Impact of Significant Sac Shrinkage on Endograft Tortuosity at 5 Years Postendovascular Aortic Aneurysm Repair: A Retrospective Analysis.

Background: Significant sac shrinkage after endovascular aortic aneurysm repair (EVAR) is generally considered a positive outcome indicative of durable clinical success. However, its impact on endograft configuration is rarely addressed. Sac remodeling and volume loss due to shrinkage can potentially cause deformation of endograft components, resulting in limb angulation and compression. We investigated the hypothesis that significant sac shrinkage could affect endograft tortuosity at 5 years post-EVAR.

Methods: We retrospectively reviewed patients who underwent elective EVAR for infrarenal abdominal aortic aneurysm between June 2007 and December 2018. Patients with early postoperative and 5-year follow-up computed tomography images were included. Patients treated with modular bifurcated endografts (Zenith, Endurant, Excluder, and Incraft) were analyzed. The "shrinkage" group comprised patients with >10 mm diameter reduction, while the "stable" group had ± 5 mm diameter change at 5 years. Tortuosity index (TI) was calculated as the ratio of centerline distance to straight-line distance between proximal and distal endograft edges. The association between sac shrinkage and ≥5% increase of TI (≥5%ΔTI) was analyzed for both ipsilateral and contralateral sides.

Results: Of 136 patients enrolled, 80 were in the shrinkage group and 56 in the stable group. On the ipsilateral side, ≥5%ΔTI was observed in 24 cases (17.6%). The patients with ipsilateral ≥5%ΔTI had significantly shorter median neck lengths (22 mm vs. 30 mm, P = 0.030). Sac shrinkage ≥15 mm was negatively associated with ≥5%ΔTI compared to stable sac (P = 0.027). Logistic regression showing sac shrinkage ≥15 mm had a significant negative correlation with ≥5%ΔTI (P = 0.025, hazard ratio [95% confidence interval]: 0.218 [0.057-0.824]). On the contralateral side, ≥5%ΔTI (19 cases, 14.0%) was associated with shorter neck length but not with sac shrinkage. In the shrinkage group, cross-leg positioning resulted in a significant increase in ipsilateral TI at 5 years compared to straight positioning (median ΔTI: 1.8% vs. 0.0%, P = 0.013). No reinterventions for leg-related events were necessary during the 5-year follow-up period.

Conclusions: Contrary to our initial hypothesis, significant sac shrinkage does not adversely affect endograft configuration and may help stabilize tortuosity on the ipsilateral side. However, in patients with crossed-leg configuration, continued vigilant observation may be warranted even after achieving sac shrinkage, as it could exacerbate tortuosity. Shorter neck length was associated with increased tortuosity on both sides. Further research is needed to confirm these findings and consider potential confounding factors, including the impact of different endograft designs.