J. Mike Walker '66 Department of Mechanical Engineering, Texas A&M University, College Station, Texas, USA.
Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA.
Artif Organs. 2024 Apr;48(4):375-385. doi: 10.1111/aor.14679. Epub 2023 Nov 14.
Hemocompatibility-related adverse events (HRAE) occur commonly in patients with left ventricular assist devices (LVADs) and add to morbidity and mortality. It is unclear whether the outflow graft orientation can impact flow conditions leading to HRAE. This study presents a simulation-based approach using exact patient anatomy from medical images to investigate the influence of outflow cannula orientation in modulating flow conditions leading to HRAEs.
A 3D model of a proximal aorta and outflow graft was reconstructed from a computed tomography (CT) scan of an LVAD patient and virtually modified to model multiple cannula orientations (n = 10) by varying polar (cranio-caudal) (n = 5) and off-set (anterior-posterior) (n = 2) angles. Time-dependent computational flow simulations were then performed for each anatomical orientation. Qualitative and quantitative hemodynamics metrics of thrombogenicity including time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell platelet activation potential (ECAP), particle residence time (PRT), and platelet activation potential (PLAP) were analyzed.
Within the simulations performed, endothelial cell activation potential (ECAP) and particle residence time (PRT) were found to be lowest with a polar angle of 85°, regardless of offset angle. However, polar angles that produced parameters at levels least associated with thrombosis varied when the offset angle was changed from 0° to 12°. For offset angles of 0° and 12° respectively, flow shear was lowest at 65° and 75°, time averaged wall shear stress (TAWSS) was highest at 85° and 35°, and platelet activation potential (PLAP) was lowest at 65° and 45°.
This study suggests that computational fluid dynamic modeling based on patient-specific anatomy can be a powerful analytical tool when identifying optimal positioning of an LVAD. Contrary to previous work, our findings suggest that there may be an "ideal" outflow cannula for each individual patient based on a CFD-based hemocompatibility profile.
左心室辅助装置（LVAD）患者常发生与血液相容性相关的不良事件（HRAE），增加发病率和死亡率。目前尚不清楚流出导管的方向是否会影响导致 HRAE 的血流条件。本研究采用基于模拟的方法，使用来自医学图像的精确患者解剖结构来研究流出套管方向对导致 HRAE 的血流条件的影响。
从 LVAD 患者的计算机断层扫描（CT）扫描重建近端主动脉和流出导管的 3D 模型，并通过改变极（头足）（n=5）和偏移（前后）（n=2）角度来虚拟地修改模型以模拟多个套管方向（n=10）。然后对每个解剖方向进行时变计算血流模拟。分析血栓形成的定性和定量血液动力学指标，包括时间平均壁切应力（TAWSS）、振荡剪切指数（OSI）、内皮细胞血小板激活潜能（ECAP）、颗粒停留时间（PRT）和血小板激活潜能（PLAP）。
在所进行的模拟中，发现内皮细胞激活潜能（ECAP）和颗粒停留时间（PRT）在极角为 85°时最低，而与偏移角无关。然而，当偏移角从 0°变为 12°时，产生与血栓形成关联最小的参数的极角会发生变化。对于偏移角分别为 0°和 12°，剪切流最低的分别为 65°和 75°，时间平均壁切应力（TAWSS）最高的分别为 85°和 35°，血小板激活潜能（PLAP）最低的分别为 65°和 45°。
本研究表明，基于患者特定解剖结构的计算流体动力学建模可以成为识别 LVAD 最佳定位的强大分析工具。与以前的工作相反，我们的研究结果表明，根据基于 CFD 的血液相容性特征，对于每个个体患者，可能存在“理想”的流出导管。
