Hemodynamic Impact of Stenting on Carotid Bifurcation: A Potential Role of the Stented Segment and External Carotid Artery

Carotid stenting near the bifurcation carina is associated with adverse events, especially in-stent restenosis, thrombosis, and side branch occlusion in clinical data. This study is aimed at determining the potential biomechanical mechanisms for these adverse events after carotid stenting. The patient-specific carotid models were constructed with different stenting scenarios to study the flow distribution and hemodynamic parameters, such as wall shear stress (WSS), flow velocity, relative residence time (RRT), and oscillating shear index (OSI) in the carotid bifurcation. The results suggested that the existing stents surely reduced blood flow to the external carotid artery (ECA) but enhanced local flow disturbance both in ECA and stented internal carotid artery (ICA), and the inner posterior wall of the stented ICA and the outer posterior wall of ECA might endure a relatively low level of WSS and remarkably elevated OSI and RRT. In addition, the implanted stent leads to more ECA adverse flow than ICA after stenting. While disturbed flow near the strut increased as stent length increased, blood flow and areas of local flow disturbance in ECA slightly decreased as stent length increased. In conclusion, the results revealed that ECA might be in relatively high levels of abnormal local hemodynamics after stenting, followed by stented ICA, leading to potential adverse events after intervention.

Hemodynamic Impact of Stenting on Carotid Bifurcation: A Potential Role in the Stented Segment and External Carotid Artery

Carotid stenting near the bifurcation carina is associated with adverse events, especially in-stent restenosis, in-stent thrombosis, and side branch occlusion in clinical data. This study aims to determine the potential biomechanical mechanisms for these adverse events after carotid stenting. The patient-specific carotid models were constructed with different stenting scenarios to study the flow distribution and hemodynamic parameters, such as wall shear stress (WSS), flow velocity, relative residence time (RRT), and oscillating shear index (OSI) in the carotid bifurcation. The results suggested that existing stent obviously reduced blood flow to external carotid artery (ECA) but enhanced local flow disturbance both in ECA and stented internal carotid artery (ICA), and the inner-posterior wall of stented ICA and the outer-posterior wall of ECA might endure a relatively low level of WSS and remarkably elevated OSI and RRT. In addition, the implanted stent leads to more ECA adverse flow than stented ICA. While disturbed flow in the vicinity of strut increased as stent length increased, blood flow and areas of local flow disturbance in ECA slightly decreased as stent length increased. In conclusion, the results revealed that ECA might be in relatively high levels of abnormal local hemodynamics after stenting, followed by stented ICA, leading to potential adverse events after interventions.

The severity of microstrokes depends on local vascular topology and baseline perfusion

Cortical microinfarcts are linked to pathologies like cerebral amyloid angiopathy and dementia. Despite their relevance for disease progression, microinfarcts often remain undetected and the smallest scale of blood flow disturbance has not yet been identified. We employed blood flow simulations in realistic microvascular networks from the mouse cortex to quantify the impact of single capillary occlusions. Our simulations reveal that the severity of a microstroke is strongly affected by the local vascular topology and the baseline flow rate in the occluded capillary. The largest changes in perfusion are observed in capillaries with two in- and two outflows. This specific topological configuration only occurs with a frequency of 8%. The majority of capillaries has one in- and one outflow and is likely designed to efficiently supply oxygen and nutrients. Taken together, microstrokes bear potential to induce a cascade of local disturbances in the surrounding tissue, which might accumulate and impair energy supply locally.

Numerical Flow Disturbance Testing of the Innovative Ultrasonic Flow Meter

Ultrasonic flow meters are devices for fluid flow measurement using the ultrasonic principle. Within the technical requirements for gas meters, the flow disturbance test is required. The aim of this study was the CFD analysis of the fluid flow field inside the ultrasonic gas meter regarding the influence of flow disturbance. The methodology for numerical analysis and results assessment was defined. The velocity profiles in the area for ultrasonic measurement have been obtained. The evaluation of the profiles was aimed to confirm that the velocity field (profile) is flow independent. Furthermore, it was necessary to prove insensitivity to input disturbance. The obtained results lead to the statement that the velocity profiles can be considered invariant when the flow rate changes and the disturbance do not affect the velocity field in the ultrasonic measurement area. The influence of disturbance should be negated due to the flow meter channel used.