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Annals of Biomedical Engineering

, Volume 43, Issue 10, pp 2334–2348 | Cite as

Quantification of Shear Deformations and Corresponding Stresses in the Biaxially Tested Human Myocardium

  • Gerhard SommerEmail author
  • Daniel Ch. Haspinger
  • Michaela Andrä
  • Michael Sacherer
  • Christian Viertler
  • Peter Regitnig
  • Gerhard A. Holzapfel
Article

Abstract

One goal of cardiac research is to perform numerical simulations to describe/reproduce the mechanoelectrical function of the human myocardium in health and disease. Such simulations are based on a complex combination of mathematical models describing the passive mechanical behavior of the myocardium and its electrophysiology, i.e., the activation of cardiac muscle cells. The problem in developing adequate constitutive models is the shortage of experimental data suitable for detailed parameter estimation in specific functional forms. A combination of shear and biaxial extension tests with different loading protocols on different specimen orientations is necessary to capture adequately the direction-dependent (orthotropic) response of the myocardium. In most experimental animal studies, where planar biaxial extension tests on the myocardium have been conducted, the generated shear stresses were neither considered nor discussed. Hence, in this study a method is presented which allows the quantification of shear deformations and related stresses. It demonstrates an approach for experimenters as to how the generation of these shear stresses can be minimized during mechanical testing. Experimental results on 14 passive human myocardial specimens, obtained from nine human hearts, show the efficiency of this newly developed method. Moreover, the influence of the clamping technique of the specimen, i.e., the load transmission between the testing device and the tissue, on the stress response is determined by testing an isotropic material (Latex). We identified that the force transmission between the testing device and the specimen by means of hooks and cords does not influence the performed experiments. We further showed that in-plane shear stresses definitely exist in biaxially tested human ventricular myocardium, but can be reduced to a minimum by preparing the specimens in an appropriate manner. Moreover, we showed whether shear stresses can be neglected when performing planar biaxial extension tests on fiber-reinforced materials. The used method appears to be robust to quantify normal and shear deformations and corresponding stresses in biaxially tested human myocardium. This method can be applied for the mechanical characterization of any fiber-reinforced material using planar biaxial extension tests.

Keywords

Biaxial extension test Shear deformation Shear stress Passive human left ventricular myocardium Mechanical property 

Notes

Acknowledgments

The authors are grateful to A. Abbasi for her substantial contributions to the experiments, and to F. Heinzel from Medical University of Graz, Department of Cardiology, for many discussions on this subject matter. We thank also Daniel Han for his editorial support during preparing this manuscript. This project was supported by the Austrian Science Fund (FWF) with Grant number P 23830-N13. The authors gratefully acknowledge this support.

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Copyright information

© Biomedical Engineering Society 2015

Authors and Affiliations

  • Gerhard Sommer
    • 1
    Email author
  • Daniel Ch. Haspinger
    • 1
  • Michaela Andrä
    • 2
  • Michael Sacherer
    • 3
  • Christian Viertler
    • 4
  • Peter Regitnig
    • 4
  • Gerhard A. Holzapfel
    • 1
  1. 1.Institute of BiomechanicsGraz University of TechnologyGrazAustria
  2. 2.Division of Cardiac, Thoracic and Vascular SurgeryKlinikum Klagenfurt am WörtherseeKlagenfurtAustria
  3. 3.Department of CardiologyMedical University GrazGrazAustria
  4. 4.Institute of PathologyMedical University GrazGrazAustria

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