Disruption of a Covered Nitinol Self Expanding Stent Graft Implanted in the Common Femoral Artery

Systematic Review of Femoral Artery Stent Fractures

Objective

Primary stenting for long femoropopliteal (FP) lesions remains controversial because of the high risk of stent fracture (SF). This study aimed to summarise current knowledge on SF from randomised control trials about FP stenting.

Methods

A systematic review of the Medline database was performed by a combined strategy of MeSH terms: femoral artery, popliteal artery, stenting, and stent fracture. SF was classified according to a standard classification: 1 = single strut fracture; 2 = ≥ two struts fracture; 3 = type 2 with deformation; 4 = multiple struts fracture with acquired transection; 5, type 4 with gap in the stent body.

Results

The literature search identified 25 publications including covered stents (CSs; n = 3), drug eluting stents (DESs; n = 8), bare metal stents (BMS; n = 17), and bioabsorbable stents (n = 1). Data were extracted from 4 047 patients; mean age ± standard deviation was 68.9 ± 3.0 years and 69% were male. The median lesion length was 87.6 mm (interquartile range [IQR] 70.0, 149) with a median chronic total occlusion proportion of 36.8% (IQR 29.0, 56.5). In 208 patients treated with CS, SF rates ranged from none to 2.6% at 36 months with no clinical correlation. In 1 106 patients treated with DES, SF rates were relatively low in large cohorts, ranging from 0% at 12 months to 1.9% at 60 months. In smaller cohorts (under 100 patients per group), they ranged from 12.5% at six months to 46.7% at 12 months, with no clinical repercussion. In 1 610 patients treated with BMS, SF rates ranged from 2% to 32.7% at 12 months and from 2.9% to 48.9% at 24 months, with no clinical repercussion.

Conclusion

SF rates in large cohorts were low in CF and DES, and quite common in BMS, although none of them had clinical consequences. However, longer follow up and detailed, accurate reports are needed to assess eventual real clinical outcomes.

DEGRADATION PHENOMENA ON LAST GENERATIONS OF POLYETHYLENE TEREPHTHALATE KNITTED VASCULAR PROSTHESES

Objectives

The aim of this study was to analyze a series of new generations of explanted knitted polyethylene terephthalate (PET) vascular grafts (VGs) presenting nonanastomotic degradations according to preoperative computed tomography angiography (CTA) when available in order to better understand the mechanisms leading to rupture.

Methods

Explanted knitted PET VGs were collected as part of the Geprovas European Collaborative Retrieval Program. VGs implanted after 1990 presenting a nonanastomotic rupture of the fabric were included. Clinical data and pre-explantation CTA data when available were retrieved for each VG. The ruptures were characterized by macroscopic examination and optical microscopy according to a standardized protocol.

Results

Nineteen explants were collected across 11 European centers, 13 were implanted as infrainguinal bypasses, 3 at the aortic level, and 1 as an axillobifemoral bypass. The mean implantation duration was 9.2 years. Pre-explantation CTA data were available for 8 VGs and showed false aneurysms at the adductor canal level on 4 VGs, at the inguinal ligament level on 2 VGs, and in the proximal or middle third thigh level on 3 VGs. Examination revealed longitudinal ruptures on 9 explanted VGs (EVGs), transversal ruptures on 15 EVGs, 45°-oriented ruptures on 5 EVGs, V-shaped ruptures on 7 EVGs, and punctiform ruptures on 2 EVGs. Ruptures involved the remeshing line on 11 EVGs, the guideline on 10 EVGs, and the crimping valley on 15 EVGs.At the microscopic level, two main degradation phenomena could be identified: a decrease in the density of the meshing and local ruptures of the PET fibers. Fourteen EVGs presented a loosening of the remeshing line and 17 EVGs an attenuation of the crimping.

Conclusions

New-generation PET VG degradation seems to result from both anatomic constraints and intrinsic textile structure phenomena.

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).