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What is a Stroke?
A stroke describes the symptoms produced when an area of the brain is starved of oxygen. The brain contributes 2% to total body mass but utilises 20% of the blood supply. It is unable to store oxygen and is totally dependent on blood to provide it with nutrients and remove waste. Brain cells can survive 3 – 4 minutes without oxygen after which they begin to die.
The carotid arteries (one on the right and one on the left) run in the neck and supply blood from the heart to the brain. Narrowing within these vessels known as “carotid stenosis”, accounts for 20 – 30% of all strokes and transient ischaemic attacks. Carotid stenosis is found in 4% of men over the age of 50 but only 3% of women.
The risk of a stroke or TIA increases with age but they do occur in younger people particularly in smokers and diabetic patients. Men are at higher risk of having a stroke but women are a greater risk of dying from one.
Why does Carotid Stensois develop?
Narrowing of the carotid arteries is caused by “atheroma”. Atheroma is a fatty material (known as a “plaque”) that develops within the lining of artery walls in a process called “atherosclerosis”. All people will develop small amounts of atheroma in their arteries during their lifetime but patients with certain risk factors form extensive plaques more quickly. As increasing amounts of atheroma is laid down it causes the artery wall to bulge inwards thereby limiting the amount of blood that can flow down the artery. In time the artery can even become blocked by atheroma. It is common for patients to have more than one narrowing or blockage within the same artery.
The same process occurs in all arteries but results in different problems depending on what the artery supplies:
Arteries to the Legs may → PAD.
Arteries to the Heart may → angina and heart attacks.
Arteries to the Brain may → strokes and mini–strokes (TIA).
Typically, the carotid arteries become diseased a few years later than arteries supplying the heart (coronary arteries). People who have coronary artery disease, and atherosclerosis elsewhere have a higher risk of developing carotid artery disease.
What Risk Factors increase formation of Atheroma?
Why does Carotid Stenosis cause Stroke and TIA?
The plaques that are seen in carotid stenosis are variable in nature. Some are unstable and can rupture releasing clots of fatty material into the circulation. Furthermore, blood flow through the narrowed artery is turbulent which can trigger blood clots to form and potentially release small fragments of clot into the circulation. Once dislodged, either form of clot can be carried in the bloodstream to the brain where they eventually lodge and block small arteries. As a result specific parts of the brain do not receive blood so their cells are starved of oxygen and begin to die. If the blockage is quickly dislodged or broken down before cells die, then a TIA will result, but if it is not then a stroke will develop.
How is a stroke or TIA diagnosed?
At your initial clinic visit, a thorough history of your symptoms will be obtained. Your consultant will ask questions about the type, severity and duration of your symptoms. Risk factors will be identified such as smoking, diabetes, high blood pressure and high cholesterol. You will be asked specific questions to look for arterial narrowing in other parts of the body. They will also want to know about your current medications and other medical illnesses.
You consultant will then complete a “neurological” examination to test the function of nerves supplying the arms, legs and face. They will also examine your abdomen and feel your leg pulses, before listening to your heart and neck.
Based on the clinical impression a series of tests may be organised for you. Many or all of these may have already been performed if you attended an NHS hospital when you first developed symptoms.
ECG – a tracing of the heart rhythm.
Carotid duplex ultrasound scan – the most important scan that will show the extent of the narrowing and the nature of the plaques causing them. It will be performed on both sides of the neck to look at both arteries.
CT scan of the brain – to confirm if there is evidence of a stroke.
ECHO – ultrasound scan of the heart.
Your consultant will go through the scan results with you and recommend the most appropriate treatment. If you have had a proven TIA or stroke and have carotid artery disease that is amenable to surgery it is advised that this is performed within 2 weeks of symptom onset.
The treatment offered to you is determined by a number of different factors. They include:
The severity of carotid stenosis – this is revealed by the carotid ultrasound. Guidelines suggest that only patients with narrowings of 70 – 99% are suitable for operative treatment.
The presence of symptoms – Patients with symptomatic narrowings have been shown to have much greater benefit from operative treatment than those who have no symptoms but a proven stenosis on scanning.
The medications you have been taking – If you have been on aspirin or clopidogrel and suffer a TIA or stroke you may be suitable for operative treatment even if the narrowing is less than 70%.
Neck mobility – operative treatment requires a good range of neck movement. Patients who do not have this will not be suitable.
Once a stroke or TIA has been diagnosed, your consultant will discuss treatment options with you. There are 2 main forms of treatment that are offered:
Medical (tablet) therapy and lifestyle changes.
Carotid Endarterectomy (CEA).
Medical Therapy & Lifestyle changes
What is it?
Medical therapy is the use of tablets to limit further plaque formation in the arteries and reduce the risk of heart attacks and strokes. If you are not already on them, your consultant may recommend starting the following tablets which should be taken for life:
Clopidogrel (75mg taken once a day) – clopidogrel also reduces the stickiness of platelets. It does not cause irritation of the stomach like aspirin and is used for patients who may have had previous ulcers or reflux disease.
When is medical therapy and lifestyle advice recommended?
These measures are recommended for ALL patients with proven atherosclerotic arterial disease of any location including the carotids. It is the single best treatment to reduce the risk of strokes and heart attacks.
Carotid Endarterectomy (CEA)
What is it?
CEA has been the standard surgical treatment for symptomatic, significant carotid disease since its introduction in 1954. It is performed under local or general anaesthetic in order to prevent future strokes. 2 very large trials have shown significant reductions in stroke and death rates for symptomatic patients undergoing CEA compared to symptomatic patients who do not. The operation takes around 2 hours and involves an incision in the neck to expose the carotid artery which is then opened and the fatty plaque material (atheroma) cored out. Patients usually go home 1 – 2 days after surgery.
Before your Operation
Guidelines state that carotid endarterectomy should be performed within 2 weeks of TIA or stroke symptoms developing. Consequently there is not often time for a “pre–operative assessment”. Most patients are usually admitted to hospital the day before their operation where blood tests, a chest x – ray and an ECG (tracing of the heart rhythm) will be performed. An anaesthetist may consult with you to optimise medications you may be taking for diabetes, heart and lung disease.
You will be admitted to the ward the day before your surgery. If you have a general anaesthetic, you should not eat for 6 hours prior to treatment. However, you may drink “clear fluids” like water up to 2 hours before.
Your surgeon will visit you before the operation and ask you to sign a consent form once he has explained the procedure to you.
Patients having local anaesthetic should be aware that they may be asked to perform a series of simple tasks at certain points of the operation. These include reading out words from a card, squeezing a toy or just conversing with a member of theatre staff. This is important and allows medical staff to assess how good the circulation to your brain is at any stage of the procedure. Furthermore, patients will need to stay very still during the operation in what may be a potentially uncomfortable position.
How is Carotid Endarterectomy performed?
If you are having a general anaesthetic, you will be put to sleep by an anaesthetist shortly before the operation starts. Patients having local anaesthetic will remain awake and be given a series of injections to numb the skin of the neck where the incision will be placed. In both cases the skin will be shaved and cleaned.
An oblique cut is made in the neck in order for the surgeon to expose the carotid artery and the arteries that it eventually divides into. Clamps are applied above and below the narrowed part of the artery so that a repair can be performed without substantial blood loss. Blood supply to the brain is maintained by the carotid artery on the other side or a “shunt” is used that detours blood around the artery that is being repaired.
In the next stage of the operation, the diseased section of the carotid artery is cut open and the fatty plaque removed. An artificial “patch” is then used to close the artery. The clamps are removed from the artery to make sure there are no leaks from the patch. When your surgeon is satisfied and normal blood flow in the artery has resumed the rest of the wound will be closed with stitches. Those in the skin will dissolve by themselves and do not require removal. Finally a drainage tube will be placed inside the wound and emerge through the skin. It will be attached to a bottle and the amount of fluid draining subsequently will be monitored. The operation is complete and you will be taken to the recovery area.
After the Operation
You will be observed closely in the recovery area for anything up to 4 hours after your operation. If there are no problems, patients are then transferred back to the ward where they are offered something to eat and drink and encouraged to mobilise.
The drainage tube can be removed the next day if only a small amount of blood stained fluid has collected.
Most patients will be started on aspirin, clopidogrel or asasantin tablets the day after the operation. This should be continued indefinitely.
The vast majority of patients are discharged 1 – 2 days post–operatively.
The stitches dissolve and do not need to be removed. Once the wound is healing nicely the dressing does not need to be replaced.
Normal activities and low grade exercises like walking are encouraged once you get home.
We advise against strenuous activity and driving for 2 weeks after the operation. You should also consult with your insurance company.
The majority of patients having the operation have retired but those still in employment should have at least 2 weeks off work.
Your consultant will organise a follow–up appointment with you after 6 weeks to discuss your treatment and assess your recovery.
Success rates with Carotid Endarterectomy
CEA is performed to prevent future strokes. Large trials have shown that in suitable patients CEA reduces the estimated 2 year risk of stroke or death by more than 80 percent, from greater than 1 in 4 to less than 1 in 10. The technique used in the operation is very effective at preventing recurrent narrowing of the artery which occurs in less than 7% of cases.
Risks of Carotid Endarterectomy
All operations have associated risk, however we would not advocate a procedure unless it was in a patients’ best interest. Patients who experience a TIA or stroke and have carotid stenosis are at high risk of a further stroke in the next 30 days and it is this group of patients that benefit most from carotid endarterectomy.
All patients should be aware of possible complications of CEA including:
Wound infection - rare to have deep infection