title: 3-D computational analysis of the stress distribution on the leaflets after edge-to-edge repair of mitral regurgitation.
abstract: OBJECTIVE
  Edge-to-edge repair is an effective, recently introduced method to correct mitral insufficiency by suturing the leaflets at the site of regurgitation, though durability of the method has not been proven. To overcome the limitations of the clinical approach, simulations may be used to predict clinical outcome. In this study, the mechanical stress acting on leaflets imposed by the edge-to-edge suture was evaluated as a means of assessing the clinical risk of late fibrosis or tissue degeneration.
  
  
  METHODS
  A 3-D finite element simulated the stress pattern following edge-to-edge repair. Valve behavior was evaluated both in systole and in diastole. Both 4-mm and 8-mm edge-to-edge sutures were simulated, as well as annular dilation.
  
  
  RESULTS
  Systolic simulations validated the model by comparison with previous models of the mitral valve. Diastolic stresses were negligible in the native mitral valve; after edge-to-edge repair (8-mm suture), circumferential and longitudinal stress values were 308 kPa and 489 kPa, respectively, and comparable with those observed at systolic peak (449 kPa and 617 kPa, respectively). With a 4-mm suture, longitudinal stresses decreased both close to the suture (-41.5%) and in the annular region (-68%), while circumferential stresses increased (+37%) close to the suture and decreased (-27%) in the annular region. A 20% dilation of the annulus was followed by increased stresses in the annular region and close to the suture.
  
  
  CONCLUSIONS
  Leaflet distortion and altered stress distribution occur on the leaflets after edge-to-edge repair. Diastolic peak stress values were comparable with those calculated in systole. The clinical implication is a doubled exposure of valve components to systolic stresses, as if the heart rate were doubled. The use of a prosthetic annuloplasty ring is favorable in the presence of annular dilation to reduce stresses acting on the leaflets after edge-to-edge repair.
authors.affiliation: Department of Bioengineering, Politecnico di Milano and CeBITeC, IRCCS San Raffaele and Politecnico di Milano, Milan, Italy.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Votta
authors.forename: Francesco
authors.initials: F
authors.lastname: Maisano
authors.forename: Monica
authors.initials: M
authors.lastname: Soncini
authors.forename: Alberto
authors.initials: A
authors.lastname: Redaelli
authors.forename: Franco M
authors.initials: FM
authors.lastname: Montevecchi
authors.forename: Ottavio
authors.initials: O
authors.lastname: Alfieri
mesh_terms: D002815:Chordae Tendineae / Q000503:physiopathology; D003971:Diastole / Q000502:physiology; D006350:Heart Valve Prosthesis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008422:Materials Testing; D008944:Mitral Valve Insufficiency / Q000503:physiopathology* / Q000601:surgery*; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013536:Suture Techniques; D013599:Systole / Q000502:physiology; D016896:Treatment Outcome