Abstract 8713: Relative Impact of Surgeon and Center Volume on Outcome Following the Norwood Operation

Abstract

Background: Prior studies have shown that center volume is associated with outcome after the Norwood operation. In adults undergoing cardiac surgery, this volume-outcome relationship has been found to be largely related to surgeon volume. It is unknown whether this is also true for the Norwood operation. We evaluated the relative impact of surgeon and center volume on mortality in a large Norwood cohort. Methods: Infants in the Society of Thoracic Surgeons Congenital Heart Surgery Database undergoing the Norwood operation (2000-2009) were included. Nested regression models were used to evaluate the relationship between in-hospital mortality and annual center and surgeon volume adjusting for patient demographic/anatomic factors. Results: 2555 infants underwent surgery at 53 centers [64% (0-10 cases/yr), 25% (11-20 cases/yr), and 11% (>20 cases/yr)] by 111 surgeons [50% (0-6 cases/year), 39% (7-12 cases/yr), and 11% (>12 cases/yr)]. Overall unadjusted mortality was 22%. In adjusted analysis (Figure), lower center volume was associated with higher mortality (p=0.03 when analyzed as continuous variable; OR for centers with 0-10 vs. >20 cases/yr = 1.6, 95% CI 1.1-2.3, p=0.03). Surgeon volume was not significantly associated with mortality when analyzed as a continuous or categorical variable. When analyzed together, surgeon volume accounted for only a small proportion (11%) of the effect of center volume. At high volume centers, low and high volume surgeons had similar adjusted mortality rates [19% (95%CI 12-27%) vs. 19% (95%CI 16-22%), p=0.7] which were lower than mortality at low volume centers. Conclusions: This analysis suggests outcome following the Norwood operation is influenced more by center rather than surgeon volume. Further investigation is necessary to identify characteristics of high volume centers which may influence outcome, such as processes of care, training and availability of personnel, or senior surgeon mentoring.