Mojumder J, Choy J S, Leng S, Zhong L, Kassab G S, Lee L C
Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA.
California Medical Innovations Institute, San Diego, CA, USA.
Exp Mech. 2021 Jan;61(1):131-146. doi: 10.1007/s11340-020-00643-z. Epub 2020 Aug 11.
The mechanical stimulus (i.e. stress or stretch) for growth occurring in the pressure-overloaded left ventricle (LV) is not exactly known.
To address this issue, we investigate the correlation between local ventricular growth (indexed by local wall thickness) and the local acute changes in mechanical stimuli after aortic banding.
LV geometric data were extracted from 3D echo measurements at baseline and 2 weeks in the aortic banding swine model (n = 4). We developed and calibrated animal-specific finite element (FE) model of LV mechanics against pressure and volume waveforms measured at baseline. After the simulation of the acute effects of pressure-overload, the local changes of maximum, mean and minimum myocardial stretches and stresses in three orthogonal material directions (i.e., fiber, sheet and sheet-normal) over a cardiac cycle were quantified. Correlation between mechanical quantities and the corresponding measured local changes in wall thickness was quantified using the Pearson correlation number (PCN) and Spearman rank correlation number (SCN).
At 2 weeks after banding, the average septum thickness decreased from 10.6 ± 2.92mm to 9.49 ± 2.02mm, whereas the LV free-wall thickness increased from 8.69 ± 1.64mm to 9.4 ± 1.22mm. The FE results show strong correlation of growth with the changes in maximum fiber stress (PCN = 0.5471, SCN = 0.5111) and changes in the mean sheet-normal stress (PCN= 0.5266, SCN = 0.5256). Myocardial stretches, however, do not have good correlation with growth.
These results suggest that fiber stress is the mechanical stimuli for LV growth in pressure-overload.
发生在压力超负荷左心室（LV）中的生长机械刺激（即应力或拉伸）尚不完全清楚。
为解决这一问题，我们研究了局部心室生长（以局部壁厚为指标）与主动脉缩窄后机械刺激的局部急性变化之间的相关性。
从主动脉缩窄猪模型（n = 4）基线和2周时的三维超声心动图测量中提取左心室几何数据。我们根据基线时测量的压力和容积波形，开发并校准了动物特异性的左心室力学有限元（FE）模型。在模拟压力超负荷的急性效应后，量化了一个心动周期中三个正交材料方向（即纤维方向、片层方向和片层法线方向）上最大、平均和最小心肌拉伸及应力的局部变化。使用Pearson相关系数（PCN）和Spearman等级相关系数（SCN）量化机械量与相应测量的局部壁厚变化之间的相关性。
缩窄后2周，平均室间隔厚度从10.6±2.92mm降至9.49±2.02mm，而左心室游离壁厚度从8.69±1.64mm增加到9.4±1.22mm。有限元结果显示生长与最大纤维应力变化（PCN = 0.5471，SCN = 0.5111）和平均片层法线应力变化（PCN = 0.5266，SCN = 0.5256）之间存在强相关性。然而，心肌拉伸与生长的相关性不佳。
这些结果表明纤维应力是压力超负荷时左心室生长的机械刺激因素。
