Center-Level CABG and Valve Operative Outcomes and Volume-outcome
Relationships in New York State
Background: We analyzed center-level outcome correlations between valve
surgery and coronary artery bypass graft (CABG) in New York (NY) State
and how volume-outcome effect differ between case types. Methods: We
used the 2014-2016 NY cardiac surgery outcomes report. Center-level
observedto-expected (O/E) ratio for operative mortality provided
risk-adjusted operative outcomes for isolated CABG and valve operations.
Correlation coefficient characterized the concordance in center-level
outcomes in CABG and valve. Discordant outcomes were defined as having
O/E ratio >2 in one operation type with O/E ratio ≤1 in
another. Linearized slope of volume-outcome effect in case types offered
insights into centers with discordant performances between procedures.
Results: Among 37 NY centers, annual center volumes were 220±120 cases
for CABG and 190±178 cases for valve operations. Modest center-level
correlation between CABG and valve O/E ratio was shown (R2 = 0.31). Two
centers had discordant performance between valve and CABG (O/E ≤1 for
CABG while O/E > 2 for valve procedures). No centers had
CABG O/E ratio > 2 while valve O/E ratio ≤1. Linearized
slope describing volume-outcome effects showed stronger effect in valve
operations compared to CABG: O/E ratio declined 0.1 units per 100 CABG
volume increase, while O/E ratio declined 0.33 units per 100 valve
volume increase. Conclusions: In NY hospitals, favorable valve outcomes
may indicate good CABG outcomes but good CABG outcomes may not ensure
valve outcomes. Outcome variation in valve operation could be related to
stronger volume-outcome effect in valve operations relative to CABG.
Valve operations may benefit from regionalization.