title: Predicting cardiovascular intensive care unit readmission after cardiac surgery: derivation and validation of the Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease (APPROACH) cardiovascular intensive care unit clinical prediction model from a registry cohort of 10,799 surgical cases.
abstract: BACKGROUND
  In medical and surgical intensive care units, clinical risk prediction models for readmission have been developed; however, studies reporting the risks for cardiovascular intensive care unit (CVICU) readmission have been methodologically limited by small numbers of outcomes, unreported measures of calibration or discrimination, or a lack of information spanning the entire perioperative period. The purpose of this study was to derive and validate a clinical prediction model for CVICU readmission in cardiac surgical patients.
  
  
  METHODS
  A total of 10,799 patients more than or equal to 18 years in the Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease (APPROACH) registry who underwent cardiac surgery (coronary artery bypass or valvular surgery) between 2004 and 2012 and were discharged alive from the first CVICU admission were included. The full cohort was used to derive the clinical prediction model and the model was internally validated with bootstrapping. Discrimination and calibration were assessed using the AUC c index and the Hosmer-Lemeshow tests, respectively.
  
  
  RESULTS
  A total of 479 (4.4%) patients required CVICU readmission. The mean CVICU length of stay (19.9 versus 3.3 days, P <0.001) and in-hospital mortality (14.4% versus 2.2%, P <0.001) were higher among patients readmitted to the CVICU. In the derivation cohort, a total of three preoperative (age ≥ 70, ejection fraction, chronic lung disease), two intraoperative (single valve repair or replacement plus non-CABG surgery, multivalve repair or replacement), and seven postoperative variables (cardiac arrest, pneumonia, pleural effusion, deep sternal wound infection, leg graft harvest site infection, gastrointestinal bleed, neurologic complications) were independently associated with CVICU readmission. The clinical prediction model had robust discrimination and calibration in the derivation cohort (AUC c index = 0.799; Hosmer-Lemeshow P = 0.192). The validation point estimates and confidence intervals were similar to derivation model.
  
  
  CONCLUSIONS
  In a large population-based dataset incorporating a comprehensive set of perioperative variables, we have derived a clinical prediction model with excellent discrimination and calibration. This model identifies opportunities for targeted therapeutic interventions aimed at reducing CVICU readmissions in high-risk patients.
authors.affiliation: Divisions of Critical Care and Cardiology, 2C2 WMC University of Alberta Hospital, 8440-112 St, Edmonton, AB, Canada, T6G 2B7. sv9@ualberta.ca.|Division of Cardiology, 2C2 WMC University of Alberta Hospital, 8440-112 St, Edmonton, AB, Canada, T6G 2B7. sv9@ualberta.ca.
authors.forename: Sean
authors.initials: S
authors.lastname: van Diepen
authors.affiliation: Division of Cardiology, 2C2 WMC University of Alberta Hospital, 8440-112 St, Edmonton, AB, Canada, T6G 2B7. mmg2@ualberta.ca.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Graham
authors.affiliation: Division of Cardiac Surgery, Mazankowski Alberta Heart Institute, 8440-112 St, Edmonton, AB, Canada, T6G 2B7. Jayan@ualberta.ca.
authors.forename: Jayan
authors.initials: J
authors.lastname: Nagendran
authors.affiliation: Division of Cardiology, 2C2 WMC University of Alberta Hospital, 8440-112 St, Edmonton, AB, Canada, T6G 2B7. cnorris@ualberta.ca.|Division of Cardiac Surgery, Mazankowski Alberta Heart Institute, 8440-112 St, Edmonton, AB, Canada, T6G 2B7. cnorris@ualberta.ca.|School of Public Health, University of Alberta, 116 Street and 85 Avenue, Edmonton, AB, Canada, T6G 2R3. cnorris@ualberta.ca.|Heart Health and Stroke Strategic Clinical Network, 8440 112 Street, Edmonton, AB, Canada, T6G 2B7. cnorris@ualberta.ca.
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Norris
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000416:Alberta / Q000453:epidemiology; D006348:Cardiac Surgical Procedures / Q000592:standards* / Q000639:trends; D003327:Coronary Disease / Q000175:diagnosis / Q000401:mortality / Q000601:surgery*; D005260:Female; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D007362:Intensive Care Units / Q000592:standards* / Q000639:trends; D007902:Length of Stay / Q000639:trends; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D063868:Patient Outcome Assessment; D010359:Patient Readmission / Q000592:standards* / Q000639:trends; D011237:Predictive Value of Tests; D012042:Registries / Q000592:standards*