Biomechanical Analysis of Endovascular Abdominal Aortic Aneurysm Repair

Abstract. Longitudinal haemodynamic force (LF) acting on a bifurcated stent-graft has been estimated previously using a mathematical model which assumes steady flow of an invisid fluid. An experimental method was developed, using an instrumented stent-graft model, to measure LF under human physiological and pathological blood flow conditions. The physical stent-graft model, with main trunk diameter of 30mm and limb diameters of 12mm, was fabricated from aluminium. Strain gauges were bonded onto the main trunk to determine the longitudinal strain which is related to LF. After calibration, the bifurcated was placed in a pulsatile flow system with glycerol solution as circulating fluid. Strain was determined using a Wheatstone bridge signal conditioning circuit. The signals were averaged over 600 cardiac cycles and saved to a PC for subsequent processing. LF was strongly dependent on pressure and diameter but less so on flow rate. The pulsatile flow resulted in transient force which was higher than that predicted by the simplified mathematical model, but lower at peak systole. Under certain conditions, e.g., large device diameter, hypertension and large main trunk-to-iliac limb diameter ratio, the LF may exceed the fixation force of current clinical endovascular stent-grafts.