Dr. Salloum is Cardiology Fellow, Division of Cardiovascular Medicine, and Dr. Campbell is Assistant Professor of Neurology, Division of Interventional Neurology, The University of Texas Medical School at Houston and The Memorial Hermann Heart Center, Houston, Texas.
Sometimes, the progress of a new medical technique is a little like the rise of a new boxing champion. It is not enough for a young challenger to be more exciting, more promising — even a little bit better — than the champ. Before a newcomer can be accepted, the reigning champion must be clearly and decisively defeated. In medicine, doctors tend to stick with a tried and true traditional procedure until an innovative new technique is conclusively shown to be superior. Such seems to be the case with the treatment of carotid artery disease.
Carotid artery disease typically begins with narrowing caused by the buildup of plaque inside the artery. The traditional way of dealing with the blockage is to perform a type of surgery called carotid artherectomy (also called carotid endarerectomy), which involves cutting out and repairing part of the artery. There is, however, a new less invasive technique called carotid stenting, in which a tube-shaped piece of material is inserted into a damaged artery to help it do its job of maintaining adequate blood flow. For many people, carotid stenting appears to be safer and more effective.The question today is whether stenting should replace carotid artherectomy as the standard treatment.
One of the body's largest blood vessels, the carotid artery carries blood from the heart to the head and brain. Like any artery, it is subject to internal plaque buildup that can cause atherosclerosis (narrowing), blockages and other types of damage, all of which can interrupt blood flow to the brain. This interruption can produce a TIA (Transient Ischemic Attack, a precursor to stroke), stroke or even death. TIAs most commonly occur in the middle-aged or elderly, appearing and disappearing suddenly, lasting anywhere from a minute to several hours. Symptoms include confusion, vertigo, and vision or speech problems but not loss of consciousness.
It is estimated that 25% of the 500,000 strokes that occur yearly in the United States are caused by atherosclerosis of the carotid artery. The current medical consensus is to treat this with carotid artherectomy surgery, combined with drugs.
In this Corner: "The Champion"
Carotid artherectomy is a very serious operation. It involves a surgical incision in the neck, opening up the carotid artery and "coring out" fatty plaque deposits, as well as, in many cases, a section of the artery itself. Before the operation, doctors measure the extent of the blockage by doing a test called an arteriography, in which a radioactive opaque dye is injected into the bloodsteam. This allows doctors to see how an area of narrowing or other damage is affecting blood flow through the carotid artery to the brain.
As with any surgery, carotid artherectomy carries a degree of risk which has to be weighed against its benefits. The benefits are clear - a successful operation will eliminate symptoms and reduce a person's risk of suffering a TIA or stroke. As for the risks, follow up studies on people who have undergone this operation have shown that the likelihood of suffering a serious health complication after surgery is about 2.6%. In other words, out of 100 people who have this surgery, between two and three persons will have a serious complication. This figure includes a death rate of 1.1%, a 0.9% chance of suffering from a disabling stroke after the operation; and a 4.5% chance of a non-disabling stroke.
The current medical consensus is that so long as the overall complication rate remains below 3%, carotid endartherectomy is beneficial for most patients who have at least a 60% narrowing of their carotid artery. One important point to keep in mind, however, is that these statistics are based on surgeries performed by particularly highly skilled surgeons on healthier than average patients. For both reasons, these statistics may underestimate the down side of carotid artherectomy for the average person.
And in this Corner: "The Challenger"
Carotid stenting is far less invasive. First, a guiding tube with a special guide wire is inserted into the artery via a small incision in the groin. The guiding tube and wire are advanced to the origin of the carotid artery leading to the brain. The wire is then maneuvered through the blocked region. An inflatable balloon is advanced over the wire into the blocked region of the artery and carefully inflated to open up the narrowed part of the artery. The balloon is then deflated and removed over the wire. A stent, which will be left in place, is then delivered over the same wire and allowed to expand, stretching open the previously blocked region. Finally, the wire is withdrawn. The stent is left in place to open up and strengthen the damaged section of the artery.
As for the risks of this kind of procedure, a recent study found that the overall mortality rate after stenting was 0.86%. Major strokes occurred in 1.49% of patients. The combined rates of death, major and minor stroke were 5.07%. Other studies have reported similar results.
The Blow By Blow
At first glance, the complication rates for carotid artery stenting may seem greater than for carotid artherectomy. However, a closer look at the data shows that the artherectomy studies used healthier subjects and that patients who were given carotid stents tended to be much sicker to begin with. The true complication rate for stenting may well be lower.
Restenosis, or re-narrowing of a damaged artery after it has been repaired, is not nearly as much of a problem with carotid arteries as it is with coronary arteries. Even so, the rate of restenosis after carotid stenting seems to be much lower than after artherectomy.
A much shorter hospital stay, on average only 1.86 days after the procedure, compared to several times that for artherectomy, is a clear advantage of carotid stenting.
Because stenting uses a smaller incision and eliminates the need for cutting through the neck, there is a much lower risk of infection and other wound complications than with artherectomy. Cranial nerve palsy, a form of brain damage that is one of the chief complications of artherectomy procedures, has not yet been reported after carotid stenting.
Because carotid stenting is so new, the technology it uses was originally designed to be used on different kinds of blood vessels elsewhere in the body. Catheters and stents that are specifically made for the carotid vessels, as well as other improvements that will inevitably follow greater experience in carotid stenting, will surely result in significantly fewer complications.
A Split Decision
For most people, the choice of carotid stenting versus artherectomy is a close call. Stenting is less invasive and, from many points of view, safer. Artherectomy has been a familiar and reliable procedure with a proven track record. Even though carotid stenting is in its infancy, however, there are many patients for whom it is clearly superior to artherectomy. One example would be people who have developed narrowing of the carotid artery after having had an artherectomy or other type of surgery. These kinds of surgery are difficult or dangerous to have done more than once.
Carotid artery stenting can also help patients whose arterial damage is so severe that surgery cannot be done. Until now, patients like these have been more or less at the mercy of their atherosclerotic plaque and its effects. There are, however, a minority of patients for whom stenting can be as risky or riskier than artherectomy.
Probably the best approach today is to offer carotid artery disease patients a choice. One person whose complex medical profile and severe disease makes them a poor candidate for artherectomy is probably better served by stenting. Another person, elderly but relatively healthy and suffering from severe carotid artery damage, might be better off undergoing traditional artherectomy surgery.
Right now, the answer to our original question — which procedure is is better? — must be that "it depends". Ongoing research studies, comparing carotid endartherectomy to carotid stenting, will soon give us a more definite answer. What we can say at this point is that it seems certain that stenting will play a growing role in the treatment of carotid disease.