Asymptomatic carotid stenosis carries a stroke risk of approximately 2% per year. This stroke risk appears related to the severity of stenosis and remains constant with time, unlike the risk following a neurological event in a symptomatic carotid stenosis.2 A trial comparing surgery to aspirin for asymptomatic carotid stenosis showed no benefit from surgery although randomisation was incomplete.10 In a multicentre trial of 1662 patients (asymptomatic carotid atherosclerosis study, ACAS) with over 60% asymptomatic carotid stenoses randomised to surgery or medical treatment, at five years the combined stroke and mortality rate for surgery was 5.1% compared to 11% for medical treatment.3 Although all centres were validated for low surgical morbidity, the stroke rate associated with arteriography was considered to be high at 1.2%. There should be caution when applying the results of this trial to a wide body of surgeons, especially as the absolute risk reduction for stroke was 1% per year. While surgery carries an advantage over antiplatelet medication, 20 patients have to undergo carotid endarterectomy to prevent one stroke in every five years.3 This compares with four endarterecto-mies to prevent one stroke a year in symptomatic patients.6 Surgery for asymptomatic disease may not be appropriate when many healthcare systems are critically examining cost and benefit. Application of the ACAS criteria would lead to a 10 fold increase in rates of carotid endarterectomy; to put this in perspective, it is estimated that in Scotland 40 000 people would have an appropriate stenosis. The ACAS trial did not address asymptomatic stenoses in patients over 79 years old, and although many series have shown that surgery can be performed safely in octogenarians, their low life expectancy may preclude benefit from carotid endarterec-tomy.
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