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Annals of Biomedical Engineering

, Volume 40, Issue 7, pp 1455–1467 | Cite as

On the In Vivo Deformation of the Mitral Valve Anterior Leaflet: Effects of Annular Geometry and Referential Configuration

  • Rouzbeh Amini
  • Chad E. Eckert
  • Kevin Koomalsingh
  • Jeremy McGarvey
  • Masahito Minakawa
  • Joseph H. Gorman
  • Robert C. Gorman
  • Michael S. SacksEmail author
Article

Abstract

Alteration of the native mitral valve (MV) shape has been hypothesized to have a profound effect on the local tissue stress distribution, and is potentially linked to limitations in repair durability. The present study was undertaken to elucidate the relation between MV annular shape and central mitral valve anterior leaflet (MVAL) strain history, using flat annuloplasty in an ovine model. In addition, we report for the first time the presence of residual in vivo leaflet strains. In vivo leaflet deformations were measured using sonocrystal transducers sutured to the MVAL (n = 10), with the 3D positions acquired over the full cardiac cycle. In six animals a flat ring was sutured to the annulus and the transducer positions recorded, while in the remaining four the MV was excised from the exsanguinated heart and the stress-free transducer positions obtained. In the central region of the MVAL the peak stretch values, referenced to the minimum left ventricular pressure (LVP), were 1.10 ± 0.01 and 1.31 ± 0.03 (mean ± standard error) in the circumferential and radial directions, respectively. Following flat ring annuloplasty, the central MVAL contracted 28% circumferentially and elongated 16% radially at minimum LVP, and the circumferential direction was under a negative strain state during the entire cardiac cycle. After valve excision from the exsanguinated heart, the MVAL contracted significantly (18 and 30% in the circumferential and radial directions, respectively), indicating the presence of substantial in vivo residual strains. While the physiological function of the residual strains (and their associated stresses) are at present unknown, accounting for their presence is clearly necessary for accurate computational simulations of MV function. Moreover, we demonstrated that changes in annular geometry dramatically alter valvular functional strains in vivo. As levels of homeostatic strains are related to tissue remodeling and homeostasis, our results suggest that surgically introduced alterations in MV shape could lead to the long term MV mechanobiological and microstructural alterations that could ultimately affect MV repair durability.

Keywords

Flat ring annuloplasty Repair surgery Stress-free state 

Notes

Acknowledgments

This research project was supported in part by grants from the National Heart, Lung and Blood Institute of the National Institute of Health, grant numbers F32HL110651, HL63954, and HL73021. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Heart, Lung and Blood Institute of the National Institute of Health. R. Gorman and J. Gorman are supported by individual Established Investigator Awards from the American Heart Association, Dallas, TX. The help from Christopher Caruthers is much appreciated.

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Copyright information

© Biomedical Engineering Society 2012

Authors and Affiliations

  • Rouzbeh Amini
    • 1
  • Chad E. Eckert
    • 1
  • Kevin Koomalsingh
    • 2
  • Jeremy McGarvey
    • 2
  • Masahito Minakawa
    • 2
  • Joseph H. Gorman
    • 3
  • Robert C. Gorman
    • 2
  • Michael S. Sacks
    • 1
    • 4
    Email author
  1. 1.Department of BioengineeringUniversity of PittsburghPittsburghUSA
  2. 2.Gorman Cardiovascular Research Group, University of PennsylvaniaPhiladelphiaUSA
  3. 3.Gorman Cardiovascular Research Group, Glenolden Research LaboratoryUniversity of PennsylvaniaGlenoldenUSA
  4. 4.Department of Biomedical EngineeringInstitute for Computational Engineering and Sciences (ICES), University of Texas at AustinAustinUSA

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