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 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 ± 2.92 mm to 9.49 ± 2.02 mm, whereas the LV free-wall thickness increased from 8.69 ± 1.64 mm to 9.4 ± 1.22 mm. 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.

中文翻译：

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压力过载期间左心室生长的机械刺激

在压力超负荷的左心室 (LV) 中发生的生长的机械刺激（即压力或拉伸）尚不完全清楚。为了解决这个问题，我们研究了局部心室生长（由局部壁厚索引）与主动脉束带后机械刺激的局部急性变化之间的相关性。LV 几何数据是在基线和 2 周的主动脉带状猪模型 (n = 4) 中从 3D 回波测量中提取的。我们针对在基线测量的压力和体积波形开发并校准了 LV 力学的动物特异性有限元 (FE) 模型。在模拟压力过载的急性效应后，在三个正交材料方向（即纤维、表和表正常）在一个心动周期进行量化。使用 Pearson 相关数 (PCN) 和 Spearman 秩相关数 (SCN) 量化机械量和相应测量的壁厚局部变化之间的相关性。结扎后 2 周，平均隔膜厚度从 10.6 ± 2.92 mm 下降到 9.49 ± 2.02 mm，而 LV 游离壁厚度从 8.69 ± 1.64 mm 增加到 9.4 ± 1.22 mm。有限元分析结果显示，增长与最大纤维应力（PCN = 0.5471，SCN = 0.5111）和平均板正应力（PCN = 0.5266，SCN = 0.5256）的变化密切相关。然而，心肌伸展与生长没有很好的相关性。这些结果表明，纤维应力是压力过载时 LV 生长的机械刺激。使用 Pearson 相关数 (PCN) 和 Spearman 秩相关数 (SCN) 量化机械量和相应测量的壁厚局部变化之间的相关性。结扎后 2 周，平均隔膜厚度从 10.6 ± 2.92 mm 下降到 9.49 ± 2.02 mm，而 LV 游离壁厚度从 8.69 ± 1.64 mm 增加到 9.4 ± 1.22 mm。有限元分析结果显示，增长与最大纤维应力（PCN = 0.5471，SCN = 0.5111）和平均板正应力（PCN = 0.5266，SCN = 0.5256）的变化密切相关。然而，心肌伸展与生长没有很好的相关性。这些结果表明，纤维应力是压力过载时 LV 生长的机械刺激。使用 Pearson 相关数 (PCN) 和 Spearman 秩相关数 (SCN) 量化机械量和相应测量的壁厚局部变化之间的相关性。结扎后 2 周，平均隔膜厚度从 10.6 ± 2.92 mm 下降到 9.49 ± 2.02 mm，而 LV 游离壁厚度从 8.69 ± 1.64 mm 增加到 9.4 ± 1.22 mm。有限元分析结果显示，增长与最大纤维应力（PCN = 0.5471，SCN = 0.5111）和平均板正应力（PCN = 0.5266，SCN = 0.5256）的变化密切相关。然而，心肌伸展与生长没有很好的相关性。这些结果表明，纤维应力是压力过载时 LV 生长的机械刺激。