Cerebral Ischaemic Events in Asymptomatic Carotid Stenosis under Best Medical Therapy: Five Year Results of a Prospective Study (Carotid Asymptomatic Stenosis Study).

Abstract

The role of carotid revascularisation in asymptomatic carotid artery stenosis (ACAS) remains debated. Advances in best medical therapy (BMT) may have lowered the risk of cerebral ischaemic events (CIEs), but optimal treatment strategies are still unclear. This study presents the five year results from a prospective, observational cohort of ACAS patients treated with BMT in a real world setting. The Carotid Asymptomatic Stenosis Study (CARAS) study (NCT04825080) enrolled patients with ACAS ≥60% (North American Symptomatic Carotid Endarterectomy Trial [NASCET] criteria) who were ineligible for revascularisation due to high surgical risk or absence of plaque vulnerability, between 2019 and 2020, with planned five year follow up. BMT was defined as appropriate use of antiplatelets, statins, antihypertensives, and smoking cessation. The primary endpoint was the rate of ipsilateral CIE (stroke, transient ischaemic attack [TIA], or amaurosis fugax). Secondary endpoints were plaque progression, identification of predictors of CIE, BMT adherence, and survival. Follow up included annual clinical and duplex scan assessments and six month telephone interviews. The study enrolled 307 patients with a mean age of 80 ± 7 years; 54.4% were men. Bilateral carotid artery stenosis ≥60% was present in 61 (19.9%) patients. At enrolment, 238 (77.5%) patients were on BMT. During follow up, there were eight (2.6%) ipsilateral strokes and 14 (4.6%) TIAs, for a total of 20 CIEs (two patients had TIA and stroke). The five year survival was 80 ± 2%, and the cumulative CIE rate was 6 ± 2% and CIE annual rate was 1.3%. Sixty five (21.2%) patients had carotid stenosis progression, which was associated with a higher risk of CIE compared with patients with stable plaques (9.2 ± 4% vs. 4.5 ± 1%; p = .010). Similarly, bilateral carotid artery stenosis ≥60% was associated with a higher CIE rate (9.3 ± 4% vs. 3.4 ± 1%; p = .001). These two factors were independently associated with high risk of CIE in the multivariable Cox analysis (hazard ratio [HR] 3.2, 95% confidence interval [CI] 1.1 - 9.2; and HR 3.6, 95% CI 1.2 - 10.5). ACAS patients under BMT have a relatively low CIE risk, but plaque progression and contralateral stenosis increase it. These findings may help refine indications for carotid revascularisation.