Cartoid Artery Disease
The blood is supplied to the brain is via the carotid and vertebral arteries. There are 130,000 strokes per year in England and Wales. Between 15-25% of strokes are caused by an abnormally narrow carotid artery. Platelet debris can build within an ulcerated plaque. This debris can be carried by the fast flowing blood in the artery to the brain causing a transient ischaemic attack (TIA), mini stroke or stroke.
A TIA (transient ischaemic attack) is a temporary event in which there is a loss of power or sensation, loss of speech or loss of vision that lasts less than 24 hours. A TIA or stroke, caused by a carotid stenosis, causes a loss of power or sensation that affects the opposite side of the body to the carotid narrowing. However, if the vision is affected by a TIA this occurs on the same side as the stenosis. True visual disturbances caused by TIAs are called Amaurosis Fugax.
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Cholesterol retinal emboli |
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Carotid angiogram
with stenosis |
Brain scan of
patient with stroke |
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Narrowed internal
carotid artery |
Platelet emboli |
Medical treatment
Maximal medical therapy (lowering lipids, controlling blood pressure, controlling diabetes, and an anti-platelet drug) is vital and should be started as soon as possible. It is also crucial to stop smoking. Surgery with maximal medical therapy has been shown to be safer than medical therapy alone in a number of prospective randomised trials.
Investigations
Patients who have had a TIA or minor stroke should be seen by a specialist with an interest in TIAs and strokes quickly. The Royal College of Physicians 2004 Stroke Guidelines recommends that the patient is seen within 7 days. Following the index (or first) neurological event, the risk of a further event is highest in the first 72 hours.
History, examination and special investigations should be undertaken. The latter include checking the blood fat or cholesterol levels and checking for diabetes. A jelly scan (Duplex) of the neck vessels should also be performed.
The role of surgery
In the 1950s Felix Eastcott reported a case of a patient with 'recurrent attacks of hemiplegia' or TIAs who was successfully treated with surgery.
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Eastcott's Lancet Paper |
A number of studies have clearly shown that in patients with neurological symptoms and a ‘critical stenosis’ ( >70%) that surgery (carotid endarterectomy) with drugs is better than drugs alone at preventing a stroke. This presumes that the surgical team undertaking the operation is competent and has a low complication rate.
Recently it has been shown that patients without symptoms and a critical stenosis may also benefit from surgery.
The Team
Successful complex surgery involves a large team of people from a number of disciplines. This starts with an astute referral from a general practitioner, an eye specialist or another colleague. Ward nurses, theatre nurses, high dependency nurses, vascular technicians, operating department assistants, anaesthetists, surgeons and not least the patient each play a vital role in the overall success rate.
The Operation
In some patients, surgery may be appropriate to remove the narrowed segment of artery. The aim of the operation is to restore the narrow artery to normal, by clearing out the atheroma (narrowing). If the artery is particularly narrow the vessel can be widened with a patch made from the patients’s vein or dacron. The operation can be done under local or general anaesthesia. The Operation is usually performed using magnification equipment.
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| Dacron carotid patch |
Carotid patch in situ |
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Operating caries a slight risk of a stroke or heart attack. In most people the risk of having a stroke is considerably greater if surgery is not performed. The risks associated with surgery vary from individual to individual.
In order to operate on the carotid artery it is necessary to temporarily clamp the artery. In some patients there is an inadequate collateral blood supply to the brain and a temporary shunt (by-pass) needs to be inserted to restore the blood supply.
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| Ulcerated plaque |
Shunt in place |
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| Stenotic plaque |
Shunt |
Equipment
Over the years I have found that the standard carotid clamps do not always allow the best possible access for surgery. In order to improve access in such situations, I have designed my own internal carotid artery clamp that allows access to particularly high lesions.
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Carotid Clamp |
Crescendo or Recurrent TIAs and High Risk Carotid Surgery
At the C&W CVU we have pioneered a treatment for unstable or recurrent TIAs. Following the first or index event these patients continue to have further symptoms. This particular group is at high risk of a further TIA or stroke. In a proportion of these patients it is possible to detect clumps of platelets (HITS or high intensity signals ) in the blood flowing in the brain using a Trans-Cranial Doppler. Those patients with many HITS (or a high embolic load) appear to be at greater risk of having further problems.
It is possible to give drugs to thin the blood (anti-platelet agents), and it possible to vary the dose of drug given depending upon the effect the drugs are having. The treatment involves adjusting the amount of anti-platelet drugs according to the number of micro-emboli or HITS detected by the Trans Cranial Doppler (This is known technically as TCD-directed anti-platelet therapy). Carotid surgery can then be safely performed on the next elective (planned) list.
Control of emboli in patients with recurrent or crescendo transient ischaemic attacks using preoperative transcranial Doppler-directed Dextran therapy. Lennard NS, Vijayasekar C, Tiivas, Chan CWM, Higman DJ, Imray CHE. British Journal Surgery 2003; 90(2):166-70
Timing of surgery in symptomatic carotid disease. Imray CHE, Higman DJH, Tiivas C. Lancet 2004; 363(9420):1553-4.
CHE Imray, C Tiivas Are some strokes preventable? A potential role for transcranial Doppler in TIAs of carotid origin. Lancet Neurology 2005; 4(9): 580-6
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| Platelet aggregates |
Transcranial Doppler |
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Brain scan of Circle of Willis |
Combined Coronary Artery and Carotid Artery Disease
Patients undergoing coronary artery surgery have a small but definite risk of a TIA or stroke. This risk increases when one or both of the carotid arteries are narrow or blocked. Working very closely with cardiology and cardiothoracic colleagues it has been possible to develop an approach to these high-risk patients. The carotid surgery is performed under local anaesthesia prior to the coronary surgery. We are currently writing up our experience of over 100 combined cases, we believe this is the largest series to date in the UK.
Ulcerated Plaque
The presence of an ulcerated plaque within the carotid artery appears to increase the risk of further symptoms / TIAs. This needs to be borne in mind when deciding how quickly to operate as this group of patients are at greater risk of a stroke than those in whom no ulcerated plaque is identified.
Trickleflow
Just before a carotid artery blocks, speed of the blood flowing through the artery may slow to ‘trickle flow’. At UHCW all patients undergo a repeat Duplex and TCD immediately prior to surgery. This is to confirm which side of the neck requires an operation, the patency of the carotid artery and to identify the position of the temporal bone window (natural ‘window’ in the skull through which the TCD machine can monitor the blood flow in the middle cerebral artery).
Occlusion
A carotid artery may occasionally block without symptoms. The risk of further platelet debris passing up to the brain is virtually nil once this has occurred. Patients are best treated WITHOUT an operation in this situation.
Subintimal Carotid Artery Disection
This is a rare condition that can occur after blunt trauma to the neck or occasionally it occurs spontaneously without an apparent cause. The artery splits internally causing blood to track between the layers of the blood vessel (see diagram).
This can reduce the blood supply to the brain or cause platelet debris to shower to brain, both of which can cause a TIA or stroke.
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| Subintimal dissection |
MRA scan showing reduced diameter of vessel (a) |
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MRA scan showing reduced diameter of vessel (b) |
Carotid Stenting
This relatively new technique allows a metal stent or mesh into the narrowed artery. Theoretical concerns about the procedure itself causing further debris or emboli to go to the brain has been partly countered by the introduction of ‘cerebral protection devices’. As techniques develop this approach is likely to be particularly useful in the patient who is at high risk of open surgery.
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Hybrid Procedures (subclavian, inominate arteries)
Occasionally there are a number of narrow arteries that are best dealt with by a combination of open surgery and endovascular stenting. A close collaboaration between the surgeon and interventional radiologist is vital.
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Subclavian Steal Syndrome
In this relatively rare condition there is blockage in the artery that supplies the arm (subclavian). In order for blood to get to the affected arm it flows up the vertebral artery on the opposite side and back down the vertebral artery on the affected side in order to supply the arm.
Treatment is usually via an endovascular approach, stenting the narrow or occluded subclavian artery. If the subclavian artery is occluded it is often helpful to approach the blockage from the affected arm in addition to the standard groin approach. Sometimes surgery is required bypassing from the common carotid to the subclavian artery.
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Vertebral Artery Surgery
The vertebral artery, which supplies the circulation to the back of the brain (posterior circulation), occasionally narrows. The narrowing can cause a stroke and occasionally surgery can be undertaken to prevent further strokes. In this patient there was a very tight stenosis at the origin of the vertebral artery, and the patient had had a posterior circulation stroke. The vertebral artery was transposed onto the common carotid artery.
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What’s New?
A couple of important papers have recently been published showing:
1. Carotid surgery in symptomatic patients should be performed soon after the initial or index event. Any significant delay to surgery reduces the benefit of surgery. Ideally patients should have a carotid Duplex scan within 2-7 days of their TIA. Surgery is most beneficial if performed within 14 days of their TIA.
2. There is a significant benefit to undertaking carotid surgery in patients under 75 who have not yet had symptoms from their narrow carotids, so long as their general health is good, and the hospital where the surgery was to be performed had good results.
3. The GALA trial (comparing the outcome of carotid surgery either under general anaesthesia or local anaesthesia) has completed the first phase of study.
4. Carotid stenting may offer an alternative to open surgery and trials to evaluate the relative safety of the two approaches continue.
5. A number of new antiplatelet agents (both oral and intravenous) have been introduced and the full role in the treatment of carotid disease is being evaluated. Using a combination of aspirin 75mg and Clopidogrel 75mg reduces the platelet microemboli and appears to reduce the risk of a subsequent TIA or stroke in the period immediately after the index or first TIA.
6. Control of platelet emboli both before and after surgery appears to reduce the risk of stroke. Few units in the UK currently use these techniques.
Carotid related papers by Chris Imray
