SS12 - Proximal Sealing Is a Moving Target: Why Sealing Length Dynamics—and Type II Endoleak—Matter After EVAR

Objectives: To investigate the longitudinal behavior of the proximal sealing zone after standard infrarenal EVAR and to assess whether achieved sealing state and its temporal evolution predict late type 1a endoleak (EL1A).

Methods: This retrospective multicenter study included consecutive patients undergoing elective EVAR for infrarenal fusiform abdominal aortic aneurysm without adjunctive proximal procedures between 2012 and 2022. Pre- and post-operative computed tomography angiographies (CTAs) were analyzed using centerline-based morphometrics. Anticipated sealing was defined preoperatively, while achieved postoperative sealing was quantified using sealing length (SL) and surface-based metrics derived from truncated-cone geometry.
The primary outcome was the occurrence of EL1A. Secondary outcomes included postoperative sealing zone morphology, differences between anticipated and achieved sealing, and associations between sealing metrics and EL2. Interobserver reproducibility was assessed using intraclass correlation coefficients.

Results: The study included 501 patients with 1,692 CTAs and a median follow up of 56 months. Early achieved postoperative sealing differed significantly from preoperative expectations with a device-dependent effect. Longitudinal modelling demonstrated significant remodeling of the proximal sealing zone, with mean annual increases in sealing length (+1.31 mm/year), sealing surface (+99.7 mm²/year). Thirty-nine patients developed EL1A and 70 developed EL2. While sealing zone at the first CTA was a strong predictor of EL1A, adding cumulative sealing length change to baseline sealing length improved prognostic discrimination for EL1A (C-index 0.839 vs 0.825); patients without sealing length gain (ΔSL ≤ 0) had a more than threefold increased EL1A risk (adjusted HR 3.43, 95% CI 1.45–8.10), while type II endoleak markedly altered sealing zone evolution, abolishing sealing length gain (−0.90 vs +1.86 mm/year; p=0.016) and shifting surface-based sealing trajectories towards net loss.

Conclusions: Achieved proximal sealing after EVAR differs from planning and continues to remodel. Baseline sealing length is the dominant determinant of late EL1A, but integrating sealing length change provides additional prognostic information. Type II endoleak does not directly predict EL1A but identifies patients with adverse sealing zone evolution. Combining baseline sealing state with its subsequent change refines risk stratification beyond static postoperative assessment.