title: Welder identity, weld date, and the risk of outlet strut fracture in Björk-Shiley convexo-concave valves: the Dutch cohort study.
abstract: OBJECTIVE
  To establish whether there is an association between subsequent fracture of the outlet strut and welder identity and the weld date of Björk-Shiley convexo-concave (BScc) valves.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  All Dutch BScc valve recipients (n = 2266).
  
  
  METHODS
  Documented outlet strut fracture during follow up.
  
  
  RESULTS
  Weld dates were known for 97.0% of all BScc valves (n = 2534) implanted in Dutch patients (n = 2266) and welder identity was known for 52.2%. During a mean follow up of 9.4 years, 46 fractures were documented. For 60 degrees valves welded from 1981 to 1984 the fracture rate (0.22 per 100 person-years (95% CI 0.13 to 0.34)) was higher than that for valves welded before 1981 (0.04 (95% CI 0.01-0.10)). When all fracture related risk factors were taken into account, fracture rates per welder did not show any statistically significant differences.
  
  
  CONCLUSIONS
  Welder identity does not contribute to the risk of strut fracture. Other factors in the production of BScc valves may explain the increased risk for valves welded from 1981 to 1984.
authors.affiliation: Department of Clinical Epidemiology, School of Medicine, Utrecht University, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Kallewaard
authors.forename: A
authors.initials: A
authors.lastname: Algra
authors.forename: Y
authors.initials: Y
authors.lastname: van der Graaf
mesh_terms: D015331:Cohort Studies; D005500:Follow-Up Studies; D006350:Heart Valve Prosthesis; D006801:Humans; D009426:Netherlands; D011475:Prosthesis Failure; D014896:Welding