title: In situ evolution of the mechanical properties of stretchable and non-stretchable ePTFE vascular grafts and adjacent native vessels.
abstract: BACKGROUND
  The purpose of this study was to evaluate the evolution of the mechanical properties of stretchable and non-stretchable ePTFE vascular grafts over time following implantation, as well as those of the adjacent native vessels.
  
  
  METHODS
  One stretchable and one non-stretchable graft were implanted in either carotid position of six sheep. After twelve weeks, the samples, as well as the distal adjacent native vessel, were explanted and evaluated mechanically by means of uniaxial tensile tests. These tests were performed in the axial as well as in the circumferential direction. Also, patches of these grafts were implanted subcutaneously in the abdominal wall of the same animals. At 2, 4, 6, and 8 weeks, patches were explanted and evaluated mechanically. Baseline mechanical tensile tests were also performed on non-implanted grafts and on native sheep carotid arteries.
  
  
  RESULTS
  Statistical analysis shows a significant effect of implantation time on the tensile mechanical properties of ePTFE vascular grafts. This effect is present for stretchable as well as non-stretchable grafts, in axial as well as in circumferential direction of the material. Also the adjacent native vessels have a tendency to lose mechanical stiffness and strength in the circumferential direction, an effect which is most pronounced for stretchable grafts.
  
  
  CONCLUSIONS
  The mechanical properties of ePTFE vascular grafts and the adjacent native vessels significantly change as a function of implantation time. Compared to the native vessels, the grafts are still significantly stronger and stiffer, though longer term experiments are needed to evaluate whether and how much the decline would continue in time.
authors.affiliation: 1 Biomechanics Section, Department of Mechanical Engineering, KU Leuven - Belgium.
authors.forename: Nele
authors.initials: N
authors.lastname: Famaey
authors.forename: Jelle
authors.initials: J
authors.lastname: Verhoeven
authors.forename: Steven
authors.initials: S
authors.lastname: Jacobs
authors.forename: Matteo
authors.initials: M
authors.lastname: Pettinari
authors.forename: Bart
authors.initials: B
authors.lastname: Meyns
mesh_terms: D034861:Abdominal Wall / Q000601:surgery*; D000818:Animals; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation*; D002339:Carotid Arteries / Q000601:surgery*; D004548:Elasticity; D008422:Materials Testing; D023421:Models, Animal; D011138:Polytetrafluoroethylene; D011474:Prosthesis Design; D012756:Sheep; D013314:Stress, Mechanical; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D011138:Polytetrafluoroethylene