Carotid Stenting Mortality Linked to Operator Experience

Download this article's Factoid in PDF (& PPT for Gold Subscribers)


Older patients who undergo carotid artery stenting (CAS) have a higher rate of 30-day mortality if their physician performs a low volume of such procedures each year or is in the early stages of gaining experience, researchers report in a study published in the September 28, 2011, issue of the Journal of the American Medical Association. The mortality rate in the Medicare population was higher than previously reported in clinical trials and registries, raising concern that limited experience among clinicians may be jeopardizing outcomes, investigators noted.

The first CAS system was approved by the U.S. Food and Drug Administration (FDA) in 2004 and since then use of carotid stenting has rapidly disseminated into routine clinical practice. However, issues regarding training and minimum volume requirements remain unsettled, and the exact number of operators performing CAS and their experience and outcomes remain largely unknown, according to Brahmajee K. Nallamothu, MD, MPH, of the University of Michigan Cardiovascular Center (Ann Arbor, MI), and colleagues.

In an attempt to address some of these issues, the study authors analyzed Medicare data for 24,701 CAS procedures performed by 2,339 operators between 2005 and 2007.

Mortality Correlates with Experience

Overall, 1,792 new operators performed 11,846 carotid stenting procedures after a national coverage decision by the Centers for Medicare & Medicaid Services (CMS) in March 2005.

The cumulative 30-day mortality rate was 1.9%, with 4.8% failing to use an embolic protection device. The median annual operator volume was 3 cases per year.

Observed 30-day mortality was higher among patients treated by operators with lower annual case volumes (table 1).

Table 1. Thirty-Day Mortality According to Operator Case Volumea

 

 

Very Low
(< 6)

Low
(6-11)

Medium
(12-23)

High
(≥ 24)

30-Day Mortality

2.5%

1.9%

1.6%

1.4%

aP < 0.001.

After multivariable adjustment, patients treated by very low-volume operators had a higher risk of 30-day mortality compared with patients treated by high-volume operators (adjusted OR 1.9; 95% CI 1.4-2.7; P < 0.001).  

The findings were similar in patients treated early vs. late as new operators gained experience. Compared with patients who represented an operator’s 12th procedure or higher, those who were among an operator’s first 11 CAS procedures had a higher risk of 30-day mortality (adjusted OR 1.7; 95% CI 1.2-2.4; P = 0.001).

In addition, patients treated by operators performing fewer than 6 CAS procedures per year showed a higher likelihood of not receiving embolic protection compared with patients treated by operators performing 24 or more such procedures per year (adjusted OR 8.1; 95% CI 4.4-14.9; P < 0.001).

Mortality Rate Nearly Double That of Trials, Registries

The study authors point out that mortality rates in trials and registries such as CREST and CARE are closer to 1% compared with the nearly 2% in the current study.

“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,” they write.

Fewer than 1 in 8 operators in the Medicare study had annual operator volumes of 12 procedures or more. However, the study authors note that restricting use of carotid stenting to highly experienced operators only “is complicated and involves balancing safety concerns with the potential long-term harm of limiting access to an innovative procedure early during its dissemination.”

Still, they say the findings are of concern and suggest that more data on operator experience should be collected in an effort to optimize outcomes.

Potential for Misuse

In an editorial accompanying the study, Ethan A. Halm, MD, MPH, of the University of Texas Southwestern Medical Center (Dallas, TX), says the problem is likely to worsen before it improves because of the increasing number of cardiologists, interventional radiologists, and surgeons performing CAS.

Dr. Halm observes, ‘Selectively referring’ patients to the most experienced, highest-volume operators “would be optimal, but is often unrealistic. Pragmatically, the least experienced operators should be ‘selectively avoided’ unless they can provide acceptable outcome data or other convincing evidence of proficiency.”

Another concern, Dr. Halm notes, is that one-third of the Medicare patients were age 80 or older and 82% were age 70 or older, a subgroup that has been shown to do significantly better with carotid endarterectomy (CEA) than with CAS in several large trials, including CREST.

“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,” Dr. Halm writes. “The most judicious approach would be to continue CMS restrictions on reimbursement of CAS and requirements for credentialing operators and facilities. Ideally, this would also include new requirements for mandatory reporting of audited

30-day death and stroke rates and new … studies to clarify the indications, appropriateness, and outcomes of CAS in both ideal and real-world practice.

“Most critically needed are studies comparing the effectiveness of CAS and CEA with ‘best’ medical therapy among asymptomatic patients with carotid artery disease,” he adds.

Boosting Numbers Could Lead to Overuse

In a telephone interview with TCTMD, Christopher K. Zarins, MD, of Stanford University School of Medicine (Stanford, CA), agreed with Dr. Halm that these data raise concern about CAS being used in older patients.

“Unlike CREST, where the endpoint was stroke and death, the endpoint here is mortality only and the mortality rate is pretty concerning,” Dr. Zarins said. “But the real concern is that the majority of patients were asymptomatic and the marginal benefit in an asymptomatic patient is not great, but if you increase mortality and stroke—which we don’t know because we don’t have the stroke rate—you lose even that marginal benefit of the treatment.”

But Dr. Zarins also cautioned that urging operators to have a certain level of experience, or minimum number of cases, may be a problem too because it could lead to unnecessary stenting.

“I don’t think numbers prove quality,” he said. “You could be an excellent, experienced physician with good judgment and get good results and not be doing the maximum number of cases, and conversely you could be young and inexperienced and doing a huge number of cases and have terrible results. We need to focus on the right numbers, which are the results, not the number of cases.”

 


Sources:
1. Nallamothu BK, Gurm HS, Ting HH, et al. Operator experience and carotid stenting outcomes in Medicare beneficiaries. JAMA. 2011;306:1338-1343.

2. Halm EA. Carotid stenting at the crossroads: Practice makes perfect, but some may be practicing too much (and not enough). JAMA. 2011;306:1378-1380.

 

 

Related Stories:

Disclosures
  • The study was supported by a grant from the National Institutes of Health.
  • Drs. Nallamothu and Zarins report no relevant conflicts of interest.
  • Dr. Halm reports receiving a grant on a related topic from the National Institutes of Health and consulting fees/honoraria from the Foundation for Informed Medical Decision Making.

Comments