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Treatment to clear up blockage in the carotid arteries of the neck to prevent stroke is highly variable across the country, potentially illustrating a lack of consensus among doctors about the best way to treat at-risk patients, according to an analysis conducted by researchers at the Duke Clinical Research Institute.

The study, published in the Archives of Internal Medicine, analyzed rates of surgery and stenting among Medicare beneficiaries nationwide immediately before and after a 2004 change in coverage that made the less invasive option of stenting available to more patients.

It found that the number of procedures to treat carotid artery disease dropped slightly (6 percent) from 2003 to 2006. During that time there was a seven- to nine-fold difference between communities with the highest and lowest rates of surgery to remove blockages, known as carotid endarterectomy, across the country.

Significant geographic variation was also found in the use of stents, although less data was available for analysis.

"After adjusting for clinical characteristics, we found clear treatment patterns emerge," said Manesh Patel, MD, assistant professor of medicine at Duke and the study’s lead author. "Uptake (of stenting) was rapid and high in some areas where doctors were already conducting carotid revascularization to clear blockages. In areas where doctors had been doing more surgery, patients tended to start getting more stents."

The lowest rates of both procedures were in New England, Mountain (Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming) and Pacific (Alaska, California, Hawaii, Oregon, and Washington) regions.

The highest rates were found in the East South Central (Alabama, Kentucky, Mississippi, and Tennessee), East North Central (Illinois, Indiana, Michigan, Ohio, and Wisconsin) and West North Central (Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, and South Dakota) regions.

The new study follows conflicting findings in recent randomized trials comparing stents to endarterectomy in patients with carotid artery disease.

The Duke team also analyzed the use of imaging tests performed before the procedures to aid doctors in determining the course of treatment.

“One of the more striking findings of this study is the wide variation in the use of imaging prior to carotid endarterectomy or carotid stenting,” said Lesley Curtis, PhD, associate professor at Duke and senior author.

She noted that more than a quarter of patients in the study received only one test, an ultrasound, while other patients underwent additional imaging tests such as MRA and X-ray angiography.

“These data underscore the need for clear clinical criteria for the use of carotid imaging and subsequent interventions,” Curtis added.

Men and patients with a history of peripheral vascular disease were more likely to undergo carotid revascularization. Patients with a history of carotid artery disease or who had previously undergone a carotid endarterectomy were more likely to get a stent.

“More attention should be directed toward management of stroke risk, including the use of revascularization among patients already experiencing symptoms," Patel said. "We also need further research to understand the best treatment for those patients without symptoms. While our findings show vast differences in the methods of revascularization across the country, the overarching question remains: Which patients are the best candidates for revascularization?”

The study was funded by the Agency for Heathcare Research and Quality.

The research team also includes Melissa Greiner, Lisa DiMartino, Kevin Schulman, Pamela Duncan, and David Matchar.