JAMA: Lower operator volume affects 30-day mortality during CAS
After covered stent deployment, lateral view, demonstrating Jostent covered stent in cavernous segment of internal carotid artery along guide wire.
Image source: Korean J Radiol 2010;11(6):603–611.
As carotid artery stenting (CAS) use becomes more prevalent, particularly with expanded indications, a study published Sept. 28 in the Journal of the American Medical Association found that lower operating volume and early experience increased 30-day mortality rates in older patients. In an accompanying editorial, Ethan A. Halm, MD, MPH, University of Texas Southwestern Medical Center, Dallas, wrote that while the current study showed that “practice makes perfect,” it also may have demonstrated that physicians may be “practicing [CAS] too much.”

The use of CAS has nearly doubled since its approval by the FDA in 2004, Brahmajee K. Nallamothu, MD, MPH, of the University of Michigan Medical School, Ann Arbor, and colleagues wrote. Despite the increase in use and its potential benefits, there are still risks involved with the procedure. “Carotid stenting is a technically demanding procedure and earlier studies have demonstrated a substantial learning curve with it,” the authors wrote. Yet recommendations for case volumes and operator experience vary.

To evaluate the association between outcomes and operator experience and annual volume, Nallamothu and colleagues performed an observational study that used administrative data on Medicare beneficiaries ages 65 or older who underwent CAS between 2005 and 2007.

The researchers used 30-day mortality rates stratified by very low, low, medium and high annual operator volumes (less than six, six to 11, 12-23 and more than 24 procedures per year, respectively), and early vs. late treatment during a new operator's experience as the study’s primary endpoint.

In total, 24,701 procedures were performed by 2,339 operators. A total of 639 operators performed six or more procedures per year and 272 operators performed 12 or more procedures per year. Of the total procedures, 11,846 were performed by 1,792 new operators who first performed CAS after the Centers for Medicare & Medicaid Services (CMS) coverage decision.

Nallamothu and colleagues reported 30-day mortality rates to be 1.9 percent. Operators failed to use an embolic protection device in 4.8 percent of cases. The researchers reported median annual operator volume among Medicare beneficiaries to be three per year and 11.6 percent of operators performed 12 or more procedures per year during the study period.

Thirty-day mortality rates were higher in patients treated by operators with less experience. These rates were 2.5 percent, 1.9 percent, 1.6 percent and 1.4 percent, respectively, across the four categories of very low, low, medium and high. The 30-day mortality rates were higher in patients treated early vs. late, 2.3 percent vs. 1.4 percent.

The researchers concluded that patients treated by operators with a lower volume case load had a higher risk of 30-day mortality compared with patients treated by high-volume operators.

“Although the higher mortality rates we identified are likely being driven to a large extent by an older and less selected population of patients, we identified an additional factor that may be contributing: limited operator experience with carotid stenting as the procedure has disseminated into routine clinical practice,” Nallamothu et al noted.

During the study, Nallamothu and colleagues found that only one in eight operators had annual operator volumes that equated to 12 or more.

The authors said ensuring that physicians are adequately trained for new and complex procedures remains a “challenge.” In fact, due to the fact that CAS is performed by a variety of different specialists—cardiologists, radiologists and staff from surgery—the varying clinical backgrounds and skill sets make it difficult to standardize education programs.

“Of course, making policy decisions about restricting use of carotid stenting to highly experienced operators is complicated and involves balancing safety concerns with the potential long-term harm of limiting access to an innovative procedure early during its dissemination,” the authors wrote.

“[C]ollecting more detailed data about operator experience during the early dissemination of new procedures, like carotid stenting, may help optimize outcomes,” the authors concluded.

Halm said that Nallamothu et al found that when carotid endarterectomy (CEA) was performed in an early dissemination phase, one-third of cases were deemed inappropriate. Halm wrote that these findings “suggest that a substantial proportion of CAS cases would also probably be deemed inappropriate.” This, he concluded, was because there was a high proportion of older, sicker patients who were asymptomatic during the trial.

“A procedure performed in a patient who would not be expected to benefit from it is inappropriate and wasteful regardless of how skilled the operator or how low the complication rate,” Halm said.

Halm also added that it may be difficult to know whether a procedure will be performed by a skilled operator. “In the absence of knowing a physician’s actual clinical outcomes or experience, referrals to most CAS proceduralists may result in suboptimal outcomes because most are very low-volume operators who are early in the learning curve.

“Pragmatically, the least experienced operators should be 'selectively avoided' unless they can provide acceptable outcome data or other convincing evidence of proficiency,” Halm concluded.

"Without careful policies to ensure appropriate use and dissemination of CAS, the procedure may be misused and overused, as was seen early in the diffusion of CEA and percutaneous coronary interventions," Halm noted. "The most judicious approach would be to continue CMS restrictions on reimbursement of CAS and requirements for credentialing operators and facilities.”