Relative impact of surgeon and center volume on early mortality after the norwood operation

Background: Previous studies suggest center volume is associated with outcome after the Norwood operation; however, the impact of surgeon volume is less clear. We evaluated the relative impact of surgeon and center volume on mortality in a large Norwood cohort. Methods: Patients in the Society of Thoracic Surgeons Congenital Heart Surgery Database undergoing the Norwood operation (2000 to 2009) were included. Using multivariable logistic regression, we evaluated the relationship between in-hospital mortality and annual center and surgeon volume, adjusting for patient factors. Results: A total of 2,555 patients were operated on at 53 centers by 111 surgeons. Overall unadjusted mortality was 22.1%. When analyzed individually, both lower center and surgeon volume were associated with higher mortality (odds ratio for centers with 0 to 10 vs >20 cases per year 1.56 [95% confidence interval 1.05 to 2.31]; odds ratio for surgeons with 0 to 5 vs >10 cases per year 1.60 [95% confidence interval 1.12 to 2.27]). When analyzed together, the addition of surgeon volume to the center volume models attenuated but did not completely mitigate the association of center volume with outcome (relative attenuation of odds ratio = 34%). Adjusted mortality rates in low, medium, and high volume centers were 25.6%, 22.3%, and 17.7%, respectively. Across all center volume strata, lower volume surgeons had higher adjusted mortality rates. Conclusions: Both center and surgeon volumes appear to influence Norwood outcomes. These data suggest outcomes may potentially be improved through strategies that take advantage of the positive influence of both of these variables. This could include further investigation into the feasibility of regional collaborations, and the development of quality improvement initiatives within and across centers.