Impact of aorto-iliac hemodynamics and geometry on thrombotic complications following abdominal aortic endovascular aneurysm repair

Objective: This study investigated the relationship between hemodynamic and geometry factors and the risk of thrombosis following aortic endovascular aneurysm repair (EVAR). Materials and Methods: A retrospective analysis was conducted on data from 47 patients underwent abdominal EVAR. 29 thrombotic iliac limbs were compared with 65 normal iliac limbs. Additionally, 36 normal and 11 thrombotic aortic segments were also evaluated. Patient-specific 3D models of aorto-iliac lumen were reconstructed from computed tomography angiography (CTA). These models were used to extract geometric parameters and to perform computational fluid dynamics (CFD) simulations to assess Time-average wall shear stress (TAWSS) and oscillatory shear index (OSI). Results: Thrombotic iliac segments showed lower TAWSS (0.14 Pa vs. 0.78 Pa, p < 0.001), higher OSI (0.049 vs. 0.0001, p < 0.001), higher maximum iliac circumference (43.69 mm vs. 40.47 mm, p = 0.007), higher maximum iliac sectional area (150.66 mm² vs. 126.65 mm², p = 0.006) and an elevated iliac tortuosity index (mean difference: 0.026, p = 0.002) comparing to non-thrombotic segments. Thrombotic aortic segments exhibited lower TAWSS (0.08 Pa vs. 0.103 Pa, p = 0.498), higher maximum aortic circumference (79.98 ± 6.78 mm vs. 70.94 ± 10.57 mm, p = 0.011) and sectional area (495.69 ± 87.2 mm² vs. 398.89 ± 123.34 mm², p = 0.021). Conclusion: Post-EVAR thrombotic events in iliac limbs were associated with lower TAWSS, higher OSI, larger vessel dimensions and elevated tortuosity index. In aortic segments, thrombosis complications were associated with only larger vessel dimensions. These findings emphasize the importance of geometric and hemodynamic factors in developing thrombosis following EVAR.