title: Mechanisms of aortic valve incompetence in aging: a finite element model.
abstract: OBJECTIVE
  The effect of aging on aortic valve and root function was examined using a three-dimensional finite element model of the aortic root and valve.
  
  
  METHODS
  Three models representing normal (< 35 years), middle (35-55 years) and older (> 55 years) age groups, were created by assigning tissue thickness and stiffness that increased with age (using ANSYS software). Diastolic pressure was applied; stresses and strains were then evaluated for the valve and root, and percent leaflet coaptation was calculated.
  
  
  RESULTS
  Leaflet stresses were increased with aging, whereas leaflet strain and coaptation were decreased with aging. Specifically, leaflet stresses were increased by 6-14% in the middle-age model, and by 2-11% in the older-age model, as compared with normal in specified leaflet regions. Conversely, leaflet strains were decreased by 27-41% and 42-50% in the middle-age and older-age models, respectively. This reduced strain resulted in markedly decreased coaptation (9% and 30% reduction for middle- and older-age models). In the root, stress remained fairly constant with age, but strain in the root was progressively reduced with age (11% and 35% reduction for the middle and older-age models, respectively).
  
  
  CONCLUSIONS
  In these models, increased stiffness and thickness due to aging reduces leaflet deformation and restricts coaptation. Clinically, valvular regurgitation may result due to leaflet thickening and stiffening with normal aging. Our model can now be utilized to evaluate the root-valve relationship in the presence of bioprosthetic valves or root replacements.
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic Foundation, Ohio, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Grande
authors.forename: R P
authors.initials: RP
authors.lastname: Cochran
authors.forename: P G
authors.initials: PG
authors.lastname: Reinhall
authors.forename: K S
authors.initials: KS
authors.lastname: Kunzelman
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D001022:Aortic Valve Insufficiency / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D006801:Humans; D008875:Middle Aged; D008962:Models, Theoretical; D011379:Prognosis