THE DECLINE IN CORONARY-ARTERY BYPASS GRAFT-SURGERY MORTALITY IN NEW-YORK-STATE - THE ROLE OF SURGEON VOLUME

Objective.-To examine the longitudinal relationship between surgeon vo lume and in-hospital mortality for coronary artery bypass graft (CABG) surgery in New York State and to explain changes in mortality that oc curred over time. Design.-Observation of clinically risk-adjusted oper ative mortality over time.Setting.-All 30 New York State hospitals in which CABG surgery was performed for 1989 through 1992. Patients.-All 57187 patients undergoing isolated CABG surgery in New York State in 1 989 through 1992 in the 30 hospitals. Main Outcome Measures.-Actual, e xpected, and risk-adjusted mortality. Results-Risk-adjusted in-hospita l mortality decreased for all categories of surgeons. Low-volume surge ons (less than or equal to 50 operations per year) experienced a 60% r eduction in risk-adjusted mortality in the 4-year period, whereas the highest-volume surgeons (>150 operations per year) experienced a 34% r eduction. The percentage of patients undergoing CABG surgery by low-vo lume surgeons decreased from 7.6% in 1989 to 5.7% in 1992, a 25% decre ase. Conclusions.-The overall decline in risk-adjusted mortality could not be explained by shifts in patients away from low-volume surgeons to high-volume surgeons. The proportionately larger decrease in risk-a djusted mortality for low-volume surgeons could not be explained by ch anges in patient case mix or by improvements in the performance of sur geons with persistently low volumes. Part of the decrease was a result of the exodus of low-volume surgeons with high risk-adjusted mortalit y (in all years studied), the markedly better performance of surgeons who were new to the system (especially in 1991 and 1992), and the perf ormance of surgeons who were not consistently low-volume surgeons (esp ecially in 1992).