Both carotid artery stenting (CAS) and carotid endarterectomy (CEA) offer comparable long-term results and similar rates of fatal or disabling strokes, according to research results published in the Lancet.
Current evidence suggests “approximate similarity” in long-term protective effects with both CAS and CEA. However, these randomized trials have included limited numbers of asymptomatic patients. Therefore, researchers conducted the ACST-2 Trial—an international, multicenter, randomized trial in 33 countries—evaluating the long-term protective effects of CAS and CEA.
Eligible patients had severe unilateral or bilateral carotid artery stenosis with no relevant neurological symptoms in the preceding 6 months, CT or MRI confirmation of CAS or CEA suitability, patient-physician agreement that a carotid procedure should be performed, and no known circumstances precluding patients from a long-term follow up.
Participants were randomly assigned 1:1 to ipsilateral CAS or CEA. Primary outcome included procedural mortality and morbidity and nonprocedural stroke.
A total of 3625 patients from 130 centers in 33 countries were enrolled between 2008 and 2020 (CAS n=1191; CEA n=1814). In the CAS group, 87% of patients underwent their procedure within 1 year (median, 14 days; interquartile range [IQR], 4-33) of randomization. Six percent of these patients crossed over to the CEA group and an additional 6% had no intervention. In the CEA group, the procedure took place within 1 year (median, 14 days; IQR, 4-33); 3% crossed over to CAS and 4% had no intervention.
Reasons for crossover from CAS to CEA included findings of highly calcified stenosis or a more tortuous carotid artery than anticipated, while reasons for crossover from CEA to CAS included patient or physician preference or patient reluctance to undergo general anesthesia.
Among patients who underwent CAS or CES, there was a “small excess” of nondisabling strokes following CAS (45 vs 32) and a “small excess” of myocardial infarction following CEA (4 vs 13); the overall risk of death or disabling stroke, however, was similar (1% vs 0.9%).
Mean hospital stay for patients without complications was 1 day shorter with CAS (4.2±9 days vs 5.4±10 days); two-third of procedural events took place before these medians.
Among 1788 patients who underwent CEA as their first intervention, 5.4% experienced cranial nerve palsy at 1 month; no cranial nerve palsy was seen with CAS.
Mean follow-up duration was 4.9±3.1 years (range, 0-13). Annual follow-up is still ongoing, with a “wide use” of antithrombotic, antihypertensive, and lipid-lowering therapies and no material differences in use between the CAS and CEA groups. In those who had a carotid procedure without a stroke, slightly more in the CAS group experienced a stroke during follow-up.
Over 5-year follow-up, there was no difference between CAS and CEA in incidence of fatal or disabling stroke; total numbers were 155 and 128 in each group, respectively. Nonprocedural stroke incidence RR was 1.16 (95% CI, 0.86-1.57), based on 91 vs 79 strokes.
When overall findings for nonprocedural stroke was subdivided by various baseline characteristics, investigators found little prognostic relevance and no significant evidence of heterogeneity of the treatment effect in terms of age, sex, stenosis, plaque echolucency, or other factors.
A limitation of the ACST-2 trial is the small study sample although it is the largest carotid intervention trial conducted to date.
“There is now as much evidence among asymptomatic as among symptomatic patients, and the findings in both types…are remarkably similar,” the researchers wrote, “with CEA slightly but nonsignificantly better than CAS for nondisabling stroke.”
“Overall, the ratio of long-term stroke incidence rates is 1.11. 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,” they concluded. “Further follow-up of ACST-2 and other trials will provide additional evidence on the durability of their protective effects.”
Halliday A, Bulbulia R, Bonati LH, Chester J, Cradduck-Bamford A, Peto R; for the ACST-2 Collaborative Group. Second asymptomatic carotid surgery trial (ACST-2): a randomized comparison of carotid artery stenting versus carotid endarterectomy. Lancet. Published online August 29, 2021. doi:10.1016/S0140-6736(21)01910-3