Stent Frame Movement Following Endovascular Aneurysm Sealing in the Abdominal Aorta

Purpose: We investigated the incidence and extent of stent migration after endovascular sealing of\ud abdominal aortic aneurysms (EVAS), its relationship with adherence to the instructions for use of the\ud Nellix endograft and its association with aneurysm growth.\ud Methods: In this retrospective single centre study, the clinical data and follow-up CT images of\ud patients undergoing infra-renal EVAS with a minimum follow-up of 1 year were reviewed. The first\ud postoperative CT scan at one month and the subsequent scans were used to measure the distances\ud between the proximal end of the stent and reference visceral vessels using a previously validated\ud technique. Device migration was based on the Society of Vascular Surgery definition of >10mm\ud downward movement of either Nellix stent in the proximal landing zone; furthermore, we defined\ud proximal displacement a downward movement of ≥4mm. Patients were categorised according to\ud adherence to the old (2013) or new (2016) Nellix IFU. Aneurysm diameter was measured for each\ud scan and a change of ≥5mm was deemed indicative of aneurysm growth.\ud Results: Seventy-five patients were eligible for inclusion in our study. Over a 4-year period, migration\ud ≥4mm occurred in 42 (56%) patients and migration of ≥10mm in 16 (21%), with similar incidence in\ud right and left stents. Migration ≥4mm was significantly more frequent among patients whose\ud anatomy did not conform to any IFU (p=0.025). Presence of aneurysm growth ≥5mm was observed\ud in 14 patients (19%) and was significantly associated with proximal displacement ≥4mm (p=0.03).\ud Conclusion: Infra-renal EVAS may be complicated by proximal displacement and migration,\ud particularly when performed outside IFU. The definition of migration used for EVAR is inappropriate\ud for EVAS; a new consensus on definition and measurement technique is necessary.