Background and purpose Hemodynamics is thought to play an important role in the mechanisms of aneurysm pathogenesis, progression and rupture. The purpose of this study was to define quantitative measures related to qualitative flow characteristics previously analyzed and to investigate their relationship to aneurysm rupture. Methods The hemodynamic environments in 210 cerebral aneurysms were analyzed using image-based CFD under different flow conditions. Quantitative hemodynamic variables were defined and extracted from the simulation results. A statistical analysis of the relationship to the previous history of aneurysm rupture was performed, and the variability with flow conditions was assessed. Results Ruptured aneurysms were more likely to have larger inflow concentrations, larger maximum wall shear stress (WSS), larger shear concentrations and lower viscous dissipation ratios than unruptured aneurysms. Areas under low WSS and measures of abnormally low shear force distributions of ruptured and unruptured aneurysms were not statistically different. Although the values of hemodynamic quantities changed with different flow conditions, the statistical differences or ratios between their mean values over the ruptured and unruptured groups were maintained, for both pulsatile and steady flows. Conclusions Concentrated inflow streams and WSS distributions with elevated levels of maximal WSS and low aneurysmal viscous dissipation are statistically associated with a clinical history of prior aneurysm rupture. In contrast, the area and total viscous shear force applied in the aneurysm region subjected to abnormally low WSS levels are not. This study highlights the potential for image-based CFD for investigating aneurysm evolution mechanisms and for clinical assessment of aneurysm risks.

Background and purpose Hemodynamic factors are thought to play an important role in the initiation, growth and rupture of cerebral aneurysms. This report describes a study of the associations between qualitative intra-aneurysmal hemodynamics and the rupture of cerebral aneurysms. Methods 210 consecutive aneurysms were analyzed using patient-specific CFD simulations under pulsatile flow conditions. The aneurysms were classified into categories depending on the complexity and stability of the flow pattern, size of the impingement region, and inflow concentration by two blinded observers. A statistical analysis was then performed with respect to history of previous rupture. Inter-observer variability analysis was performed. Results Ruptured aneurysms were more likely to have complex flow patterns (83%, p<0.001), stable flow patterns (75%, p=0.0018), 66% concentrated inflow (66%, p=<0.0001), and small impingement regions (76%, p=0.0006) compared to unruptured aneurysms. Inter-observer variability analyses indicate that all the classifications performed are in very good agreement, i.e. well within the 95% confidence interval. Conclusions A qualitative hemodynamic analysis of cerebral aneurysms using image based patient-specific geometries has shown that concentrated inflow jets, small impingement regions, complex flow patterns, and unstable flow patterns are correlated with a clinical history of prior aneurysm rupture. These qualitative measures provide a starting point for more sophisticated quantitative analysis aimed at assigning aneurysm risk of future rupture. These analyses highlight the potential for CFD to play an important role in the clinical determination of aneurysm risks.

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The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.