title: How small is too small? A systematic review of center volume and outcome after cardiac transplantation.
abstract: BACKGROUND
  The aim of this study was to assess the relationship between the volume of cardiac transplantation procedures performed in a center and the outcome after cardiac transplantation.
  
  
  RESULTS
  PubMed, Embase, and the Cochrane library were searched for articles on the volume-outcome relationship in cardiac transplantation. Ten studies were identified, and all adopted a different approach to data analysis and varied in adjustment for baseline characteristics. The number of patients in each study ranged from 798 to 14401, and observed 1-year mortality ranged from 12.6% to 34%. There was no association between the continuous variables of center volume and observed mortality. There was a weak association between the continuous variables of center volume and adjusted mortality up to 1 year and a stronger association at 5 years. When centers were grouped in volume categories, low-volume centers had the highest adjusted mortality, intermediate-volume centers had lower adjusted mortality, and high-volume centers had the lowest adjusted mortality but were not significantly better than intermediate-volume centers. Category limits were arbitrary and varied between studies.
  
  
  CONCLUSIONS
  There is a relationship between center volume and mortality in heart transplantation. The existence of a minimum acceptable center volume or threshold is unproven. However, a level of 10 to 12 heart transplants per year corresponds to the upper limit of low-volume categories that may have relatively higher mortality. It is not known whether outcomes for patients treated in low-volume transplant centers would be improved by reorganizing centers to ensure volumes in excess of 10 to 12 heart transplants per year.
authors.affiliation: Scottish National Advanced Heart Failure Service, Golden Jubilee National Hospital, Clydebank, Glasgow, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Pettit
authors.forename: Pardeep S
authors.initials: PS
authors.lastname: Jhund
authors.forename: Nathaniel M
authors.initials: NM
authors.lastname: Hawkins
authors.forename: Roy S
authors.initials: RS
authors.lastname: Gardner
authors.forename: Saleem
authors.initials: S
authors.lastname: Haj-Yahia
authors.forename: John J V
authors.initials: JJ
authors.lastname: McMurray
authors.forename: Mark C
authors.initials: MC
authors.lastname: Petrie
mesh_terms: D016027:Heart Transplantation / Q000009:adverse effects / Q000401:mortality; D061847:Hospitals, High-Volume / Q000706:statistics & numerical data; D061846:Hospitals, Low-Volume / Q000706:statistics & numerical data; D006801:Humans; D016015:Logistic Models; D015999:Multivariate Analysis; D016017:Odds Ratio; D010043:Outcome and Process Assessment, Health Care / Q000706:statistics & numerical data; D019984:Quality Indicators, Health Care / Q000706:statistics & numerical data; D018570:Risk Assessment; D012307:Risk Factors; D016019:Survival Analysis; D013997:Time Factors; D016896:Treatment Outcome