Endovascular Stent Surgery Health Article

Definition

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.

Purpose

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.

Demographics

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.

Description

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 is a circulatory disorder resulting from plaque blockages in the arteries of the heart. The heart is a muscle that requires a constant flow of blood and oxygen through its blood vessels so that it can perform the critical function of supplying the whole body with blood. When fatty deposits form in the heart's two main arteries, the arteries become narrowed and the flow of blood and oxygen is blocked. Blockages can cause pain in the chest (angina) and eventually, when the blood vessels are occluded (closed up), a heart attack.
• The carotid arteries in the neck carry blood and oxygen to the brain. When these major arteries are blocked by plaque, the narrowing can interrupt the flow of blood to the brain and cause a disabling stroke. A carotid endarterectomy is a surgical procedure performed on people with significant stenosis (50 to 70% narrowing); in this procedure, a surgeon removes the fatty deposits to correct the narrowing and allow blood and oxygen to flow freely to the brain. Although an effective surgical measure, it is a surgery that presents high risks to patients who are already greatly compromised. Endovascular stent surgery is a less invasive procedure, with fewer risks, and is sometimes the surgeon's choice to prevent stroke in certain high-risk patients.
• An aortic aneurysm, which is a life-threatening bulging of the aorta, can occur anywhere along this major artery, either in the abdomen (abdominal aortic aneurysm or AAA) or in the chest area (thoracic aneurysm). When the aorta is blocked by significant amounts of plaque, pressure may cause it to bulge like a balloon directly above or below the blockage, causing a weakening of the vessel wall. The aorta may eventually rupture, causing massive bleeding and death. Sometimes the aneurysm is diagnosed when the victim complains of pain; but there may also be no obvious symptoms. Sometimes the vessel ruptures, causing massive internal bleeding and eventual loss of consciousness, requiring emergency surgery. Endovascular stent surgery is the least invasive method of surgical intervention to repair an 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.