Prediction of iliac limb occlusion after endovascular aneurysm repair for abdominal aortic aneurysm by anatomical and near-wall hemodynamic characteristics combining numerical simulation and in vitro experiment.
Objective: Iliac limb occlusion (ILO) is a serious complication of endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA), and most require timely reintervention. The study aims to explore pathogenesis, risk factors and prediction models of ILO combining anatomical and near-wall hemodynamic characteristics.
Methods: 75 AAA patients with EVAR (occlusion 25; patency 50) were included. Pre-EVAR and early post-EVAR anatomical (proximal neck angulation, radius, curvature, torsion and tortuosity) and near-wall hemodynamic parameters (time-averaged wall shear stress [TAWSS], oscillatory shear index [OSI] and relative residence time [RRT]) were quantified based on numerical simulation validated through in vitro experiment. The causation of ILO was investigated statistically in three perspectives: differences between patent and occluded patients, effect of EVAR and asymmetries between occluded and patent iliac arteries (IAs). A new parameter, the difference ratio of EVAR (DRE) or IAs (DRI), was proposed to evaluate the degree of changes caused by EVAR and asymmetries between bilateral IAs.
Results: The occluded patients had higher TAWSS (p = 0.004) and larger torsion of common IA (p = 0.033) at pre-EVAR than patent patients. At early post-EVAR, OSI and RRT of future occluded IA were significantly higher than patent IA. The difference ratio of pre-EVAR and early post-EVAR RRT (DRE of RRT) on occluded IA was also higher than that on patent IA (p = 0.025). A prediction model for ILO (area under curve = 0.924) was developed combining anatomical and near-wall hemodynamic variables, where DRI of pre-EVAR OSI had the highest odds ratio [OR] of 5.45 (1.77‒16.74, p = 0.003), and pre-EVAR radius of external IA had the lowest OR of 0.06 (0.01‒0.45, p = 0.007).
Conclusions: High TAWSS and large torsion at pre-EVAR, and excessive increase in RRT by EVAR (DRE) might induce ILO. Higher asymmetry of pre-EVAR OSI between bilateral IAs (DRI) and smaller radius of pre-EVAR external IA were significantly associated with increased ILO risk. The above findings can provide some theoretical guidance to predict and reduce the risk of ILO.