title: Viscoelasticity of dynamically fixed bioprosthetic valves. II. Effect of glutaraldehyde concentration.
abstract: OBJECTIVE
  We have previously shown the benefits of dynamic fixation over conventional static fixation of bioprosthetic valves. In an attempt to increase the durability of bioprosthetic heart valves, we explored the benefit of low-concentration glutaraldehyde dynamic fixation.
  
  
  METHODS
  Pig aortic valves obtained fresh from the abattoir and excised with the entire root were dynamically fixed in glutaraldehyde phosphate buffer solutions varying in concentration from 0.05% to 2.5%. Denaturation temperatures were measured and mechanical testing was performed at low (3 mm/sec) to high physiologic rates (30 mm/sec) at 37 degrees C in isotonic modified Hanks solution.
  
  
  RESULTS
  When fixed dynamically in 0.05% glutaraldehyde solution for 24 hours, the tissue reached a degree of cross-linking (denaturation temperature = 82.8 degrees +/- 0.6 degree C) significantly higher than that obtained for 0.05% static fixation (denaturation temperature = 79.3 degrees +/- 0.9 degree C) (p < 0.05) but similar to that for conventional static fixation in 0.5% glutaraldehyde solution (denaturation temperature = 83.5 degrees +/- 0.3 degree C). After fixation in low-concentration glutaraldehyde (0.05%), final relaxation slopes and moduli in the circumferential direction were significantly higher than those for the statically fixed tissue but similar to those for the fresh tissue. However, both dynamic and static fixation had the effect of increasing tissue extensibility to similar extents in both directions, irrespective of glutaraldehyde concentration.
  
  
  CONCLUSIONS
  Dynamic glutaraldehyde fixation of a porcine aortic valve at lower concentrations resulted in a better degree of cross-linking and a material with biomechanical properties that more closely mimic those of natural heart valve tissue.
authors.affiliation: J.P. Robarts Research Institute, University of Western Ontario, London, Canada.
authors.forename: A C
authors.initials: AC
authors.lastname: Duncan
authors.forename: D
authors.initials: D
authors.lastname: Boughner
authors.forename: I
authors.initials: I
authors.lastname: Vesely
mesh_terms: D000818:Animals; D001021:Aortic Valve; D001696:Biomechanical Phenomena; D001705:Bioprosthesis; D004548:Elasticity; D005404:Fixatives / Q000494:pharmacology*; D005976:Glutaral / Q000494:pharmacology*; D006350:Heart Valve Prosthesis; D008422:Materials Testing; D013552:Swine; D013718:Tensile Strength; D016707:Tissue Fixation; D014783:Viscosity
chemical_list: D005404:Fixatives; D005976:Glutaral