title: How Local Annular Force and Collagen Density Govern Mitral Annuloplasty Ring Dehiscence Risk.
abstract: BACKGROUND
  Annuloplasty ring dehiscence is a well described mode of mitral valve repair failure. Defining the mechanisms underlying dehiscence may facilitate its prevention.
  
  
  METHODS
  Factors that govern suture dehiscence were examined with an ovine model. After undersized ring annuloplasty in live animals (n = 5), cyclic force (FC) that acts on sutures during cardiac contraction was measured with custom transducers. FC was measured at ten suture positions, throughout cardiac cycles with peak left ventricular pressure (LVPmax) of 100, 125, and 150 mm Hg. Suture pullout testing was conducted on explanted mitral annuli (n = 12) to determine suture holding strength at each position. Finally, relative collagen density differences at suture sites around the annulus were assessed by two-photon excitation fluoroscopy.
  
  
  RESULTS
  Anterior FC exceeded posterior FC at each LVPmax (eg, 2.8 ± 1.3 N versus 1.8 ± 1.2 N at LVPmax = 125 mm Hg, p < 0.01). Anterior holding strength exceeded posterior holding strength (6.4 ± 3.6 N versus 3.9 ± 1.6 N, p < 0.0001). On the basis of FC at LVPmax of 150 mm Hg, margin of safety before suture pullout was vastly higher between the trigones (exclusive) versus elsewhere (4.8 ± 0.9 N versus 1.9 ± 0.5 N, p < 0.001). Margin of safety exhibited strong correlation to collagen density (R(2) = 0.947).
  
  
  CONCLUSIONS
  Despite lower cyclic loading on posterior sutures, the weaker posterior mitral annular tissue creates higher risk of dehiscence, apparently because of reduced collagen content. Sutures placed atop the trigones are less secure than predicted, because of a combination of reduced collagen and higher overall rigidity in this region. These findings highlight the inter-trigonal tissue as the superior anchor and have implications on the design and implantation techniques for next-generation mitral prostheses.
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Pierce
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Siefert
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Paul
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Wells
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Bloodworth
authors.affiliation: Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takebayashi
authors.affiliation: Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Chikashi
authors.initials: C
authors.lastname: Aoki
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
authors.forename: Morten O
authors.initials: MO
authors.lastname: Jensen
authors.affiliation: Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Cardiology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Gillespie
authors.affiliation: Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gorman
authors.affiliation: Gorman Cardiovascular Research Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Gorman
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia. Electronic address: ajit.yoganathan@bme.gatech.edu.
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000818:Animals; D003094:Collagen / Q000378:metabolism*; D004195:Disease Models, Animal; D006350:Heart Valve Prosthesis; D008943:Mitral Valve / Q000601:surgery*; D058386:Mitral Valve Annuloplasty / Q000379:methods*; D008944:Mitral Valve Insufficiency / Q000601:surgery; D011183:Postoperative Complications; D011474:Prosthesis Design; D012756:Sheep; D013536:Suture Techniques / Q000295:instrumentation*; D013537:Sutures
chemical_list: D003094:Collagen