Back to 85th Annual Meeting
Back to Program Outline

33. Effect of patient and prosthesis size on operative mortality after aortic valve replacement
Charles R. Bridges, Joseph C. Cleveland, Edward B. Savage, James S. Gammie, Sean M. O'brien, Fred H. Edwards, Elizabeth R. Delong, Eric D. Peterson, Frederick L. Grover; Philadelphia, PA; Denver, CO; Chicago, IL; Baltimore, MD; Durham, NC; Jacksonville, FL; , NC; , CO

OBJECTIVE: Controversy exists as to the best definition of small patient/prosthesis size and its impact on mortality after AVR. Definitions utilized previously have included those based on indexed effective orifice area (EOA/body surface area (BSA)) and indexed geometric orifice area (GOA/BSA), expressed as [cm²/m²]. The earlier retrospective studies included CABG patients and involved selected, relatively small populations that may not be representative of the national experience.
METHODS: A review of the Society of Thoracic Surgeons National Cardiac Database (2000 - 2003) yielded 39,697 patients that underwent isolated AVR. This analysis is based on the cohort of 33,611 patients with the eight most prevalent valve types with nominal sizes 19 mm through 29 mm. Both univariate analysis and multivariate logistic regression models were employed to determine the effects of BSA, EOA, GOA, indexed EOA and indexed GOA on risk-adjusted operative mortality.
RESULTS: In a bootstrap analysis, EOA consistently ranked first as the best univariate predictor of mortality among variables related to prosthesis or patient size. The C-statistics for EOA, EOA/BSA, GOA and GOA/BSA were 0.61, 0.57, 0.56 and 0.51, respectively. In a multivariate analysis which included only EOA/BSA as a surrogate for patient/prosthesis size, EOA/BSA was inversely correlated with operative mortality (Model 1). When EOA rather than EOA/BSA was the surrogate for patient/prosthesis size, it had an even more significant effect on mortality (Model 2). An unanticipated finding was that with EOA in the model, EOA/BSA was no longer a significant predictor of operative mortality (Model 3). When EOA/BSA was excluded, elevated BSA was associated with a significant reduction in mortality (Model 1). This protective effect of BSA was no longer significant if EOA was included as a risk factor (Models 2 & 3). In addition, the effect of EOA on mortality did not differ significantly over different levels of BSA (data not shown.)
CONCLUSIONS. : Both EOA or EOA/BSA alone are strong independent predictors of operative mortality after isolated AVR. With the inclusion of both predictors in a multivariable model, however, only EOA remains as a significant independent predictor of operative mortality after AVR. The apparent protective effect of larger BSA on mortality may simply be a surrogate of a larger EOA and the associated reduction in operative mortality. Collectively these data suggest that small prosthesis size adversely impacts operative mortality after AVR.

Back to 85th Annual Meeting
Back to Program Outline