Carotid endarterectomy (CEA) has a small but significant effect on stroke prevention through eight years compared with no surgery, investigators who carried out a cohort analysis in a large integrated health system found.
A research team led by Robert Chang, MD, assistant chair of vascular surgery at Kaiser Permanente Foundation Hospital in San Francisco, made the discovery following a retrospective study that sought to emulate a randomized trial using observational data. The findings were delivered during SVS ONLINE Scientific Session 7 on July 1.
“Since the publication of the ACAS (Asymptomatic Carotid Atherosclerosis Study) trial in 1995, the evolution of medical management and the optimal role of carotid endarterectomy in stroke prevention has been an area of intense debate and study,” explained Chang.
“According to data from ACAS, ACST (Asymptomatic Carotid Surgery Trial) and the 10-year ACST report, the number needed to treat in order to prevent one stroke was 17, 19 and 22, respectively. Similarly, performing 100 CEAs compared with medical management alone would prevent 5.9, 5.3 and 4.6 strokes, respectively.” Short of the results of studies like CREST 2 (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial), further population- based research is needed to assess the contemporary benefit of CEA, he argued.
The purpose of the study by Chang et al was to examine the effectiveness of CEA with standard medical management compared with standard medical management alone for the prevention of stroke in asymptomatic patients.
The investigators identified all patients with 70-99% asymptomatic carotid stenosis with no prior intervention within the previous six months. Some 3,824 eligible patients met eligibility criteria.
Participants were followed from their first imaging study between 2008 and 2012 through the earliest of: ipsilateral ischemic stroke (the primary outcome), death, health plan disenrollment, or December 2017, the researchers noted. Event-free survival was followed over eight years between two treatment strategies: intervention within 12 months from cohort entry versus no intervention during the entire follow-up.
The mean age of the cohort was 74, 58% of whom were male, while 73% were white, 12.3% were active smokers and 21.7% were diabetic. A total of 1,467 underwent CEA, with 2,357 not doing so. During the study, 38% completed follow-up without an outcome, 46% died, 12% lost membership, and 158 patients, or 4.1%, experienced the primary outcome.
“When we look at the risk difference calculated as a percentage, we show a statistically significant advantage with surgery starting in year two, with a relatively small absolute effect,” Change told attendees. “Starting in year three, the risk difference favoring surgery is between 2 and 3% out to eight years.”
The findings show that for every 100 patients, three strokes could be prevented if these 100 patients underwent surgery compared to if they did not out to eight years, he continued. “As surgeons, we appear to do a good job of selecting patients for surgery, perhaps in a way that escapes capture in an electronic system.”
The adjusted hazard ratio (0.81, 95% CI, 0.68–0.93) and cumulative risk differences for each year of follow-up demonstrated the protective effect of intervention starting in year two through year eight compared with patients not receiving either intervention.
Summing up, Chang added: “Further study is required to identify unmeasured confounders and the relationship with mortality in this high-risk population. The small absolute effect and the resource utilization needed to bring about such an effect requires further research into appropriate patient selection.
“As we await the results of ongoing randomized trials, population-based research can inform this challenging problem in vascular surgery.”