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Determinação do impacto do oversizing da endoprótese sobre a aorta torácica. Estudo experimental em porcos / Impact of stent-graft oversizing on the thoracic aorta: experimental study in a porcine model






Introduction: The use of endovascular techniques to treat the various disorders of the aorta has supplanted traditional open techniques, and is particularly promising in trauma1. The traumatic rupture of the aorta is the second leading cause of death by traffic accident2, 3, and repair of these lesions with endoluminal stents has showed lower mortality and paraplegia when compared to open surgery, however the long-term results are not yet available2-7. The endoprosthesis approved and commercially available during this study were designed to aneurysmal disease, with a diameter greater than the diameter of the aorta of young people ( ) \" z \" prosthesis with the aortic wall, affecting the vascularization and raising the risk of complications related to stent-graft implantation8-12. Purpose: Analyze, from an experimental animal model, the biomechanical and histological effects of four different levels of stents-graft oversizing in non-atherosclerotic aortas; such as those aorta found in young individuals who undergo stent-graft repair for traumatic aortic injuries. Methods: The diameter of the porcine thoracic aorta is similar to the aorta of young adults (18-20 mm), so 25 pigs were randomized into 5 groups: 1 control (without stent-graft) and 4 oversizing groups (A: 10%-19%, B: 20%-29%, C: 30%-39%, and D: .40%). Two types of biomechanical tests were performed on all aortas 4 weeks after endoprosthesis deployment: The \"detachment\" of the stent, and the biomechanics test of aortic fragments collected. The fragments were submitted to a histological and an immunohistochemistry analysis. Results: The results of the detachment test, which analyzed the strength necessary to remove the stent-graft from the aorta, were similar in the 4 groups (A: 42 N, B: 41 N, C: 46 N e D: 46 N, p= 0,881204). The second test was performed in 3 aortic segments. Maximum strength, maximum stress, and maximum tension supported by the aortic wall had a negative and linear correlation with oversizing. There were significant differences in all 4 groups when compared with the control group. The maximum deformation and strain, which reflect the elastic properties of the aortic wall, were very similar in all 4 groups. But a significant decrease in elasticity was found when compared each group with the control group (p = 0.0000001). Histological and immunohistochemistry analysis supported that the aortic wall has a signifi-?-actin by increasing the oversize (p = 0.000198 p = 0.002031, respectively). The amount of elastic fiber showed a significant drop regardless of the oversizing (p = 0.0000001). Conclusion: The four levels of oversizing studied did not show significant differences in the detachment test. Biomechanical tests of the fragments of the aorta showed a decrease in resistance of the aortic wall with increase in oversize. The elasticity of the aortic wall undergoes significant change independent of the oversizing used. The histopathological and immunohistochemical examinations confirmed the breakdown in the structure of the aortic wall with the use of stents-graft, resulting in decreased amount of elastic and muscle fibers.


aorta torácica biomecânica biomechanics displacement force endovascular procedures/adverse effects estresse de parede força de destacamento modelo porcino modelos animais models animal oversizing oversizing porcine model procedimentos endovasculares/efeitos adversos shear strength sobredimensionamento stent-graft stents strain tensão de parede tension thoracic aorta wall stress