Stroke: Evaluating Risk
Guest: Dr. Jay Robison - Surgery
Host: Dr. Linda Austin – Psychiatry
Dr. Linda Austin: I am Dr. Linda Austin. I am interviewing Dr. Jay Robison who is Professor of Surgery and a vascular surgeon here at the Medical University of South Carolina. Dr. Robison, let’s talk about carotid artery disease. I know that is an area where there is some controversy about what the best treatment is. First of all, tell us what is at the heart of carotid artery disease. What is going on when a person has problems there?
Dr. Jay Robison: We worry about carotid disease because of its potential for stroke. Stroke is a devastating thing to happen to anybody. What we are interested in doing is preventing stroke. We think that carotid artery disease can contribute to stroke in about one third of the cases of stroke. So, the idea is to try to identify those patients that have a predisposition to stroke and to intervene before they actually have a problem.
Dr. Linda Austin: How does carotid disease cause stroke?
Dr. Jay Robison: We believe that there are two contributing factors to stroke in carotid disease. One of them is, as plaque builds up in the carotid artery, usually right in the mid portion of the neck, the carotid artery delivers blood to the brain, but as plaque builds up, it can actually restrict the flow of blood to the brain. The other contributing factor is that as this plaque builds up, little bits and pieces of it can either break off, I consider it similar to having rust in your pipes, and little flecks of that atherosclerotic plaque can break off and go up to the brain and cause either a mini stroke or a TIA, transient ischemic attack, or a flow blown stroke that causes a permanent neurologic deficit.
Dr. Linda Austin: Are these TIAs, the transient ischemic attacks, we will have to talk about just exactly what that is, kind of a warning bell that a person might be at risk for a stroke?
Dr. Jay Robison: Absolutely. It is usually manifest by either a problem with speech or loss of vision in one eye, or loss of function or numbness of one arm or leg. They are usually very brief. They can completely resolve within just a few minutes. Sometimes patients will actually discount them as being insignificant symptoms. But, they are significant warning signs of stroke. One out of every three people that has a TIA will suffer a very severe stroke over a period of years.
Dr. Linda Austin: So, let’s imagine a patient comes to you and they have had a TIA, one of these little, very brief, episodes, how do you, as a vascular surgeon, begin to evaluate that and figure out what your next step will be?
Dr. Jay Robison: Since carotid disease is one of the more common causes, that is the first thing that we look it. We are able to do that with an ultrasound of the neck and determine whether there is a significant narrowing there at the branch point of the carotid artery. If it is significant, that is, if it is more than about a 70 percent blockage in that artery, we attribute most of those symptoms to that carotid artery. If it is less than a 70 percent blockage, then we go and look for other potential causes, that is, anywhere from the heart to the heart valves, all the way up into the brain itself, in the arteries inside the brain.
Dr. Linda Austin: Now, let’s imagine the person does have a significant blockage and they do have symptoms, what do you do?
Dr. Jay Robison: Well, there are really three options. One of them is medical treatment with either aspirin or some of the new powerful blood thinning agents, like plavix or coumadin. The second treatment is the standard treatment we have used for significant blockages in the carotid artery for many years, and that is surgery, carotid arterectomy. That is done usually under an anesthetic in the operating room with a three to four inch incision in the neck where the artery is actually opened up and cleaned out, and then frequently patched open, and the patient is usually discharged the next day after surgery. It is very successful and very good at preventing subsequent stroke.
The third, more recent, treatment that is available to these patients is what we call carotid stenting and angioplasty, which is very similar to the technique that is used in the heart to insert a small wire, or end catheter, into the artery, in this case, the carotid artery, and then a balloon and a stent is put into the artery to kind of open it up and to restore blood flow into the brain. Importantly, in the last few years, advanced technology has allowed us to put little filter devices up beyond the level of the area that is narrow to catch any little particles that might break off and go to the brain during the procedure. So, it has made the procedure much safer than it has been in the past.
Dr. Linda Austin: What about the person who has significant narrowing of the artery but they do not have any symptoms? Do they need to be treated?
Dr. Jay Robison: That is a point of real controversy. In the past, we believed that a large number of those patients, if they have a very significant restriction in their blood flow, they are at higher risk for having a stroke. However, it is not 100 percent of people with, say, 70 to 75 percent narrowing are going to have a stroke. Only a small percentage of them will have a stroke over a period of time. So, there is a lot of controversy about whether to intervene for those patients that do have an asymptomatic stenosis. There is some pretty good evidence that accumulated from some randomized prospective trials, about 10 years ago now, that suggested at least carotid endarectomy is effective in reducing the chance of having a stroke by as much as three times. But, you have to keep in mind that if only one out of eight patients was at risk for having a stroke over a long period of time, say, three to five years, it takes about 15 operations to prevent one stroke.
Dr. Linda Austin: In other words, you have to do 15 different people?
Dr. Jay Robison: Fifteen different people.
Dr. Linda Austin: For there to be one of those people, statistically, who would have had a stroke?
Dr. Jay Robison: Absolutely. That is exactly right. So, the number of patients needed to treat with surgery is 15 to prevent one stroke. Now, it turns out that we cannot predict which one of those 15 people would be at high risk for having a stroke, so we have to take all those folks on. It turns out that it is very cost effective treatment because stroke is such a devastating complication to have. That is one thing that many of our patients really fear having, a stroke, where they are really truly debilitated or cannot function and cannot speak, or cannot understand what people are telling them.
Dr. Linda Austin: Going back to the device that you described that was like a little filter that would keep little particles, little bits and pieces of plaque, from going up to the brain, does that clog up over time, like a drain?
Dr. Jay Robison: Well, the filter device is actually only put in temporarily, during the procedure, and it is put in over a very fine wire that is snaked through the little narrowing, and then it kind of opens up like an umbrella and captures any particulate matter that might be dislodged during the procedure itself. Once the procedure is over and flow is restored, then the umbrella is collapsed and all that particulate matter is captured and brought out from the patient.
Dr. Linda Austin: That is so clever.
Dr. Jay Robison: I wish I had thought of it. Actually, there is another way to prevent that particulate matter from going to the brain during one of these procedures. That has to do with reversing the flow from the brain so that all that material washes out through a filter. There are some studies that we are actually doing at the medical university now involving reversal of flow to prevent that particulate matter from going to the brain during the performance of this procedure. So, it is an interesting alternative to the filter concept to prevent little particulate matter from going to the brain and causing a stroke or a TIA during the performance of a carotid stent or angioplasty.
During surgery, on the other hand, we take a lot of care to protect that artery as well by temporarily clamping that artery to prevent dislodgement of that matter. Then, subsequently, we can even bypass the artery that we are working on with a temporary shunt, or external device, to maintain blood flow to the brain while we are working on the artery in question.
Dr. Linda Austin: It is a complex thing to talk about because the anatomy is complex. I do not know if it can be adequately described. But, as you were talking, Jay, I had this image of the vessels that go into the Circle of Willis, which is kind of like a rotary, like a traffic rotary, that has a number of roads going into it so you can block off, temporarily, one of those roads and still have others going in and then the circulation coming out from the Circle of Willis to feed the brain. Am I right in thinking that is kind of what makes that possible?
Dr. Jay Robison: That is a great analogy. It would work great if everybody had an intact Circle of Willis, or intact rotary. But, sometimes there are little blocks in the road that prevent that Circle of Willis from providing all areas of the brain with blood flow when you temporarily interrupt one of them. It is very hard to predict who is going to have an intact Circle of Willis to maintain all that blood flow during the time of the procedure. There are ways that we try to assess that during surgery. Everybody has a different way of doing it. Different surgeons have evolved different techniques that work for them. In our case, at the medical university, we routinely employ EEG monitoring, monitor the brain waves during the procedure so that when we temporarily interrupt the blood supply, we can monitor how much brain function there is during the procedure. And, if there is any question, and frequently even if there is no change in the EEG, we will insert a temporary shunt to maintain blood flow just in case there is some undetected blockage in the Circle of Willis, just to maintain blood flow to the brain.
Dr. Linda Austin: Fascinating. Thanks so much for talking with is today.
Dr. Jay Robison: Absolutely. I enjoyed it.
If you have any questions about the services or programs offered at the Medical University of South Carolina or if you would like to schedule an appointment with one of our physicians, please call MUSC Health Connection: (843) 792-1414.