In vitro measurement of the axial migration force on the proximal end of a bifurcated abdominal aortic aneurysm stent-graft model

Abstract

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.