Custom-made Stent-Grafts for Aortic Aneurysm Repair Using Gianturco Z Stents and Woven Polyester: Healing in an Animal Model

Degradation Phenomena on "Homemade" Explanted Aortic Textile Endografts

Objective

In the 1990s, the concept of “homemade” endografts (EGs) using commercially available materials was proposed in clinical practice for endovascular abdominal aortic repair (EVAR). The aim of this study was to analyse the ageing phenomena of these EGs in light of explant analyses.

Methods

The study focused on five explanted homemade EGs collected from 2012 to 2014. The explants were assessed in accordance with the ISO 9001/13485 certified standard protocol, which included naked eye evaluation, organic remnant cleaning, and microscopic and endoscopic examinations and analysis (magnification range from 20% to 200%). The observations report followed a classification based on 12 features assessing the fabric cover, the stitch filament, and the stents.

Results

The reasons for explantation were type 1 endoleak in three cases and aneurysm sac growth in two. The implantation duration ranged from 56 to 202 months. Sixty three per cent of the fabric surface lesions (holes and tears) were related to abrasion between the fabric and the stents. Up to 33% of the knots used to connect adjacent stents were broken on one EG. Other defects including running suture rupture and stent corrosion were also observed. The overall hole cumulated surface ranged from 0.377 mm² (56 month of implantation) up to 3.21 mm² (78 month of implantation).

Conclusion

In this study, various ageing phenomena on homemade textile EGs were identified and classified. The main damaging mechanisms were related to abrasion stress leading to tears and holes in the fabric, stitch ruptures, and detachment of stent segments responsible for serious EG deformations and further degradation.

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Main homemade endografts damaging mechanisms are related to abrasion stress (friction wear).

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Abrasion stent–metal, knot ruptures, and kinking phenomena were associated.

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Some damaging mechanisms were related to the creation technique (one piece stent skeleton).

Transrenal deployment of a modular stent graft to repair AAAs with short necks: experiments in dogs

Severely angulated (> 60 degrees ) or short (< 15 mm) proximal necks remain significant anatomical limitations for endovascular stent-graft repairs for abdominal aortic aneurysms. Ensuring proper proximal fixation of the stent-graft to the host artery without the short-or long-term risks of endoleak or migration represents a particular technical challenge for these anatomical circumstances. An innovative balloon expandable stent combined with a weft-knitted prosthesis was specifically designed for these situations by modelling the stent to the neck anatomy without overdistension or potential barotrauma allowing better incorporation of the device. The Latecba stent-graft consists of a 2 parts modular design. The first one, Module A, is deployed at the transrenal level and consists of a Palmaz type stent whose first half is bare and second half is sutured to a crimped weft-knitted polyester graft whose distal end holds a constriction. The second Module B is a non-crimped weft-knitted graft attached to 2 stainless steel stents. The first stent is entirely contained in the proximal textile tube, allowing fixation to module A. The second stent, which is left uncovered over the distal third, ensures proper fixation of the stent-graft distally. Following the creation of a prosthetic aneurysm in the infrarenal aorta in 32 dogs, 29 received the Latecba stent-graft for scheduled durations of 10 days, 1 month, 3 months and 6 months. Proper deployment of the stent-grafts was achieved without difficulty. All 29 animals survived and the devices were all patent at sacrifice. No device defects or migrations were observed and the stent-grafts proved to be efficient in this setting to exclude the aneurysm. Analyses of the explanted devices (gross observations, RX, CT scan, IVUS, angioscopy) confirmed the stability of this modular stent-graft. Further on-going clinical investigations are warranted to validate this concept before this stent-graft becomes commercially available without any restriction.