Study Observes Early Risk With Stenting vs Surgery in Asymptomatic Carotid Disease

In asymptomatic patients, carotid artery stenting (CAS) more than doubles the risk of postoperative stroke or in-hospital death compared with carotid endarterectomy (CEA), reports a retrospective study published online November 25, 2014, ahead of print in Stroke.

Low annual case volume—individual operators averaged only 1.5 per year—may be responsible for the excess in adverse outcomes associated with CAS, suggest Anthony S. Kim, MD, MAS, of the University of California, San Francisco, and colleagues.

For the retrospective cohort study, the researchers identified 21,678 patients with asymptomatic carotid stenosis who underwent CAS (n = 3,962; 18.3%) or CEA (n = 17,716; 81.7%) at 188 University HealthSystem Consortium hospitals between 2010 and 2012.

There were numerous differences between CEA and CAS patients. The latter tended to be younger, black, and have comorbidities including CAD, PAD, chronic kidney disease, and heart failure. Yet they also were less likely to have the risk factors of hypertension, hyperlipidemia, and smoking. In all, 59% of patients were considered high risk for CEA due to age greater than 80 years, congestive heart failure, CAD, or chronic lung disease.

Median annual volume of CAS procedures was 1.5 per physician and 4.2 per hospital. For CEA, the median values were 3 per physician and 20.2 per hospital. Hospitals averaged a median of 26.7 carotid revascularizations per year; CAS procedures accounted for a greater proportion of cases at the hospitals with higher annual volume (P < .001).

Risk Still Apparent After Adjustment

The crude rate of postoperative stroke or in-hospital death was higher in CAS-treated patients (4.0% vs 1.5%), a difference that remained both in logistic regression analysis adjusting for age, sex, race, and comorbidities (OR 2.54; 95% CI 2.07-3.11)and in propensity score analysis of 3,935 matched pairs (OR 2.50; 95% CI 1.85-3.37; P < .001 for all).

Hospitals performing a higher proportion of CAS had greater odds of inducing postoperative stroke or in-hospital death than those where CAS was less common, even after adjustment for patient-level variables (P < .001). At the physician level, higher case volume was associated with better outcomes for CEA but not CAS. “[But] because the annual caseload for CAS was low in this study, the failure to define a clear volume-outcome relationship should be interpreted with caution,” the researchers stress.

Yet overall, the study findings “are consistent with the view that widespread prophylactic use of CAS for asymptomatic carotid stenosis is not justified without additional evidence of clear benefit,” they conclude.

Dr. Kim told TCTMD in an email that the study contributes to the evidence base “but by no means settles the issue on its own.” High-quality data from registries and, ideally, randomized trials are required, he added.

A Shift Toward CAS

In an editorial accompanying the paper, A. Ross Naylor, MD, of Leicester Royal Infirmary (Leicester, England), reports that the proportion of asymptomatic patients in the US receiving CAS grew from 3% in 1998 to 13% in 2008.

“This happened despite the absence of adequately powered randomized trials and was largely the consequence of industry-sponsored high risk for surgery registries that ultimately demonstrated risks compatible with the 3% American Heart Association (AHA) threshold,” Dr. Naylor comments. That growth continued, he adds, with publication of CREST and the subsequent endorsement by guidelines of CAS as an alternative to CEA in highly selected, average-risk asymptomatic patients.

According to Dr. Kim, the rising popularity “of CAS is probably influenced by some combination of supply and demand—supply given that there are fewer surgeons than endovascular interventionalists, and demand in that some patients may find the idea of recovery from an endovascular procedure more appealing rather than a surgical procedure, particularly when there are no current symptoms.”

Low Case Volume a Problem

But the low volume of CAS procedures is “somewhat disturbing,” writes Dr. Naylor, pointing out that the situation makes it difficult to monitor and improve performance.

“CAS practitioners have worked extremely hard to prove that appropriately credentialed physicians can safely perform CAS within registries and randomized trials,” he comments. “However, CAS practitioners now face a period of enhanced scrutiny on real-world practices and many will surely question (on clinical governance grounds alone) whether it remains appropriate for some of their colleagues to perform 1 to 2 CAS procedures each year, especially in the (already controversial) patient with asymptomatic disease.”

William A. Gray, MD, of Columbia University Medical Center (New York, NY), took a stronger stand in a telephone interview with TCTMD. Speaking to operators conducting only 1 case per year, he said: “You should be ashamed of yourself…. You shouldn’t do it.”

Case volumes across the country are inconsistent, Dr. Gray said. He reported that the Centers for Medicare and Medicaid Services (CMS) has approved 1,300 US sites to do CAS, of which 300 are higher-volume centers that took part in the industry-sponsored studies.

According to Dr. Gray, “CMS has refused to reinitiate or re-allow these registries and single-arm studies to continue, so volumes in the United States for carotid stenting have plummeted. That has a material impact on outcomes.”

Earlier this year, he said, a multispecialty group of physicians unsuccessfully petitioned CMS to require “coverage with evidence development” for CAS. Such a policy—already in place for TAVR, for example—“would not expand coverage but actually reduce the number of sites, concentrate the volume and experience, and presumably provide better outcomes for the patients,” he asserted.

Dr. Gray took issue with the current paper, however, arguing that data on CAS and CEA are incomparable. “These are fundamentally different patient sets in terms of their severity of illness,” he stressed, adding that neurological assessment is required by CMS for CAS patients but is rare in those undergoing CEA.

 

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Sources:
1. Choi JC, Johnston SC, Kim AS. Early outcomes after carotid artery stenting compared with endarterectomy for asymptomatic carotid stenosis. Stroke. 2014;Epub ahead of print.
2. Naylor AR. The brighter the light, the darker the shadow [editorial]. Stroke. 2014;Epub ahead of print.

 

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