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Objective: To investigate incidences of ipsilateral ischemic stroke (IS) and other outcomes for medically and surgically treated asymptomatic carotid stenosis (ACS).

Methods: The Swedish vascular registry (Swedvasc) was used to identify patients undergoing carotid intervention, who had a contralateral nonoperated ACS (medically treated ACS), as well as patients with surgically treated ACS from 2008 to 2017. Swedvasc was merged with the national stroke register to determine stroke incidence. Hospital records were obtained to determine stroke type and laterality. Primary outcome was ipsilateral IS beyond the perioperative 30-days period. Secondary outcomes included any stroke and all-cause mortality. For surgically treated ACS, perioperative stroke or death and the composite outcome perioperative stroke or death plus late ipsilateral IS were analyzed. Cox regression was used to analyze the influence of clinical risk factors and assess risk differences between groups.

Results: There were 1457 patients with medically treated ACS and 1023 patients with surgically treated ACS. Patients with medically treated ACS were almost 5 years older than those with surgically treated ACS. Mean yearly incidences of outcomes for medically and surgically treated ACS were 1.1% and 0.3% for ipsilateral IS, 2.4% and 1.2% for any stroke, and 5.6% and 3% for all-cause mortality. Clinical risk factors were not significantly associated with ipsilateral IS in either group, including severity of baseline stenosis (50%-69% vs 70%-99%). Comparing ipsilateral IS for medically treated ACS with perioperative stroke or death (2.6%) plus late ipsilateral IS for surgically treated ACS resulted in a projected minimum number needed to treat by surgery of 71 to avoid one ipsilateral IS over 5 years.

Conclusions: The incidence of ipsilateral IS was low in patients with medically treated ACS and very low in those treated surgically. The present results suggest that the best medical treatment is preferable for most patients with ACS.