Background Blebs are important secondary structures of intracranial aneurysms associated with increased rupture risk and can affect local wall stress and hemodynamics. Mechanisms of bleb development and evolution are not clearly understood. We investigate the relationship between blebs with different wall characteristics and local hemodynamics and rupture sites.
Methods Blebs with different wall appearances in intra-operative videos were analyzed with image-based computational fluid dynamics. Thin red blebs were compared against thick atherosclerotic/hyperplastic white/yellow blebs. Rupture points were identified in videos of ruptured aneurysms harboring blebs.
Results Thin blebs tended to be closer to the inflow than atherosclerotic blebs of the same aneurysm (P=0.0234). Blebs near the inflow had higher velocity (P=0.0213), vorticity (P=0.0057), shear strain rate (P=0.0084), wall shear stress (WSS) (P=0.0085), and WSS gradient (P=0.0151) than blebs far from the inflow. In a subset of 12 ruptured aneurysms harboring blebs, rupture points were associated with thin blebs in 42% of aneurysms, atherosclerotic blebs in 25%, and were away from blebs in the remaining 33%.
Conclusions Not all blebs are equal; some have thin translucent walls while others have thick atherosclerotic walls. Thin blebs tend to be located closer to the inflow than atherosclerotic blebs. Blebs near the inflow are exposed to stronger flows with higher and spatially variable WSS than blebs far from the inflow which tend to have uniformly lower WSS. Aneurysms can rupture at thin blebs, atherosclerotic blebs, and even away from blebs. Further study of wall failure in aneurysms with different bleb types is needed.
Data availability statement
Data are available upon reasonable request. The data that support the findings of this study are available from the corresponding author, upon request.
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Contributors SFSA, JF, SM, AMR, and JRC designed the study. AKY, CJS, APS, SAH, FTC, BRJ, MN, and JF contributed to data collection. FM contributed to methodology development. FM and JRC designed the software tools. BJC simulated vascular reconstructions. SFSA and JRC identified blebs in the dataset. SFSA curated the data. SFSA and JRC performed the data analysis. SFSA, FM, AMR, and JRC contributed to the interpretation of the results. AMR and JRC acquired funding, supervised students, and coordinated the project. SFSA and JRC drafted the manuscript. All authors contributed to manuscript editing and approved the final manuscript.
Funding This work was supported by National Institutes of Health (NIH) grant R01NS097457.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.