Optimal chimney graft configuration in an abdominal aortic aneurysm : a finite element analysis

• Main Author: Valério, André Miguel dos Santos Almeida Luzia
• Publication Date: 2014
• Format: Master thesis
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.14/16142
• topic: Abdominal aortic aneurysm; Endovascular aneurysm repair; Chimney graft; Gutter; Finite element analysis; Aneurisma na aorta abdominal; Reparo endovascular do aneurisma; Enxerto em chaminé; Goteira; Análise em elementos finitos

In Abdominal Aortic Aneurysms (AAA’s), fenestrated devices can preserve blood flow to renal or visceral branches, but customization, planning and manufacturing of such stent-grafts requires time, during which the patients remain at risk of rupture and is not available for urgent cases. Furthermore, this custom-made technology is very expensive. The chimney (or sandwich) technique uses off-the-shelf stent-grafts in parallel to the main aortic stent-graft to maintain perfusion of side branches in aneurysms with short or inexistent proximal aortic necks. Early experience with the chimney technique has shown promising results, but there is controversy regarding the optimal configurations of stent grafts. Inadequate sealing between a chimney graft (CG) and main graft leads to the formation of so-called gutters between the grafts and the aortic wall, which could lead to type Ia endoleaks (direct pressurization of the aneurysm sac). The main goal of this work is to evaluate an optimal configuration in a chimney graft technique (smallest possible gutter and acceptable graft compression, <50%). To achieve that, an abdominal aorta segment and two models with different diameters (6 and 28 mm) of stent grafts were designed and tested in a total of 15 different configurations with SolidWorks software. This Finite Element Analysis (FEA) allowed to capture the deformation of sandwiched stent grafts under radial compressive forces due to the oversizing inside abdominal aorta. The formed gutter areas were measured using the same software. Results and conclusions: The average gutter area obtained for the CG configurations with one main body is 0.6392. The study showed also that the number of CG’s raises the gutter area but not significantly and the main graft compression for the use of one, two, three and four parallel stents is 14.6%, 43.2%, 61.8% and 76.8% respectively. This means that only configurations with less than 2 CG’s, have acceptable graft compression and the CG technique is compromised with more than 2 parallel stents. Furthermore, chimney configurations with closer parallel stents have small gutters when compared with configurations with the same number of CG’s in other dispositions. Conclusions about configurations with two main bodies were not taken due to computational/formulation problems, future work should analyze this topic.