title: Normal aortic valves stay open much longer in systole than porcine substitutes.
abstract: OBJECTIVE
  To compare the opening mechanics of porcine valve substitutes with those of a normal human aortic valve.
  
  
  BACKGROUND
  All commercially available porcine valves are pretreated with glutaraldehyde. This study was undertaken to evaluate the consequences of such treatment on valve mechanics.
  
  
  METHODS
  The opening mechanics of the aortic valve, especially the time taken to open fully from a closed position, and the duration for which the valve is maximally open, were compared in a normal aortic valve, a stent-mounted porcine valve, and a stentless porcine valve, using a finite element model.
  
  
  RESULTS
  Despite a 4-fold higher gradient, stent-mounted porcine valves were slower in attaining the fully open position, and the time for which the valve was fully open was almost 25% less than a normal valve. In stentless valves, the compliant root made the initial opening mechanics similar to those of a normal valve. Once this effect was over, the effect of porcine leaflet properties took over, and there was a corresponding delay in the valve opening.
  
  
  CONCLUSIONS
  Fixing the root with a stent and stiffening the leaflets with glutaraldehyde result in delayed valve opening and decrease the duration for which the valve is fully open, thus contributing to inferior hemodynamics.
authors.affiliation: Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, India.
authors.forename: Maboo
authors.initials: M
authors.lastname: Subhani
authors.forename: Ramarathnam Krishna
authors.initials: RK
authors.lastname: Kumar
authors.forename: Komarakshi R
authors.initials: KR
authors.lastname: Balakrishnan
mesh_terms: D000818:Animals; D001021:Aortic Valve / Q000502:physiology*; D001705:Bioprosthesis; D003198:Computer Simulation; D020342:Finite Element Analysis; D005404:Fixatives / Q000494:pharmacology; D005976:Glutaral / Q000494:pharmacology; D006350:Heart Valve Prosthesis; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008422:Materials Testing; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D013599:Systole / Q000187:drug effects; D013997:Time Factors
chemical_list: D005404:Fixatives; D005976:Glutaral
keywords: Aortic valve; biomechanics; bioprosthesis; computer simulation; finite element analysis