title: Evaluation of cardiac surgery mortality rates: 30-day mortality or longer follow-up?
abstract: OBJECTIVE
  The aim of our study was to investigate early mortality after cardiac surgery and to determine the most adequate follow-up period for the evaluation of mortality rates.
  
  
  METHODS
  Information on all adult cardiac surgery procedures in 10 of 16 cardiothoracic centres in Netherlands from 2007 until 2010 was extracted from the database of Netherlands Association for Cardio-Thoracic Surgery (n = 33 094). Survival up to 1 year after surgery was obtained from the national death registry. Survival analysis was performed using Kaplan-Meier and Cox regression analysis. Benchmarking was performed using logistic regression with mortality rates at different time points as dependent variables, the logistic EuroSCORE as covariate and a random intercept per centre.
  
  
  RESULTS
  In-hospital mortality was 2.94% (n = 972), 30-day mortality 3.02% (n = 998), operative mortality 3.57% (n = 1181), 60-day mortality 3.84% (n = 1271), 6-month mortality 5.16% (n = 1707) and 1-year mortality 6.20% (n = 2052). The survival curves showed a steep initial decline followed by stabilization after ∼60-120 days, depending on the intervention performed, e.g. 60 days for isolated coronary artery bypass grafting (CABG) and 120 days for combined CABG and valve surgery. Benchmark results were affected by the choice of the follow-up period: four hospitals changed outlier status when the follow-up was increased from 30 days to 1 year. In the isolated CABG subgroup, benchmark results were unaffected: no outliers were found using either 30-day or 1-year follow-up.
  
  
  CONCLUSIONS
  The course of early mortality after cardiac surgery differs across interventions and continues up to ∼120 days. Thirty-day mortality reflects only a part of early mortality after cardiac surgery and should only be used for benchmarking of isolated CABG procedures. The follow-up should be prolonged to capture early mortality of all types of interventions.
authors.affiliation: Department of Cardio-Thoracic Surgery, University Medical Center Utrecht, Utrecht, Netherlands.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Siregar
authors.forename: Rolf H H
authors.initials: RH
authors.lastname: Groenwold
authors.forename: Bas A J M
authors.initials: BA
authors.lastname: de Mol
authors.forename: Ron G H
authors.initials: RG
authors.lastname: Speekenbrink
authors.forename: Michel I M
authors.initials: MI
authors.lastname: Versteegh
authors.forename: George J
authors.initials: GJ
authors.lastname: Brandon Bravo Bruinsma
authors.forename: Michiel L
authors.initials: ML
authors.lastname: Bots
authors.forename: Yolanda
authors.initials: Y
authors.lastname: van der Graaf
authors.forename: Lex A
authors.initials: LA
authors.lastname: van Herwerden
mesh_terms: D000368:Aged; D006348:Cardiac Surgical Procedures / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D012044:Regression Analysis; D016896:Treatment Outcome
keywords: Cardiac surgery; Database; Health policy; Outcomes; Risk analysis/modelling; Statistics