Aneurysm Growth Occurs at Region of Low Wall Shear Stress

Many recent studies suggest that hemodynamic factors such as wall shear stress (WSS) and pressure contribute to the genesis and growth of intracranial aneurysms. Recently there have been a number of computational hemodynamics studies that calculate the values of wall shear stress in arterial and aneurismal flows. However there is a lack of comprehensive error analysis in many of the computational hemodynamics studies. This is perhaps the reason for speculative and ambiguous conclusions drawn by various studies as to the nature of wall shear stress responsible for aneurysm growth. In the current study, geometry involving an actual aneurysm is built from angiogram images. Another geometry consisting of the primary artery where the aneurysm formed is also built by removing the aneurysm volume. The two geometries are meshed using three different grid densities. Second order schemes are used to simulate the pulsatile hemodynamics through each of the geometries. Various representative planes along the geometries are considered and the major flow variables and WSS are plotted as a function of grid densities. The procedure for estimation of discretization error, suggested by ASME Journal of Fluids Engineering, is applied at various representative locations along the aneurysm and arterial geometry. The results suggest high dependence of calculated WSS on local grid density. The contours of WSS in the arterial geometry suggest that high WSS does not necessarily occur at the location where the aneurysm originated. Possible remedies are suggested so that this uncertainty could be eliminated from future studies.

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Aneurysm Growth and Thrombus Formation in the Basilar Artery

Advances in Bioengineering ◽

10.1115/imece2004-62424 ◽

2004 ◽

Author(s):

Liang-Der Jou ◽

Brad Dispensa ◽

David Saloner ◽

William L. Young

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Basilar Artery ◽

Thrombus Formation ◽

Aneurysm Rupture ◽

Mr Images ◽

Flow Simulations ◽

Aneurysm Growth ◽

Shear Stress Level ◽

Wall Shear

Modifying aneurysm hemodynamics may reduce the likelihood of aneurysm rupture. In this study, hemodynamics in a growing aneurysm and a thrombus-developing basilar aneurysm is studied. The locations of thrombus and growth were identified by co-registering MR images of aneurysms at two different times. The thrombus (~6mm) appeared at the superior side of the aneurysm, where the flow impinged on the wall, and aneurysm growth (~3mm) was found at the inferior side (lower part) of the aneurysm. The wall shear stress was calculated from flow simulations. The location of growth has a very low wall shear stress (< 0.01N/m2). The change of hemodynamics during thrombus development was not significant, but the thickest thrombus was shown to have a wall shear stress level between 0.2 and 1N/m2.

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Hemodynamic changes after intracranial aneurysm growth

Journal of Neurosurgery ◽

10.3171/2021.6.jns204155 ◽

2021 ◽

pp. 1-7

Author(s):

Bart M. W. Cornelissen ◽

Eva L. Leemans ◽

Cornelis H. Slump ◽

René van den Berg ◽

Henk A. Marquering ◽

...

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Patient Specific ◽

Hemodynamic Changes ◽

Large Variability ◽

Unruptured Intracranial Aneurysms ◽

Hemodynamic Characteristics ◽

Aneurysm Growth ◽

Wall Shear

OBJECTIVE For accurate risk assessment of unruptured intracranial aneurysms, it is important to understand the underlying mechanisms that lead to rupture. It is known that hemodynamic anomalies contribute to aneurysm growth and rupture, and that growing aneurysms carry higher rupture risks. However, it is unknown how growth affects hemodynamic characteristics. In this study, the authors assessed how hemodynamic characteristics change over the course of aneurysm growth. METHODS The authors included patients with observed aneurysm growth on longitudinal MRA in the period between 2012 and 2016. Patient-specific vascular models were created from baseline and follow-up images. Subsequently, intraaneurysmal hemodynamic characteristics were computed using computational fluid dynamics. The authors computed the normalized wall shear stress, oscillatory shear index, and low shear area to quantify hemodynamic characteristics. Differences between baseline and follow-up measurements were analyzed using paired t-tests. RESULTS Twenty-five patients with a total of 31 aneurysms were included. The aneurysm volume increased by a median (IQR) of 26 (9–39) mm3 after a mean follow-up period of 4 (range 0.4–10.9) years. The median wall shear stress decreased significantly after growth. Other hemodynamic parameters did not change significantly, although large individual changes with large variability were observed. CONCLUSIONS Hemodynamic characteristics change considerably after aneurysm growth. On average, wall shear stress values decrease after growth, but there is a large variability in hemodynamic changes between aneurysms.

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Oscillation of Wall Shear Stress in Growing Intracranial Aneurysms: A Case Study

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53844 ◽

2011 ◽

Author(s):

Shin-ichiro Sugiyama ◽

Akira Takahashi ◽

Teiji Tominaga

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Intracranial Aneurysms ◽

High Wall Shear Stress ◽

General Consensus ◽

Aneurysm Growth ◽

Wall Shear

Hemodynamics is thought to influence the initiation, growth, and rupture of intracranial aneurysms. While there seems to be general consensus that high wall shear stress results in the initiation of intracranial aneurysms, the hemodynamic conditions that drive the development of aneurysms after initiation are still not completely elucidated. High wall shear stress has been postulated to account for aneurismal progression from the distal neck where flow impinges, whereas low wall shear stress has been associated with aneurysm growth in the dome.1

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