Purpose

Abdominal Aortic Aneurysms (AAA) have extreme medical prevalence as an asymptomatic cause of death in developed countries. The probability of AAA rupture is promoted by the localized oxygen loss in the AAA wall which occurs in part because many AAAs contain a layer called intraluminal thrombus (ILT). Considering this strong clinical association, the purpose of this study is to investigate the key features that constitute to the oxygen diffusion, and therefore hypoxia in AAA.

Methods

A three-dimensional model of AAA containing ILT is created and numerical simulations are performed to simulate blood flow and oxygen distribution within the AAA. The model accounts for blood flow in the lumen and oxygen transport in the lumen, ILT, and arterial wall. The sub-model of the ILT is fully coupled with the wall sub-model as well as with the subdomain of the blood flow. The sensitivity of the oxygen flow with respect to the parameters of the problem is also analyzed.

Results

Model simulations are used to investigate the relation between AAA physical properties, hemodynamics, and oxygen concentration in different geometries of AAA. The results demonstrate that the diameter of the AAA bulge has little effect on the oxygen flow, but that the thickness of the ILT layer has a profound effect. Moreover, a significant sensitivity to the oxygen supply from vasa vasorum and its notable impact on oxygen transport within AAA are observed. The variability of the arterial wall oxygen concentration to the oxygen reaction rate remains however very low.

Conclusion

The presence of an ILT significantly impairs oxygen transport from the lumen to the wall. This study confirms that consideration of ILT size and anatomy may be important in considering the severity of a AAA, however, other parameters can also affect thrombus-mediated oxygen delivery within the aneurysmal wall.

中文翻译：

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腹主动脉瘤中的耦合血流动力学和氧气扩散：一项计算敏感性研究

目的

在发达国家，腹主动脉瘤 (AAA) 作为一种无症状的死亡原因具有极高的医学流行率。AAA 破裂的可能性是由 AAA 壁中的局部氧损失促进的，这部分是因为许多 AAA 包含称为腔内血栓 (ILT) 的层。考虑到这种强烈的临床关联，本研究的目的是研究构成 AAA 中氧扩散的关键特征，从而研究缺氧。

方法

创建包含 ILT 的 AAA 的三维模型，并进行数值模拟以模拟 AAA 内的血流和氧气分布。该模型考虑了管腔中的血流和管腔、ILT 和动脉壁中的氧运输。ILT 的子模型与壁子模型以及血流子域完全耦合。还分析了氧气流量对问题参数的敏感性。

结果

模型模拟用于研究不同几何形状的 AAA 物理特性、血流动力学和氧浓度之间的关系。结果表明，AAA 凸起的直径对氧气流量的影响很小，但 ILT 层的厚度具有深远的影响。此外，观察到对来自血管滋养管的氧气供应的显着敏感性及其对 AAA 内氧气运输的显着影响。然而，动脉壁氧浓度对氧反应速率的可变性仍然非常低。

结论

ILT 的存在显着削弱了从管腔到壁的氧气运输。该研究证实，在考虑 AAA 的严重程度时，考虑 ILT 大小和解剖结构可能很重要，但是，其他参数也会影响动脉瘤壁内血栓介导的氧气输送。