Numerical Investigation of Aneurysm Initiation and Hemodynamics Associated with Vascular Anastomosis Direction in a Rat Model
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Previous studies have demonstrated that hemodynamic factors are involved in aneurysm initiation. While the Left-to-Right (LtR) model, where the common carotid artery is anastomosed from left to right, has been used to investigate this mechanism, the impact of reversing the shunt direction to Right-to-Left (RtL model) remains unexplored. This study employed computational fluid dynamics (CFD) on a rat aneurysm model to clarify how changes in shunt direction alter local hemodynamics and influence aneurysm initiation. We analyzed 10 RtL models and 70 LtR models. Three-dimensional geometries were reconstructed from pre-aneurysm MRA images, followed by mesh generation. Unsteady simulations were performed using an inlet pulsatile waveform scaled to rat arterial conditions, with outlet static pressure set to 0 Pa. The pressure loss coefficient (PLc) and the dimensionless maximum flow velocity were obtained for all cases. The inlet diameter reduction ratio was quantified from the STL geometries for 25 selected cases, defined as the ratio of the bifurcation diameter to the proximal diameter at 1 mm upstream. The RtL model showed a higher aneurysm initiation rate of 61% compared with 31% in the LtR model. CFD analysis revealed that PLc values were 14.9±5.42 in de novo cases and 12.7±3.45 in stable cases. Furthermore, the RtL model exhibited higher PLc values (19.1±6.33) than the LtR model (12.5±3.05). This difference was associated with the diameter reduction ratio, which showed a strong negative correlation with PLc (r = -0.82). The RtL model had a smaller diameter ratio of 0.853±0.069 compared with 0.927±0.059 in the LtR model, resulting in higher flow velocity at the bifurcation, with values of 2.68±0.716 and 2.12±0.229, respectively. The RtL model demonstrated a higher aneurysm initiation rate than the LtR model, associated with increased PLc due to structural differences. These findings may help identify key hemodynamic factors contributing to aneurysm initiation.
