Biomechanical and histological analyses of a multilayer stent in a swine model of suprarenal aortic aneurysm.

Objectives: To analyze and compare, in an animal model, the treatment of thoracoabdominal aneurysms with multilayer stents and its hemodynamic effects through the biomechanical and histological analysis of the aortic wall in contact with the stent.

Methods: Large White pigs were randomized into two groups: Stent (n=6) and Control (n=5, non-stent). All animals were subjected to the creation of a suprarenal aneurysm with a bovine pericardial patch. In the Stent group, a multilayer stent was implanted immediately after aneurysm formation. After four weeks, all animals were subjected to angiographic assessment and intravascular ultrasound, and the stent was explanted before euthanasia for histological and biomechanical analyses.

Results: At histological analysis, the groups did not differ significantly in maximum thickness of the intima (=0.526), media (=0.129), or adventitia (=0.662). Thrombus formation was observed in 100% of the animals on the intima and media layers of the stented aorta vs. none in the Control group (=0.048). At biomechanical analysis, no statistical differences were observed in aortic wall elasticity (=0.158), strength (=0.360), or thickness (=0.323).

Conclusion: We identified thrombosis of the aneurysmal sac through the presence of thrombi on the intima of the aorta in 100% of the animals in the Stent group; as for the biomechanical analysis, this study showed no statistical differences in vessel wall thickness, strength, and elasticity between groups.