title: Should volume standards for cardiovascular surgery focus only on high-risk patients?
abstract: BACKGROUND
  Payers and policy makers are attempting to concentrate selected cardiovascular procedures in high-volume centers. A recent analysis of coronary artery bypass grafting (CABG), however, suggests that volume-based referral initiatives should focus only on high-risk patients.
  
  
  RESULTS
  Using the national Medicare database (1994 to 1999), we studied the operative mortality in patients undergoing 4 cardiovascular procedures (CABG, aortic valve replacement, mitral valve replacement, and elective abdominal aortic aneurysm repair). We defined 2 categories of patient risk: high-risk (patients in the highest 25th percentile of predicted risk on the basis of a logistic regression model) and low-risk (patients in the lowest 75th percentile). We then compared operative mortality in patients undergoing surgery at very-high volume hospitals (VHVH, highest 20th percentile of procedure volume) and very-low volume hospitals (VLVH, lowest 20th percentile of procedure volume). Absolute differences in operative mortality between VLVH and VHVH were somewhat larger in high-risk patients. However, volume-related differences in mortality were also significant for low-risk patients undergoing one of the 4 procedures. In relative terms, the effect of hospital volume was similar in both high- and low-risk patients. For high- and low-risk patients, the relative risk (RR) of mortality between VHVH and VLVH were nearly equal for CABG (RR=0.78 for low-risk patients, RR=0.77 for high risk patients), aortic valve replacement (0.73 versus 0.76), mitral valve replacement (0.73 versus 0.74), and abdominal aortic aneurysm repair (0.51 versus 0.54).
  
  
  CONCLUSIONS
  Although the merits of volume-based referral initiatives can be debated on many grounds, there seems to be little rationale for restricting these initiatives to high-risk patients.
authors.affiliation: VA Outcomes Group, Department of Veterans Affairs Medical Center, White River Junction, Vt 05009, USA. philip.goodney@hitchcock.org
authors.forename: Philip P
authors.initials: PP
authors.lastname: Goodney
authors.forename: F L
authors.initials: FL
authors.lastname: Lucas
authors.forename: John D
authors.initials: JD
authors.lastname: Birkmeyer
mesh_terms: D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000601:surgery; D001021:Aortic Valve / Q000601:surgery; D016507:Cardiology Service, Hospital / Q000592:standards* / Q000706:statistics & numerical data*; D013504:Cardiovascular Surgical Procedures / Q000401:mortality* / Q000592:standards* / Q000706:statistics & numerical data; D001026:Coronary Artery Bypass / Q000401:mortality / Q000592:standards / Q000706:statistics & numerical data; D017052:Hospital Mortality; D006760:Hospitalization; D006801:Humans; D006278:Medicare; D008943:Mitral Valve / Q000601:surgery; D012017:Referral and Consultation / Q000592:standards*; D018570:Risk Assessment; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology