title: An annular prosthesis for the treatment of functional mitral regurgitation: finite element model analysis of a dog bone-shaped ring prosthesis.
abstract: BACKGROUND
  Undersized annuloplasty is commonly used in the treatment of functional mitral regurgitation. However, in the case of severely dilated ventricles, annuloplasty may be inadequate to counteract leaflet tethering. My colleagues and I hypothesized that modifying the shape of the annular prosthesis to account for the specific anatomy of functional mitral regurgitation could challenge extreme leaflet tethering.
  
  
  METHODS
  Using finite element model simulations, we tested valve competence after the implantation of conventional D-shaped versus dog bone-shaped annuloplasty rings, the latter of which was designed to selectively reduce the septolateral dimension of the annulus. Three models were compared: model A, simulating the native mitral valve; model B, simulating the same valve after annuloplasty with a conventional D-shaped annuloplasty; and model C, simulating a dog-bone annuloplasty ring implantation. Each model was then challenged by progressively pulling the tip of the papillary muscles away from the annulus plane to simulate ventricular remodeling and leaflet tethering. Valve competence was compared in each model for each degree of leaflet tethering.
  
  
  RESULTS
  After maximal leaflet tethering simulation (4-mm apical displacement of the papillary tips), the regurgitant area increase was 70.4 mm2 for model A and 52.9 mm2 for model B. In model C, the regurgitant area was only negligibly affected by papillary displacement, increasing to 3.9 mm2.
  
  
  CONCLUSIONS
  An annular prosthesis with selective reduction in the septolateral dimension is more effective than a conventional prosthesis for treating leaflet tethering in functional mitral regurgitation. Use of disease-specific annular prostheses is needed to improve the results of valve reconstruction.
authors.affiliation: Cardiac Surgery Division, IRCCS San Raffaele Hospital, Milan, Italy. francesco.maisano@hsr.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Maisano
authors.forename: Alberto
authors.initials: A
authors.lastname: Redaelli
authors.forename: Monica
authors.initials: M
authors.lastname: Soncini
authors.forename: Emiliano
authors.initials: E
authors.lastname: Votta
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Arcobasso
authors.forename: Ottavio
authors.initials: O
authors.lastname: Alfieri
mesh_terms: D000818:Animals; D004285:Dogs; D020342:Finite Element Analysis; D019918:Heart Valve Prosthesis Implantation / Q000379:methods*; D008944:Mitral Valve Insufficiency / Q000601:surgery*; D010210:Papillary Muscles / Q000503:physiopathology; D013314:Stress, Mechanical