Carotid Stenting vs Surgery: Latest Data on Restenosis Rates

June 25, 2018

Carotid artery stenting is associated with a higher long-term risk for moderate or higher restenosis than is the surgical procedure of endarterectomy, but this did not seem to translate into an obvious higher risk for stroke with stenting, new findings from the International Carotid Stenting Study (ICSS) show.

While restenosis after revascularization of the carotid artery increased the risk for subsequent stroke overall, this risk appeared to be more pronounced in patients who had undergone endarterectomy.

The ICSS is the largest randomized trial to date comparing stenting with endarterectomy for symptomatic carotid stenosis. Initial results showed a higher early risk for stroke with stenting, but long-term follow-up showed similar stroke rates with the two procedures and no difference in the long-term risk for severe (≥70%) restenosis.  

The researchers now report a prespecified secondary analysis of the study focusing on long-term risk for at least moderate (≥50%) restenosis and whether this predisposed to a higher risk for subsequent stroke after either procedure.

The results are reported in a paper published online in Lancet Neurology on May 31.

"We did find quite a difference in moderate restenosis with a higher rate after stenting compared to surgery (40% vs 29%)," senior author Martin Brown, FRCP, Stroke Research Centre, Department of Brain Repair and Rehabiliation, Institute of Neurology, University College London, United Kingdom, commented to Medscape Medical News.

"In addition, although the rates of severe restenosis were not significantly different, there was a numerical increase in the stenting group (10.6% vs 8.5%), but the numbers are small, so I think we can say it is quite common to have some restenosis in both groups and those undergoing stenting do seem to be more likely to get restenosis, but the important question is whether that led to symptoms (ie, stroke) or not," he said.

Their results suggest that restenosis was associated with new ipsilateral stroke, "but this was more pronounced in the surgery group," he added. "So this makes things quite confusing — restenosis rates are higher in the stented group but the restenosis in the surgery group appears to be more closely linked to future stroke."

Brown suggested that the results may be explained by different mechanisms of restenosis in stented vs surgery patients.

"Restenosis after stenting may involve more smooth muscle hypertrophy, which may have a smoother presentation and so is less likely to cause symptoms, whereas restenosis after endarterectomy may be more due to the recurrence of atherosclerosis and may be different in terms of risk," he commented.

"At the end of the day the risk of stroke associated with restenosis is low in both groups and that is reassuring," he noted. In patients with restenosis, the cumulative 6-year risk for stroke was 6.9% compared with 2.5% among those without restenosis.  

He says overall results from the ICSS do not definitely favor either procedure. "I don't think we can say one procedure is definitely better than the other. After our initial results were reported showing an increased rate of early stroke in the stented group, then stenting fell out of favor. But over the long term, late stroke rates were similar in the two groups."

In addition, the early increased stroke risk was seen only in older patients, and there was no difference between the two procedures in terms of early or late stroke risk in those under age 70 years, Brown added.

"In some centers patients under 70 are mainly stented and those over 70 get surgery, but other factors also come into play, such as the anatomy and position of the stenosis. In the UK we don't have very many interventionalists with a large experience of carotid stenting, so we tend to do mostly surgery, but in the US and some European countries more stenting is performed," he said.

"I would say our latest results are overall quite reassuring in that they suggest that while moderate restenosis is quite common — and a bit higher with stenting vs surgery — it does not often lead to stroke, and there isn't much to choose between the two procedures in this regard." 

Endarterectomy remains "the gold standard," Brown concluded, "but stenting is still an acceptable choice for some patients and it is a valuable alternative to surgery for suitable patients."  

The current paper reports long-term (median, 4 years) follow-up carotid ultrasound results from 1530 of the original 1713 patients with symptomatic carotid stenosis who had been randomly assigned to stenting or endarterectomy.

The cumulative 5-year risk for moderate or higher (≥50%) restenosis was 40.7% with stenting and 29.6% with endarterectomy (unadjusted hazard ratio [HR], 1.43; 95% confidence interval [CI], 1.21 - 1.72; P < .0001).

In patients with moderate or higher stenosis, the cumulative risk for ipsilateral stroke at 6 years was increased in the overall study population (unadjusted HR, 3.18; 95% CI, 1.52 - 6.67; P = .002) and in those who underwent endarterectomy (HR, 5.75;  95% CI, 1.80 - 18.33; P = .003). No significant increase in stroke risk after restenosis was recorded in the stenting group (HR, 2.03; 95% CI, 0.77 - 5.37; P = .154).

In patients with severe (≥70%) stenosis, risk for restenosis did not differ between treatment groups (cumulative 5-year risk, 10.6% with stenting vs 8.5% with endarterectomy; unadjusted HR, 1.20; 95% CI, 0.86 - 1.69; P = .27), and no increased risk for ipsilateral stroke was noted (HR, 1.79; 95% CI, 0.64 - 4.99; P = .263).

Routine Surveillance

In an accompanying Comment, Seemant Chaturvedi, MD,  University of Miami Miller School of Medicine, Florida, says that these latest results suggest that the value of information obtained from routine surveillance after endarterectomy or stenting is uncertain for guiding a change in treatment.

"Although an increased risk of stroke was seen in patients with at least moderate (≥50%) stenosis, the mechanism of the stroke was not clear, and this information could be important because if a stroke is due to cardiac embolism or is a lacunar stroke, then operating on the restenotic lesion will not be helpful and could be harmful," he writes.

He also says the practical conclusions that clinicians should take from this study are unclear.

He points out that intensified medical treatment seems reasonable, but its efficacy has not been proven in clinical trials of patients with a previous stroke. And endarterectomy or stenting procedures for asymptomatic stenosis are of uncertain value.

Chaturvedi calls for future studies to try to understand the mechanism of ipsilateral stroke in patients with restenosis and to address the pathology of these lesions.

Noting that female sex, diabetes, dyslipidemia, continued smoking, and impaired cerebrovascular reactivity have been associated with restenosis, he writes: "Since predictors of restenosis exist, a targeted imaging programme focused on patients with the highest risk for restenosis might be a more sensible strategy than indiscriminate surveillance of all patients."

He notes that current guidelines from the American Heart Association and the American Stroke Association state that routine long-term follow-up imaging with carotid duplex ultrasound is not warranted in patients after revascularization. 

By identifying the group of patients at increased risk for stroke, the current study shows that follow-up imaging has some prognostic value, but the treatment steps to address the increased stroke risk are uncertain, he concludes.

The ICSS  was funded by grants from the UK Medical Research Council, the Stroke Association, Sanofi-Synthélabo, and the European Union. Brown reports grants from the Medical Research Council, the Stroke Association, Sanofi-Synthélabo, and the European Union.

Lancet Neurol. Published online May 31, 2018. Abstract, Comment 

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