Cardiac Tissue Fiber Orientations

The anisotropy of cardiac tissue requires the assignment of a local orientation definition to the elements in the model.

As shown in the figure below from Holzapfel and Ogden, the fiber orientations associated with the structures in the heart are complex due to:

  • The complex organic geometry of the heart
  • Orientations changing across the surface of the heart
  • Orientations changing through the thickness of the heart wall
Schematic Representation of Muscle Fiber Orientation Within the Left Ventricle

Local material orientations are not defined in Mechanical Scenario Creation for the atria, ventricles, SVC, aortic arch, and pulmonary trunk. However, the orientations are defined as discrete fields in the Abaqus input files that are generated by the simulation process.

This methodology requires that a separate orientation be defined at the centroid of each element. The fiber angles, α, in the ventricles are approximately equal to –60° on the epicardium and +60° on the endocardium as shown in Streeter et al., which is consistent with Genet et al. The fiber orientations in the atria (as well as the superior vena cava (SVC), aortic arch, and pulmonary trunk) were approximated using Figure 20 in the euHeart Final Project Report. The model includes three Discrete Field definitions.

After running the analysis, you can visualize the fiber orientation (as shown in the figure below) by examining the results with Physics Results Explorer. From the Plots section of the action bar, click Create Symbol Plot, then select ORIENT (at element integration point) for the stress components variable.

Fiber Orientations of the Heart Model

A simulation process is provided to redefine the initial fiber orientations for the atria, ventricles, or any portion thereof, as a result of any modifications you make to the model geometry; for example, after creating a partition in the ventricle that is then remeshed. For more information, see Remeshing and Matching Meshes.