The Natural History of Moderate Carotid Artery Stenosis in a Large Community-Based Cohort and Implications for Carotid Surveillance Among Asymptomatic Individuals

Moderate asymptomatic internal carotid artery stenosis is a poorly defined risk factor for ischemic stroke. In the present study, we have described the long-term risk of stroke in an integrated health care system. All adult patients with asymptomatic moderate internal carotid artery stenosis (50%-69% using the North American Symptomatic Carotid Endarterectomy Trial criteria) from 2008 to 2012 were identified, with follow-up through 2017. Asymptomatic stenosis was defined as no ipsilateral stroke within 6 months of inclusion or a history of ipsilateral carotid intervention. The primary outcome was acute ischemic stroke (AIS) attributed to the carotid artery. Secondary outcomes included disease progression, ipsilateral intervention, ischemic events of another etiology, and long-term survival. Censoring occurred at intervention, death, or loss to follow-up. Overall, 11,614 arteries with moderate stenosis in 9803 patients were identified. Their mean age was 74.2 ± 9.9 years, and 51.4% were women. The mean follow-up was 5.1 ± 2.9 years. The overall mortality rate was 44.6%, with 10.5% of patients lost to follow-up. During the follow-up period, 19,808 studies had been performed in 5951 patients (60.7%), revealing stenosis progression in 1674 arteries (14.4%), including 1614 (13.9%) with progression to severe stenosis and 60 (0.5%) with progression to occlusion. The mean interval to stenosis progression was 2.6 ± 2.1 years. Carotid intervention occurred in 708 arteries (6.1%). Of the 708 arteries, 468 (66.1%) had progressed to severe stenosis. A total of 180 AISs (1.6%) were identified as attribuTable to carotid disease (annual risk, 0.31%; 95% confidence interval, 0.21%-0.41%). Of the 180 patients with AIS, 31 (17.2%) had undergone subsequent intervention. After AIS, 29 patients (16.1%) had died within 30 days and 38 (21.1%) within 1 year; 72 patients (40%) were alive at the end of follow-up. Of the identified AISs, 50 arteries (27.8%) had progressed to severe stenosis or occlusion. Strokes caused by non–carotid etiologies were identified in 599 arteries (5.2%). In the present community-based sample of patients with asymptomatic moderate internal carotid artery stenosis followed up for 5 years, a few patients exhibited disease progression, and the annual incidence of associated stroke was low. Future research is needed to optimize the management strategies for this population.