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Schematic of blood flow behaviour in representative carotid arteries of subjects in (A) N, (B) PC and (C) PA groups. CCA: common carotid artery, ICA: internal carotid artery, ECA: external carotid artery, N: normal, PC: primary closure, PA: patch angioplasty.
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We investigated differences in haemodynamic forces between carotid arteries that underwent primary closure (PC) or patch angioplasty (PA) using computational fluid dynamics (CFD). A total of 30 subjects were enrolled in this study, consisting of 10 subjects who underwent PC, 10 who underwent PA and 10 healthy subjects. Three-dimensional models of c...
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... geometry determines fluid behaviours and the corresponding haemodynamic forces in the vascular wall. A sudden change of bifurcation geometry by CEA induces a recirculating flow in a wide area primarily consisting of the carotid bulb and proximal ICA ( Figure 4). Three geometric parameters-the expansion ratio (ER), tortuosity and angle-were calculated from the 3D models to quantify the morphological characteristics of the bifurcation geometry, as described by Thomas et al. (2005). ...
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Citations
... Jung et al. 19 investigated hemodynamic differences between CAs treated with primary closure vs patch angioplasty. Proper closure technique selection and avoidance of excessive vessel wall dilation were associated with reduced flow recirculation and decreased risk of atherosclerotic plaque formation. ...
... The term Physics of Fluids ARTICLE pubs.aip.org/aip/pof (r Á ½lðrv þ ðrvÞ T Þ) represents the divergence of the stress tensor, 19 which can split into two terms as follows: ...
... The inlet of CA adopted periodic numerical boundary conditions, and the flow rate of the common carotid artery varies over time, as depicted in Fig. 3(b). 19 During the first cardiac cycle, an outlet pressure of 85.5 mm Hg 24 at the end of diastole in normal adults was selected for simulation. Starting from the second cycle, the three-element Windkessel model illustrated in Fig. 3(c) was applied as the outlet boundary condition. ...
Internal carotid artery (CA) stenosis is a primary etiological factor for stroke and transient ischemic attack. The severity of arterial stenosis significantly impacts patient health and treatment decisions. Therefore, we conducted computational fluid dynamics analyses on five carotid arteries (CAs) of severe stenosis and compared them with five CAs in the control group. We improved the three-element Windkessel model method by pre-calculating the constant-pressure outlet simulation of the first cardiac cycle, which accelerated the stability of the model. The research results show that vortices were observed at the bifurcation of the CAs in the control group, whereas in the severe stenosis group, vor-tices predominantly occurred within the carotid sinus downstream of the stenotic segment. Notably, the vortex flow in the carotid aneurysm downstream of the stenotic segment arises due to the cross-sectional constriction induced by stenosis, which always flows in a clockwise direction and may contribute to the formation of aneurysms distal to the stenotic region. A high time-averaged wall shear stress value can effectively identify the stenosis site of CAs, while a high relative residence time value marks the protrusion near the stenosis segment. This study delved into the hemodynamic parameters between the CAs of the severe stenosis group and the control group and provided robust clinical evidence for carotid atherosclerotic disease.
... A primary etiological factor of stroke is carotid artery stenosis, which is predominantly caused by the build-up of atherosclerotic plaque [1]. Furthermore, the formation and development of atherosclerotic plaques are highly influenced by the hemodynamic environment in the carotid artery [2]. However, the impact of an elevated heart rate on the hemodynamic milieu in carotid arteries of differing stenosis degrees, utilizing healthy carotid arteries as reference controls, has been seldom reported in the open literature. ...
In the current global health context, stroke has emerged as the third most prominent cause of mortality, following cardiovascular disease and neoplasms, substantially impacting human health. A primary etiological factor of stroke is carotid artery stenosis, which is predominantly caused by the build-up of atherosclerotic plaque [1]. Furthermore, the formation and development of atherosclerotic plaques are highly influenced by the hemodynamic environment in the carotid artery [2]. However, the impact of an elevated heart rate on the hemodynamic milieu in carotid arteries of differing stenosis degrees, utilizing healthy carotid arteries as reference controls, has been seldom reported in the open literature.
To address the research gap, digital twins of both healthy carotid arteries and those with varying degrees of stenosis were constructed in this work. Specifically, computational fluid dynamics (CFD) simulations on carotid arteries exhibiting varying degrees of stenosis were conducted to procure hemodynamic results under various heart rates [3]. The reduced order model (ROM) Builder Pre module was employed to export the simulation results as training files, encompassing solely grid node coordinates and individual hemodynamic parameters (e.g., velocity, pressure, and wall shear stress) [4, 5]. Subsequently, the Ansys Twin Builder module's reduced-order model derived a correlation between each grid node's hemodynamic parameters and the inlet boundary, thereby constructing a digital twin of the carotid artery. By modulating the inlet velocity of this digital twin, we obtained the distribution of hemodynamic parameters in the carotid artery in real-time response, thus enabling real-time visualization of flow field distribution under various heart rates. Contrasting with high-order models that employ Navier-Stokes equations to solve for carotid artery hemodynamic parameters in each scenario, the ROM necessitates only the training of hemodynamic results from typical previous scenarios.
The present work is expected to shed light on the deleterious implications of an augmented heart rate during physical exercise in individuals afflicted with carotid artery stenosis. The advent of a digital twin is poised to significantly broaden the spectrum of heart rates encompassed in this research.
... Employing ParaView, the calculations results post-processing were conducted for all 89 designed models to obtain the distributions of hemodynamic indices OSI (Oscillatory Shear Index), TAWSS (Time-Averaged Wall Shear Stress), RRT (Relative Residence Time) [2,14,15] on their walls. Given its reliance on both the shear stress and the oscillation of near-wall flow, an RRT-index was taken as a prime indicator of atherogenesis risks. ...
... Given its reliance on both the shear stress and the oscillation of near-wall flow, an RRT-index was taken as a prime indicator of atherogenesis risks. On the wall of each model, zones were built in which the RRT exceeds the critical value of 6.25 Pa -1 , [15,16] referred to as "critical zones". Thereafter, assessments of integral RRT values (referred to as RRT_int) were provided across the most important in the medical sense parts of these zones. ...
Arterial bifurcations are known to be high-risk areas for the initiation of atherosclerosis. The appearance and growth of atherosclerotic plaques in the bifurcation of the carotid artery can result in severe consequences such as cerebrovascular accidents. The common signs of an atherogenic risk center around the surpassing critical values by certain hemodynamic indices, which are distributed over the artery wall. These indices are related to the effect of blood flow on the arterial wall, and their distribution is influenced by both the bifurcation’s geometric shape and the flow structure at its inlet. The objective of this study is to carry out a comparative analysis of hemodynamic indices in personal-specific models of carotid bifurcation with centrally symmetric and asymmetric input flows. The examined geometric models of bifurcation are based on computed angiography data obtained from the individuals free of apparent pathology. By using computational fluid dynamics within these models, the distribution of hemodynamic indices in a steady periodic flow is calculated and critical zones are determined for them. All the models are divided into two groups – those with symmetric and those with asymmetric input flows. For each model with asymmetric input flow, an alternative geometry is designed to ensure inlet flow symmetry, and comparative numerical calculations of the blood flow are carried out. The results of comparative analysis reveal that the distribution of hemodynamic indices is simpler for the group with symmetric input flow. A comparison of the averages between these two groups with symmetrical and natural asymmetric input flows indicates a 55% better result for the latter group. Furthermore, for almost all models with asymmetric input flow, their alternative models give worse hemodynamic results. Thus, hemodynamic indices in simpler models with symmetrical input flow can serve as an upper estimate for indices in models with natural asymmetric flow. A total of 89 models are included in the study.
... The FSI method considers the solid (structure) deformation while analyzing the fluid motion, and it solves the problem based on the fluid-solid coupling effect. The CFD method was used to study the differences in hemodynamics of carotid arteries undergoing primary closure or stent placement (Jung et al. 2022). Rahma and Abdelhamid (2023) explored the hemodynamic parameters of cerebral aneurysms and their impact on aneurysm rupture, and analyzed the effect of the flow recirculation on the hemodynamic parameters of the convex wall. ...
An interventional robot is a means for vascular diagnosis and treatment, and it can perform dredging, releasing drug and operating. Normal hemodynamic indicators are a prerequisite for the application of interventional robots. The current hemodynamic research is limited to the absence of interventional devices or interventional devices in fixed positions. Considering the coupling effect of blood, vessels and robots, based on the bi-directional fluid–structure interaction, using the computational fluid dynamics and particle image velocimetry methods, combined with the sliding and moving mesh technologies, we theoretically and experimentally study the hemodynamic indicators such as blood flow lines, blood pressure, equivalent stress, deformation and wall shear stress of blood vessels when the robot precesses, rotates or does not intervene in the pulsating blood flow. The results show that the intervention of the robot increase the blood flow rate, blood pressure, equivalent stress and deformation of the vessels by 76.4%, 55.4%, 76.5%, and 346%, respectively. The operating mode of the robot during low-speed operation has little impact on the hemodynamic indicators. Using the methyl silicone oil as the experimental fluid, the elastic silicone pipe as the experimental pipe, and the intervention robot having a bioplastic outer shell, the velocity of the fluid around the robot is measured on the developed experimental device for fluid flow field in a pulsating flow when the robot runs. The experimental results are similar to the numerical results. Our work provides an important reference for the hemodynamic study and optimization of the mobile interventional devices.
Carotid endarterectomy is the main way to combat atherosclerosis of the carotid arteries, which disrupts cerebral circulation. The generally accepted marker of atherogenesis risk are hemodynamic indices associated with near-wall shear stress. The purpose of the work is to conduct a comparative analysis of hemodynamic indices in various carotid bifurcation models. The influence of a virtual change in the geometric shape of the model in order to optimize hemodynamic indices is also being studied. On the basis of computed angiography data, carotid bifurcation models are constructed, in which critical zones of hemodynamic indices are built using computational fluid dynamics. A comparative analysis of the critical zones for different classes of models is carried out. Comparison of averaged indices for critical zones between 'normal' and post-operative groups gave more than 5-x worse results for the latter. The same results for the near-bifurcation parts of the zones give a 25% better result for postoperative models. Virtual ‘removal’ of insignificant plaques leads to a deterioration of the indices of up to 40% in the places of the plaque’s former location. The described method makes it possible to build the indices critical zones and compare them for various types of models. A technique for virtual changing the shape of a vessel (virtual surgery) is proposed. The novelty of the approach lies in the use for comparative analysis both real vessel models and hypothetical ‘improved’ virtual ones, as well in the proposed division of post-operative model’s critical zones into subzones of different genesis.
