Role of aortic stent graft oversizing and barb characteristics on folding

ObjectiveTo evaluate folding in infrarenal stent grafts in relation to oversizing, barb angle, and barb length using computed tomography images of stent grafts deployed in explanted bovine aortas.MethodsComputed tomography data from an in vitro investigation on the effect of oversizing of 4% to 45% (n = 19), barb length of 2 to 7 mm (n = 11), and barb angle of 10° to 90° (n = 7) on device fixation were examined for instances of folding. Folding was classified as circumferential or longitudinal and quantified on an ordinal scale based on codified criteria. Cumulative fold ranking from 0 (no fold) to 6 (two severe folds) for each deployment was used as the measure of folding observed.ResultsOf the 37 cases, cumulative mean ± standard deviation fold ranking for stent grafts oversized >30% (n = 5) was significantly greater than the rest (3.4 ± 1.7 vs 0.5 ± 1.2, respectively; Mann-Whitney U test; P < .005). When barb length was varied from 2 to 7 mm (oversizing held at 10%-20%), folding was noted in one of 11 cases. Similarly, when barb angle was varied from 0° (vertical) to 90° (horizontal), folding was not noted in any of the seven cases. The pullout force was not significantly different between stent grafts with and without folding (5.4 ± 1.95 vs 5.12 ± 1.89 N, respectively; P > .5). At least one instance of folding was noted in the seven of seven (100%) stent grafts with oversizing >23.5% and in only five of 30 (14%) stent grafts with oversizing <23.5%.ConclusionsStent graft folding was prevalent when oversized >30%. Large variations in barb length and angle did not aggravate folding risk when oversized within the recommended range of 10% to 20%.

Clinical RelevanceIn endovascular repair, a better understanding of the nature of stent graft deployment can improve treatment outcomes and device design. Folding of stent grafts affects graft apposition and, consequently, performance. In this study, the roles played by key stent graft variables on the propensity for folding were assessed in a controlled in vitro setting.