Operator Experience and Carotid Stenting Outcomes in Medicare Beneficiaries

Study Questions:

What is the association between outcomes and measures of operator experience for carotid stenting?


This was an observational study using administrative data on fee-for-service Medicare beneficiaries ages 65 years or older undergoing carotid stenting between 2005 and 2007. The main outcome measure was 30-day mortality stratified by very low, low, medium, and high annual operator volumes (<6, 6-11, 12-23, and ≥24 procedures per year, respectively) and treatment early versus late during a new operator’s experience (first to 11th procedure and 12th procedure or higher).


During the study period, 24,701 procedures were performed by 2,339 operators. Of these, 11,846 were performed by 1,792 new operators who first performed carotid stenting after the Centers for Medicare and Medicaid Services national coverage decision. Overall, 30-day mortality was 1.9% (n = 461), and rate of failure to use an embolic protection device was 4.8% (n = 1,173). The median annual operator volume among Medicare beneficiaries was 3.0 per year (interquartile range, 1.4-6.5), and 11.6% of operators performed 12 or more procedures per year during the study period. Observed 30-day mortality was higher among patients treated by operators with lower annual volumes (2.5% [95% confidence interval {CI}, 2.1%-2.9%], 1.9% [95% CI, 1.6%-2.3%], 1.6% [95% CI, 1.3%-1.9%], and 1.4% [95% CI, 1.1%-1.7%] across the four categories; p < 0.001) and among patients treated early (2.3%; 95% CI, 2.0%-2.7%) versus late (1.4%; 95% CI, 1.1%-1.9%; p < 0.001) during a new operator’s experience. 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 odds ratio, 1.9; 95% CI, 1.4-2.7; p < 0.001). Similarly, the authors found a higher risk of 30-day mortality in patients treated early versus late during a new operator’s experience (adjusted odds ratio, 1.7; 95% CI, 1.2-2.4; p = 0.001).


The authors concluded that among older patients undergoing carotid stenting, lower annual operator volume and early experience are associated with increased 30-day mortality.


This study suggests that adjusted outcomes following carotid stenting are worse among very low-volume operators and early during an operator’s experience. The authors reported that fewer than one in eight operators had annual operator volumes of 12 procedures or more during the study period, and patients treated by very low-volume operators and those treated early during a new operator’s experience had significantly higher 30-day risk-adjusted mortality. Despite limitations of these administrative data, it appears that collecting more detailed data about operator experience during the early dissemination of new procedures, like carotid stenting, may help improve outcomes.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention

Keywords: Embolic Protection Devices, Fee-for-Service Plans, Centers for Medicare and Medicaid Services (U.S.), Medicare, Stents

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