title: A computational pipeline for quantification of mouse myocardial stiffness parameters.
abstract: The mouse is an important model for theoretical-experimental cardiac research, and biophysically based whole organ models of the mouse heart are now within reach. However, the passive material properties of mouse myocardium have not been much studied. We present an experimental setup and associated computational pipeline to quantify these stiffness properties. A mouse heart was excised and the left ventricle experimentally inflated from 0 to 1.44kPa in eleven steps, and the resulting deformation was estimated by echocardiography and speckle tracking. An in silico counterpart to this experiment was built using finite element methods and data on ventricular tissue microstructure from diffusion tensor MRI. This model assumed a hyperelastic, transversely isotropic material law to describe the force-deformation relationship, and was simulated for many parameter scenarios, covering the relevant range of parameter space. To identify well-fitting parameter scenarios, we compared experimental and simulated outcomes across the whole range of pressures, based partly on gross phenotypes (volume, elastic energy, and short- and long-axis diameter), and partly on node positions in the geometrical mesh. This identified a narrow region of experimentally compatible values of the material parameters. Estimation turned out to be more precise when based on changes in gross phenotypes, compared to the prevailing practice of using displacements of the material points. We conclude that the presented experimental setup and computational pipeline is a viable method that deserves wider application.
authors.affiliation: Department of Mathematical Sciences and Technology, Centre for Integrative Genetics, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Oyvind
authors.initials: O
authors.lastname: Nordbø
authors.affiliation: Department of Biomedical Engineering, King's College London, St. Thomas׳ Hospital, Westminster Bridge Road, London SE17EH, UK.
authors.forename: Pablo
authors.initials: P
authors.lastname: Lamata
authors.affiliation: Department of Biomedical Engineering, King's College London, St. Thomas׳ Hospital, Westminster Bridge Road, London SE17EH, UK.
authors.forename: Sander
authors.initials: S
authors.lastname: Land
authors.affiliation: Department of Biomedical Engineering, King's College London, St. Thomas׳ Hospital, Westminster Bridge Road, London SE17EH, UK.
authors.forename: Steven
authors.initials: S
authors.lastname: Niederer
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo, Kirkeveien 166, 4th Floor Building 7, 0407 Oslo, Norway; Bjørknes College, Oslo, Norway.
authors.forename: Jan M
authors.initials: JM
authors.lastname: Aronsen
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo, Kirkeveien 166, 4th Floor Building 7, 0407 Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, 0407 Oslo, Norway.
authors.forename: William E
authors.initials: WE
authors.lastname: Louch
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo, Kirkeveien 166, 4th Floor Building 7, 0407 Oslo, Norway.
authors.forename: Ivar
authors.initials: I
authors.lastname: Sjaastad
authors.affiliation: Department of Engineering Cybernetics, Faculty of Information Technology, Mathematics and Electrical Engineering, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Harald
authors.initials: H
authors.lastname: Martens
authors.affiliation: Department of Animal and Aquacultural Sciences, Centre for Integrative Genetics, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Arne B
authors.initials: AB
authors.lastname: Gjuvsland
authors.affiliation: Department of Biomedical Engineering, King's College London, St. Thomas׳ Hospital, Westminster Bridge Road, London SE17EH, UK.
authors.forename: Kristin
authors.initials: K
authors.lastname: Tøndel
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Postboks 8905, Medisinsk teknisk forskningssenter, NO-7491 Trondheim, Norway.
authors.forename: Hans
authors.initials: H
authors.lastname: Torp
authors.affiliation: Radcliffe Department of Medicine, Division of Cardiovascular Medicine, University of Oxford, Welcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN, UK.
authors.forename: Maelene
authors.initials: M
authors.lastname: Lohezic
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Postboks 8905, Medisinsk teknisk forskningssenter, NO-7491 Trondheim, Norway.
authors.forename: Jurgen E
authors.initials: JE
authors.lastname: Schneider
authors.affiliation: KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, 0407 Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
authors.forename: Espen W
authors.initials: EW
authors.lastname: Remme
authors.affiliation: Department of Biomedical Engineering, King's College London, St. Thomas׳ Hospital, Westminster Bridge Road, London SE17EH, UK.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Smith
authors.affiliation: Faculty of Medicine, Norwegian University of Science and Technology, P.O. Box 8905, N-7491 Trondheim, Norway.
authors.forename: Stig W
authors.initials: SW
authors.lastname: Omholt
authors.affiliation: Department of Animal and Aquacultural Sciences, Centre for Integrative Genetics, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Ås, Norway. Electronic address: jonovik@gmail.com.
authors.forename: Jon Olav
authors.initials: JO
authors.lastname: Vik
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology*; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging; D004548:Elasticity / Q000502:physiology*; D020342:Finite Element Analysis; D006321:Heart / Q000502:physiology*; D051379:Mice; D008955:Models, Cardiovascular; D016276:Ventricular Function / Q000502:physiology
keywords: Myocardial stiffness; Parameter estimation; Passive inflation; Speckle tracking; Transversal isotropy