Abstract TP360: Increased Aneurysm Rupture Risk at Posterior Communicating Arteries May Relate to Local Hemodynamics

Introduction: Multiple studies indicate intracranial aneurysms near the posterior communicating arteries (PComA) have a higher chance of rupture than those in other locations. However, many PComA aneurysms are located within the ICA, and not the PComA itself. The purpose of this research was to investigate a mechanism that might indicate why this location is more dangerous than nearby locations within the ICA. We compared blood flow between aneurysms in three ICA locations: near the ophthalmic arteries (OphA), the superior hypophyseal arteries (SHA) and the PComA. Methods: This study was approved by the IRB. 3D CTA images and patient histories for 34 saccular, unruptured ICA aneurysms were collected. These were distributed: 10 OphA, 12 SHA, and 12 PComA. 3D ICA geometry was segmented and reconstructed from images. A computational fluid dynamics simulation model of pulsatile blood flow was implemented using patient-specific ICA combined with a pulsatile flow profile derived from phase-contrast MR. Blood was modeled as an incompressible Newtonian fluid and the unsteady 3D Navier-Stokes equations were solved with finite element approach. The resulting hemodynamics were then measured at multiple locations and timepoints over the cardiac cycle. Hemodynamics at different locations were compared using the Kruskal-Wallis test. Results: No differences in average flow within the aneurysms were observed between the three ICA locations. However, flow in the ICA immediately preceding the aneurysm (inlet) was significantly higher at the PComA location (p < 0.01). Time-averaged wall shear stress (WSS) differed between the three locations (p < 0.05, higher at PComA). When the pulsatililty of blood flow over the cardiac cycle was analyzed, pulsatility index (PI) was significantly different between the three locations at the aneurysm dome (p < 0.05) and in the ICA immediately following the aneurysm (outlet) (p < 0.05). A similar measure of WSS, WSSPI, showed significant differences at the aneurysm dome (p < 0.05) and aneurysm outlet (p < 0.05). Conclusion: Significant hemodynamic differences were observed between common aneurysm locations close within the ICA. In particular, the higher blood flow rate and WSS we observed for aneurysms located near the PComA may contribute to the higher risk of rupture often observed at this location. These findings further indicate an aneurysm’s specific location within a particular artery might help predict aneurysm natural history.