Abdominal aortic aneurysm neck dilatation and sac remodeling in fenestrated compared to standard endovascular aortic repair

Objective Contemporary commercially available endovascular devices for the treatment of abdominal aortic aneurysm (AAA) include standard endovascular aortic repair (sEVAR) or fenestrated EVAR (fEVAR) endografts. However, aortic neck dilatation (AND) can occur in nearly 25% of patients following EVAR, resulting in loss of proximal seal with risk of aortic rupture. AND has not been well characterized in fEVAR, and direct comparisons studying AND between fEVAR and sEVAR have not been performed. This study aims to analyze AND in the infrarenal and suprarenal aortic segments, including seal zone, and quantify sac regression following fEVAR implantation compared to sEVAR. Method A retrospective review of prospectively collected data on 20 consecutive fEVAR patients (Cook Zenith (R) Fenestrated) and 20 sEVAR (Cook Zenith (R)) patients was performed. Demographic data, anatomic characteristics, procedural details, and clinical outcome were analyzed. Pre-operative, post-operative (1 month), and longest follow-up CT scan at an average of 29.3 months for fEVAR and 29.8 months for sEVAR were analyzed using a dedicated 3D workstation (iNtuition, TeraRecon Inc, Foster City, California). Abdominal aortic aneurysm neck diameter was measured in 5 mm increments, ranging from 20 mm above to 20 mm below the lowest renal artery. Sub-analysis comparing the fEVAR to the sEVAR group at 12 months and at greater than 30 months was performed. Standard statistical analysis was done. Results Demographic characteristics did not differ significantly between the two cohorts. The fEVAR group had a larger mean aortic diameter at the lowest renal artery, shorter infrarenal aortic neck length, increased prevalence of nonparallel neck shape, and longer AAA length. On follow-up imaging, the suprarenal aortic segment dilated significantly more at all locations in the fEVAR cohort, whereas the infrarenal aortic neck segment dilated significantly less compared to the sEVAR group. Compared to the sEVAR cohort, the fEVAR patients demonstrated significantly greater positive sac remodeling as evident by more sac diameter regression, and elongation of distance measured from the celiac axis to the most cephalad margin of the sac. Device migration, endoleak occurrence, re-intervention rate, and mortalities were similar in both groups. Conclusion Compared to sEVAR, patients undergoing fEVAR had greater extent of suprarenal AND, consistent with a more diseased native proximal aorta. However, the infrarenal neck, which is shorter and also more diseased in fEVAR patients, appears more stable in the post-operative period as compared to sEVAR. Moreover, the fEVAR cohort had significantly greater sac shrinkage and improved aortic remodeling. The suprarenal seal zone in fEVAR may result in a previously undescribed increased level of protection against infrarenal neck dilatation. We hypothesize that the resultant decreased endotension conferred by better seal zone may be responsible for a more dramatic sac shrinkage in fEVAR.