Risk Factors for Early and Late Type Ib Endoleak Following Endovascular Abdominal Aortic Aneurysm Repair

Objectives: A type Ib endoleak (T1bEL) is a postoperative complication that usually requires additional interventions following endovascular aortic aneurysm repair. Previous studies have focused on iliac artery tortuosity or common iliac artery (CIA) diameter. However, we investigated the various risk factors for early and late T1bELs more comprehensively. Methods: This retrospective case-control study of a prospectively maintained database compared anatomical, demographic and technical factors between patients with early or late T1bELs and a control group. Early T1bEL was defined as a T1bEL occurring within 6 months of endovascular aneurysm repair (EVAR), while late T1bEL was defined as a T1bEL, initially identified more than 6 months after EVAR. Anatomical values including neck diameter, length, and angle; maximum sac diameter and length; CIA length, diameter, and tortuosity; and distal sealing length were measured and included in the analysis. We performed uni-and multivariable analyses using logistic regression and Cox proportional hazard models. Results: This study included 635 iliac limbs of 383 patients. Overall, T1bELs occurred in 22 iliac limbs during the follow-up period (22/635, 3.5%). Among them, the early and late T1bEL groups each included 11 limbs. The median follow-up duration of the 383 patients was 23 (8-58) months, and in the early T1bEL and early control groups, the durations were 15 (9-35) and 29 (15-60) months, respectively (P = 0.01). The median overall follow-up durations in the late T1bEL and late control groups were 87 (76-102) and 62 (48-80) months, respectively (P = 0.01). The median follow-up duration until the occurrence of late T1bEL was 44 (32-82) months, which was shorter than that of the late control group (P = 0.03). No significant differences in sex, age, or brand of stent-graft were observed between the T1bEL and control groups. In the multivariable analysis, patients in the early T1bEL group had significantly more tortuous and short CIAs, and short distal sealing lengths (P = 0.02, P = 0.04, P = 0.03, respectively), and the late T1bEL group had significantly larger maximum aortic aneurysm sac diameters, short CIAs and short distal sealing lengths (P < 0.001, P = 0.02, P = 0.002, respectively). The suspected mechanisms of the T1bELs were CIA dilatation with or without sac expansion and aggravation of sac angulation. Except for one patient with aortic dissection, T1bELs were treated with iliac limb extensions.