Computational fluid dynamics analysis of wall shear stress in iliac vein stent: Influence of curvature and in-stent restenosis

ObjectivesThis study aimed to assess the relationship between wall shear stress (WSS), the curvature of the iliac vein, and iliac venous in-stent restenosis (ISR) using computational fluid dynamics (CFD) analysis.MethodsNine limbs in nine patients were enrolled, in which patients received stent placement for a de novo iliac venous lesion and developed non-occlusive ISR. Initial follow-up computed tomographic venography (CTV) occurred within 1 year after stent placement. Two venous models were created from the CTV: one based on the lumen visualized on CTV (ISR-included stenosis model) and one based on the underlying iliac vein stent free of any ISR (ISR-removed, virtual healthy model). CFD analysis was performed to obtain WSS on each model. WSS was assessed on the greater curve, lesser curve, a healthy stent wall (HS wall), and an intimal hyperplasia/mural thrombus-attaching stent wall (IH/MT wall).ResultsThe median (interquartile) WSS on the greater curve was significantly higher than on the lesser curve: 0.179 (0.0686-0.266) versus 0.121 (0.0434-0.167) in the virtual healthy model, and 0.274 (0.153-0.557) versus 0.193 (0.116-0.367) in the stenosis model (both p < .001).The WSS on the IH/MT wall and on the HS wall were 0.106 (0.0358-0.164) and 0.161 (0.0804-0.248) in the virtual healthy model and 0.253 (0.114-0.501) and 0.226 (0.131-0.432) in the stenosis model, respectively. The WSS was significantly lower on the IH/MT wall than on the HS wall in the virtual healthy model (p < .001), but it demonstrated no significant differences in the stenosis model (p = .838).ConclusionThe iliac venous stent curvature could be a morphological risk factor of ISR, and WSS analysis could help predict future ISR. In the stenosis model, there were no significant differences in WSS between the IH/MT wall and the HS wall, implying that ISR builds up to a point of WSS equilibration.