Carotid Artery Occlusion

Carotid atherosclerosis is one of the main risk factors for ischaemic cerebrovascular events (CVEs).

The area of the carotid artery most commonly affected by atherosclerosis is the bifurcation of the common carotid artery.

Carotid endarterectomy is strongly recommended for severe symptomatic stenosis but not routinely recommended for asymptomatic patients or lesser degrees of stenosis. Trials define symptomatic patients as those having transient ischaemic attacks (TIAs) or minor strokes within 3 months of entry into the trial.

• Carotid stenosis is responsible for about 30% of CVEs.¹
• The prevalence of haemodynamically significant carotid stenosis varies with age and other risk factors, such as cigarette smoking and high-fat diet. Estimates indicate that 5 per 1,000 persons aged 50-60 years and approximately 10% of persons older than 80 years have carotid stenosis greater than 50%.²

Risk factors²

• Smoking
• Family history of CVE
• Ischaemic changes on electrocardiogram
• Obesity
• Raised blood pressure
• Elevated plasma glucose levels

Aetiology

• Atherosclerosis (90% of all cases)
• Aneurysms
• Arteritis
• Carotid dissection
• Coils and kinks
• Fibromuscular dysplasia
• Vasospasm

• Patients may present with TIAs or CVEs.
• Typical symptoms are contralateral weakness or sensory disturbance, ipsilateral blindness, and (if the dominant hemisphere is involved) dysphasia, aphasia or speech apraxia.
• Cognitive impairment and decline are associated with asymptomatic high-grade stenosis of the left internal carotid artery.³
• Asymptomatic patients are most often identified when a cervical bruit is heard on physical examination.

Signs

• Detection of a carotid bruit is a common physical examination finding that may lead to a referral for carotid duplex ultrasound.
• Carotid bruits are not sensitive or specific enough to confirm or exclude significant carotid stenoses.⁴ Lack of carotid bruits in CVD patients does not exclude a carotid stenosis.
• A carotid "bruit" may also be caused by a cardiac murmur transmitted to the neck or may be due to stiff, calcified or torturous vessels in the absence of stenosis.

• Echo colour Doppler ultrasonography is the screening method of choice. It is very accurate and non-invasive.
• Carotid angiography is the gold standard for diagnosis but may be associated with a 1-2% risk of stroke. Less invasive techniques, such as MR angiography and angio-CT, are becoming increasingly commonly used.
• One recent study comparing Doppler ultrasound, digital subtraction angiography (DSA) and the 3D CT volume rendering technique found that the decision to operate on an internal carotid artery stenosis may be strongly influenced by the diagnostic method used. DSA and 3D CT correlated well, whereas Doppler ultrasound tended to differ in higher degrees of stenosis, underestimating (compared with DSA) the degree of stenosis.⁵
• Carotid magnetic resonance angiography: very sensitive and specific but its exact role is not clearly proven or well defined.⁶
• Other investigations:
  • Full blood count, electrolytes, renal function, lipid profile.
  • Electrocardiogram: evidence of prior myocardial infarction (MI) and ischaemic changes (the most common cause of mortality following carotid endarterectomy is MI).
  • CT scan or MRI of the brain: for all symptomatic patients in order to rule out other intracranial lesions and identify the presence of new and old cerebral infarcts.

The following are associated with an increased incidence of carotid arterial stenosis:

• Coronary artery disease
• Peripheral arterial disease
• Hypertension
• Diabetes

• Best medical management of carotid stenosis includes lowering of blood pressure, treatment with statins and antiplatelet therapy in symptomatic patients.⁷
• Treat associated cardiovascular risk factors - see separate articles:
  • Stroke Prevention
  • Primary Prevention of Cardiovascular Disease
  • Secondary Prevention of Ischaemic Heart Disease
• Antiplatelet agents:
  • Low-dose aspirin.
  • Clopidogrel is an alternative to aspirin, in cases of intolerance of aspirin, in preventing recurrence of stroke.
• Anticoagulation: the use of warfarin in patients with non-cardiac emboli is controversial.

Surgical

• Carotid endarterectomy (surgical removal of the fatty deposits and blood clots from inside the carotid artery wall):
  • Reduces the risk of disabling stroke or death by 48% in a person with severe symptomatic carotid stenosis (more than 70% stenosis) who has had a TIA.⁸
  • In trials of carotid endarterectomy in people with TIA, the peri-operative risk of disabling stroke or of death is less than 5%.
  • Carotid endarterectomy should be performed as soon as the patient is fit for surgery - preferably within two weeks of developing symptoms.⁹
  • Despite a 3% peri-operative stroke or death rate, carotid endarterectomy for asymptomatic carotid stenosis reduces the risk of any stroke by approximately 30% over 3 years. However, the absolute risk reduction is small (1% per annum over the first few years of follow-up in recent trials).¹⁰
  • Indications include:
    • Symptomatic patients with greater than 70% stenosis: clear benefit was found in the North American Symptomatic Carotid Endarterectomy Trial (NASCET).¹¹
    • Symptomatic patients with 50-69% stenosis: benefit is marginal and appears to be greater for male patients.¹⁰
    • Asymptomatic patients with greater than 60% stenosis: benefit is significantly less than symptomatic patients with greater than 70% stenosis.¹⁰
    • In general, symptomatic patients with greater than 50% stenosis and healthy, asymptomatic patients with greater than 60% stenosis warrant consideration for carotid endarterectomy.¹⁰
• Carotid angioplasty and stenting:
  • Stenting with the use of an emboli protection device is a less invasive revascularisation strategy than endarterectomy in carotid artery disease. For patients with severe carotid artery stenosis and co-existing conditions, carotid stenting with the use of an emboli protection device appears to be as safe and as effective as carotid endarterectomy.¹²
  • Endovascular treatment and carotid endarterectomy appear to have similar early risks of death or stroke and similar long-term benefits in the treatment of carotid artery stenosis.¹⁰
  • However, one study has shown that angioplasty can be as effective at preventing stroke over 3 years as carotid endarterectomy, with similar major risks.¹³
  • This procedure is currently indicated in selected cases such as restenosis and stenoses, located both proximally and distally to the carotid bifurcation.¹⁴

• Carotid atherosclerosis is one of the main risk factors for ischaemic stroke. The annual risk of ipsilateral stroke for asymptomatic severe stenoses is as low as 1 to 2%, but increases to 13% in patients with recent ischaemic symptoms. The risk decreases after the first 2-3 years from the symptomatic episode, dropping to 3%.¹⁴
• Patients with carotid artery stenosis are also at increased risk of MI and sudden death.

• Following endarterectomy, recurrent stenosis occurs in 1-20% of cases, and reoperation is necessary in 1-3% of cases.¹⁵
• Ipsilateral stroke was found to occur in 9% treated with surgery and 26% with medical management after 2 years of follow-up.¹⁵

• Primary prevention of cardiovascular disease.