title: Hospital coronary artery bypass graft surgery volume and patient mortality, 1998-2000.
abstract: OBJECTIVE
  To evaluate the association between annual hospital coronary artery bypass graft (CABG) surgery volume and in-hospital mortality.
  
  
  BACKGROUND
  The Leapfrog Group recommends health care purchasers contract for CABG services only with hospitals that perform >or=500 CABGs annually to reduce mortality; it is unclear whether this standard applies to current practice.
  
  
  METHODS
  We conducted a retrospective analysis of the National Inpatient Sample database for patients who underwent CABG in 1998-2000 (n = 228738) at low (12-249 cases/year), medium (250-499 cases/year), and high (>or=500 cases/year) CABG volume hospitals. Crude in-hospital mortality rates were 4.21% in low-volume hospitals, 3.74% in medium-volume hospitals, and 3.54% in high-volume hospitals (trend P < 0.001). Compared with patients at high-volume hospitals (odds ratio 1.00, referent), patients at low-volume hospitals remained at increased risk of mortality after multivariable adjustment (odds ratio 1.26, 95% confidence interval = 1.15-1.39). The mortality risk for patients at medium-volume hospitals was of borderline significance (odds ratio 1.11, 95% confidence interval = 1.01-1.21). However, 207 of 243 (85%) of low-volume and 151 of 169 (89%) of medium-volume hospital-years had risk-standardized mortality rates that were statistically lower or comparable to those expected. In contrast, only 11 of 169 (6%) of high-volume hospital-years had outcomes that were statistically better than expected.
  
  
  CONCLUSIONS
  Patients at high-volume CABG hospitals were, on average, at a lower mortality risk than patients at lower-volume hospitals. However, the small size of the volume-associated mortality difference and the heterogeneity in outcomes within all CABG volume groups suggest individual hospital CABG volume is not a reliable marker of hospital CABG quality.
authors.affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Saif S
authors.initials: SS
authors.lastname: Rathore
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Epstein
authors.forename: Kevin G M
authors.initials: KG
authors.lastname: Volpp
authors.forename: Harlan M
authors.initials: HM
authors.lastname: Krumholz
mesh_terms: D017677:Age Distribution; D000368:Aged; D000704:Analysis of Variance; D002423:Cause of Death; D001026:Coronary Artery Bypass / Q000401:mortality* / Q000706:statistics & numerical data*; D003327:Coronary Disease / Q000401:mortality / Q000601:surgery; D005260:Female; D017052:Hospital Mortality / Q000639:trends*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care; D011336:Probability; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012494:Sampling Studies; D017678:Sex Distribution; D017749:Total Quality Management; D014481:United States