Chapter 21 – Adaptive Reorientation of Myofiber Orientation in a Model of Biventricular Cardiac Mechanics: The Effect of Triaxial Active Stress, Passive Shear Stiffness, and Activation Sequence

Patient-specific finite element models of cardiac mechanics may assist in clinical decision making by estimating maps of electrical and mechanical tissue properties from clinically observed cardiac deformation. In models of left ventricular mechanics, cardiac deformation was shown to be crucially dependent on cardiac myofiber orientation. Since in vivo assessment of myofiber orientation is inaccurate, a model of adaptive reorientation of myofiber orientation was proposed as method for estimating myofiber orientation. In the present study, we evaluate this adaptation model in a model of biventricular mechanics. Adaptive reorientation of myofibers resulted in an endo-to-epicardial component of fiber orientation, an improved pump function, and more realistic shear strain patterns. Predicted fiber orientation was well defined, and fairly independent of settings of passive shear stiffness, triaxial active stress development, and activation sequence. This finding supports the suggestion to use the model for estimating myofiber orientation in patient-specific models.