(IP043) Temporal Changes in Neck Morphology Prior to EVAR can Predict Type 1a Endoleak

Objectives: Type 1a endoleak (T1a) is defined as perfusion of the abdominal aortic aneurysm (AAA) sac via the proximal seal zone following endovascular aortic aneurysm repair (EVAR). Despite appropriate EVAR graft sizing and adherence to instructions for use (IFU) T1a are seen in 3-20% of patients. Currently there are no well-defined methods to predict patients on IFU who may be at risk of T1a. We sought to determine the association of pre-EVAR neck growth with T1a and hypothesized that increasing pre-operative proximal neck diameter (Dprox) would be associated T1a.

Methods: We identified patients who underwent EVAR and had ≥2 pre-operative CTA ≥6 months apart from 2010-2024. Patients with non-contrast CT scans, treated off IFU, and those treated with prophylactic endo-anchors were excluded. Patient sex, device type, and size were collected. AAA neck morphology measurements [including Dprox, length, suprarenal angle, infrarenal angle, total volume (TotVol), lumen volume (LumVol), thrombus volume (ThromVol), and calcium volume (CaVol)] were measured from both pre-operative CTAs using PRAEVAorta a fully automated software for segmentation and geometric analysis of large vessels (Nurea, Bordeaux, France). Pre-operative AAA neck morphology measurements and their change over time were compared between patients who had T1a (diagnosed at time of intervention or on post-op CTA) and those who did not (Fig 1).

Results: The cohort included 144 patients (12.1% female, average age = 72.3±9.1 years). Twenty-two (17.7%) developed a T1a endoleak (21 at time of intervention, 1 during post-operative surveillance). On univariate analysis, T1a endoleak was associated with female sex (27.3% vs 8.6%, p=0.016), suprarenal angle [23.7 (15.2-31.0) vs 16.9 (9.8-26.9), p=0.044, ], and change in CaVol [0.02 (0.00-0.04) vs 0.00 (0.00-0.01) cm3/year, p = 0.024]. Neither age, device specifications (graft type, supra-renal fixation, and proximal graft size), nor standard neck measurements (Dprox, length, and infrarenal angle) were associated with T1a. Additionally, T1a was not associated with change in Dprox, length, suprarenal angle, infra-renal angle, TotVol, LumVol, or ThromVol (Table I). Change in CaVol remained associated with T1a in a multivariable model [143.21 (1.74-11772.87); p=0.027] adjusted for sex [3.86 (1.00-14.84); p=0.050], supra-renal angle [1.05 (1.00-1.09); p=0.052], and change in Dprox [0.92 (0.67-1.27); p=0.616].

Conclusions: Increasing amounts of AAA neck calcium are a strong predictor of T1a, despite devices being on IFU. Attention should be made to the change in calcium over time when considering optimal surgical management of AAA. Future studies will focus on 3D-growth patterns in AAA neck and their ability to predict T1a.