title: Risk stratification for open heart operations: comparison of centers regardless of the influence of the surgical team.
abstract: BACKGROUND
  Risk-adjusted mortality was previously used to compare institutions as a whole or surgeons. Because the same surgical team is working in two different hospitals, the aim of our study was to assess whether the institution can make a difference in surgical mortality.
  
  
  METHODS
  Preoperative data of 554 patients in institution A and 500 in institution B were prospectively collected during the same period of time. All patients were operated on by the same surgeon with the same first assistant and anesthesiology staff in both institutions. Patient population was stratified according to Parsonnet's predictive model, in five risk groups, and mortality was adjusted by the direct standardization method.
  
  
  RESULTS
  At institution A it was observed that in-hospital mortality was 2.3% (95% confidence interval, 1.3% to 4.0%), and in institution B 4.0% (95% confidence interval, 2.5% to 6.1%). The difference between the two mortality rates (1.7%; 95% confidence interval, -0.5% to 3.8%) is not statistically significant (p = 0.16), nor is the difference within each class. The standardized mortality ratio was 3.6% (95% confidence interval, 2.7% to 4.8%) and 5.8% (95% confidence interval, 4.6% to 7.2%), respectively. The difference of 2.2% (95% confidence interval, 0.5% to 3.8%) is statistically significant (p = 0.01).
  
  
  CONCLUSIONS
  The institution can affect mortality of patients undergoing open heart operations, regardless of the influence of the surgical team.
authors.affiliation: Arturo Pinna Pintor Foundation-Torino, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Pinna-Pintor
authors.forename: M
authors.initials: M
authors.lastname: Bobbio
authors.forename: L
authors.initials: L
authors.lastname: Sandrelli
authors.forename: M
authors.initials: M
authors.lastname: Giammaria
authors.forename: F
authors.initials: F
authors.lastname: Patané
authors.forename: S
authors.initials: S
authors.lastname: Bartolozzi
authors.forename: G
authors.initials: G
authors.lastname: Bergandi
authors.forename: O
authors.initials: O
authors.lastname: Alfieri
mesh_terms: D006348:Cardiac Surgical Procedures / Q000401:mortality*; D016001:Confidence Intervals; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D015996:Survival Rate