TY - JOUR
T1 - Effects of activation pattern and active stress development on myocardial shear in a model with adaptive myofiber reorientation
AU - Pluijmert, M.H.
AU - Bovendeerd, P.H.M.
AU - Kroon, W.
AU - Prinzen, F.W.
AU - Delhaas, T.
PY - 2014
Y1 - 2014
N2 - 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 Ecr 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 at,0 and the effect on global pump function were minor. Triaxial active stress development decreased amplitudes of Ecr towards values within the experimental range and resulted in a similar base-to-apex gradient during ejection in model computed and measured Ecr. 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.
AB - 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 Ecr 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 at,0 and the effect on global pump function were minor. Triaxial active stress development decreased amplitudes of Ecr towards values within the experimental range and resulted in a similar base-to-apex gradient during ejection in model computed and measured Ecr. 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.
U2 - 10.1152/ajpheart.00571.2013
DO - 10.1152/ajpheart.00571.2013
M3 - Article
C2 - 24322610
VL - 306
SP - H538-H546
JO - American Journal of Physiology : Heart and Circulatory Physiology
JF - American Journal of Physiology : Heart and Circulatory Physiology
SN - 0363-6135
ER -