Is the impact of hospital and surgeon volumes on the in-hospital mortality rate for coronary artery bypass graft surgery limited to patients at high risk?
BACKGROUND
Restriction of volume-based referral for CABG surgery to high-risk patients has been suggested, and earlier studies have reached different conclusions regarding volume-based referral for low-risk patients.


RESULTS
Patients who underwent isolated CABG surgery in New York from 1997 through 1999 (n=57 150) were separated into low-risk and moderate-to-high-risk groups with a predicted probability of in-hospital death of 2% as the cutoff point. The provider volume-mortality relationship was examined for both groups. For annual hospital volume thresholds between 200 and 600 cases, the adjusted ORs of in-hospital mortality for high-volume to low-volume hospitals ranged from 0.45 to 0.77 and were all significant for the low-risk group; for the moderate-to-high-risk group, ORs ranged from 0.62 to 0.91, and most were significant. The number needed to treat at higher-volume hospitals to avoid 1 death was greater for the low-risk group (a range of 114 to 446 versus 37 to 184). As the annual surgeon volume threshold increased from 50 to 150 cases, the ORs for high- to low-volume surgeons increased from 0.43 to 0.74 for the low-risk group; for the moderate-to-high-risk group, ORs ranged from 0.79 to 0.86. Compared with patients treated by surgeons with volumes of <125 in hospitals with volumes of <600, patients treated by higher-volume surgeons in higher-volume hospitals had a significantly lower risk of death; in particular, the OR was 0.52 for the low-risk group.


CONCLUSIONS
For both low-risk and moderate-to-high-risk patients, higher provider volume is associated with lower risk of death.
Wu
Chuntao
C
University at Albany, State University of New York, One University Place, Rensselaer, NY 12144-3456, USA. ctw09@health.state.ny.us
Hannan
Edward L
EL
Ryan
Thomas J
TJ
Bennett
Edward
E
Culliford
Alfred T
AT
Gold
Jeffrey P
JP
Isom
O Wayne
OW
Jones
Robert H
RH
McNeil
Barbara
B
Rose
Eric A
EA
Subramanian
Valavanur A
VA
D001026:Coronary Artery Bypass / Q000401:mortality* / Q000706:statistics & numerical data; D017052:Hospital Mortality; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D009518:New York / Q000453:epidemiology; D016017:Odds Ratio; D012017:Referral and Consultation / Q000706:statistics & numerical data*; D012042:Registries; D012307:Risk Factors; D013503:Surgery Department, Hospital / Q000706:statistics & numerical data; D013903:Thoracic Surgery / Q000706:statistics & numerical data*; D016896:Treatment Outcome; D016526:Workload / Q000706:statistics & numerical data*