Reviwer : Dr. Ümit Yaşar Sinan

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

Published Congress: ESC 2021

Link: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01910-3/fulltext

Background:

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. About half are to prevent recurrent stroke in symptomatic patients and half are for primary stroke prevention in asymptomatic patients. Among asymptomatic patients with severe (eg, 70–99%) stenosis, successful CEA approximately halves the long-term stroke risk. Both CAS and CEA, however, carry a short-term risk of stroke, which is about twice as great for symptomatic as for asymptomatic patients. The evidence thus far from randomised trials of CAS versus CEA suggests approximate similarity of the long term protective effects of the two procedures, but it has involved only limited numbers of asymptomatic patients.

Objective:

The ACST-2 trial, with a larger number of participants, aimed to provide more robust comparisons of the long-term protective effects of CAS versus CEA.

Methods:

ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention.

Results:

Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres in 33 countries were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Patients characteristics were similar between groups. Among those who actually had CAS or actually had CEA, there was a small excess of non-disabling strokes after CAS (45 vs 32, including 15 vs 6 with no residual symptoms at all [mRS score 0]) and a small excess of myocardial infarction after CEA (4 vs 13), but the overall risk of death or disabling stroke was similar: CAS 1.0% (17 of 1653) versus CEA 0.9% (15 of 1788). The mean duration of follow-up was 4.9 years and the use of antithrombotic, antihypertensive, and lipid-lowering therapy were similar between those allocated CAS and CEA. At 5-year follow-up there was no difference between CAS and CEA in the incidence of fatal or disabling stroke. Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21).

Conclusion:

With ACST-2 included, there is now as much evidence among asymptomatic as among symptomatic patients, and the findings in both types of patient are remarkably similar, with CEA slightly but non-significantly better than CAS, at least for non-disabling stroke. Overall, the ratio (CAS vs CEA) of long-term stroke incidence rates is 1.11 (95% CI 0.91–1.32; p=0.21). As previous studies have shown successful CEA to be substantially protective, this RR of 1.11 (which includes the ACST-2 result) shows that the protective effects of CAS and CEA are similar for at least the first few years. Further follow-up of ACST-2 and other trials will provide additional evidence on the durability of their protective effects.

Interpretations:

Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable.