How Compression Inside a Delivery System can Degrade the Cover of Aortic Endografts

The goal of the present study was to identify the potential degradations undergone by textile endoprostheses (EPs) over the crimping process related to the catheter insertion purpose. In particular, we studied how the device design parameters can influence the wrinkling of the textile material, assuming that wrinkling induces stress concentration and may jeopardize the lifetime of the device.

Custom-designed EPs were obtained from various stent designs and textile constructions. Monofilament and multifilament materials were considered for the cover. Stent segment size, distance, and wire diameter were considered as variable for the stent. The EPs of 26-mm diameter were then crimped in a mock transparent 6-mm diameter catheter sheath for 8 and 30 days duration. After releasing the EPs from the sheath, the textile cover was characterized for roughness properties to identify the crease level induced on the surface by crimping.

Results brought out that the monofilament material was characterized by a larger number of deeper creases in the zones where the stent was in contact with the cover. Conversely, the multifilament was more folded in the zones between stent segments. Moreover, it appeared that the stent design influenced the creases' topography. The textile seemed to be less prone to heavy wrinkling with stent segments made from larger wire diameter and larger segment size. Regarding the crimping duration, it came out that a longer stay in the sheath tends to promote more significant wrinkling.

In this work, it was shown that wrinkling of the textile cover occurs in the EPs already at crimping level. However, an appropriate design of the EPs should limit the phenomenon and improve the performances of the EPs.