Tzirakis Konstantinos, Kamarianakis Yiannis, Kontopodis Nikolaos, Ioannou Christos V
Department of Mechanical Engineering, Hellenic Mediterranean University, 71410 Heraklion, Crete, Greece.
Data Science Group, Institute of Applied and Computational Mathematics, Foundation for Research and Technology-Hellas, 70013 Heraklion, Crete, Greece.
Bioengineering (Basel). 2023 Jun 28;10(7):776. doi: 10.3390/bioengineering10070776.
During the vascular surgical reconstruction of aorto-iliac occlusive/aneurysmal disease, bifurcated grafts are used where vascular surgeons intra-operatively select the size and the relative lengths of the parent and daughter portions of the graft. Currently, clinical practice regarding the selection of the most favorable geometric configuration of the graft is an understudied research subject: decisions are solely based on the clinical experience of the operating surgeon. This manuscript aims to evaluate the hemodynamic performance of various diameters, D, of bifurcated aortic grafts and relate those with proximal/distal part length ratios (the angle φ between the limbs is used as a surrogate marker of the main body-to-limb length ratio) in order to provide insights regarding the effects of different geometries on the hemodynamic environment. To this end, a computationally intensive set of simulations is conducted, and the resulting data are analyzed with modern statistical regression tools. A negative curvilinear relationship of TAWSS with both φ and D is recorded. It is shown that the angle between limbs is a more important predictor for the variability of TAWSS, while the graft's diameter is an important determinant for the variability of OSI. Large percentages of the total graft area with TAWSS < 0.4 Pa, which correspond to thrombogenic stimulating environments, are only observed for large values of φ and D > 20 mm. This variable ranges from 10% (for the smallest values of φ and D) to 55% (for the largest φ and D values). Our findings suggest that grafts with the smallest possible angle between the limbs (i.e., smallest parent-to-daughter length ratio) present the most favorable hemodynamic performance, yielding the smallest percentage of total graft area under thrombogenic simulating environments. Similarly, grafts with the smallest acceptable diameter should be preferred for the same reason. Especially, grafts with diameters greater than 20 mm should be avoided, given the abrupt increase in estimated thrombogenic areas.
在腹主动脉-髂动脉闭塞性/动脉瘤性疾病的血管外科重建手术中，使用分叉移植物，血管外科医生在手术中选择移植物母支和子支的尺寸及相对长度。目前，关于选择移植物最有利几何构型的临床实践是一个研究不足的课题：决策仅基于主刀医生的临床经验。本手稿旨在评估不同直径（D）的分叉主动脉移植物的血流动力学性能，并将其与近端/远端部分长度比相关联（肢体之间的角度φ用作主体与肢体长度比的替代指标），以便深入了解不同几何形状对血流动力学环境的影响。为此，进行了一组计算密集型模拟，并使用现代统计回归工具对所得数据进行分析。记录了壁面切应力（TAWSS）与φ和D均呈负曲线关系。结果表明，肢体之间的角度是TAWSS变异性的更重要预测因素，而移植物直径是振荡剪切指数（OSI）变异性的重要决定因素。仅在φ值较大且D>20 mm时，才观察到壁面切应力<0.4 Pa的移植物总面积的很大百分比，这对应于血栓形成刺激环境。该变量范围从10%（对于最小的φ和D值）到55%（对于最大的φ和D值）。我们的研究结果表明，肢体之间角度尽可能小的移植物（即最小的母支与子支长度比）具有最有利的血流动力学性能，在血栓形成模拟环境下产生的移植物总面积百分比最小。同样，出于相同原因，应首选可接受直径最小的移植物。特别是，鉴于估计的血栓形成区域会突然增加，应避免使用直径大于20 mm的移植物。
