Introduction: Recent evidence suggests a link between the magnitude and distribution of hemodynamic factors and formation and rupture of intracranial aneurysms. However, there are many conflicting results. Our goal is to quantify the effect of hemodynamic factors on aneurysm formation and their association with ruptured aneurysms.
Methods: We performed a systematic review and meta-analysis through October 2014. Analysis of the effects of hemodynamic factors on aneurysm formation was performed by pooling the results of studies that compared geometrical models of intracranial aneurysms and "preaneurysm" models where the aneurysm was artificially removed. Furthermore, we calculated pooled standardized mean differences between ruptured and unruptured aneurysms to quantify the association of hemodynamic factors with ruptured aneurysms. Standard PRISMA guidelines were followed.
Results: The hemodynamic factors that showed high positive correlations with location of aneurysm formation were high wall shear stress (WSS) and high gradient oscillatory number, with pooled proportions of 78.8% and 85.7%, respectively. Positive correlations were largely seen in bifurcation aneurysms, whereas negative correlations were seen in sidewall aneurysms. Mean and normalized WSS were significantly lower and low shear area significantly higher in ruptured aneurysms.
Conclusions: Pooled analyses of computational fluid dynamics models suggest that an increase in WSS and gradient oscillatory number may contribute to aneurysm formation, whereas low WSS is associated with ruptured aneurysms. The location of the aneurysm at the bifurcation or sidewall may influence the correlation of these hemodynamic factors.
Patient Care: Clinical decision making in the context of unruptured aneurysms
remains complex and hemodynamic factors are thought to play an
important role. Given the divergence in conclusions of previous studies and the
complexity of hemodynamics, we have performed a pooled
analysis of the studies with the goal to provide guidance on which
parameters are most relevant with respect to IA formation and rupture.
Learning Objectives: By the conclusion of this session, participants should be able to describe the role of computational fluid dynamics (CFD) techniques to assess hemodynamic risk factors for intracranial aneurysm formation and rupture.