Carotid Artery Stenting Outcomes Vary Widely by Hospital

Salynn Boyles

F3.largeIn-hospital outcomes among patients undergoing CAS in the US varied fourfold after adjusting for differences in patient risk factors in an analysis of data from a large, nationwide stenting registry. From MedPage Today.

In-hospital outcomes among patients undergoing carotid artery stenting (CAS) in the U.S. varied fourfold after adjusting for differences in patient risk factors in an analysis of data from a large, nationwide stenting registry.

Significant variation was seen among hospitals performing CAS in both in-hospital stroke and death, with the risk-adjusted variation ranging from 1.2% to 4.7%, researcher Beau M. Hawkins, MD, of the University of Oklahoma Health Sciences Center, Oklahoma City, and colleagues wrote in the journal JACC: Cardiovascular Interventions, published online May 18.

The finding suggests that significant quality differences may exist among U.S. hospitals performing CAS, the researchers noted.

“Future work is needed to identify additional sources of this variation and to develop initiatives to improve the quality of care for patients receiving CAS,” they wrote.

Specifically, a more systematic way of identifying CAS hospital outliers is needed, study co-author Kenneth Rosenfield, MD, of Massachusetts General Hospital and Harvard Medical School, told MedPage Today.

“Carotid endarterectomy (CEA) and CAS both need to have similar outcomes assessment by unbiased individuals,” Rosenfield said. “And, of course, just like any high level procedure, both CAS and CEA should be done only by those appropriately trained, who select their cases well and use proper technique.”

Learning Curve Steep for CAS

Carotid artery stenting is an increasingly used alternative to CEA in the U.S., with one study of Medicare recipients showing a more than fourfold rise in the CAS procedures between 1998 and 2007, while the use of CEA declined.

“CAS is a procedure with a well-established learning curve and is performed by providers from a variety of medical specialties with patient selection practices and technical expertise that may differ,” Hawkins and colleagues wrote. “For these reasons, significant variation in CAS outcomes might be anticipated.”

In an effort to better understand the extent to which CAS outcomes vary by hospital, the researchers analyzed in-hospital stroke and death data from the American College of Cardiology’s Carotid Artery Revascularization and Endarterectomy (CARE) registry.

The analysis included close to 19,400 CAS procedures conducted at 188 hospitals performing five or more of the procedures between 2005 and 2013. Using a previously validated risk model, the researchers estimated unadjusted and risk standardized in-hospital stroke and death rates by individual hospital.

Among the major findings:

  • The mean unadjusted in-hospital stroke/death rate across the cohort was 2.4%.
  • The unadjusted stroke/death rate variations ranged from 0% to 18.8%, while the adjusted rate ranged from 1.2% to 4.7%.
  • The odds of experiencing stroke or death differed by around 50% (mean odds ratio 1.51) among two randomly selected hospitals treating an identical patient.
  • Physician and hospital volume were not significant predictors of outcomes after adjustment for case mix (P=0.15 and P=0.09, respectively)

The finding that increased hospital CAS volume did not predict outcomes contradicted several other studies showing an improvement in outcomes among patients treated at high CAS-volume hospitals.

The researchers speculated that therapeutic advances, such as embolic protection, and improved patient selection may have mitigated the association between volume and outcomes.

“The best outcomes were in hospitals performing fewer than one (CAS) a month, the next best were in those performing about 1.5 a month and the worst in those performing about 2 a month,” interventional cardiologist Kirk N. Garratt, MD, of North Shore LIJ Health System told MedPage Today in an email exchange. Garratt was not involved with the study.

“This seems to imply that you can’t improve your odds of a good outcome by choosing a hospital with the greatest volume and experience in this complex procedure, which is opposite of what we expect for complex medical procedures,” Garratt said.

Operator Skill Likely Cause of Hospital Variation

John W. Hirshfeld Jr., MD, who practices interventional cardiology at the University of Pennsylvania Health System, Philadelphia, noted that the CAS variability is similar to the variability reported for CEA.

“CAS, like CEA is a technically demanding and complex procedure, not a generic procedure,” he told MedPage Today. “Thus, it is logical to find that CAS operator proficiency varies. Because it is possible to perform CAS with a very low risk-adjusted frequency of stroke and death, CAS operators should be held to that high standard.”

Potential study limitations cited by the researchers included the limited generalizability to non-CARE facilities, the inclusion of only events that took place in the hospital setting, and possible unmeasured confounders that may have influenced the findings.

“The fact that risk adjustment has such a big effect on the range of risk shows just how important patient characteristics are in determining outcomes,” Garratt noted, adding that the complexity of the blood vessel undergoing stenting is an important factor.

“Some blood vessel features were included, but not all, and some important things, like the degree of hardening of the artery and how much it twists, weren’t studied but have a big impact. I suspect that if we had more complete information about the blood vessels getting stents, we’d find that the differences are not actually very great at all.”

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