Role of aortic stent graft oversizing and barb characteristics on folding.

OBJECTIVE: To 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.
METHODS: Computed 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.
RESULTS: Of 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%.
CONCLUSIONS: Stent 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%.