Increased aneurysm wall permeability colocalized with low wall shear stress in unruptured saccular intracranial aneurysm

Hemodynamic insult has long been speculated to be a key factor in intracranial aneurysm (IA) formation,1 but the specifics of hemodynamic insult contributing to this process are not understood. Despite other risk factors, IAs are predominantly found at locations associated with unique hemodynamic stress such as at the apices of arterial bifurcations or outer curves, prominent in high wall shear stress (WSS) and wall shear stress gradients (WSSG).2 Furthermore, it appears that increased flow at these locations is required to trigger the initiation of aneurysmal remodeling.3 We have previously shown that increasing flow in the rabbit basilar artery (BA), secondary to common carotid artery (CCA) ligation, resulted in nascent aneurysm development at the basilar terminus (BT).4 However, it is unclear if certain hemodynamic stress thresholds must be exceeded to trigger aneurysmal remodeling, and whether sustained insult is necessary.

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Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation

Clinical Neurology and Neurosurgery ◽

10.1016/j.clineuro.2009.12.018 ◽

2010 ◽

Vol 112 (4) ◽

pp. 306-313 ◽

Cited By ~ 37

Author(s):

Pankaj K. Singh ◽

Alberto Marzo ◽

Bethany Howard ◽

Daniel A. Rufenacht ◽

Philippe Bijlenga ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Intracranial Aneurysm ◽

Oscillatory Shear ◽

Oscillatory Shear Index ◽

Aneurysm Formation ◽

Wall Shear

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Abstract 13: Wall Shear Stress Associated to Intracranial Aneurysm Wall Inflammation

Stroke ◽

10.1161/str.47.suppl_1.13 ◽

2016 ◽

Vol 47 (suppl_1) ◽

Author(s):

Juan Cebral ◽

BongJae Chung ◽

Fernando Mut ◽

Anne Robertson ◽

Riikka Tulamo ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Tissue Sample ◽

Flow Characteristics ◽

Inflammatory Cells ◽

Patient Specific ◽

Wall Structure ◽

Aneurysm Wall ◽

Wall Shear ◽

Inflammation Group

Introduction: Inflammation has been proposed as a possible mechanism involved in the degradation and weakening of the walls of intracranial aneurysms. Hypothesis: Abnormal wall shear stress (WSS) levels induce wall inflammation which then affects the wall structure and mechanics Methods: A total of 20 aneurysms which underwent surgical clipping were studied. Patient-specific computational fluid dynamics models were constructed from pre-surgical CTA images. Numerical simulations were carried out using pulsatile flows. After clipping the aneurysm, a tissue sample was resected from the dome and analyzed histologically with CD45 to search for evidence of wall inflammation. For analysis, the aneurysm series was divided in two different manners. First, aneurysms were classified into an “inflammation” group if the number of CD45+ cells was larger than the median of CD45+ cells in the entire sample of 20 aneurysms; otherwise they were classified as “no-inflammation”. Hemodynamic variables were then statistically compared between these two groups. Secondly, aneurysms were subdivided into three groups according to their mean WSS: 1) “low WSS” if WSS<0.5*median(WSS), 2) “high WSS” if WSS>2*median(WSS), and 3) “mid WSS” otherwise. The numbers of CD45+ cells in each group were then statistically compared. Results: Aneurysms in the “inflammation” group had significantly larger mean WSS (p=0.018), shear rate (p=0.015), vorticity (p=0.018), and viscous dissipation (p=0.015) than aneurysms in the “no-inflammation” group. Conversely, aneurysms in the “high WSS” group had significantly larger numbers of CD45+ cells (p=0.0046) than the “mid WSS” and “low WSS” groups. Interestingly, aneurysms with stable flow patterns also tended to have larger numbers of inflammatory cells (p=0.040) than aneurysms with unstable flows. Conclusion: These preliminary results suggest that there is a connection between intra-aneurysmal flow characteristics and wall inflammation in cerebral aneurysms. In particular, inflamed walls seem to be associated with higher levels of wall shear stress.

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Effects of blood flow characteristics on rupture of cerebral aneurysm: Computational study

International Journal of Modern Physics C ◽

10.1142/s0129183121501436 ◽

2021 ◽

pp. 2150143

Author(s):

Xiao-Yong Shen ◽

M. Barzegar Gerdroodbary ◽

Amin Poozesh ◽

Amir Musa Abazari ◽

S. Misagh Imani

Keyword(s):

Blood Flow ◽

Shear Stress ◽

High Risk ◽

Wall Shear Stress ◽

Flow Pattern ◽

Cerebral Aneurysm ◽

Computational Study ◽

Fluid Dynamic ◽

Aneurysm Wall ◽

Wall Shear

In recent decades, cardiovascular disease and stroke are recognized as the most important reason for the high death rate. Irregular bloodstream and the circulatory system are the main reason for this issue. In this paper, Computational Fluid dynamic method is employed to study the impacts of the flow pattern inside the cerebral aneurysm for detection of the hemorrhage of the aneurysm. To achieve a reliable outcome, blood flow is considered as a non-Newtonian fluid with a power-law model. In this study, the influence of the blood viscosity and velocity on the pressure distribution and average wall shear stress (AWSS) are comprehensively studied. Moreover, the flow pattern inside the aneurysm is investigated to obtain the high-risk regions for the rupture of the aneurysm. Our results indicate that the wall shear stress (WSS) increases with increasing blood flow velocity. Furthermore, the risk of aneurysm rupture is considerably increased when the AWSS increases more than 0.6. Indeed, the blood flow with high viscosity expands the high-risk region on the wall of the aneurysm. Blood flow indicates that the angle of the incoming bloodstream is substantially effective in the high-risk region on the aneurysm wall. The augmentation of the blood velocity and vortices considerably increases the risk of hemorrhage of the aneurysm.

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Colocalization of thin-walled dome regions with low hemodynamic wall shear stress in unruptured cerebral aneurysms

Journal of Neurosurgery ◽

10.3171/2013.2.jns12968 ◽

2013 ◽

Vol 119 (1) ◽

pp. 172-179 ◽

Cited By ~ 39

Author(s):

Laith M. Kadasi ◽

Walter C. Dent ◽

Adel M. Malek

Keyword(s):

Shear Stress ◽

Steady State ◽

Wall Shear Stress ◽

Cerebral Aneurysms ◽

Pressure Differential ◽

Time Dependent ◽

Aneurysm Wall ◽

Thin Walled ◽

Wall Shear ◽

Unruptured Cerebral Aneurysms

Object Wall shear stress (WSS) plays a role in regulating endothelial function and has been suspected in cerebral aneurysm rupture. The aim of this study was to evaluate the spatial relationship between localized thinning of the aneurysm dome and estimated hemodynamic factors, hypothesizing that a low WSS would correlate with aneurysm wall degeneration. Methods Steady-state computational fluid dynamics analysis was performed on 16 aneurysms in 14 patients based on rotational angiographic volumes to derive maps of WSS, its spatial gradient (WSSG), and pressure. Local dome thickness was estimated categorically based on tissue translucency from high-resolution intraoperative microscopy findings. Each computational model was oriented to match the corresponding intraoperative view and numerically sampled in thin and normal adjacent dome regions, with controls at the neck and parent vessel. The pressure differential was computed as the difference between aneurysm dome points and the mean neck pressure. Pulsatile time-dependent confirmatory analysis was carried out in 7 patients. Results Matched-pair analysis revealed significantly lower levels of WSS (0.381 Pa vs 0.816 Pa; p < 0.0001) in thin-walled dome areas than in adjacent baseline thickness regions. Similarly, log WSSG and log WSS × WSSG were both lower in thin regions (both p < 0.0001); multivariate logistic regression analysis identified lower WSS and higher pressure differential as independent correlates of lower wall thickness with an area under the curve of 0.80. This relationship was observed in both steady-state and time-dependent pulsatile analyses. Conclusions Thin-walled regions of unruptured cerebral aneurysms colocalize with low WSS, suggesting a cellular mechanotransduction link between areas of flow stasis and aneurysm wall thinning.

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Propose a Wall Shear Stress Divergence to Estimate the Risks of Intracranial Aneurysm Rupture

The Scientific World JOURNAL ◽

10.1155/2013/508131 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

Y. Zhang ◽

H. Takao ◽

Y. Murayama ◽

Y. Qian

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Intracranial Aneurysm ◽

Risk Estimation ◽

Aneurysm Rupture ◽

Patient Specific ◽

Luminal Surface ◽

Risk Of Rupture ◽

Computational Fluid Dynamics Cfd ◽

Wall Shear

Although wall shear stress (WSS) has long been considered a critical indicator of intracranial aneurysm rupture, there is still no definite conclusion as to whether a high or a low WSS results in aneurysm rupture. The reason may be that the effect of WSS direction has not been fully considered. The objectives of this study are to investigate the magnitude of WSS (WSS) and its divergence on the aneurysm surface and to test the significance of both in relation to the aneurysm rupture. Patient-specific computational fluid dynamics (CFD) was used to compute WSS and wall shear stress divergence (WSSD) on the aneurysm surface for nineteen patients. Our results revealed that if highWSSis stretching aneurysm luminal surface, and the stretching region is concentrated, the aneurysm is under a high risk of rupture. It seems that, by considering both direction and magnitude of WSS, WSSD may be a better indicator for the risk estimation of aneurysm rupture (154).

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