Analysis of hemodynamics and wall mechanics at sites of cerebral aneurysm rupture.
BACKGROUND
It is thought that aneurysms evolve as the result of progressive degradation of the wall in response to abnormal hemodynamics characterized by either high or low wall shear stress (WSS).


OBJECTIVE
To investigate the effects of these two different hemodynamic pathways in a series of cerebral aneurysms with known rupture sites.


METHODS
Nine aneurysms in which the rupture site could be identified in three-dimensional images were analyzed. The WSS distribution was obtained from computational fluid dynamics (CFD) simulations. Internal wall stresses were computed using structural wall models under hemodynamic loads determined by the CFD models. Wall properties (thickness and stiffness) were modulated with the WSS distribution (increased or decreased in regions of high or low WSS) to test possible wall degradation pathways. Rupture probability indices (RPI) were calculated to compare different wall models.


RESULTS
Most rupture sites aligned with the intrasaccular flow stream and downstream of the primary impaction zone. The model that best explained the rupture site (produced higher RPI) in eight of the nine aneurysms (89%) had thinner and stiffer walls in regions of abnormally high WSS. The remaining case (11%) was best explained by a model with thinner and stiffer walls in regions of abnormally low WSS.


CONCLUSIONS
Aneurysm rupture seems to be caused by localized degradation and weakening of the wall in response to abnormal hemodynamics. Image-based computational models assuming wall thinning and stiffening in regions of abnormally high WSS were able to explain most of the observed rupture sites.
Center for Computational Fluid Dynamics, George Mason University, Fairfax, Virginia, USA.
Juan R
JR
Cebral
CASE-High Performance Computational Mechanics, Barcelona Supercomputing Center, Barcelona, Spain.
Mariano
M
Vazquez
Center for Computational Fluid Dynamics, George Mason University, Fairfax, Virginia, USA.
Daniel M
DM
Sforza
CASE-High Performance Computational Mechanics, Barcelona Supercomputing Center, Barcelona, Spain.
Guillaume
G
Houzeaux
Department of Interventional Neuroradiology, UCLA Medical Center, Los Angeles, California, USA.
Satoshi
S
Tateshima
Department of Interventional Neuroradiology, Instituto Clínico ENERI, Buenos Aires, Argentina.
Esteban
E
Scrivano
Department of Interventional Neuroradiology, Instituto Clínico ENERI, Buenos Aires, Argentina.
Carlos
http://orcid.org/0000-0003-2292-3263
C
Bleise
Department of Interventional Neuroradiology, Instituto Clínico ENERI, Buenos Aires, Argentina.
Pedro
P
Lylyk
Department of Interventional Neuroradiology, Inova Fairfax Hospital, Falls Church, Virginia, USA.
Christopher M
CM
Putman
D017542:Aneurysm, Ruptured / Q000175:diagnosis* / Q000503:physiopathology; D004730:Endothelium, Vascular; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional / Q000379:methods*; D002532:Intracranial Aneurysm / Q000175:diagnosis* / Q000503:physiopathology; D008955:Models, Cardiovascular