Fetal-type posterior communicating artery increases hemodynamic stress in posterior communicating artery bifurcation aneurysms: a CFD-based analysis.

Backround: The flow characteristics of bifurcation aneurysms in the posterior communicating artery (PCOM) have rarely been studied. The likelihood of a complete PCOM aneurysm occlusion after endovascular treatment is reduced with the presence of a fetal posterior communicating artery (fPCOM). As a result, anatomical variations in PCOM aneurysms represent a major challenge for the endovascular treatment. This study addresses hemodynamic variations in PCOM aneurysms of either fetal or adult type.

Methods: 3D-DSA data of 14 patients with bifurcation aneurysms located in the PCOM junction were collected. Nine patients presented with a fPCOM and five patients an adult PCOM (aPCOM). Patient-specific 3D models containing at least one bifurcation distal the aneurysm in the anterior circulation as well as the PCOM itself were extracted using image-based blood flow simulations. Seven hemodynamic parameters were calculated for all aneurysm models to characterize the intra-aneurysmal blood flow. The PCOM outflow was artificially varied to represent both fPCOM and aPCOM conditions for each model resulting in 28 simulations.

Results: Fetal‑type PCOM showed higher intra‑aneurysmal mean velocity (median 0.09 vs. 0.06 m/s), maximum velocity (0.17 vs. 0.14 m/s), averaged wall shear stress (1.67 vs. 1.27 Pa), neck inflow rate (40.9 vs. 22.4 ml/min), and inflow concentration index (0.56 vs. 0.40), with lower pulsatility index (1.73 vs. 1.89). Those differences were significant whereas mean oscillatory shear index did not differ significantly.

Conclusion: The presence of anatomical variations affects the hemodynamic parameters of PCOM bifurcation aneurysms. In particular, the presence of an fPCOM has an unfavorable effect on the intra-aneurysmal flow dynamics.