IEEE Trans Biomed Eng. 2021 Oct;68(10):2918-2929. doi: 10.1109/TBME.2021.3056022. Epub 2021 Sep 20.
Aortic dissection is a life-threatening event which starts most of the time with an intimal tear propagating along the aortic wall, while blood enters the medial layer and delaminates the medial lamellar units. Studies investigating the mechanisms underlying the initiation sequence of aortic dissection are rare in the literature, the majority of studies being focused on the propagation event. Numerical models can provide a deeper understanding of the phenomena involved during the initiation and the propagation of the initial tear, and how geometrical and mechanical parameters affect this event. In the present paper, we investigated the primary factors contributing to aortic dissection.
A two-layer arterial model with an initial tear was developed, representing three different possible configurations depending on the initial direction of the tear. Anisotropic damage initiation criteria were developed based on uniaxial and shear experiments from the literature to predict the onset and the direction of crack propagation. We used the XFEM-based cohesive segment method to model the initiation and the early propagation of the tear along the aorta. A design of experiment was used to quantify the influence of 7 parameters reflecting crack geometry and mechanics of the wall on the critical pressure triggering the dissection and the directions of propagation of the tear.
The results showed that the obtained critical pressures (mean range from 206 to 251 mmHg) are in line with measurement from the literature. The medial tensile strength was found to be the most influential factor, suggesting that a medial degeneration is needed to reach a physiological critical pressure and to propagate a tear in an aortic dissection. The geometry of the tear and its location inside the aortic wall were also found to have an important role not only in the triggering of tear propagation, but also in the evolution of the tear into either aortic rupture or aortic dissection. A larger and deeper initial tear increases the risk of aortic dissection.
The numerical model was able to reproduce the behaviour of the aorta during the initiation and propagation of an aortic dissection. In addition to confirm multiple results from the literature, different types of tears were compared and the influence of several geometrical and mechanical parameters on the critical pressure and direction of propagation was evaluated with a parametric study for each tear configuration.
Although these results should be experimentally validated, they allow a better understanding of the phenomena behind aortic dissection and can help in improving the diagnosis and treatment of this disease.
主动脉夹层是一种危及生命的事件，大多数情况下，它始于主动脉壁内的一个内膜撕裂，血液进入中膜并使中膜层分层。文献中很少有研究调查主动脉夹层起始序列的机制，大多数研究都集中在传播事件上。数值模型可以更深入地了解主动脉夹层起始和初始撕裂传播过程中涉及的现象，以及几何和力学参数如何影响这一事件。在本文中，我们研究了导致主动脉夹层的主要因素。
建立了一个带有初始撕裂的两层动脉模型，根据撕裂的初始方向代表了三种不同的可能构型。基于文献中的单轴和剪切实验，开发了各向异性损伤起始准则，以预测裂缝的起始和传播方向。我们使用基于 XFEM 的内聚段方法来模拟撕裂在主动脉中的起始和早期传播。使用实验设计来量化 7 个反映壁的裂纹几何形状和力学的参数对触发夹层的临界压力和撕裂传播方向的影响。
结果表明，得到的临界压力（均值范围为 206 至 251mmHg）与文献中的测量值一致。中膜拉伸强度被发现是最具影响力的因素，表明中膜退化是达到生理临界压力并在主动脉夹层中传播撕裂所必需的。撕裂的几何形状及其在主动脉壁内的位置也被发现不仅对撕裂传播的触发，而且对撕裂演变为主动脉破裂或主动脉夹层起着重要作用。较大和较深的初始撕裂增加了主动脉夹层的风险。
数值模型能够再现主动脉在主动脉夹层起始和传播过程中的行为。除了确认文献中的多个结果外，还比较了不同类型的撕裂，并通过对每种撕裂构型的参数研究，评估了几个几何和力学参数对临界压力和传播方向的影响。
尽管这些结果需要通过实验验证，但它们可以帮助更好地理解主动脉夹层背后的现象，并有助于改善对这种疾病的诊断和治疗。
