Hemodynamics and bleb formation in intracranial aneurysms.
OBJECTIVE
Intracranial aneurysms with irregular shapes and blebs or secondary outpouchings have been correlated with increased rupture risk. The purpose of this study was to investigate possible associations between the local hemodynamics and the formation of blebs in cerebral aneurysms.


METHODS
Computational models of 20 cerebral aneurysms harboring 30 well-defined blebs were constructed from 3D rotational angiographies. Models representing the aneurysm before bleb formation were constructed by virtually removing the blebs from the anatomic models. Computational fluid dynamics simulations of the aneurysm before and after bleb formation were performed under pulsatile flows. Flow and WSS visualizations were used to analyze the local hemodynamics in the region of the aneurysm that developed the bleb.


RESULTS
Most blebs (80%) occurred at or adjacent to the aneurysm region with the highest WSS before bleb formation, and near the flow impaction zone. Most blebs (83%) were found in regions of the aneurysm previously subjected to high or moderate WSS and progressed to low WSS states after the blebs were formed. Most blebs (77%) were aligned or adjacent to the inflow jet, whereas 17% were aligned with the outflow jet, and only 6% were not aligned with the flow direction. In addition, 90% of the aneurysms had maximal WSS higher than or similar to the WSS in the parent artery.


CONCLUSIONS
Blebs form at or adjacent to regions of high WSS and are aligned with major intra-aneurysmal flow structures. Formation of blebs results in a lower WSS state with formation of a counter current vortex. These findings imply that locally elevated WSS could contribute to the focalized wall damage that formed these structures.
Center for Computational Fluid Dynamics, Department of Computational and Data Sciences, College of Sciences, George Mason University, Fairfax, Virginia 22030, USA. jcebral@gmu.edu
J R
JR
Cebral
M
M
Sheridan
C M
CM
Putman
D002533:Cerebral Angiography; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D016208:Databases, Factual; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology*; D008955:Models, Cardiovascular; D012039:Regional Blood Flow / Q000502:physiology; D012307:Risk Factors; D013314:Stress, Mechanical; D013599:Systole / Q000502:physiology