Comparison of visibility and material properties of the iCover and VBX stent grafts when used as bridge stents in fenestrated endografts. An in-vitro study.

Abstract

Background: To in-vitro compare different material properties of two balloon-expandable covered-stents, VBX (W.L. Gore & Associates, Flagstaff, AZ, USA) and iCover (iVascular, Barcelona, Spain), as bridging stents in fenestrated aortic endoprosthesis.

Methods: Four experiments were designed to evaluate a total of 12 stents (6 VBX 6x59 mm and 6 iCover 6x57 mm). Visibility of the stents was evaluated by computed tomography (CT) comparing Hounsfield units (HU) of the radiopaque marks of the balloon, the first and second stent crown and the whole crimped and expanded stent. Material assessment was analyzed performing three experiments: 1) evaluation of the diameter in three different zones, the percentage of stent shortening and its integrity after the expansion and flaring inside a 6-mm-diameter handmade fenestration; 2) evaluation of the residual lumen area of the stent with a 90° angulation; 3) water permeability test; measuring the water entry pressure and the integral water leakage at 120 mmHg. All models underwent a CT scan immersed in a 37 °C water bath and analyzed in the workstation Osirix Imaging Software v 3.8.1, 32 bit (Pixmeo, Geneva, Switzerland) by two different observers.

Results: In the crimped configuration, both stents showed statistically significant differences in radiopacity. iCover was more radiopaque than VBX for the entire stent as well as for the first and second stent crowns (4935.23 vs. 2574.39 HU; 723.81 vs. 262.63 HU; and 535.94 vs. 259.02 HU, respectively; P<0.001). For the expanded stent, iCover appeared to be more radiopaque than VBX; 1662.61 vs. 930.71 HU, P<0.001. However, VBX balloons had more intense radiopaque marks than iCover; 1454.89 vs. 1107.79 HU, P<0.001. The expansion into the fenestration did not show significant differences in the diameters after flaring, but VBX presented a greater shortening percentage; 8.32% vs. 2.57%, P<0.001. The reduction in the total area at 90º was 12% iCover vs. 19% VBX, P=0.152. The water entry pressure was 120 mmHg for both. The integral water leakage at 120 mmHg was 0 in both cases.

Conclusions: VBX and iCover stents showed similar properties that demonstrate their competence in in-vitro conditions.