Carotid Artery Stenting

Where is the carotid artery, and what does it look like?

The carotid artery is in the neck.  There are usually two carotid arteries, one on each side of the neck (so called left carotid artery and right carotid artery). The carotid arteries start deep at the base of the neck, within the chest.  They pass up through the neck, close to the front, and at about the level of the angle of the lower jaw divide, one branch supplying the tissues of the face and scalp, the other heading towards the base of the brain.  The brain is supplied with blood from the two carotid arteries, along with two other arteries (the vertebral arteries), joining together to ensure the brain receives the blood that it needs. ( http://wikipedia.org/wiki/Common_carotid_artery )

Why does the carotid artery need treatment?

Carotid artery disease causes strokes and carotid artery treatment is intended to reduce the risk of strokes in the future. If a person has already had a stroke, treating the carotid artery will not improve the stroke that has already occurred.

Stroke is a major cause of disability and death in the modern world. Strokes may be caused by either bleeding into the brain or by a part of the brain losing its blood supply and dying. Lose of the supply of blood may be caused a blood clot lodging in an artery.  A proportion of strokes are caused in this manner, and a source of the blood clots may be the carotid artery (although there are other sources). If the carotid artery develops a narrow area (usually secondary to a disease process called atherosclerosis or “hardening of the arteries”) as blood flows through this narrow area, the blood forms swirls and some bits may clot. This tendency is made worse by the disease in the artery wall tending to make the blood clot.  The blood continuing to flow past these areas causes these clots to be carried to the brain, where they cause blockage of an artery, and the loss of blood to the area of the brain supplied by the artery. This may lead to permanent loss of brain function (this area dies). Sometimes the clot breaks up over time, and the brain regains the function from this region.  In this way transient (short lived) symptoms occur, and complete recovery may occur (this is called a TIA- Transient Ischaemic Attack). The greater the narrowing in the carotid artery, the more likely it is that this will cause clot, both now and in the future. For this reason, if symptoms occur, in the area of the brain supplied by the narrow carotid artery, a doctor may recommend that this be treated. Sometimes the narrowing in the carotid may be very severe, but still not cause symptoms.  In such circumstances, despite the fact that the narrow area has not caused problems, a doctor may advise that this be treated to try to prevent strokes. On the other hand, some blood clots can form in carotid arteries where the degree of narrowing is relatively slight. In this situation, treatment with drugs is usually recommended.

What options are available for carotid artery treatment?

Treatment for the carotid artery falls into three broad categories:

1. “Best Medical Therapy” – The vast majority of people with carotid artery disease will be offered this treatment, and includes:

1. Antiplatelet medication. The blood contains cells called platelets. These are responsible for helping the body to form blood clots, to stop bleeding.  This is usually a very useful function.  However, people with diseases of their arteries sometime form harmful clots in the regions of the disease. Antiplatelet medications are designed to interfere with the platelets ability to form these harmful clots. One side effect of this is that the patient will often notice that if they do cut themselves (such as when shaving), then they will tend to bleed more than they did before they started taking these medications. Fortunately this bleeding is rarely more than an inconvenience. Patients will similarly notice that they tend to bruise more easily.  These are rarely more significant than an irritation, and these side effects have to be weighed against the benefit of a significant reduction in the risk of further strokes or heart attacks. Examples of these medicines are aspirin, Clopidogrel (Plavix) and Dipyridamole (Persantin)
2. “Statins” (so called as their names tend to end in “statin”). These are drugs whose actions are to reduce the amount of cholesterol in the blood.  They are designed to work in conjunction with the adoption of a healthy diet (lots of fruit and vegetables, avoidance of red meat etc). There are a variety of types of these drugs available, some work well for some people whilst others work better for others.  It is often a matter of trying different preparations (with the help of the General Practitioner) to find the one which suits an individual the best.  They do have some side effects, including some muscle fatigue and liver biochemical changes, but usually one can be found that suits. It is generally held that people who have vascular disease will benefit from taking a “statin” both for cholesterol lowering, but also because they tend to make the disease in the arteries less likely to cause clots to form.
3. Blood pressure control treatment. High blood pressure is closely linked to problems with artery disease and stroke.  Many General Practices offer blood pressure clinics, and many people who have carotid artery disease will already be taking blood pressure control treatments. Those who are not taking treatment, who are found to have disease in their carotid arteries, will have their blood pressure checked and medication offered to keep this at a reasonable level. If the blood pressure is normal, there will be no need for treatment.

2. Carotid Endarterectomy (CEA). When the level of disease in the carotid artery, where it divides into two, is sufficiently severe (usually around half or more of the artery filled with disease), an operation may be offered to remove this disease.  This is more likely to be offered if the disease has caused problems such as TIA. With the patient either asleep (general anaesthetic) or numbed (local anaesthetic), an incision (surgical cut) is made in the neck, the artery opened (having made sure that excessive bleeding will not occur), and the diseased area removed.  The artery is then repaired, and the incision stitched up. More information on this can be obtained from the Vascular Society website ( http://www.circulationfoundation.org.uk/vascular_disease/carotid_endarterectomy ).

3.Carotid Artery Stenting (CAS). Rather than remove the material in the carotid artery, as is done with CEA, the other alternative is to place a metal stent (please see the section on stents) inside the artery, in order that the material be pushed out of the way, resulting in a larger channel for blood and one that is less likely to cause clots to form. A number of stents are made specifically for the carotid artery which may be used as an alternative to CEA. In addition stenting treatment may be used in other areas of the carotid artery, right from the lowest part deep inside the chest, right the way up to the base of the brain. These are areas which are very difficult and hazardous to reach using traditional surgical techniques ( http://wikipedia.org/wiki/Carotid_stenting ).

When is carotid artery stenting an option?

Carotid artery stenting is often looked upon as an alternative to carotid endarterectomy (the more traditional surgical option).  This is indeed the case in some circumstances when surgery is at a higher than normal risk of complications. Such times include:

When previous surgery has been performed, either for the same problem (which has recurred) or other neck surgery.

When surgery on the other side has resulted in nerve damage, which would be problematic should that be repeated on the side in question.

When the carotid artery branches high in the neck, which makes it difficult to reach surgically.

When the patient has had radiotherapy (X-ray treatment) to the neck in the past.

Other diseases, like problematic heart disease or patients who need heart surgery.

There are a number of studies that have been undertaken comparing open surgery and stenting when both could reasonably be expected to be relatively straight forward.  These studies have shown that both procedures are effective at preventing stroke over the longer term, and they seem to be approximately equivalent at stroke prevention. In the short term (within the first month of the procedures), the number of major strokes and deaths is similar in both treatment types.  However, there does seem to be differences in the less severe problems as a result of these procedures.  For stenting there appears to be a greater incidence of minor strokes (strokes which either recover over a period of time or leave patients with less severe disability). On the other hand an open operation in the neck can cause nerve damage in the neck (which may cause voice changes, numbness in the neck and tongue or pain associated with the incision) or bleeding in the neck. Neither of these occur when a person has a stent placed.  In addition, open operations cause more stress to the person’s heart, and heart attacks are more common with open surgery than they are with stenting.

As a result there are times when there is little to choose between the two procedures, and at times patients may express a preference for one or the other (on the basis of the risks outlined above).  It should be remembered that both procedures are best performed (in terms of outcomes) in hospitals where they are regularly performing these procedures.  There are relatively few hospitals in the UK where carotid artery stenting is being performed regularly, however a person may wish to ask for their problem to be considered at one of those hospitals.

Carotid artery stenting is not always possible, or else carries a higher risk of complications and problems.  This is usually related to the way their arteries are arranged. If there are blockages to the arteries to the legs, then performing the procedure may be difficult, and if the arteries in the chest and neck a very curly then getting the stent into place is made problematic.  In such circumstances stenting may be impossible or run higher risks of complications.

All of the above details apply to a person who has narrow areas where the carotid artery divides into two.  This is the most common place for disease to occur, however, it is possible for the carotid artery to develop disease anywhere else from it’s start in the chest, all the way up to the base of the brain. If this happens, open surgery can be very difficult, or even impossible.  On the other hand carotid artery stenting may be much less risky to do, and is usually preferable.

As a result of the issues discussed above, a patient with a narrowing in the carotid artery that has caused problems, or sometimes discovered during other investigations, may get benefit from treatment.  Sometimes a stenting procedure is preferable, at others an open operation is a better option. There a number of circumstances where either option could be considered, with each option carrying different problems, each of which might be preferable.  The decisions as to the relative benefits can be difficult, and should be made by a team including the patient, Radiologists, Surgeons and Stroke Prevention Physicians.

How is carotid artery stenting done?

Carotid artery stenting is usually performed by Interventional Radiologists.  In some countries Vascular Surgeons, Cardiologists or Neurologists also perform this procedure.  In the UK, at present, it is Interventional Radiologists who undergo the training for such procedures.

Carotid artery stenting (CAS) is usually performed under local anaesthetic, which is placed in the groin. CAS can be done by putting local anaesthetic in the arm, but this way is more difficult, and is generally only used if the arteries to the legs are blocked. A small needle is put into the artery at the groin, and a small wire (called a guidewire) passed into the artery. A small (approximately 2 mm diameter) tube is passed over the guidewire and the remainder of the procedure is done through this tube (the local anaesthetic allows all this to be done with only the sensation of pressure). Using specially shaped small tubes and wires, and guided by x-ray pictures, the tubes are passed up through the main artery in the tummy and chest until the carotid artery is entered. Once this has been successfully done, the tube in the groin is introduced further. A tiny wire is passed to cross the narrow area (this is usually directed and controlled by x-ray images) which is used to guide placement of the stent. Often a balloon is used both to make way for the stent, and after it has been placed to seat the stent onto the proper position. Once the stent has been successfully placed, the wires are removed, the tube taken out and the hole in the artery at the groin closed. This closure can either be done by the doctor/nurse pressing on the groin for 5-10 minutes or by the use of a special device for this purpose (which removes the need for pressure and allows for faster mobility).

What is special about stents used for the carotid artery?

There are a number of stents that have been specially designed to be placed in the carotid artery. These have been designed specifically for the needs of this artery at the place where the artery divides. If disease should occur lower down in the carotid artery, then stents often used in other areas are suitable.

The specific stents made for the carotid artery are all “self expanding”.  What this means is that they are made of metal, which springs open to a predefined size. The stents are pressed down onto their delivery system            , where they are kept very thin to allow them to be passed to where they are needed.  They are then released, in a controlled fashion, so that they fill the artery, and push the unwanted material out of the way. Often it is necessary to help the stent to open to the correct size, by finally expanding them with a balloon.

If there is disease either in the chest or up close to the brain, “balloon mounted” stents are often used. These will not expand to size on their own, so they are put onto the balloons and expanded up to size once this has been put into the correct place. The balloon is then deflated, leaving the stent in place. These stents have the advantage of being easier to place in the correct position, but the disadvantage of not being able to withstand compression. If these stents are compressed, they lose their shape and may cause the artery to block.  They are, therefore, not suitable for use in the neck, where they may be compressed by outside forces and movement, where the self expanding stents are used.  

A procedure can be seen at http://www.youtube.com/watch?v=Z4kXDT22bDE.

What are the complications of carotid artery stenting?

Complications from carotid artery stenting can be considered either as occurring around the time of the procedure (within 30 days of the procedure) or later. The list below is not exhaustive, but rather is intended to explain the more common or worrying problems that may occur.

The recognised early complications include:

• Stroke. This may cause significant disability (or even death), or may be relatively mild. It is uncommon, and in experienced hands happens in about 3-4% of cases, when there have been recent symptoms precipitating the procedure, or around 1-2% if the carotid artery disease is found incidentally. The majority of these events are more minor, but may leave a patient with severe disability (weakness affecting the arm and/or leg, or speech problems). Most of these events are caused by pieces of the disease becoming dislodged at the time of the procedure and causing problems with blood flow to the brain. In a small proportion of cases, the increased blood flow to the brain causes bleeding into the brain, and this is often a much more devastating event.
• Bleeding/bruising. Almost all patients have some bruising at the groin, where the tubes have been placed in order to get the stent into place. Occasionally this bleeding is significant and  requires a further operation to stitch the area that is bleeding.  This problem is more likely considering the medicines that are given to a patient during carotid artery stenting (blood thinning medications), however this is restricted by the use of devices used to stitch or plug the hole at the end of the procedure.  Such devices are usually used by Radiologists performing carotid artery stents.
• Damage to the arteries. Very rarely the arteries which connect the access site in the groin to the carotid arteries are diseased and may become damaged during the passage of the tubes used for carotid artery stenting.  This is most likely to occur in the artery at the groin used for entry of the tubes, and if it occurs may lead to poor blood flow into that leg.  If this was to occur, it manifests itself by problems walking, or leg pain immediately after the carotid artery stenting procedure. This is one of the reasons why patients are usually kept in hospital for a while after the procedure, to ensure that should such problem occur, then they will be recognised and appropriately treated. It is possible that such complications could result in loss of that limb, but this is almost unheard of.

Longer term the problems that can occur include:

• Stroke. Stroke can occur after both carotid artery stenting and the surgical alternative ( carotid endarterectomy). The likelihood of this occurring is approximately the same whichever procedure is undertaken, and is around 1% per year in the longer term.  This likelihood will have been considered by the medical team when suggesting to a person that they may benefit from intervention. Intervention would not usually be considered, unless the person had disease which would be much more likely than this to cause stroke, and that the procedure could be expected to be performed with a less than 6% risk of stoke for disease causing symptoms and less than 3% for disease found incidently.
• Restenosis.  This is the term used for re-narrowing of the area treated by the stent. Some people seem to be more prone to this happening, and may well have had the same problem irrespective of whether they were offered carotid artery stenting or endarterectomy. A minor degree of this is almost inevitable in all stents, but it rarely causes problems in terms of symptoms.  If symptoms should occur then the area can be retreated, either by placement of another stent, or by removing the stent and treating the artery with an open operation (LINK TO VS SITE). This problem is particularly likely to happen if the reason for placing the stent in the first place was because the person had received x ray treatment to their neck in the past.

What can be done to prevent stroke at the time of carotid artery stenting?

As indicated in the section on the complications of carotid artery stenting, stroke can occur at the time of the procedure, and subsequently. A number of steps can be taken by the medical team to reduce the risk:

• The team of doctors, nurses and radiographers who are undertaking carotid artery stenting will be regularly performing the procedure and will be able to tell you, as a patient, what experience they have of doing the procedure. There are a number of studies which show that regular practice and experience of these (and other similar) procedures is useful in keeping the complications down to a minimum.
• A team of doctors will examine and assess people who may benefit from carotid artery stenting. They will only suggest this procedure having considered all of the options that are available.
• The arteries from the chest to the brain need to be imaged (pictures and scans), usually using a combination of ultrasound scanning, along with CT and/or MRI and/or angiography.  The choice of the type of imaging will be dependent upon different patient features and needs. In this way the carotid stenting procedure can be planned and the equipment required predicted.  Such imaging and planning will determine if carotid stenting is likely to be possible, and to predict the likely degree of difficulty (and therefore the likely risk of complications).
• Patients who undergo carotid artery stenting will have their medications optimised for the procedure.  This usually means ensuring that they are taking a statin, and are taking dual antiplatelet medications (usually aspirin and Clopidogrel). Please see the section on treatments for carotid artery disease.
• Dedicated stents designed for use in the carotid artery are usually used. Please see the section on carotid artery stents.
• There are a series of specially designed devices, called “Cerebral Protection Devices” (sometimes shortened to CPD’s in some literature).  These have been specifically designed to reduce the risk of stroke at the time of carotid artery stenting.  There are a number of these available, and the individual devices can be found on the internet.  So far no one device has been found to be more effective than another, and indeed there are some data which would question the effectiveness of these devices. If you are considering having a carotid stent fitted, it may be worthwhile asking your particular doctor if he/she is practiced at using these devices, and to discuss with him/her if it would be likely to be beneficial in your particular case.

What are the advantages of carotid stenting as a treatment?

Please refer to the section explaining the treatment options that are available for the carotid artery.

All people who are known to have carotid artery disease will have their medications altered to try to reduce their risk of stroke or further stroke.

When the level of carotid artery disease goes above a critical level additional treatment is often recommended.  This can be in the form of either an operation (carotid endarterectomy – see VS SITE) or carotid artery stenting.  The other sections on this information site give details as to when these might be an option, and when not.

Both carotid artery stenting and endarterectomy offer the potential benefit of preventing stokes in the future. Carotid endarterectomy offers:

• A tried and tested treatment
• Long term follow up information
• Can be performed under general anaesthetic (patient asleep) or local anaesthetic (usually involving having the neck area numbed).
• Probably lower incidence of “minor” strokes

Carotid stenting offers:

• A newer treatment, but inevitably with less long term follow up data
• Minimally invasive (“keyhole”) treatment
• Almost always done under local anaesthetic.
• Less likely to cause heart complications
• No problems with nerve damage in the neck
• Less significant bleeding problems.

Why is carotid artery stenting not offered more frequently?

Carotid artery stenting is a relatively new procedure, and it is not practiced in many hospitals in the UK.  There remains significant controversy as to the relative places that carotid artery stenting and carotid endarterectomy have in the armoury of stroke prevention treatment.  Some patients are better offered the endarterectomy option, others are better served with stenting.  There are a group of patients where this is less clear, and this is where the controversy lies.

In addition, it seems fairly clear for both procedures, that it is very important that the team performing the procedure (whichever it is) should be experienced at doing it, and should be regularly performing that procedure. At present only a small number of places fulfil those criteria for carotid artery stenting.

Most vascular units are in a position to offer carotid endarterectomy, under the care of a suitably trained and practiced team.  In many of these units, to access carotid artery stenting requires a referral to one of the small number of centres performing this procedure. It is unfortunate that at the present time, this inevitably results in some level of delay in the treatment for these patients. The British Society of Interventional Radiology (BSIR), along with a number of other organisations are working hard to ensure that there are robust processes for such referrals to occur, with the minimum delay caused. As time goes on, more information will become available to make it clearer if more centres are needed to treat patients with stents. If you feel that you might benefit from a stent rather than an operation, you should discuss this with your medical team. There may be good reasons why stenting is not a good option, in which case your doctors will explain this to you.  If they feel that a stent may be beneficial, they can refer you to an experienced team for consideration.