Abstract 401: Experimental Aneurysm in Rats Excluded by Stent Graft: A New Model to Assess the Impact of Endovascular Aneurysm Repair on the Pathophysiology of Abdominal Aortic Aneurysm.

Introduction Biological study of the impact of endovascular aortic repair (EVAR) on pathophysiology of aortic abdominal aneurysms (AAA) can only be performed indirectly in humans, by imaging or search for peripheral biomarkers in the circulating blood. Therefore biological mechanism’s modifications into the aneurismal wall related to its endovascular exclusion are still to be elucidated, and small animal models should bring a valuable help in this field. We describe a new experimental model of stentgraft implantation for the exclusion of AAA in rats. Methods Aneurysms were induced as previously described by intra-aortic elastase injection in Wistar rats, or by aortic decellularized xenograft transplantation in Lewis rats. At least 15 days later, the midline laparotomy was reopened, and 3mm covered stentgraft were inserted and deployed in the AAA to obtain its exclusion. The patency of the graft and the AAA exclusion could be assessed by a global arteriogram through the carotid artery. After closure of the laparotomy, the rats were awakened and returned to a normal diet. Results This experimental model of AAA exclusion by a stentgraft allows many in vivo and ex vivo studies of the pathophysiology of AAA after EVAR. Histological modifications of the aortic wall and the intra-luminal thrombus could be assessed. The impact of EVAR on the adventitial immuno-inflammatory activity could be studied by different imaging such as MRI, scintigraphy or PET-scan. In situ biological and enzymatic activities could be evaluated to better understand the local mechanisms leading to AAA shrinkage or expansion after EVAR. Conclusion Exclusion by stentgraft of experimental AAA in rats is the first described model of EVAR in small animals. It is feasible and reproducible for both elastase and xenograft experimental AAA models. This model will definitely help to a better analysis and understanding of the impact of stentgrafting on biological mechanisms in the aneurismal wall, that lead to EVAR success with shrinkage of aneurismal sac or EVAR failure with its continuing expansion.