In an in vitro model, the axial migration force on a non-rigid AAA stent-graft was strongly dependent on pressure, bifurcation angle, and tortuosity, with up to 40% of the force potentially attenuated by compressive forces.
Model data link AAA stent-graft forces to pressure and geometry; leaves open clinical relevance for migration risk.
The drag forces acting on rigid abdominal aortic aneurysm stent-graft models have been previously determined by numerical, analytical, and experimental means. It is not clear what effect the assumption of rigidity has on the axial component of proximal migration (ACPM) force acting on the proximal end of a non-rigid stent-graft model. In this study the ACPM force was measured for a non-rigid stent-graft model of 24 mm proximal and 12 mm distal diameters using a custom-built migration force rig. A flow loop containing a working fluid that consisted of 42% water and 58% glycerol mixture by volume provided physiological flow conditions. The stent-graft model consisted of a woven Dacron graft supported by an external polymer rib. The effect of systolic pressure and stent-graft geometry on the ACPM force was also investigated. The ACPM force ranged between 2.96 and 4.92 N and was strongly dependant on pressure. Increasing the bifurcation angle or tortuousity was also seen to increase the ACPM force. Using analytical methods it was determined that almost 40 per cent of the ACPM force may be attenuated by compressive forces in the stent-graft model. The amount of drag force attenuated could be an important design consideration to prevent migration in future stent-grafts.
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Corbett et al. (2011) studied this question.
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