Defining the Threshold Surgeon Volume Required to Optimize Patient Outcomes for Carotid Endarterectomy
J. Gregory Modrall, MD, Shirling Tsai, MD, Bala Ramanan, MD, Melissa Kirkwood, MD, Mujtaba Ali, MD, John E. Rectenwald, MD, Carlos H. Timaran, MD, Eric B. Rosero, MD.
University of Texas Southwestern Medical Center, Dallas, TX, USA.
OBJECTIVE: The outcomes for common vascular operations, such as carotid endarterectomy (CEA), are influenced by surgeon volume. However, the minimum number of operations required to achieve favorable outcomes is not known. The objective of the current study was to define the threshold annual surgeon volume for carotid endarterectomy (CEA) required to optimize patient outcomes.
METHODS: The Nationwide Inpatient Sample was analyzed to identify patients undergoing CEA between 2003 and 2009. Annual surgeon volume was correlated with a composite endpoint of in-hospital stroke or death. Mixed linear regression analyses were conducted to estimate the effect of annual surgeon volume on the composite outcome. Receiver operating characteristic curves were used to calculate the Youden Index, which defined the optimal surgeon volume required to minimize in-hospital stroke and death.
RESULTS: A total of 104,918 CEA cases with surgeon identifiers were included in the analysis. The crude in-hospital stroke and death rate for CEA was 1.26 %. As expected, the stroke and death rate after CEA was higher for symptomatic patients, compared to asymptomatic patients (6.46 % vs. 0.72%; P <0.0001). For symptomatic patients, the relationship between surgeon volume and the composite endpoint was not significant (P = 0.435; Figure). In contrast, there was a strong relationship between surgeon and outcomes for asymptomatic patients undergoing CEA (P < 0.0001; Figure). For asymptomatic patients, the threshold annual number of CEAs required to optimize outcomes was 20 CEAs per year (sensitivity = 74.9%, specificity = 2.6%, Youden index = 0.475).
CONCLUSION: Surgeon volume is a significant determinant of outcomes for patients with asymptomatic carotid disease, but not for symptomatic carotid disease. It is likely that surgeon volume does not impact outcomes for symptomatic patients due to the dominant effect of a symptomatic plaque on outcomes. For asymptomatic carotid disease, a threshold number of CEAs required for optimal outcomes may be defined. These data may provide an argument for regionalization of care or establishing minimum case numbers for credentialing of surgeons.
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