Comparison of the Biomechanical Properties of the Advanta V12/iCast and Viabahn Stent-Grafts as Bridging Devices in Fenestrated Endografts: An In Vitro Study.

To compare experimentally the biomechanical properties of the Viabahn Balloon-Expandable Stent Graft (VBX) with the widely used Advanta V12/iCast in the role of bridging stent-grafts for fenestrated endovascular aortic repair. Test sheets made of polyester having 2 rows of 5 fenestrations in 6-mm and 8-mm diameters were used to simulate a commercially made fenestrated aortic endograft. In total, 40 stent-grafts measuring 6×39 mm and 8×39 mm (10 of each size for each stent-graft) were implanted in fenestration sheets immersed in a 37°C water bath. After flaring, all stent-grafts were evaluated using microscopy and radiography. Biomechanical evaluation included pullout and the shear stress force testing; results are reported in Newtons (N) as the median (minimum-maximum). After flaring, no damage or fracture to the stent-graft structures were detected. Pullout forces for the 6-mm stent-grafts were 27.1 N (20.0-28.9) for the VBX and 16.6 N (14.7-19.2) for the Advanta (p=0.008). Pullout forces for the 8-mm stent-grafts were 20.1 N (14.8-21.5) for the VBX and 15.8 N (12.4-17.5) for the Advanta (p=0.095). The shear stress forces necessary to dislocate the device at 150% stent diameter displacement was 12.5 N (VBX) vs 14.7 N (Advanta) for the 6-mm devices and 23.3 N (VBX) vs 20.2 N (Advanta) for the 8-mm stents (p>0.99 and p=0.222, respectively). In vitro tests simulating external pull and shear forces on bridging stent-grafts implanted in fenestrations showed that the VBX had resistance to dislocation equivalent to a well-known control device.