The Impact of Inflow Angle on Aneurysm Hemodynamics: A Simulation Study Based on Patient-Specific Intracranial Aneurysm Models

Abstract

The inflow angle of intracranial aneurysms (IAs) can impact the hemodynamics of IAs, therefore it is likely to contribute to IA clinical rupture risk stratification. This study aimed to assess the effect of inflow angle on the hemodynamics of IAs, as well as its potential ability to predict IA rupture risk. A novel algorithm was developed to build a series of inflow angle models on patient-specific IA models, which were reconstructed from IA 3DRA image data of eleven clinical patients. Fully coupled fluid-structure interaction (FSI) simulations were performed to quantify hemodynamic characteristics of the established IA models with various inflow angles. Hemodynamic parameters including wall shear stress (WSS), flow velocity, flow pattern, inflow zone, impingement region, pressure, and energy loss (EL) were calculated and analyzed. It was demonstrated from the analysis that a rise in the IA inflow angle is associated with the following hemodynamic changes: more direct blood flowed into the aneurysm sac, higher velocity at the upside of the aneurysm, upregulated flow velocity and WSS in the aneurysm, more complicated flow patterns, extended inflow zone, the impingement region moving upward from the neck to the apex of the aneurysm, and higher WSS and larger flow velocity at the inflow zone of the IAs. Therefore, the proposed method may be helpful in exploring the hemodynamic variations of IAs with inflow angles. The findings could be conducive to hemodynamic studies on the association between IA inflow angle and its rupture risk.

Risk Factors of Anterior Circulation Intracranial Aneurysm Rupture: Extracranial Carotid Artery Tortuosity and Aneurysm Morphologic Parameters

“…Skodvin et al ( 22 ) pointed out that the larger the FA, the more likely the aneurysm is to rupture. When the FA value increases, which could induce an unfavorable hemodynamic environment, more complicated flow pattern and the wall shear stress (WSS) of the aneurysm can be relatively increased ( 23 ), which is likely to cause the aneurysm to rupture ( 24 ). Studies have highlighted that FA, as the most common hemodynamics parameter, is the strongest influencing factor leading to aneurysmal rupture ( 25 ).…”

Inflow Angle Impacts Morphology, Hemodynamics, and Inflammation of Side‐wall Intracranial Aneurysms

“…The relationship still existed even after multivariate analysis was adjusted for confounding factors of aneurysm size and location. While previous studies using CFD simulation reported that inflow angle may positively correlate with WSS and the inflow velocity 2,8 . Actually, results from CFD were under the condition of an idealized model with other parameters controlled including aneurysm size, location, aspect ratio, and hypertension, which all could contribute to aneurysm hemodynamics change 9,10 .…”

“…Specifically, the inflow angle, which indicates the morphological connection between aneurysm and the parent artery, is considered to have more potential in prediction of aneurysm rupture than other traditional morphological parameters 2 . It has been reported that, in side‐wall aneurysms, blood flow hemodynamic environment of the aneurysm can change with the increased inflow angle 2,8 . Moreover, hemodynamics, influenced and mediated by morphological parameters, have been proposed to be a driven factor of inflammation processes in the aneurysmal wall, which has been suggested as the key mediator of aneurysm initiation and progression 9–13 .…”

“…Previous studies have reported that there were some associations between inflow angle and hemodynamics 2,8 . The rising inflow angle has been associated with hemodynamic changes including higher flow velocity and wall shear stress (WSS), higher energy transmission, and more complicated flow patterns 2,8 .…”

“…2,3 There is increasing evidence suggesting that aneurysm morphology including aneurysm size, various aneurysm size ratios, and inflow angle has a profound effect on aneurysm rupture. 2,[4][5][6][7][8] Specifically, the inflow angle, which indicates the morphological connection between aneurysm and the parent artery, is considered to have more potential in prediction of aneurysm rupture than other traditional morphological parameters. 2 It has been reported that, in side-wall aneurysms, blood flow hemodynamic environment of the aneurysm can change with the increased inflow angle.…”