Carotid Stenting

What is carotid artery disease?

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• Feeling weakness, numbness, or a tingling sensation on one side of your body, for example, in an arm or a leg
• Being unable to control the movement of an arm or a leg
• Losing vision in one eye (many people describe this sensation as a curtain or shutter coming down)
• Being unable to speak clearly

• Ageing
• Smoking
• High blood pressure (hypertension)
• High blood (serum) cholesterol (hypercholesterolaemia)
• Diabetes (especially if poorly controlled)
• Obesity

			You may hear a rushing sound, some people have described this as a dog barking. This is the pulsating blood in the carotid arteries travelling to the brain. The test is painless and does not involve radiation. The test will determine how diseased the carotid arteries are. If sufficient information is gained from this test then it is possible that no more investigations are performed.
Figure 4

• Magnetic resonance angiography (MRA)

MRA uses radio waves and magnetic fields to create detailed images. Some forms of this test can show moving blood flow and may help evaluate carotid artery disease.

 

					To improve the test's accuracy, a colourless dye called gadolinium may be injected into a vein to make the arteries more visible. Dyes used to help visualise blood vessels are called “contrast”.   The dye used may occasionally cause an allergic reaction. If you have certain types of metal in your body (for example some surgical clips) or a pacemaker, it will not be possible to perform MRA on you. The radiographic staff in x-ray will question you about all of this.
Figure 5	Figure 6

 

Figures 5 and 6: are examples of pictures of the carotid arteries obtained by MRA.

 

The scanner is noisy and patients often describe the noise as a “crashing and banging”. You may be offered headphones with music to make it more tolerable. Unfortunately, some people find MRI scanning very claustrophobic although newer scanners that are a lot more “open” are increasingly becoming available.

 

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• Angiography

In this test, the doctor injects a different type of dye (contrast) through a fine tube called a catheter that is threaded into your arteries usually from the groin. The skin at the groin is first frozen by the injection of local anaesthetic. This stings like a bee-sting but then goes numb. X-ray pictures are then taken. When the dye is injected, you may get a warm sensation like turning the central-heating on inside your body, it may feel as if you have wet yourself (passed water) and you may get a metallic taste in the mouth. These sensations relate to the dye going round the body and settle quickly. It is important to drink plenty of fluid before and after to help the kidneys flush the colourless dye out of the system. After the catheter is removed from the groin pressure is applied and you may have to lie flat for several hours. Alternatively, the groin wound may be closed with a special device allowing you to get up sooner.

 

This test is associated with a small risk of stroke. The risk is very small in experienced hands (stroke occurring in perhaps less than 1 in 300 cases). There may be bleeding or bruising at the groin (in perhaps less than 5 in 100 cases) and the dye may occasionally cause allergic reactions or irritation of the kidneys. Allergy may be more common if you have a history of allergy to drugs and certain foods, or if you have hay fever, asthma or eczema. Those people who have had a previous allergic reaction to x-ray contrast should discuss this with the physician performing the test. It may be that an alternative test which does not employ x-ray contrast can be performed.

 

If your kidney function is not normal to start off with and especially if you are a diabetic with abnormal kidney function, you may need an intravenous drip of fluids before and after this test to help protect the kidneys.

 

A limited amount of radiation is involved (the same as that involved in a trans-Atlantic flight).

 

Baring these infrequent risks in mind, angiography is still considered to be the “Gold Standard” for carotid disease meaning the test against which all others are measured.

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• CT scan and CT Angiography (CTA)

 

						CT and CTA scans take x-ray pictures in the form of slices of the brain and the arteries in your neck. CT scans can show an area of the brain that has suffered or is suffering from a reduction in flow or has become damaged due to stroke. The same dye used in angiography will be injected into an arm vein to make blood vessels visible on the x-ray image.
Figure 7			Figure 8

 

Figures 7 and 8: are examples of CT angiograms

 

The test involves a limited amount of radiation (the same as that involved in a trans-Atlantic flight) and there may be allergy to the dye used or irritation of the kidneys (see angiography, above).

 

TREATMENT OF CAROTID ARTERY DISEASE

 

The first treatment strategy is control of your risk factors.

 

Secondly, you will need to be on the best combination of medicines in order to prevent further build-up of plaque and to try to stabilise the plaque that has already built up; this is called “best medical therapy”.

 

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Medication: 

The drugs you may be offered are as follows:

• Aspirin

This thins the blood. Certain elements of the blood tend to stick to atheromatous plaque. These elements are called platelets. Aspirin inhibits the function of platelets and stops them sticking to plaque. This makes it less likely that bits will break off and embolise to the brain.

 

There may be other similar medications that you will be offered such as clopidogrel, (brand-name plavix) or dipyridamole (brand-name persantin). These also work to thin the blood and may be used in combination, for example;

· aspirin and dipyridamole

· aspirin and clopidogrel

 

Aspirin sometimes irritates the stomach lining and may not be advised if you have a history of bleeding duodenal or stomach ulcer. Your doctor will likely prescribe an alternative, like clopidogrel under these circumstances.

 

• Statins

 

These are so called because they are members of a group of drugs whose names end in the word “statin” (e.g. simvastatin, pravastatin, rosuvastatin, atorvastatin) although they may have many different brand names. These drugs inhibit the enzyme (active protein) that is involved in the production of cholesterol in the liver. They work in two important ways. Firstly they reduce serum cholesterol, thereby tending to reduce the build-up of plaque and secondly they actually have plaque-stabilising properties.

 

If you cannot tolerate statins for whatever reason, there are other medications available that are capable of controlling raised serum cholesterol.

 

• ACE inhibitors

 

These drugs control blood pressure, although there are a variety of drugs available for blood pressure control that work in different ways. ACE inhibitors (often ending in the letters “pril” – for example lisinopril, enalapril, ramipril, perindopril etc) have some important properties. They not only lower blood pressure, they also have plaque-stabilising properties.

 

If you cannot tolerate ACE inhibitors for whatever reason, there are other medications available that are capable of controlling hypertension.

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• Stroke: A small number of people, between 1 and 5 in 100, having carotid endarterectomy will have a stroke during the operation. This stroke may occasionally be fatal. All possible precautions will be taken to prevent this eventuality.
• Nerve injuries: These occur in up to 7 in 100 patients but tend to be transient (meaning they recover completely). There are a number of important nerves in the neck that lie close to the carotid artery. Although precautions are taken during the operation to safeguard these, they may occasionally be stretched or bruised. The vagus nerve supplies the voice box (larynx) and injury may result in hoarseness and weakness of the voice. The hypoglossal nerve supplies the muscles of the tongue. Damage to this nerve may affect speech by reducing the tongue’s mobility. Damage to fibres of the glossopharyngeal nerve may occasionally lead to difficulty with swallowing. The facial nerve supplies the muscles of the face. Damage to its lowest branch may lead to impaired movement of muscles around the lower jaw and neck. Skin nerves may also be damaged by the incision leading to some loss of skin sensation.
• Wound haematoma & infection: A neck haematoma (painful bruise in the form of a lump) may occur if the neck wound bleeds. Very occasionally this may compress the windpipe and cause difficulty breathing. Wounds sometimes become infected and this may need treatment with antibiotics. Bad infections are rare.
• Chest infections: These can infrequently occur following this type of surgery, particularly in smokers, and may require treatment with antibiotics and physiotherapy. This may be due to the effects of the general anaesthetic or perhaps result from damage to the nerves around the carotid artery and difficulty with swallowing (see nerve injuries).

			The drug clopidogrel is very important during carotid stenting. If you are not already on it, in addition to aspirin, it should ordinarily be started either one week before your stent procedure is planned, at a dose of 75mg / day in addition to aspirin or 15 hours beforehand (the evening before stenting) at a higher dose i.e. 300-600mg. The physician performing the stenting procedure will be able to advise you.   Asprin and clopidogrel must be taken on the morning of the stenting procedure and it is important that this combination of drugs be continued for at least 28 days after stent insertion. This is to reduce the risk of stroke.
Figure 12

			You will be monitored throughout the procedure as follows: ● An intravenous (IV) line will be inserted into a vein in your arm so that medications and fluids can be administered during the procedure, if required.   ● Electrodes (small, flat, sticky patches) will be placed on your chest. The electrodes are attached to an ECG monitor, so that a trace of the electrical activity of the heart can be made.   ● A blood pressure cuff will be placed on your arm to monitor blood pressure.   ● A small clip, attached to a pulse oximeter, will be placed on your finger. This records the oxygen level of the blood.
Figure 13

			When x-ray dye is injected in the common carotid artery it may feel as if your face and scalp are very warm, you may get a metallic taste in the mouth and you may feel as if you have passed water (see angiography, above). In addition, you may get sparkly lights in the eye on the side being treated. This is not a TIA or amaurosis fugax (see the section on carotid artery disease), this is the effect the dye sometimes has on the light-sensitive cells at the back of the eye. These effects usually wear off quickly.   A support wire may be placed in the external carotid artery, which supplies the face and scalp. This may cause a little discomfort perhaps in front of or behind the ear, but it does not last long and it is not dangerous.
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• Stroke: A small number of people, between 1 and 5 in 100, having carotid stenting will have a stroke during the procedure. This stroke may occasionally be fatal. All possible precautions will be taken to prevent this eventuality.
• Groin haematoma: This is a painful bruise in the form of a lump at the groin, where the tiny wound into the femoral artery has been made. The risk of this complication is around 5 in 100 people i.e. 5%. It may be less likely to happen when a “closure device” i.e. a plug, stitch or clip has been used to seal the wound. Most often a groin haematoma will mean that you will have to stay in bed and lie flat on your back for longer. Very occasionally, a stitch will be required to close the wound in order to prevent further bleeding. If significant bleeding occurs (this is very infrequent), a blood transfusion may be necessary. 
• Allergy to x-ray dye (See section on diagnosis of carotid artery disease): An itchy skin reaction and minimal throat tightening may occur in up to 2 in 100 people (2%). Serious reactions leading to death are much less common, occurring in no more than one in a quarter of a million cases. However, if you have had any kind of allergic reaction to contrast  before (and this does not include warmth, metallic taste, slight sickness- nausea, or a sensation of wetting yourself) you obviously do not want to experience it again. It is important to discuss any previous reactions with the physician performing the procedure, beforehand.
• Contrast nephrotoxicity (See the section on diagnosis of carotid artery disease): This is an irritation of the kidneys caused by the x-ray dye used during carotid stenting, which is the same as that used during catheter angiography and CTA, but different from that used during MRA. If your kidneys are functioning normally, the risk that you may experience some irritation of the kidneys is small (less than one in ten). In most cases such irritation is temporary and has no consequences. It will simply mean that blood tests will need to be taken regularly to monitor recovery, which is most often spontaneous. If your kidneys are already not functioning normally, especially if you are a diabetic, the risk of kidney irritation following the use of x-ray dye is higher and occasionally results in a requirement for dialysis. Even if this does happen, the requirement for dialysis is usually temporary. Many centres are careful to evaluate the risks of contrast nephrotoxicity in individual patients and avoid these risks by using alternative tests, dyes and procedures and / or pretreating patients with intravenous fluids and / or others strategies to limit the risks.
• Blood pressure changes: As may occur following carotid endarterectomy, carotid stenting may cause some fluctuations in blood pressure. Most often you will be unaware of these and in the majority of cases all that is required is monitoring (rather than any active treatment). The possibility that the blood pressure may be temporarily disturbed and that you may require monitoring is one of the reasons that your physician may prefer to keep you in hospital overnight after carotid stenting rather than allow you home on the same day.

Other complications:

There are no recorded instances of chest infection following carotid stenting or injury to the nerves around the carotid artery (as no incisions are made into the neck). Furthermore, the risk of heart attack is lower following carotid stenting than following carotid endarterectomy.

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