Carotid Stenting: An Alternative to Surgery
Robert A. Hieb, MD
Froedtert & Medical College of Wisconsin Interventional Radiologist
Patients with carotid artery disease have traditionally undergone surgery to remove plaque and reduce their risk of stroke. In late 2004, the Food and Drug Administration approved a new procedure that offers an alternative to patients considered high-risk for carotid artery surgery. The procedure is carotid stenting, where a stent is placed in the patient’s carotid artery to push the plaque out of the way and restore blood flow. Robert A. Hieb, MD, describes the new procedure and its applications.
Q. What is a carotid stent?The carotid stent is very much like stents that we use in other parts of the vascular system. They are self-expanding metal alloy stents that expand to stabilize plaque and dilate an artery that has narrowed.
Q. What are the clinical applications for carotid stenting?The clinical application and rationale to do any type of carotid intervention, whether it’s a carotid stent or a carotid endarterectomy, is to reduce the patient’s risk of stroke.
According to American Heart Association data from 2004, there are about 700,000 strokes in America every year and about one-third of those can be attributed to carotid artery disease. There are basically two kinds of patients who would be candidates to have something done to their carotid arteries. Somebody who has had a neurological event — a stroke or a transient ischemic attack (TIA) or transient monocular blindness, for example — or someone, who on physical examination and then by other non-invasive testing, is shown to have a very high grade stenosis, which is a narrowing of the carotid artery. With stenosis there is narrowing or diameter reduction where the normal flow channel is smaller because of the build up of plaque (atherosclerosis).
There are two treatment options available today for treatment of carotid disease — carotid endarterectomy, an open surgical procedure, or carotid stenting, a minimally invasive endovascular procedure. In 2006, all of the information on carotid stenting is not in, so at this point, this is not a procedure that should replace carotid endarterectomy, which has been the gold standard for treating these patients. However, carotid stenting has been shown in many clinical trials to be basically equivalent to carotid endarterectomy in certain patients.
Q. How does carotid stenting work?In a carotid artery that has been narrowed by the process of atherosclerosis, a stent is positioned across the area of narrowing. The stent is then deployed and dilated into position. The plaque would be crushed and ultimately remodeled, and the artery would be opened to a more normal caliber. The plaque is pushed out of the way, and trapped out of the flow channel of blood by the scaffolding of the stent.
Q. How is a carotid stent placed? A carotid stent procedure is performed like most of our angiographic procedures. It’s done usually through a puncture in the femoral artery of the leg. We thread a special catheter and sheath up into the carotid artery, visualize the blockage as well as the vessels inside the brain. Then the area of the blockage itself in the carotid artery in the neck would be crossed with a special wire that has attached to it what we call an Embolic Protection Device, or an EPD. The EPD is then deployed to capture any debris which could potentially dislodge during the procedure. The stent is then deployed and dilated into position with an angioplasty balloon. Finally, the EPD is removed, the catheters and sheaths removed and the access site in the femoral artery is closed.
Q. How are carotid stents different than coronary stents?Carotid stents are different. Coronary stents tend to be much smaller in diameter, much shorter and much stiffer. They also tend to be made out of a different metal and are deployed in a different manner. Coronary stents and stents that we use in kidney arteries or bowel arteries, for example, tend to be what we call balloon-expandable stents. The stents that go in a carotid artery are what we call self-expanding stents. They tend to be more flexible and more forgiving to movement and to external compression.
Q. Is carotid stenting an alternative for surgery? In appropriate patients, carotid stenting is a very good alternative to surgery, and in some patients, it’s probably a better option than surgery. However, carotid stenting in 2006 should probably not replace carotid endarterectomy.
There are probably more clinical data on carotid endarterectomy than any other operation a surgeon may perform. It’s a very well-studied operation, which is one reason carotid stenting was only recently FDA approved. If a new procedure is offered that you expect to be equivalent to a well-studied operation, then obviously you have to really look very critically and very openly at this new technology.
Even with FDA approval of carotid stenting for symptomatic, high-risk patients, a further post-market study was mandated to evaluate carotid stenting done outside of clinical trials. We have been a part of this study, called the CAPTURE Study, here at Froedtert.
Q. Who is a candidate for carotid stenting? It is a select patient population. In general, patients who have significant carotid disease but who are high risk for surgery are patients who, in 2006, absolutely should have a carotid stent. It’s been shown that in those patients that it’s at least as good as carotid surgery.
There are two different ways to define being high risk for carotid endarterectomy. Surgical high risk can relate to previous carotid surgery, other neck surgery or radiation, nerve injury in the neck from previous surgery or blockage in the carotid artery on the other side. The location of the blockage can also pose problems for the surgeon. If it occurs higher up in the neck, it might be difficult to get to surgically.
Then there’s medical high risk. This may be related to unstable heart disease, pulmonary disease or other conditions that may make surgery higher risk.
I tell patients that if you’re a 60-year-old and otherwise perfectly healthy and you just have carotid disease, you need to have a good, skilled vascular surgeon fix your carotid artery. But, if you’re 75, you have a bad heart and you have had previous neck surgery, then absolutely, have a carotid stent procedure, no question about it.
Q. What are the risks? There is a definite risk of stroke attributed to the procedure itself. In general, the risks are probably equivalent or very close to the stroke risks associated with surgery. There’s no dramatic difference. Stroke is the downside of anything done for carotid disease. The end organ is the brain, and in trying to reduce someone’s risk of stroke, you could cause a stroke. There’s a definite risk of stroke from both carotid surgery and carotid stenting. This is also the reason why some patients should be managed medically, without surgery or stenting.
Q. What are the benefits?Carotid stenting is less invasive and requires less recovery time. It’s probably overall less strenuous to the body to undergo a carotid stenting procedure than to undergo a carotid surgery. Both carotid endarterectomy and carotid stenting have been shown to reduce subsequent stroke risk.
Q. What are the short- and long-term outcomes? We know that in appropriate patients, carotid stenting is at least as good as carotid surgery in terms of immediate and short-term outcomes. However, with long-term outcomes, the data are not conclusive. We know out to a year or two or three, but we certainly don’t know what happens in 10 or 15 or 20 years. They’ve been doing carotid surgery for 30 years, so they have a very good handle on what happens 10 or 20 years after carotid endarterectomy. We don’t know that about carotid stenting.
Part of the issue is that these carotid stents and EPDs are in constant, rapid evolution. A year from now there might be a stent that is better than the stent I might be putting in somebody’s carotid tomorrow. The stents that are available to put in a carotid artery today are all basically the same. They’re all flexible, self expanding stents. On the other hand, some have what we call a closed-cell design and some have an open-cell design. There may be some instances where a closed-cell design might be preferable to an open-cell design and vice versa. We don’t know all of that yet. Even for physicians, this is a very difficult topic because of the rapid pace of technological evolution.
Q. Is it better to remove the plaque through surgery or push it out of the way and trap it through stenting?That’s part of the debate of what may still need to be learned. But I think that, in general, any method to exclude the plaque from the flow channel of the artery, whether it’s removed with the carotid endarterectomy or trapped and compressed and held out of the flow channel by the scaffolding of the stent, is good. Those are both effective ways of reducing the risk of stroke.
Q. What is interventional radiology?In general, interventional radiology is a sub-specialty of radiology that deals with the evaluation of and minimally invasive treatment for various disease states, for example, carotid disease.
An interventional radiologist is a physician who is trained to see, evaluate, consult, recommend and also perform therapy for those patients. It’s comparable to a cardiologist who performs stent procedures, but not open-heart surgery for the heart.
Source: Every Day, Interview with Robert A. Hieb, MD
Date: May - July 2006