Effect of limb oversizing on the risk of type Ib endoleak in patients after endovascular aortic repair

We assessed the association between the degree of limb oversizing and the risk of type Ib endoleak (TIBEL) in different types of iliac landing zones after endovascular aortic aneurysm repair.We performed a retrospective cohort study of patients who had undergone endovascular aortic aneurysm repair with bifurcated and limb endografts in an academic center. The main exposure was the degree of limb oversizing. The primary outcome was the occurrence of TIBELs. The secondary outcomes included limb occlusion, reintervention, and overall survival. Subgroup analyses stratified by ectatic and normal iliac landing zones were performed. Multivariate Cox regression analysis and sensitivity analyses using marginal structure model were conducted to adjust for potential confounders.A total of 750 patients with 1500 iliac limb endografts were included in our study (817 limbs with oversizing of ≤10% and 683 with oversizing >10%). The median 1-year freedom from TIBEL was 98.9% (interquartile range [IQR], 98.0%-99.8%) for limbs with oversizing of ≤10% and 99.6% (IQR, 99.0%-100%) for limbs with oversizing >10%. The median 3-year freedom from TIBEL was 95.6% (IQR, 93.1%-98.1%) and 98.2% (IQR, 96.5%-99.9%) for oversizing ≤10% and >10%, respectively. We found that limb oversizing >10% was associated with a significantly decreased risk of TIBEL (adjusted hazard ratio [HR], 0.38; 95% confidence interval [CI], 0.19-0.76) in the overall population. After stratification by ectatic iliac landing zone, we found that limb oversizing >10% was associated with a significantly decreased risk of TIBEL in the ectatic iliac landing zones (adjusted HR, 0.38; 95% CI, 0.16-0.88). However, no significant difference was found in the limb endografts landing in normal iliac arteries (adjusted HR, 0.44; 95% CI, 0.13-1.45). In the subgroup of normal iliac arteries, we observed a significantly increased risk of limb occlusion in the limbs with distal oversizing >15% compared with the limbs with distal oversizing of ≤15% (adjusted HR, 4.66; 95% CI, 1.68-12.91).Adequate limb oversizing >10% was associated with a significantly decreased risk of TIBEL in limbs with ectatic iliac landing zones. However, no additional benefit was observed for oversizing >10% in limb grafts landing in normal iliac arteries. Furthermore, excessive limb oversizing (>15%) in normal iliac landing zones can be associated with an increased risk of limb occlusion.