Department of Ocean System Engineering, Jeju National University, Jeju-do, Republic of Korea.
Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, USA.
Comput Biol Med. 2023 May;157:106767. doi: 10.1016/j.compbiomed.2023.106767. Epub 2023 Mar 9.
Erythrocyte aggregation (EA) is a highly dynamic, vital phenomenon to interpreting human hemorheology, which would be helpful for the diagnosis and prediction of circulatory anomalies. Previous studies of EA on erythrocyte migration and the Fåhraeus Effect are based on the microvasculature. They have not considered the natural pulsatility of the blood flow or large vessels and mainly focused on shear rate along radial direction under steady flow to comprehend the dynamic properties of EA. To our knowledge, the rheological characteristics of non-Newtonian fluids under Womersley flow have not reflected the spatiotemporal behaviors of EA or the distribution of erythrocyte dynamics (ED). Hence, it needs to interpret the ED affected by temporal and spatial flow variation to understand the effect of EA under Womersley flow. Here, we demonstrated the numerically simulated ED to decipher EA's rheological role in axial shear rate under Womersley flow. In the present study, the temporal and spatial variations of the local EA were found to mainly depend on the axial shear rate under Womersley flow in an elastic vessel, while mean EA decreased with radial shear rate. The localized distribution of parabolic or M-shape clustered EA was found in a range of the axial shear rate profile (-15 to 15s) at low radial shear rates during a pulsatile cycle. However, the linear formation of rouleaux was realized without local clusters in a rigid wall where the axial shear rate is zero. In vivo, the axial shear rate is usually considered insignificant, especially in straight arteries, but it has a great impact on the disturbed blood flow due to the geometrical properties, such as bifurcations, stenosis, aneurysm, and the cyclic variation of pressure. Our findings regarding axial shear rate provide new insight into the local dynamic distribution of EA, which is a critical player in blood viscosity. These will provide a basis for the computer-aided diagnosis of hemodynamic-based cardiovascular diseases by decreasing the uncertainty in the pulsatile flow calculation.
红细胞聚集（EA）是解释人体血液流变学的一种高度动态的、重要的现象，有助于循环异常的诊断和预测。以前对红细胞迁移和 Fåhraeus 效应的 EA 研究都是基于微血管。它们没有考虑到血流的自然脉动或大血管，主要集中在稳态流下沿径向的剪切率，以理解 EA 的动态特性。据我们所知，在沃默斯利流下非牛顿流体的流变特性还没有反映 EA 的时空行为或红细胞动力学（ED）的分布。因此，需要解释受时空流变化影响的 ED，以了解沃默斯利流下 EA 的作用。在这里，我们通过数值模拟 ED 来解释 EA 在沃默斯利流轴向剪切率下的流变作用。在本研究中，发现弹性血管中沃默斯利流下局部 EA 的时空变化主要取决于轴向剪切率，而平均 EA 随径向剪切率的降低而降低。在脉动周期内，当径向剪切率较低时，在轴向剪切率分布范围内（-15 到 15s）发现了局部呈抛物线或 M 形聚集 EA 的分布。然而，在刚性壁中，由于几何特性（如分叉、狭窄、动脉瘤和压力的周期性变化），轴向剪切率为零，形成了线性的红细胞聚集。在体内，轴向剪切率通常被认为不重要，尤其是在直动脉中，但由于几何特性，如分叉、狭窄、动脉瘤和压力的周期性变化，它对紊乱的血流有很大的影响。我们关于轴向剪切率的发现为 EA 的局部动态分布提供了新的见解，这是血液粘度的关键因素。这些发现将为基于血流动力学的心血管疾病的计算机辅助诊断提供依据，减少脉动流计算中的不确定性。
