Abstract

Aims

The aim of this study is to design a computer model of the left atrium for investigating fibre-orientation-dependent microstructure such as stringy fibrosis.

Methods and results

We developed an approach for automatic construction of bilayer interconnected cable models from left atrial geometry and epi- and endocardial fibre orientation. The model consisted of two layers (epi- and endocardium) of longitudinal and transverse cables intertwined-like fabric threads, with a spatial discretization of 100 µm. Model validation was performed by comparison with cubic volumetric models in normal conditions. Then, diffuse (n = 2904), stringy (n = 3600), and mixed fibrosis patterns (n = 6840) were randomly generated by uncoupling longitudinal and transverse connections in the interconnected cable model. Fibrosis density was varied from 0% to 40% and mean stringy obstacle length from 0.1 to 2 mm. Total activation time, apparent anisotropy ratio, and local activation time jitter were computed during normal rhythm in each pattern. Non-linear regression formulas were identified for expressing measured propagation parameters as a function of fibrosis density and obstacle length (stringy and mixed patterns). Longer obstacles (even below tissue space constant) were independently associated with prolonged activation times, increased anisotropy, and local fluctuations in activation times. This effect was increased by endo-epicardial dissociation and mitigated when fibrosis was limited to the epicardium.

Conclusion

Interconnected cable models enable the study of microstructure in organ-size models despite limitations in the description of transmural structures.

中文翻译：

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左心房双层互连电缆模型中弥漫性和纤维化的模拟

摘要

宗旨

本研究的目的是设计左心房的计算机模型，用于研究纤维取向依赖的微观结构，如纤维化。

方法和结果

我们开发了一种从左心房几何形状和心外膜和心内膜纤维方向自动构建双层互连电缆模型的方法。该模型由两层（外膜和心内膜）纵向和横向电缆交织而成的织物线，空间离散化为 100 µm。通过与正常条件下的立方体积模型进行比较来进行模型验证。然后，弥漫性 ( n  = 2904)、丝状 ( n  = 3600) 和混合纤维化模式 ( n = 6840) 是通过在互连电缆模型中解耦纵向和横向连接随机生成的。纤维化密度从 0% 到 40% 不等，平均丝状障碍长度从 0.1 到 2 mm。在每个模式的正常节律期间计算总激活时间、表观各向异性比和局部激活时间抖动。确定了非线性回归公式，用于将测量的传播参数表示为纤维化密度和障碍物长度（多筋和混合模式）的函数。更长的障碍物（甚至低于组织空间常数）与激活时间延长、各向异性增加和激活时间的局部波动独立相关。这种作用通过心外膜分离而增加，当纤维化仅限于心外膜时会减轻。

结论

尽管透壁结构的描述存在局限性，但互连电缆模型能够研究器官大小模型中的微观结构。