Wang Vicky Y, Lam H I, Ennis Daniel B, Cowan Brett R, Young Alistair A, Nash Martyn P
Auckland Bioengineering Institute, University of Auckland, Level 6, UniServices House, 70 Symonds Street, Auckland 1142, New Zealand.
Med Image Anal. 2009 Oct;13(5):773-84. doi: 10.1016/j.media.2009.07.006. Epub 2009 Jul 16.
The majority of patients with clinically diagnosed heart failure have normal systolic pump function and are commonly categorized as suffering from diastolic heart failure. The left ventricle (LV) remodels its structure and function to adapt to pathophysiological changes in geometry and loading conditions, which in turn can alter the passive ventricular mechanics. In order to better understand passive ventricular mechanics, a LV finite element (FE) model was customized to geometric data segmented from in vivo tagged magnetic resonance images (MRI) data and myofibre orientation derived from ex vivo diffusion tensor MRI (DTMRI) of a canine heart using nonlinear finite element fitting techniques. MRI tissue tagging enables quantitative evaluation of cardiac mechanical function with high spatial and temporal resolution, whilst the direction of maximum water diffusion in each voxel of a DTMRI directly corresponds to the local myocardial fibre orientation. Due to differences in myocardial geometry between in vivo and ex vivo imaging, myofibre orientations were mapped into the geometric FE model using host mesh fitting (a free form deformation technique). Pressure recordings, temporally synchronized to the tagging data, were used as the loading constraints to simulate the LV deformation during diastole. Simulation of diastolic LV mechanics allowed us to estimate the stiffness of the passive LV myocardium based on kinematic data obtained from tagged MRI. Integrated physiological modelling of this kind will allow more insight into mechanics of the LV on an individualized basis, thereby improving our understanding of the underlying structural basis of mechanical dysfunction under pathological conditions.
临床上诊断为心力衰竭的大多数患者的收缩泵功能正常，通常归类为舒张性心力衰竭。左心室（LV）重塑其结构和功能，以适应几何形状和负荷条件的病理生理变化，这反过来又会改变心室的被动力学特性。为了更好地理解心室的被动力学特性，使用非线性有限元拟合技术，根据从体内标记磁共振成像（MRI）数据分割得到的几何数据以及从犬心脏的体外扩散张量MRI（DTMRI）得出的肌纤维方向，定制了一个左心室有限元（FE）模型。MRI组织标记能够以高空间和时间分辨率对心脏机械功能进行定量评估，而DTMRI每个体素中最大水扩散方向直接对应于局部心肌纤维方向。由于体内和体外成像中心肌几何形状存在差异，使用宿主网格拟合（一种自由形式变形技术）将肌纤维方向映射到几何有限元模型中。与标记数据在时间上同步的压力记录用作加载约束，以模拟舒张期左心室的变形。舒张期左心室力学模拟使我们能够根据从标记MRI获得的运动学数据估计左心室被动心肌的僵硬度。这种综合生理建模将使我们能够在个体基础上更深入地了解左心室的力学特性，从而增进我们对病理条件下机械功能障碍潜在结构基础的理解。
