Endovascular stent surgery is a minimally invasive surgical procedure that uses advanced technology and instrumentation to treat such disorders of the circulatory system as blockage or damage to blood vessels caused by the build up of plaque (fatty deposits, calcium deposits, and scar tissue) in the arteries, a condition called atherosclerosis (hardening of the arteries). The surgeon may recommend the placement of an endovascular stent, a small wire-mesh tube that surgeons call a scaffold, in an affected artery. The procedure may be done in conjunction with cleaning or repairing the artery. The twofold procedure opens, enlarges, and supports artery walls for a long-lasting improvement in blood flow and a decrease in the risk of heart attack or stroke. In endovascular stent surgery ( endo , within, and vascular , blood vessel), all of the work done by the surgeon is within the blood vessels themselves. Nearly all of the medium-sized and large blood vessels in the body's vascular system can be accessed from within the vessels. This fact has contributed to a rapid increase in the performance of endovascular stent surgery.
The purpose of endovascular stent surgery is to improve or restore the flow of blood and oxygen throughout the body, a process called coronary revascularization. Endovascular stent surgery is used most often to correct the narrowing in medium-sized and large arteries blocked by plaque. Stents have been used in coronary arteries, the carotid arteries in the neck, and renal (kidney) or biliary (gall bladder) arteries. They are rarely used for smaller arteries in the legs, for example, or other smaller vessels in the body.
Endovascular stenting is also the newest treatment for such emergency vascular events, as abdominal or thoracic (related to chest and lung area) aortic aneurysms. Aortic aneurysms are life-threatening bulges in the walls of the aorta, the largest artery in the body, usually the result of progressive atherosclerosis.
Candidates for endovascular stent surgery are patients with atheroslerosis who are at high risk for heart attack and stroke. Heart disease and stroke are the leading causes of death and disability in the United States for both men and women. People at greatest risk have high blood pressure and high cholesterol, and sometimes diabetes. Typically these people may also smoke, be overweight, and have close relatives with heart disease or coronary artery disease or who have had a stroke. More than 700,000 people per year have stent surgeries to clear obstructions in the coronary arteries. Abdominal aortic aneurysms are the 13th leading cause of death in the United States, occurring primarily in people over age 67. More than 190,000 aortic aneurysms are diagnosed each year; of these, 45,000 people have surgery. Although the use of stent grafting is increasing, most aneurysms are treated with conventional open surgery procedures.
The conditions most often treated by endovascular stent surgery are: coronary artery disease; narrowing (stenosis) of the carotid artery in the neck, a risk factor for stroke; and aortic aneurysm.
Coronary artery disease and carotid stenosis can be treated in three ways: medically, which is the use of therapeutic drugs in combination with changes in diet and exercise ; by such open surgery as the highly invasive coronary artery bypass surgery (CABG); or by such minimally invasive procedures as stent implantation, balloon angioplasty , and atherectomy or endarterectomy (the cutting of plaque from the inside of vessel walls). Sometimes combinations of these methods are used. The goal of all these procedures is to improve the flow of blood and oxygen throughout the body, reduce symptoms, and reduce the risk of heart attack or stroke.
Endovascular stent surgery was introduced in the 1980s to treat occlusive (blocking) coronary artery disease, without using open surgery. More recently, endovascular stent grafting, a variation of the procedure, is also being used to repair life-threatening aortic aneurysms, which formerly could be treated only with open surgery. Because the incision for endovascular procedures is just large enough to allow passage of a small tube (catheter) into a blood vessel, the procedure does not disturb the patient's body processes as much as conventional vascular surgery . This advance in technique helps reduce the patient's stay in the hospital and makes recovery faster. At the same time, it satisfies a common goal of surgeons to use less invasive methods that offer patients the best result with the fewest risks.
An endovascular stent is a tiny wire mesh tube that can look like a cage or a coiled spring, depending on the manufacturer's design. The implantation of stents is performed through a tiny incision, using a catheter to deliver it to the site of treatment in a vessel. The stent provides a mechanical way to hold a blood vessel open and improve blood flow over the long term. Stents are sometimes implanted through the same incision after balloon angioplasty has been performed. Balloon angioplasty is another catheter-guided procedure that uses a balloon device to stretch the waxy plaque formation and open the vessel walls. Before stents were used, some patients undergoing angioplasty (in 5–10% of angioplasty procedures) suffered acute closure, which is the complete closing down of the treated artery either during or after the procedure. Stents reduce the likelihood of this medical emergency and the need for immediate cardiac surgery to correct it. Stents are implanted both to treat new blockages and to treat the repeat build-up of plaque after prior surgical treatment, a process called restenosis. Endovascular stent implantation has been shown to reduce the likelihood of restenosis. Some stents can deliver anti-plaque drugs to the area of blockage. These are called drug-eluting stents; they are aimed at preventing restenosis and eliminating the need for further surgeries.
Endovascular stent surgery is performed in a cardiac catheterization laboratory equipped with a fluoroscope, a special x-ray machine and an x-ray monitor that looks like a regular television screen. The patient will be placed on an x-ray table and covered with a sterile sheet. An area on the inside of the upper leg will be washed and treated with an antibacterial solution to prepare for the insertion of a catheter. The patient is given local anesthesia to numb the insertion site and will usually remain awake during the procedure. To implant stents in arteries, the stent is threaded through an incision in the groin up into the affected blood vessel on a catheter with a deflated balloon at its tip and inside the stent. The surgeon views the entire procedure with a fluoroscope. The surgeon guides the balloon catheter to the blocked area and inflates the balloon, causing the stent to expand and press against the vessel walls. The balloon is then deflated and taken out of the vessel. The entire procedure takes from an hour to 90 minutes to complete. The stent remains in the vessel permanently to hold the vessel walls open and allow blood to pass freely as in a normally functioning healthy artery. Cells and tissue will begin to grow over the stent until its inner surface is covered. It then becomes a permanent part of the functioning artery.
Stent surgery for emergency treatment of aortic aneurysm is called endovascular stent grafting or endovascular repair. Candidates for this treatment have either aortic aneurysms or other abnormal conditions of the aorta, such as an arteriovenous fistula (abnormal communication between an artery and a vein) or other kinds of aortic blockage. Formerly these conditions were treated by highly invasive surgical procedures, with incisions that reached from the breastbone to the navel, to access the aorta, open it, and insert and attach a slender fabric-covered tube called a graft. During the less invasive endovascular stent surgery, a collapsed metal stent-graft (also called an endograft) is threaded through an artery beginning from a small incision in the groin and ending in the aorta. Threading is done through a tube-like delivery system lying in the vessel, which allows catheters and stents to move up and down during the procedure. A stent graft is similar to the stents used in coronary artery procedures, but has a ring of tiny hooks and barbs at each end that allow it to connect to the inner wall of the artery, replacing and repairing (grafting) the weakened area. The surgeon guides the stentgraft into the aneurysm by using fluoroscopic x-ray imaging. When the stent graft is in place, its outer sheath is withdrawn and the stent graft is expanded. It will anchor itself to the inside of the artery wall with the hooks and barbs on each end. Some stent-graft systems also use balloons to push the hooks into the vessel wall. Because the procedure is minimally invasive, patients recover quickly and are usually able to eat the same day, walk on the second day, and go home in two to three days after the surgery.
Often the first test done to diagnose coronary artery disease is an electrocardiogram, to show the heart's rhythm. A stress test , or exercise electrocardiogram, may be performed as well, though this test can be too strenuous for some patients. Cardiac catheterization is considered the most definitive test. It requires the injection of a special dye into the coronary arteries at the same time that a catheter is threaded up into the heart's arteries and x rays are displayed on a monitor to show any narrowing or blockage. To diagnose clogged arteries in other areas of the body, such imaging techniques, as computed tomography (CT) or magnetic resonance imaging (MRI) may be used to visualize the presence and extent of narrowing in the blood vessels. Diagnostic procedures for aneurysm may include these same imaging tests; but often, because of the emergency nature of aneurysm, there is little time to conduct extensive testing beyond immediate confirmation of the presence of the aneurysm.
For up to twelve hours before a stent procedure or combined angioplasty and stent surgery, the patient will have to avoid eating or drinking. An intravenous line will be inserted so that medications (anticoagulants to prevent clot formation and radioactive dye for x rays) can be administered during the surgery. The patient's groin area will be shaved and cleaned with an antiseptic to prepare for the incision. About an hour before the procedure, the patient may be given a mild sedative to ensure that he or she will relax sufficiently for the procedure.
After stent surgery, the patient will spend several hours in the recovery room to be monitored for vital signs (temperature, heart rate, and breathing) and heart sounds. Pressure will be applied to the catheter insertion site in the groin to prevent bleeding; a weight may be applied to the leg to restrict movement. For the first 24 hours, the patient will have to lie flat and limit activities. Drinking fluids will be especially important to help flush out the dye that was used for x rays during the procedure. Stent recipients are usually placed on aspirin therapy or anti-clotting (anticoagulant) medication immediately after surgery. They will remain on it indefinitely to prevent clots from occurring in the stent. There are no other postoperative precautions, although dietary and lifestyle changes may be recommended to reduce such risk factors as high cholesterol and smoking that could lead to new blockages from ongoing buildup of plaque in the body's blood vessels. Patients are advised not to have magnetic resonance imaging (MRI) procedures after the surgery because of the effect of magnetism on the metal stents. Stents are not affected by metal detectors.
The greatest risk with stent implantation is the formation of clots within the stent. Aspirin and oral anti-clotting medications are usually given after stent placement to minimize this risk, which has been reported to occur in about 1–1.5% of patients undergoing endovascular stent surgeries. There has been no evidence of long-term complications from stent implantation, according to the American Heart Association.
A variety of complications can occur with stent grafting for emergency aneurysm repair. Movement of the stent within the vessel can occur in up to 10% of cases, requiring repeat surgery. Clots can occur in the vessel and migrate to other areas of the body, causing heart attack or stroke. About 2% of patients will require an additional open surgical procedure to correct the aneurysm or complications that occur after emergency endovascular repair.
People undergoing endovascular stent surgeries usually recover within a week or so, compared to months of recovery from conventional open surgery. They can quickly resume normal activities with a reduction of symptoms and little chance of repeat stenosis, depending upon their general health. The American Heart Association reports that 70–90% of procedures for coronary artery disease are endovascular stenting procedures. Stents have been shown to reduce the risk of restenosis after angioplasty or other catheter-based procedures have been performed.
Deaths have not been reported either during or immediately following endovascular stent surgeries that are linked to the surgical procedure. Stent procedures have been shown to increase survival (by reducing restenosis) among people with coronary artery disease.
The mortality rate for surgically treated abdominal aortic aneurysm is about 5% and increases to 50% for aneurysms that rupture. Thoracic aneurysms also have a mortality rate of about 5%, rising to 67% if ruptured. Stent grafting has been shown overall to have lower rates of morbidity and mortality than conventional open procedures.
Preventive measures are the same to prevent heart attack and stroke. Any adult can reduce the likelihood of plaque formation by making such dietary and lifestyle changes, as:
Stent implantation helps to clear blocked arteries and keep them open mechanically. There are no mechanical alternatives however, to reduce plaque formation. Nutritional supplements and alternative therapies that have been recommended to help reduce risks and promote good vascular health include:
Heart and Stroke Facts, and Stent Procedure. American Heart Association, 2002.
American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org .
"Angioplasty and Coronary Stent Implantation." Health Topics. Atlanta Health Pages [cited May 5, 2003]. http://www.healthpages.org/AHP/LIBRARY/HLTHTOP/index.htm .
Bellozo, J. "Endovascular Stent-Grafting Alternative to Traditional Abdominal Surgery." Scripps Health. Scripps Research Institute. August 12, 2002. [May 5, 2003]. http://www.scripps.org .
"Performing Endovascular Surgery:New Minimally Invasive Approach to Treating Vascular Disease." Patient Care. Department of Surgery, State University of New York, Stony Brook [cited May 5, 2003]. http://galactica.informatics.sunysb.edu/surgery/endovasc-1.html .
L. Lee Culvert
Endovascular stent surgery is performed by a vascular surgeon in a hospital or medical center cardiac catheterization laboratory.