Asymptomatic carotid artery stenosis is a risk factor of ischemic stroke and cardiovascular mortality. However, the optimal management of severe asymptomatic carotid stenosis with intervention (INT, CEA or CAS) or medical management (MM) is uncertain. Updated population-based studies assessing the management and outcomes in severe asymptomatic carotid artery stenosis are lacking. Therefore, we evaluated the trends in the management of asymptomatic carotid stenosis and compared outcomes based on initial management with INT compared to MM.

We used the Rochester Epidemiology Project medical record linkage system to identify all Olmsted County, MN, USA residents with asymptomatic severe (>70%) stenosis of native internal carotid arteries (ICA) at the carotid bifurcation between 2005 and 2020. Diagnostic imaging, medical records, and death certificates were reviewed to confirm the diagnosis and outcomes. Age- and sex-adjusted incidence rates were estimated using annual county-level census data. The primary outcome was overall survival. Secondary outcomes included stroke-related death and cardiovascular (CV) death. Survival was assessed with Kaplan Meier estimates and comparisons made with Log-Rank test.

We identified 692 patients (55,3% male) with severe ICA stenosis, 79 who had bilateral severe ICA stenoses. The age-sex adjusted incidence of severe ICA stenosis was 38.76 per 100,000 person-years and was higher for males (42.5 vs 31 per 100,000 person-years, age-adjusted). The age-sex adjusted incidence rate significantly decreased from 104.8 to 38.9 per 100,000 person-years (per-year relative risk=0.93, 95% CI 0.92-0.95, p<0.001). Of patients identified, 78,2% underwent initial MM and 21,8% were treated with INT. Patients with initial MM were older (76.2 vs 70.8 yrs, p<.001) and were more often women (83,8% vs 73,6%) compared to those undergoing INT. Patients with atrial fibrillation and COPD were more likely to be managed with MM. Mean follow-up was 6,4 years (range 0-16.8). During the study interval, 63,9% of the patients died with 35 stroke-related deaths: 30 (5.5%) in those initially treated with MM and 5 (3.3%) among those initially treated with INT. There were 121 CV related deaths (100, 18,5% MM and 21, 13,9% INT). Overall survival was 93%, 69%, 42%, and 20% for MM and 97%, 87%, 53%, and 32% for INT at 1, 5, 10, and 15 years, respectively (p<.001). Additionally, freedom from stroke-related death was 99%, 96%, 93% for MM and 99%, 98% and 96% at 1, 5, and 10 years (p=.11). Freedom from CV-related death was 99%, 91%, and 80% for MM and 100%, 96%, and 87% for INT at 1, 5, and 10 years (p=.005).

This study represents one of the few contemporary population-based epidemiological studies of severe asymptomatic carotid artery stenosis. Between 2005 and 2010, the identified incidence of sever ICA stenosis decreased approximately 60%. Most patients were initially managed with medical therapy alone. In accordance with established guidelines, those initially treated with medical therapy alone were older, women or had significant additional comorbidities. This is reflected in associated lower overall survival. Stroke-related death was low and did not differ between management groups. CV-related death remains a major cause for mortality, reinforcing the need for aggressive risk factor control and CV disease management for all patients with carotid artery disease. Further work on the association of intervention with nonfatal stroke and stenosis progression will further clarify factors contributing to these findings.