title: Mitral valve annular downsizing forces: implications for annuloplasty device development.
abstract: OBJECTIVE
  Mitral valve repair with annulus downsizing is a popular surgical procedure for functional mitral regurgitation. We investigated the effects of externally applied downsizing on the observed in-plane forces and valvular dimensions.
  
  
  METHODS
  Five animals were included in an acute porcine study. Three traction sutures were anchored at the right fibrous trigone (T) and suspended across the annulus for externalization at the P1, P2, and P3 annular segments. The annulus was downsized with the sutures in controlled increments while measuring the tension force in the sutures. Downsizing percentages ranged from a 2% to 32% reduction of the T-P distances. Sonomicrometry was used to measure the resulting valvular dimensions.
  
  
  RESULTS
  No difference in force was found between the P1, P2, and P3 segments across all levels of downsizing. The peak forces at 32% downsizing were 1.2 ± 0.9 N, 1.5 ± 1.0 N, and 0.8 ± 0.2 N for the T-P1, T-P2, and T-P3 segments, respectively. The maximum total suture forces in the mitral plane during downsizing increased from 0.12 ± 0.03 N to 3.5 ± 1.3 N (P < .005). Sonomicrometry showed a decrease in the systolic thickening of the posterior myocardial wall at the annular level with annular downsizing (0%-32%) from 5 ± 3 mm to 1 ± 1 mm (P < .05).
  
  
  CONCLUSIONS
  Segmental mitral valve annulus downsizing increased in-plane traction suture forces and has a significant influence on the in-plane biomechanics. These results have implications for device design in terms of mechanical strength requirements and can be used to supplement boundary conditions for computational left heart models.
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Clinical Medicine, Aarhus University Hospital, Skejby, Aarhus, Denmark. Electronic address: dr.morten.jensen@gmail.com.
authors.forename: Morten O
authors.initials: MO
authors.lastname: Jensen
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Clinical Medicine, Aarhus University Hospital, Skejby, Aarhus, Denmark.
authors.forename: Jesper L
authors.initials: JL
authors.lastname: Honge
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Clinical Medicine, Aarhus University Hospital, Skejby, Aarhus, Denmark.
authors.forename: Jon A
authors.initials: JA
authors.lastname: Benediktsson
authors.affiliation: Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Siefert
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Clinical Medicine, Aarhus University Hospital, Skejby, Aarhus, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Jensen
authors.affiliation: Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Ga.
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
authors.affiliation: School of Applied Physiology, Georgia Institute of Technology, Atlanta, Ga.
authors.forename: Teresa K
authors.initials: TK
authors.lastname: Snow
authors.affiliation: Department of Health, Aarhus University, Aarhus, Denmark.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Hasenkam
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Clinical Medicine, Aarhus University Hospital, Skejby, Aarhus, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Nygaard
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Institute of Clinical Medicine, Aarhus University Hospital, Skejby, Aarhus, Denmark.
authors.forename: Sten L
authors.initials: SL
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000295:instrumentation*; D008943:Mitral Valve / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D058386:Mitral Valve Annuloplasty / Q000295:instrumentation*; D023421:Models, Animal; D009200:Myocardial Contraction; D011474:Prosthesis Design; D013314:Stress, Mechanical; D013536:Suture Techniques; D013552:Swine; D013997:Time Factors