2 The procedure
2.1.1 Asymptomatic stenosis of the extracranial carotid arteries may be identified incidentally through imaging – for example, before cardiac surgery. Patients with carotid stenosis are at an increased risk of transient ischaemic attack (TIA) or stroke; but the risk is lower compared with patients with symptomatic stenosis.
2.1.2 Good medical control of cardiovascular risk factors is essential. Severe asymptomatic stenoses are sometimes treated by carotid endarterectomy.
2.2.1 Carotid stenting is carried out with the patient under local anaesthesia using a percutaneous transfemoral approach. A guidewire is passed into the carotid artery, commonly with a cerebral protection device at its tip, which is designed to prevent any debris from passing into the cerebral circulation during the procedure. The carotid stenosis is then usually pre-dilated using a balloon catheter. A metal mesh (stent) is inserted to treat the stenosis, with the aim of preventing both embolism and restenosis.
2.2.2 Carotid stenting is a less invasive percutaneous procedure than carotid endarterectomy which aims to avoid wound complications associated with that procedure.
Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview.
2.3.1 The efficacy outcomes described below include stroke or death that occurred more than 30 days after the procedure (unless specified otherwise). Stroke or death occurring on or before 30 days were considered to represent safety outcomes.
2.3.2 A randomised controlled trial (RCT) of 2522 patients reported that among asymptomatic patients there was no significant difference in the rate of stroke or death following stenting or endarterectomy (5% vs 3%; hazard ratio [HR] 1.86, 95% confidence interval [CI] 0.95 to 3.66; p = 0.07) at a median 2.5-year follow-up (absolute figures not stated). A non-randomised controlled study including 8706 asymptomatic patients reported no significant difference in stroke or death rate following carotid stenting (2%) and endarterectomy (2%) in asymptomatic patients (p = 0.16) (absolute figures and follow-up not stated).
2.3.3 A UK national register of 291 asymptomatic patients reported 5-year event rates as follows: stroke 4%; stroke or TIA 8%; mortality or disabling stroke 19%; and mortality 18%.
2.3.4 The Specialist Advisers listed key efficacy outcomes as long-term patency and freedom from stroke or death.
2.4.1 The UK national register of 291 asymptomatic patients reported a mortality rate of < 1% (1/181) at 30-day follow-up.
2.4.2 A meta-analysis of 2 studies including 140 asymptomatic patients reported no significant difference in stroke or death rate at 30-day follow-up between the stenting group (4% [3/73]) and the endarterectomy group (3% [2/63]) (odds ratio 1.06, 95% CI 0.16 to 6.94; p = 0.96). The UK national register of 291 asymptomatic patients reported death or disabling stroke rate of 1% (2/181) by 30-day follow-up.
2.4.3 The UK national register of 291 asymptomatic patients reported the following event rates: disabling stroke < 1% (1/181), non-disabling stroke 1% (2/181), TIA 2% (4/181) and myocardial infarction < 1% (1/181) at 30-day follow-up. The RCT of 85 asymptomatic patients reported no perioperative strokes or TIAs in either the stenting group or the endarterectomy group.
2.4.4 The RCT of 2252 patients with either symptomatic or asymptomatic stenosis reported that there was a significantly lower incidence of perioperative myocardial infarction following carotid stenting (1% [14/1262]) than following endarterectomy (2% [28/1240]) (HR 0.50, 95% CI 0.26 to 0.94; p = 0.03).
2.4.5 The Specialist Advisers listed anecdotal or reported adverse events related to this procedure as femoral artery damage and renal failure. They considered theoretical adverse events to be dissection, restenosis or contrast allergy/nephrotoxicity.