Second Asymptomatic Carotid Surgery Trial (ACST-2): Randomised Comparison of Carotid Artery Stenting vs Carotid Endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks, but from recent national registry data each causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: International multi-centre randomised trial of CAS vs CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were randomly allocated to CAS or CEA and followed at 1 month then annually, for mean 5 years. Procedural events were those within 30 days of the intervention. Intent-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and logrank methods. Trial registration: ISRCTN21144362. Findings: From 2008-20, 3625 patients in 130 centres were randomly allocated, 1811 CAS and 1814 CEA, with good compliance, good medical therapy and mean 5-year follow-up. In both groups, 1% suffered disabling stroke or death procedurally (15 allocated CAS, 18 CEA) and 2% had non-disabling procedural stroke (48 CAS, 29 CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2.5% in each group for fatal or disabling stroke, and 5.3% CAS vs 4.5% CEA for any stroke (RR=1.16, 95%CI 0.86-1.56; p=0.34). Combining RRs for any non-procedural stroke in all CAS vs CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR=1.11, 95% CI 0.94-1.31; p=0.21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects on fatal or disabling stroke are comparable. Clinical Trial Registration Details: Trial registration: ISRCTN21144362 Funding Information: ACST-2 is funded from the core support from the MRC, BHF and CR-UK for the University of Oxford’s Nuffield Department of Population Health (NDPH), and received grants from the BUPA Foundation and National Institute for Health Research (NIHR) Health Technology Assessment program. Analyses were performed in the MRC Population Health Research Unit, NDPH. AH is supported by the NIHR Oxford Biomedical Research Centre. Declaration of Interests: None declared. Ethics Approval Statement: Ethics approval was obtained at each centre and at the UK coordinating centre. Informed consent preceded randomisation.