Perirenal Fixation as an Independent Factor in Aortic Remodeling after Endovascular Aortic Aneurysm Repair

Abstract

The purpose of our study was to evaluate the influence of perirenal fixation of endovascular aortic grafts on the rate of endoleak and aortic sac remodeling. Retrospective analysis of all patients (pts.) after undergoing endovascular aortic aneurysm repair (EVAR) at our institution was performed. Pre- and postoperative aortic dimensions were obtained from CT scans and angiograms. Intraoperative angiograms were reviewed and patients grouped by the proximity of the graft to the lowest renal arteries: group I: flush with the lowest renal artery; group II: < or = 5 mm distal to lowest renal artery; and group III: >5 mm distal to lowest renal artery. Of the 96 grafts placed between 2000 and 2002, 44 were AneuRx (Medtronic, Santa Rosa, CA) and 52 were Ancure (Guidant, Menlo Park, CA) devices. There were 39 pts. in group I, 42 in group II, and 11 in group III (data on 5 pts. were not obtained). At 6 months, the mean decrease in sac diameter for all groups was 0.42 +/- 0.08 cm (1: 0.56 +/- 0.11 cm; 11: 0.38 +/- 0.11 cm; III: 0.6 +/- 0.15 cm). There was no significant difference between each group. When perirenal fixation (group I) was compared with nonperirenal fixation (groups II and III), there was a significant difference in sac shrinkage at 6 months (p < 0.05, ANOVA). Group I had shorter necks and smaller aneurysms (2.2 +/- 0.1 cm and 5.3 +/- 0.1 cm) than those of groups II and III (2.7 +/- 0.1 cm and 5.7 +/- 0.1 cm, p < 0.05, ANOVA). There was no difference in aortic neck diameter or in aortic neck diameter to graft ratio. When controlled for the variables studied (AAA diameter, length of neck, diameter of neck, diameter of neck to graft ratio, and any endoleak by 6 months), logistic regression analysis identified perirenal fixation as the only significant factor in aortic sac shrinkage of >0.4 cm by 6 months (odds ratio = 16, p < 0.01). With the same variables, a linear regression model also identified perirenal fixation as the only predictive factor in aortic shrinkage (regression coefficient = 0.46, p < 0.05). The endoleak-free survival rate with perirenal fixation was 96 +/- 5% and without it was 80 +/- 7% (Kaplan Meier, p = 0.09, log rank). Perirenal placement of endovascular grafts is associated with a trend toward fewer endoleaks, and improved aortic sac shrinkage independent of aortic neck length, AAA diameter, diameter of neck, and endoleak. Failure to achieve perirenal placement of EVAG increased the likelihood of reduced or failed aortic sac shrinkage in this series.