Abstract 11225: Effects of Institutional Volumes on Operative Outcomes for Combined Aortic Valve and Ascending Aortic Surgery
Background: Institutional case volumes predict CABG outcomes minimally, but effects on more complex procedures are unclear. This study evaluated the relationship between volumes of combined aortic valve/ascending aortic replacement (AV/AAR) procedures and operative results in North American centers.
Methods: 13,358 elective aortic root and AV/AAR procedures performed from 2004–2007 were evaluated from 741 hospitals in North America. Aortic dissection&non-elective cases were excluded. Aortic root and AV/AAR categories were analyzed as one population because of similarities in baseline and outcome characteristics. Marginal logistic regression modeling using the Generalized Estimating Equations method was employed for risk-adjustment, and baseline and operative characteristics were used as predictor variables. Outcome variables were unadjusted operative mortality (UOM) and adjusted odds ratio for mortality (AORM). The effect of institutional volume was evaluated: 1) as 4 volume categories (I=lowest volume, IV=highest volume) each having an approximately equal number of patients, and 2) as a continuous variable, using regression spline functions.
Results: Preoperative patient risk profiles were minimally different between centers, and overall UOM was 4.9%. UOM increased with decreasing case volume, from 3.4% in highest volume centers to 5.8% in lowest volume centers. In both analyses, the relationship between volume&AORM was non-linear with a negative association between volume and AORM (p<0.001), and an inflection at 30–40 cases/year (Figure).
Conclusions: Surgical results for aortic root or AV/AAR procedures are excellent throughout North America. Lower center-specific case volumes are associated with modestly higher mortalities. While high quality results exist among both low and high volume centers, this finding suggests the general need for further refinement in surgical education, center specialization, and referral structure.
- © 2010 by American Heart Association, Inc.