@misc{16648,
  author = {Joakim Sundnes and {\r A}shild Telle and Samuel Wall},
  title = {A cell-based framework for modeling cardiac mechanics},
  abstract = {The mechanical function of cardiac tissue results from the complex interplay ofcontracting cardiomyocytes and the passive extracellular matrix. Most computationalmodels of cardiac mechanics are based on a continuum approach, where the tissueis viewed as a continuous and homogeneous mix of cells and extracellular material.This approach has been successfully applied in numerous studies,and will undoubtedly remain a cornerstone of computational biomechanics.However, the extensive homogenization limits the models{\textquoteright} ability to give detailedinsight into the mechanical forces experienced by individual cardiac cells, andto delineate the mechanical contributions of myocytes and the extracellular matrix.More detailed models exist, in the form of continuum mechanics modelsof individual myocytes, but these are typically limited to a single myocyte anddo not consider the extracellular matrix.Computational models of cardiac electrophysiology are typically based on thesame continuous and homogenized concept as the mechanics model, with thebidomain model being the reference model for several decades. More recently,models have been developed that explicitly represent the cells, the membrane,and the domain between the cells. The approach is commonly referred to as the EMI(Extracellular-Membrane-Intracellular) model, and has been applied instudies of cardiac and neuronal electrophysiology. Natural extensions of theEMI framework include detailed models of intra- and extracellular ion concentrationsand electro-diffusion, as well as coupling to models for cell contraction and mechanics.We present a mechanical analogue of the EMI model, i.e., a continuum basedcardiac mechanics model that explicitly represents a three-dimensional networkof cells embedded in an extracellular matrix. Both the intra- and extracellular domainsare modeled as hyperelastic, with constitutive models based based onthe Holzapfel-Ogden model for passive myocardium. The two domainshave different passive mechanical properties, and the intracellular domain isactively contracting while the extracellular domain is completely passive.The active contraction is incorporated through a so-called active strain model,and in this first version of the model it is assumed to be synchronous and homogeneousacross the entire intracellular domain. The model was parameterized usingpublicly available experimental data for stretching and shear experiments,and was used in preliminary explorations of mechanical interactions betweenthe intra- and extracellular domains. In particular, we studied how myocytestress and strain are affected by the mechanical properties of the two domains,during passive stretching and active contraction. The results show considerablespatial variations in both stress and strain, and indicate that the detailedgeometrical representation of the cells may give improved insight into certainmechanisms of biomechanics and mechano-biology. Further development ofthe model should include a more detailed exploration of material parameters,cell geometry, and the mechanical coupling between the cells and the surroundingmatrix, as well as extending the framework to consider inhomogeneous contractionand potentially coupling of contraction to cell electrophysiology and calcium diffusion.},
  year = {2022},
  journal = {International Symposium in honor of Professor Gerhard A. Holzapfel{\textquoteright}s 60th birthday, Graz, Austria},
}