24 hours after the procedure.
* Care of the incision area. Bruising and soreness is possible and normal. Undue pain, swelling or inflammation may require medical attention.
* The function and use of medications and procedures. Patients will be prescribed medications (e.g., aspirin) to prevent the formation of blood clots (thrombosis) in the stent. These medications will be taken for life. Also, for one year following the procedure, patients will be prescribed an additional antiplatelet (clopidogrel) medication to minimize the risk of blood clot formation within the stent. Because of newer data showing that thrombosis risk among patients who received a drug-eluting stent rises after stopping clopidogrel, it is extremely important that patients take their medications exactly as prescribed, for the entire duration of the prescription.
Other medications that may be prescribed include anticoagulants and beta blockers, which have been shown to lower mortality in patients who have had a heart attack. In addition, statins, which are commonly used to lower cholesterol, may be prescribed. Studies show that statins improve the outcome for virtually all medically treated patients with coronary artery disease. Finally, in the first eight weeks after the procedure, patients will need to take antibiotics before any dental, medical or surgical procedures. Having an MRI (magnetic resonance imaging) is typically discouraged for up to six months after stent insertion, because within this time the stent may be moved by the magnetic field.
Potential risks with stenting
Complications are minimal in the period immediately after the stenting procedure. There is, however, a small chance that stents will damage the vessel when implanted, sometimes causing a tear or dissection of the artery. However, statistics have shown that this generally does not affect long-term prognosis.
To prevent the formation of obstructing blood clots (subacute thrombosis), the physician will prescribe aspirin and other antiplatelet drugs (especially clopidogrel). Subacute thrombosis is a rare complication that occurs when platelets aggregate and form a blood clot within the stent, potentially causing closing of the stent and a heart attack. It can occur with both drug-eluting and bare metal stents. Studies have shown that the rate of this serious complication ranges from 0.5 percent to 3 percent, depending on the kind of stent used, the placement of the stent, the nature of the disease and the post-stent medical therapy. It may occur up to one year after the procedure. Thrombosis rates are roughly equal among bare metal and drug-eluting stents, providing that antiplatelet therapy is used for drug-eluting stents. If patients discontinue their antiplatelet therapy early, they raise the risk of suffering from thrombosis.
There is also a risk that the artery will re-narrow (restenose) within six months at the site of the stent implantation. The risk of restenosis, however, has been dramatically reduced as a result of the widespread use of drug-eluting stents, which are coated with special agents that improve the stent's incorporation into the wall of the artery. Currently, the restenosis rate for coronary arteries treated with drug-eluting stents is less than 10 percent. The risk of restenosis is increased in patients with diabetes and “high-risk” patients with acute coronary syndromes (e.g., heart attack).
Restenosis
If restenosis does occur, the physician may recommend repeat stenting. This decision is influenced by several factors, including the size of the coronary vessel. Research suggests that patients with large vessels (3 millimeters or greater) have a significantly lower rate of restenosis with repeat stenting, as compared to balloon angioplasty. For small vessels, research suggests balloon angioplasty is the preferred therapy. And still, depending on the degree of cardiac impairment, there are patients for whom coronary artery bypass surgery may be the preferred treatment to stenting.
Neglecting to alter controllable risk factors (e.g., smoking) can also affect the success rate of the stenting and any other catheter-based procedures (e.g., angioplasty).
Recent developments in stenting
Recent or future developments in coronary stenting include:
* Custom-designed stents for an optimal fit
* Stents designed for multiple sites within the same artery (including stents with side branches)
* Delivery of radiation directly to a stent that has restenosed (intravascular brachytherapy)
* Anticoagulant-coated stents to prevent the formation of a blood clot in the stent
* Use of cholesterol-reducing drugs (e.g., statins) after stenting to enhance overall survival
* Stenting as an alternative for different patient groups, such as individuals otherwise needing bypass surgery or those having prior heart surgeries
* Stents that are deployed without the patient first undergoing balloon angioplasty, which would reduce the time of the procedure and the amount of radiation exposure due to x-ray
Stent in Place
Researchers are also finding that coronary stenting, in addition to being an effective revascularization technique, has an ability to “seal” unstable plaque. Newer imaging techniques have allowed for plaque to be classified as homogeneous or heterogeneous. Homogeneous plaque is typically white, has a smooth surface and is basically the same texture throughout. Heterogeneous plaque is yellowish and has an irregular surface with areas of hemorrhage. Studies have found that heterogeneous plaque is the likely culprit in the risk of plaque rupture and subsequent heart attack or stroke.
Research suggests that stent placement may make plaque more stable and, therefore, less likely to rupture. Patients undergoing stenting following a heart attack typically have mostly yellow-colored plaque, with protruding blood clots. After stenting, the blood clots disappear. By six months, a new layer of cells formed over the stent, with the plaque now classified as white and smooth.
For people with diabetes, whose condition increases the risk of restenosis, rosiglitazone has shown benefit in stenting. Rosiglitazone is a type of thiazolidinedione (TZD), a newer class of drug used to decrease blood sugar levels in diabetes. Elevated blood sugar levels can cause a variety of health problems, including damage to the eyes, kidneys, nerves and blood vessels. Damage to the blood vessels contributes to the thickening of their walls, causes leakage, aids in the buildup of fatty materials in the blood and fosters excess plaque growth in the arteries. By helping to minimize this process, rosiglitazone may help to reduce restenosis. Other studies, however, find that TZDs may pose an increased risk of symptoms in individuals with heart failure or impaired kidney function.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to stenting:
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How long will I be in the hospital? Can I drive myself home after I'm discharged?
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How many stents will be placed? In which arteries? What degree of blockage do I have?
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Are you using a drug-eluting stent?
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Will you perform a balloon angioplasty first?
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Which medications will you prescribe after the procedure? How long will I be taking these medications?
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Does my insurance cover stenting?
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What lifestyle changes should I make after the procedure to lower my risk of heart attack or bypass surgery?
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How will I know if the artery begins to close again? How often should I visit the doctor's for check-ups?
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Are there are any medications, herbs or dietary supplements I should avoid because they'll interfere with my stent's function?
10.
If the artery begins to close again, what are my options?
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