Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Severely stenosed carotid arteries predispose to stroke, and either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce the long-term risk of stroke. Open carotid artery surgery completely removes the atheromatous material, but stenting is less invasive. In North America, some 100 000 surgery or stenting procedures are done each year to treat carotid artery narrowing,1 and numbers are similar for Europe.2,3 About half are to prevent recurrent stroke in symptomatic patients and half are for primary stroke prevention in asymptomatic patients (ie, those whose stenosis has not caused any recent ipsilateral symptoms), but this proportion varies from one country to another.2 Among asymptomatic patients with severe (eg, 70–99%) stenosis, successful CEA approximately halves the long-term stroke risk.4,5 Both CAS and CEA, however, carry a short-term risk of stroke, which is about twice as great for symptomatic as for asymptomatic patients.3 When carotid procedures first became common, these risks were substantial, but nowadays they are much lower, particularly among asymptomatic patients. In Germany, for example, where all carotid procedures must, by law, be registered, during 2014–19, the in-hospital risk of disabling stroke or death among asymptomatic patients undergoing CAS (n=18 000) or CEA (n=86 000) was 0·7% for each procedure (appendix p 9); the additional in-hospital risk of non-disabling stroke was 1·1% for CAS and 0·7% for CEA. These rates are below the conventional 3% safety threshold, although only about two thirds of procedural strokes occur before hospital discharge. In this large German registry, the in-hospital risk of stroke after a carotid procedure was reliably shown to be unrelated to age or sex.3 In-hospital mortality from other causes was similar in both sexes but increased with age to nearly 1% after age 80 years.6