Key result
Extending the LV mechanics model with triaxial active stress development and physiological activation patterns resulted in more physiologic computed circumferential-radial shear strain.
Incorporating triaxial active stress development and physiological activation patterns into computational models of LV mechanics yields more physiological outcomes for myofiber reorientation and deformation.
Supports advanced LV computational models in research; leaves open human validation before clinical translation.
It has been hypothesized that myofiber orientation adapts to achieve a preferred mechanical loading state in the myocardial tissue. Earlier studies tested this hypothesis in a combined model of left ventricular (LV) mechanics and remodeling of myofiber orientation in response to fiber cross-fiber shear, assuming synchronous timing of activation and uniaxial active stress development. Differences between computed and measured patterns of circumferential-radial shear strain E(cr) were assumed to be caused by limitations in either the LV mechanics model or the myofiber reorientation model. Therefore, we extended the LV mechanics model with a physiological transmural and longitudinal gradient in activation pattern and with triaxial active stress development. We investigated the effects on myofiber reorientation, LV function, and deformation. The effect on the developed pattern of the transverse fiber angle α(t,0) and the effect on global pump function were minor. Triaxial active stress development decreased amplitudes of E(cr) towards values within the experimental range and resulted in a similar base-to-apex gradient during ejection in model computed and measured E(cr). The physiological pattern of mechanical activation resulted in better agreement between computed and measured strain in myofiber direction, especially during isovolumic contraction phase and first half of ejection. In addition, remodeling was favorable for LV pump and myofiber function. In conclusion, the outcome of the combined model of LV mechanics and remodeling of myofiber orientation is found to become more physiologic by extending the mechanics model with triaxial active stress development and physiological activation pattern.
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Pluijmert et al. (2013) studied Left ventricular mechanics and myofiber reorientation. Extension of LV mechanics model with physiological transmural and longitudinal gradient in activation pattern and triaxial active stress development vs. Earlier combined model with synchronous timing of activation and uniaxial active stress development was evaluated on Myofiber reorientation, LV function, and deformation (circumferential-radial shear strain E(cr)). Extending the LV mechanics model with triaxial active stress development and physiological activation patterns resulted in more physiologic computed circumferential-radial shear strain.
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