Predisposing Factors for Migration of the Iliac Limb and Reintervention after Endovascular Abdominal Aortic Aneurysm Repair

Background: Migration of the iliac limb after endovascular abdominal aortic aneurysm repair (EVAR) can result in type 1 b and 3 endoleaks, which are relatively common causes of reintervention after EVAR. The aim of the present study was to investigate the factors influencing migration of the iliac limb and methods of treatment. Methods: From April 2012 to September 2017, 4 patients experienced migration of the iliac limb, requiring additional iliac stent graft implantation intraoperatively or at follow-up at our institute. Patient 1 was a 74-year-old man in whom preoperative computed tomography angiography (CTA) revealed a large aneurysm. The patient underwent EVAR with a bifurcated stent graft, and the left iliac stent graft migrated into the aneurysm sac. Patient 2 was a 53-year-old man in whom CTA revealed a large abdominal aortic aneurysm (AAA) involving the bilateral common iliac artery (CIA), with occlusion of the left hypogastric artery. An iliac stent graft was deployed to the right CIA to preserve the hypogastric artery. CTA, at 5 years of follow-up, showed migration of the right iliac limb and impending rupture. Patient 3 was a 61-year-old man with a ruptured AAA, and CTA revealed a large AAA and dilated CIA. The patient underwent EVAR with a bifurcated stent graft. Three years after EVAR, CTA showed that the right iliac limb migrated and kinked, with rupture of the stent graft. Patient 4 was an 80-year-old man with a ruptured AAA and aortocaval fistula. CTA revealed a large aneurysm involving the bilateral CIA. The patient underwent urgent EVAR with a bifurcated stent graft, and a cuff was deployed to seal the landing zone of the left CIA to preserve the hypogastric artery. Type 3 endoleak occurred because of the migration and detachment of the left iliac limb. All 4 patients underwent additional iliac stent graft implantation to connect or reline the iliac limb. Results: The mean diameter of the aneurysms was 85.3 +/- 18.9 mm, and 2 patients were diagnosed with ruptured AAAs. The mean diameter, length, and proportional engagement rate of the CIA that experienced migration of the iliac limb were 25.50 +/- 11.1 mm, 32.8 +/- 6.6 mm, and 72.75% +/- 17.88%, respectively. Oversizing of the iliac stent graft was 10-20% in 2 patients and was less than 10% in the other 2 patients. The migrated iliac limbs were bell-bottom stent grafts. All patients underwent additional iliac stent graft implantation successfully, and there were no deaths or complications perioperatively. The patients were followed up from 7 months to 3 years and remained in good condition. Conclusions: Migration of the iliac limb after EVAR was influenced by a complex combination of several factors including a large aneurysm (>60 mm in diameter), dilated or aneurysmal CIA (>18 mm in diameter), short length of fixation (<70%), lower degree of iliac limb oversizing (<10-20%), and bell-bottom of the iliac limb. Patients with these factors require more vigorous surveillance after EVAR. The implantation of an additional stent graft is effective and is the most common reintervention procedure.