Analysis of hemodynamic changes from aneurysm inception to large sizes

Abstract

While previous studies have identified many risk factors for the progression and rupture of cerebral aneurysms, the changes in aneurysm flow characteristics during its evolution are not fully understood. This work analyzes the changes in the aneurysm hemodynamic environment from its initial development to later stages when the aneurysm has substantially enlarged. A total of 88 aneurysms at four locations were studied with image based computational fluid dynamics (CFD). Two synthetic sequences representing the aneurysm geometry at three earlier stages were generated by shrinking the aneurysm sac while keeping the neck fixed or shrinking the neck simultaneously. The flow conditions were then quantitatively compared between these two modes of evolution. As aneurysms enlarged, the inflow rate increased in growing neck sequences, but decreased in fixed neck sequences. The inflow jet became more concentrated in both sequences. The mean aneurysm flow velocity and wall shear stress decreased in both sequences, but they decreased faster in enlarging aneurysms if the neck was fixed. Additionally, the intra‐aneurysmal flows became more complex and more unstable, wall shear stress distribution became more oscillatory, and the area under low wall shear stress increased for both sequences. The evolution of flow characteristics of aneurysms with fixed and growing necks are different. The observed trends suggest that fixed neck aneurysms may evolve towards a flow environment characteristic of stable aneurysms faster than aneurysms with growing necks, which could also evolve towards a more disfavorable environment.

Hemodynamic Characteristic Analysis of Aneurysm Wall Enhancement in Unruptured Middle Cerebral Artery Aneurysm

“…Cerebral blood flow (CBF) findings can only register hemodynamic parameters of an aneurysm at a particular time. The aneurysm remodeling process is complex and may still be ongoing before rupture, so the morphology and hemodynamics within the aneurysm may vary accordingly ( 38 ). Additionally, aneurysm rupture itself could change hemodynamics, and studies comparing ruptured and unruptured aneurysms should be interpreted with caution.…”

Association of local solid mechanical, hemodynamic and morphological characteristics with ruptured intracranial aneurysm

“…Since the eventual rupture is taken as a tissue failure, it is believed that mechanical and hemodynamic analysis are physics‐based ways to evaluate the aneurysm risk. Considerable efforts have been devoted to analyzing mechanical and hemodynamic characteristics of aneurysms, as well as their associations with morphological characteristics 2–4 . However, influence of solid mechanical, hemodynamic, and morphological characteristics on rupture is not conclusive.…”

“…Considerable efforts have been devoted to analyzing mechanical and hemodynamic characteristics of aneurysms, as well as their associations with morphological characteristics. [2][3][4] However, influence of solid mechanical, hemodynamic, and morphological characteristics on rupture is not conclusive. Conflict conclusion could be found in literature, such as both abnormally low and high wall shear stress (WSS) at aneurysm regions are found in IAs.…”