Prediction of late proximal endoleak risk after EVAR by pre-operative estimation of endograft/aortic neck apposition surface

Abstract

The aim of this study was to evaluate a new measurement tool for the pre-operative computed tomography (CT) scan to estimate the endograft apposition surface on the proximal aortic neck of the aneurysm that would predict the risk of late type IA endoleak (EL1A). From databases of four high-volume centres, between 2004 and 2020 all patients who underwent EVAR with the possibility of analysing pre- and post-EVAR scans and who presented late (>2 years) EL1A in follow-up were included retrospectively (EL1A group). A control group of randomly selected EL1A-free patients were included (control group) and follow-up beyond four years. The measurement tool (Endosize®, Therenva) was used to model a virtual cylinder constrained by the centreline whose diameter was determined from the diameter of the implanted endograft. The apposition surface was calculated by determining the areas of the virtual cylinder mesh outside the mesh of the neighbouring portion of the segmented aorta by an intersection calculation of surface normals. This apposition surface and the usual anatomical data of the proximal neck were compared between the groups with univariate and multivariate analyses. Intra- and inter-observer variability in the measurement of apposition surface was analyzed using the intraclass correlation coefficient (ICC) and the method of Bland and Altman. Sixty-six comparable patients were included, 33 in the EL1A group and 33 in the control group. The mean time to EL1A onset was 50.2 ± 24.6 months in the EL1A group and the mean follow-up time was 79.8 ± 26.8 months in the control group. In univariate analysis, only the endograft apposition surface ratio on the proximal neck was significantly lower in the EL1A group compared with the control group (50.3% vs. 75.5%; p <0.0001). There was no significant difference in classic anatomical neck characteristics. There was no difference in proximal endograft oversizing or in the length from the lowest renal artery to the beginning of the covered portion of the endograft. In multivariate analysis, only the apposition surface ratio was independently correlated with the presence of EL1A (p <0.0001). The estimation of the intra- and inter-observer variability, indicates excellent reliability (ICC = 0.992; ICC = 0.956). The method estimating the pre-operative endograft apposition surface on the proximal aortic neck appears to be a reliable measuring in predicting the risk of occurrence of late EL1A after EVAR.