The purpose of this study is to determine whether carotid surgery combined with optimal medical therapy improves long-term survival free of ipsilateral stroke in patients with asymptomatic carotid stenosis at higher-than-average risk of ipsilateral stroke when compared with optimal medical therapy alone.

Carotid artery stenosis >= 50% affects about 3% of subjects >= 60 years and accounts for up to 15% of all ischemic strokes. Overall, patients with asymptomatic carotid stenosis have a low risk of ipsilateral stroke on modern medical therapy. It is therefore uncertain whether the benefit of carotid surgery still justifies the perioperative risk of stroke or death, and whether revascularisation is good value for money considering competing demands on health services. Several imaging techniques have been developed to identify patients with asymptomatic carotid stenosis at higher-than-average risk of ipsilateral stroke. Specifically, the presence of transcranial Doppler (TCD)-detected embolic signals, intraplaque haemorrhage on magnetic resonance imaging, TCD-measured impaired cerebral vasomotor reserve or rapid stenosis progression have all been shown to involve an at least 3-fold higher risk of ipsilateral stroke. However, before recommendations for clinical practice can be made regarding the use of these tools, their utility must be demonstrated in a formal randomised clinical trial. Our hypothesis is that the use of these predictors can identify a subset of patients with asymptomatic carotid stenosis who could benefit from prophylactic endarterectomy.

Carotid endarterectomy The procedure will be carried out with the technique routinely used by each surgeon. Operative reports and perioperative complications will be collected. CEA will have to be performed as soon as possible, within 60 days after randomization.

Optimal medical therapy OMT will be applied to all patients and started immediately after randomisation.

OMT will be defined by the adhoc committee and follow relevant guidelines. It will include:

• Antiplatelet therapy. If the patient requires anticoagulation for any reason (e.g. atrial fibrillation), the patient should be treated with an appropriate anticoagulant according to the practice at the centre as an alternative to antiplatelet therapy.
• Antihypertensive treatment, if required, to achieve a target blood pressure < 140/90 mmHg (higher targets may be defined by the OMT committee for selected conditions, e.g. contralateral carotid occlusion) Application of structured programs, such as stepped-care approach using ranking of antihypertensive drugs will be used.
• High-dose statin treatment (target LDL < 0.7 g/l). A stepped-care approach with raking of lipid-lowering drugs will also be used.
• Patients smoking at the time of randomisation will be encouraged to stop and join a smoking cessation and support program.
• Other lifestyle modification: reduction of alcohol consumption, choosing healthy food, increasing regular physical activity, reduction of body weight if relevant.

OMT may be modified during the course of the trial to take account revised guidelines or new evidence.

Inclusion Criteria:

• Age 50 years or over

• No ipsilateral stroke or TIA within 180 days of randomization

• Atherosclerotic carotid stenosis between 70 and 99% (NASCET method)

• At least one of the following markers of ipsilateral stroke risk:

  • Silent brain infarction on MRI, DWi, consistent with embolism from or hemodynamic consequences of the qualifyiing stenosis
  • History of contralateral TIA or ischemic stroke due to atherosclerotic carotid disease
  • Predominantly echolucent plaque on ultrasound
  • Rapid (within 1 year) carotid stenosis progresion
  • TCD-detected microembolic signals
  • Impairment of TCD-measured cerebral vasomotor reserve
  • Intraplaque haemorrhage on magnetic resonance imaging
  • Rapid and severe stenosis progression

• Patient is able and willing to give informed consent

Exclusion Criteria:

• Previous revascularization procedure in the artery to be randomised
• Patients not suitable for endarterectomy due to anatomical factors
• Carotid stenosis caused by non-atherosclerotic disease e.g. neck radiotherapy or fibromuscular disease
• Patients who have had contralateral carotid artery or vertebral artery or intracranial artery revascularisation within 6 weeks prior to randomisation
• Patients with planned revascularisation of the contralateral carotid artery or a vertebral artery or an intracranial artery within 6 weeks after randomisation or the date of CEA
• Patients who have had coronary artery bypass grafting within 3 months prior to randomisation or other major surgery within 6 weeks prior to randomisation
• Patients with planned coronary artery bypass grafting or other major surgery within 6 weeks after CEA of the artery considered for treatment in the trial
• Patients with pre-existing disability (modified Rankin score greater than 2)
• Patients who have a low 5-year life expectancy (see appendix for definition)
• Patients intolerant or allergic to all of the medications available for OMT
• Patients in clinical trials of investigational medicinal products or who have been in clinical trials within the last 4 months will not be enrolled unless otherwise agreed
• Patients who are known to be pregnant
• Patients unwilling or unable to participate in follow-up