Carotid Artery Disease - A Silent Killer
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Carotid artery stenosis and stroke
Carotid Artery Disease is caused by atherosclerosis which leads to obstruction of the carotid arteries (Carotid Artery Stenosis). The carotid arteries are the two main vessels in the neck that branch into smaller blood vessels which supply oxygenated blood to the brain.
Atherosclerosis is caused when fatty deposits (called plaques) build up inside the artery walls. As these deposits build up, they begin to restrict the flow of blood. As the disease progresses, the atherosclerotic plaques can rupture resulting in the formation of a thrombus (clot) and arterial occlusion, or material dislodged from the plaque (an embolus) can travel to the brain, both of which can cause a transient ischaemic attack (TIA) or stroke. Carotid Artery Disease is therefore a major risk factor for transient ischaemic attacks (TIAs) and stroke.
A TIA or "mini stroke" is caused by the temporary blockage of the blood supply to a part of the brain, resulting in a reversible loss of brain function that usually persists for less than 24 hours.
A TIA is often a warning of an impending cerebrovascular accident (CVA) or stroke. A stroke occurs when the blood supply is interrupted for a longer time, starving cells in the brain of oxygen and causing cell death. This results in a permanent neurological deficit that can severely affect the function associated with the area of the brain that is damaged. Approximately 80% of strokes are ischaemic, i.e. a thrombus (clot) or embolus blocks the blood supply, and 20% are haemorrhagic, caused by the rupture of a blood vessel.
Carotid Artery Disease is also linked to an increased risk of heart attack
People with Carotid Artery Disease often have atherosclerosis in the coronary arteries or peripheral vascular disease (PVD), which affects the aorto-iliac, femoral or renal arteries. This means they have a higher risk of death from heart disease, aortic aneurysms, renal failure and complications due to critical limb ischaemia (CLI). Carotid Artery Disease is also often a marker for diabetes, hypertension and other conditions.
The impact of Carotid Artery Disease
Carotid Artery Disease is responsible for nearly 50% of all TIAs1. Once a TIA occurs, the risk of developing a stroke can be as high as 20% within the first month2, and without treatment about 25% of patients will develop a stroke within 2 years. The overall risk of major vascular events remains high for 10 to 15 years after a TIA with an estimated 10-year risk of any first stroke, myocardial infarction or vascular death of 42.8%3.
The burden of stroke
Each year over 2 million new strokes occur in America and the EU, making stroke the third leading cause of death and a principal cause of long-term disability in much of the industrialized world 4,5. Worldwide, 15 million people annually suffer a stroke - of these, 5 million die (equivalent to 10% of worldwide deaths) and another 5 million are left permanently disabled 6,7.
Atherosclerotic disease accounts for approximately 25% of ischaemic strokes8,9 caused mainly by embolic events from carotid artery bifurcation or the aortic arch.
Warning signs of stroke
TIAs are the most important warning signs of an impending stroke. Symptoms include temporary episodes of headache, dizziness, numbness, blurred vision, slurred speech, confusion or paralysis that can last from a few minutes to several hours.
Depending on the degree and location of ischaemia in the brain, symptoms of a stroke include:
- Paralysis or weakness of the face, arm or leg on one side of the body
- Disturbance or loss of vision, especially in one eye
- Speech or comprehension problems
- Personality disorders
- Severe headache with no known cause
- Unexplained dizziness, confusion, unsteadiness, or sudden falls
Early diagnosis and treatment of Carotid Artery Disease can dramatically reduce the incidence of stroke
Unfortunately, many people with Carotid Artery Disease are asymptomatic and the first sign may be a TIA or catastrophic stroke. However, greater awareness of the warning signs of stroke such as a TIA and detection of a carotid stenosis in patients with peripheral vascular disease will increase the chance of early intervention to reduce the risk of stroke.
Risk factor modification
Primary prevention of stroke is critical for patients with risk factors for atherosclerosis, including hypertension, diabetes, smoking and hyperlipidaemia. In some cases, lifestyle changes such as stopping smoking and exercising regularly will prevent further progression of the disease. Like many patients with coronary artery disease caused by atherosclerosis, Carotid Artery Disease patients often have elevated cholesterol levels that contribute to the disease. A low fat diet and other cholesterol-lowering strategies are often part of a treatment plan.
Techniques used to diagnose Carotid Artery Disease include a medical history, physical examination, Doppler ultrasound, magnetic resonance angiography (MRA) and computed tomography angiography (CTA).
Asymptomatic Carotid Artery Disease can be identified by routine physical examination using a stethoscope to listen for a "bruit" (a rushing sound in the narrowed carotid artery). This should be followed up by Doppler ultrasound to measure the size of the blockage. The degree of narrowing of the carotid artery is the most important predictor of stroke.
Angiography and CT images provide an accurate means of assessing the extent of stenosis while Doppler ultrasound and magnetic resonance imaging (MRI) are better diagnostics for carotid artery plaque morphology.
The treatment for Carotid Artery Disease depends on the degree of occlusion or blockage, the presence of symptoms and the patient's risk factors. All measures are aimed at reducing the risk of TIA and stroke.
The baseline degree of carotid artery stenosis on initial duplex ultrasound is the most significant predictor of future stroke, and it retains its predictive power for more than three years.
For many patients, lifestyle changes combined with drug treatment can reduce the risk of stroke. Drugs include antiplatelet agents (aspirin, ticlopodine, clopidigrel), anticoagulant drugs (warfarin) and cholester ol-lowering agents. Pharmacological treatment for risk factor management should be considered in all patients with less severe stenosis.
A recent consensus report recommends that patients who have experienced symptoms of Carotid Artery Stenosis and have a severe narrowing benefit from a surgical intervention. This benefit is greatest for those in whom the stenosis has narrowed the artery by more than 70% of its original diameter, and is even higher if the intervention is carried out as soon as possible after diagnosis. Patients with a less severe stenosis may also benefit from intervention if they also have other factors that are associated with an increased risk of stroke, as well as patients with severe stenosis but who have not yet experienced any symptoms (asymptomatic Carotid Artery Stenosis).
Surgical intervention (carotid endarterectomy)
For many years the standard intervention for stroke prevention in Carotid Artery Disease patients was carotid endarterectomy, a surgical procedure that involves opening up the carotid artery and removing the plaque. This has a relatively high success rate in preventing stroke although it is highly invasive and may result in nerve injury and significant scarring.
For certain patients at high-risk from a surgical procedure, or where there are anatomical difficulties or co-morbid conditions, invasive surgery may be contraindicated.
Carotid Artery Stenting
Carotid Artery Stenting is a minimally-invasive procedure that can be used to widen the narrowed or blocked arteries. A catheter with a balloon and a stent is passed into the narrowed artery segment. During the procedure, the stent (a tiny cylindrical wire mesh tube) is inflated with a balloon, which is then withdrawn, while the stent remains in place to keep the diseased artery open and restore blood flow. The stent remains in the artery as a permanent implant. Plaque that is dislodged when the vessel wall is opened is captured by an embolic protection filtration system, which is removed at the end of the procedure. Carotid Artery Stenting is performed in a hospital suite equipped with X-ray instruments that enable the doctor to view the patient's arteries and accurately place the stent at the site of the stenosis.
Carotid stent implantation is an increasingly common procedure. It is less stressful for the patient than carotid endarterectomy and is not associated with surgical complications. Often these procedures are performed on an outpatient basis or require no more than an overnight hospital stay, allowing patients to return to their normal activities soon after the intervention.
The relative benefits of carotid endarterectomy and stenting are being further investigated in clinical trials. Carotid endarterectomy has been the cornerstone technique for removing Carotid Artery Disease plaque for decades, while carotid stenting is a relatively recent treatment alternative.
Carotid Artery Disease awareness issues
General practitioners frequently overlook Carotid Artery Disease because it is often asymptomatic and patients tend not to self-refer with "headache or dizziness". It is therefore under-diagnosed and subsequently under-treated, even though it should be regarded as a severe disease leading to death and/or significant disability from stroke. Screening of at-risk patients is therefore essential.
Prevention of disabling neurological events associated with Carotid Artery Disease can be addressed through:
- Increased awareness of Carotid Artery Disease and its consequences
- Improved preventative treatment (pharmacological and risk factor modification)
- Early and accurate diagnosis of Carotid Artery Disease could provide an early indication of the need for intervention and help reduce the risk of TIA and stroke
- Rapid referral to specialist units for extent and location of Carotid Artery Stenosis using Doppler ultrasound, MRA, and CTA
- Early carotid intervention
- MRI is the best technique for assessing plaque morphology and can demonstrate the degree and stenosis
Taking ACTION - The PVD awareness initiative
Patients with symptomatic peripheral vascular disease (PVD) are at increased risk of Carotid Artery Disease. However, general physicians' and patients' awareness of the disease and the seriousness of its consequences is currently still low compared with other life-threatening conditions such as myocardial infarction and cancer.
Moreover, as the older cohort expands with an ageing population, primary care providers will see an increasing number of patients at risk from the consequences of PVD.
The ACTION (Atherosclerosis Circulation Training and Information Network) awareness initiative is a campaign to raise awareness and knowledge of the timely detection of peripheral vascular disease (PVD) and Carotid Artery Disease. ACTION also aims to increase awareness of PVD and Carotid Artery Disease amongst patients, using educational posters, leaflets and videos. This innovative awareness programme is supported by vascular specialists.
Notes for editors
Incidence and prevalence of stroke in Europe
For all European countries*:
The stroke incidence rate is estimated to be:
- 235 for every 100,000 people (equivalent to more than 1 million new stroke events per year)
- In the EU, Iceland, Norway and Switzerland, there are 1.1 million new stroke events each year The prevalence of stroke is estimated to be:
- 1,337 for every 100,000 people (equivalent to more than 6 million prevalent stroke events per year)
- Currently 6 million survivors of stroke live in these countries
- If stroke incidence rates remain stable the number of new stroke events in these countries will increase to 1.5 million per year due to demographic changes alone
*Truelsen T et al. Cost of stroke in Europe. Eur J Neurol. 2005;12(Suppl 1):78-84.
Stroke mortality (2002)
|Millions 2002||Number of deaths 2002|
|Austria||8 111||7 559|
|Belgium||10 296||9 234|
|Denmark||5 351||4 871|
|Finland||5 197||4 875|
|France||59 850||37 750|
|Germany||82 414||79 326|
|Hungary||9 923||17 148|
|Ireland||3 911||2 650|
|Israel||6 304||2 233|
|Italy||57 482||69 075|
|Netherlands||16 067||12 459|
|Norway||4 514||4 817|
|Portugal||10 049||20 069|
|Slovenia||1 986||2 003|
|Spain||40 977||34 880|
|Sweden||8 867||9 984|
|UK||59 068||59 322|
About Cordis Corporation
Cordis Corporation, a Johnson & Johnson company, is a worldwide leader in developing and manufacturing interventional vascular technology. Through Cordis' leadership in research, development and innovation, physicians worldwide are better able to treat the millions of patients who suffer from vascular disease. For more information about Cordis, please visit www.cordis.com
References for editors
1. Alpert JN. Extracranial carotid artery:current concepts of diagnosis and management. Tex Heart Inst J 1991;18(2):93-7.
2. The Intercollegiate Working Party for Stroke. Royal College of Physicians. National Clinical Guidelines for Stroke, 2nd edition. London, 2004.
3. Clark TG, Murphy MF and Rothwell PM. Long term risks of stroke, myocardial infarction, and vascular death in "low risk" patients with a non-recent transient ischaemic attack. J Neurol Neurosurg Psychiatry 2003;74(5):577-80.
4. White RA. Carotid artery occlusive therapy. Endovascular Today 2005(Suppl; Sept):37-41.
5. Biller J and Thies WH. When to operate in carotid artery disease. Am Fam Physician 2000;61(2):400-6.
8. North American Symptomatic Endarterectomy Trial (NASCET) Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 1991;325(7):445-53.
9. Weinberger J. Diagnosis and prevention of atherosclerotic cerebral infarction. CNS Spectr 2005;10(7):553-64.