Effect of Stent Graft Active Fixation and Oversizing on Aortic Neck Degeneration After Endovascular Aneurysm Exclusion for Infrarenal Aortic Aneurysm

Abstract

Aortic neck degeneration after endovascular aneurysm repair (EVAR) has been implicated in the long-term development of endoleak and the subsequent reintervention. Optimal endograft sizing is a vital aspect to successful repair. This study looked at percentage of graft oversizing as well as type of fixation on aortic neck degeneration. We retrospectively evaluated all EVARs completed at Loyola University from 2006 to 2015 after Institutional Review Board approval. Exclusion criteria were patients without follow-up scans within a year. We collected demographics, comorbidities, graft type, size, aortic neck diameter, and maximum sac size diameters from the preoperative and follow-up scans. We reviewed and collected data of 432 patients but analyzed 154. We measured the largest aortic diameter on axial images 1 cm above and 1 cm below the renal arteries. Change in suprarenal and infrarenal aortic measurements were evaluated by calculating the millimeter difference from each scan compared with the preoperative scan. Linear mixed effects models were used to estimate patients’ mean differences over time. We compared three groups of neck fixation grafts. Those with active suprarenal fixation had a significant change in suprarenal aortic diameter at 4-year follow-up (1.86 mm; confidence interval [CI], 0.65-3.06) compared to those with active infrarenal (0.22 mm; CI, −0.67 to 1.11) or passive suprarenal fixation (1.52 mm; CI, −0.11 to 3.15; Fig 1). Those with active suprarenal fixation were the only ones to have significant increase in suprarenal aortic diameter (P = .0026). Degree of oversizing was also divided into three groups. Oversizing by <10% had less impact on the suprarenal aorta than >15% oversizing at 4 years (0.41 mm [CI, −0.31 to 1.14] vs 3.26 mm [CI, 1.63-4.88]; P < .001; Fig 2). Oversizing had a more pronounced effect on the infrarenal aorta: 4.43 mm [CI, 2.79-6.08], 5.57 mm [CI, −0.25 to 11.38], and 6.48 mm [CI, 2.99-9.97] for <10%, 10% to 15%, and >15% oversizing at 4 years, respectively. Stent grafts with active fixation below the renal arteries as well as oversizing by <10% seem to have the least effect on aortic neck degeneration over time. These factors should be considered in performing EVARs as aortic neck degeneration could lead to endoleaks. Further research defining the optimal stent graft type and oversizing is warranted.Fig 2Suprarenal aortic diameter change over time for each stent graft type. CI, Confidence interval.View Large Image Figure ViewerDownload Hi-res image Download (PPT)