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Short Report| Volume 47, ISSUE 2, P160-163, February 2014

Poor Long-term Stability of the Corvita Abdominal Stentgraft

Open ArchivePublished:November 13, 2013DOI:https://doi.org/10.1016/j.ejvs.2013.10.010

      Introduction

      The endovascular treatment of abdominal aortic aneurysms was introduced in the early 1990s, with different generations of devices using various options for either the stent skeleton or the membrane.

      Report

      Corvita generated one of these devices using braided stainless steel and a porous spun polycarbonate urethane membrane.

      Discussion

      In this report, we describe a case involving Corvita stentgraft explantation for complete aneurysm reperfusion after 13 years, demonstrating major degradation of the polyurethane membrane.

      Keywords

      Introduction

      The endovascular treatment of abdominal aortic aneurysms (AAA) was introduced in the early 1990s, with different generations of devices using various options for either the stent skeleton or the membrane. The majority of the first generation devices were associated with a skeleton made of nitinol Z-shaped rings attached together to a woven polyester membrane using ligatures. Failures related to either stent corrosion or fabric instability have been reported. The Corvita stentgraft (CSG) (Corvita Corporation, Miami, FL, USA)
      • Wilson G.J.
      • Klement P.
      • Kato Y.P.
      • Martin J.B.
      • Khan I.J.
      • Alcime R.
      • et al.
      A self expanding bifurcated endovascular graft for abdominal aortic aneurysm repair. An initial study in a canine model.
      has been proposed as another concept. This stentgraft comprises a proximal aortic trunk divided into two distinct sockets to receive two smaller diameter leg (iliac) components. All components comprise self-expanding braided wire stents integrally attached to porous spun polycarbonate urethane (PCU) liners (Corethane). One of the potential weaknesses of the concept was the uncertain in vivo long-term stability of the PCU membrane. This device has been retrieved from the market; however, there is no scientific evidence available concerning the long-term stability of this instrument. In this report, we describe the first structural investigation of an explanted CEG.

      Case Report

      A 75-year-old man was admitted to the Department of Vascular Surgery of the University Hospital of Nancy for the complete reperfusion of AAA. The patient had been endovascularly treated 13 years earlier at another institution. The patient was asymptomatic and a CT scan was performed to assess a disruption in the follow-up exam. The CT scan demonstrated the complete reperfusion of the aneurysm sac with enlargement (Fig. 1). A previous CT scan was performed 4 years previously at another institution and exhibited an indeterminate endoleak without sac enlargement. The patient underwent open surgical conversion, exhibiting a fully pulsatile aneurysm. After temporary supra-renal clamping the aneurysmal sac was opened, exhibiting the stentgraft with major lesions on the membrane. The stentgraft was explanted, and the operation was completed using prosthetic aorto-bi-iliac revascularisation. The patient recovered well without any morbidity. The explant was sent to the GEPROVAS laboratory as a part of a European retrieval explant programme and was submitted to a standardised protocol for evaluation. Naked-eye examinations followed by images investigating the body and both limbs of the stentgraft were performed. The bifurcated body measured 9 cm in length and included two channels of 3 cm length and 9 mm in diameter for limb insertion. Both extremities of the body were slightly conic, respectively, measuring 4 × 3.5 cm and 3 × 2.2 cm (Fig. 2).
      Figure thumbnail gr1
      Figure 1The CT scan performed at 13 years after the implantation of the Corvita stentgraft. (A) The complete perfusion of the aneurysmal sac (early injection time). (B) Frontal reconstruction showing the body of the stentgraft below the renal arteries associated with the reperfusion of the aneurysmal sac without module disjunctions.
      Figure thumbnail gr2
      Figure 2Macroscopic aspects of both extremities of the main body of the stent graft after explantation (Nikon D5100).
      The three components of the stentgraft were subjected to a slow cleaning process.
      • Wilson G.J.
      • Klement P.
      • Kato Y.P.
      • Martin J.B.
      • Khan I.J.
      • Alcime R.
      • et al.
      A self expanding bifurcated endovascular graft for abdominal aortic aneurysm repair. An initial study in a canine model.
      Images of the samples were captured after each change to exclude the occurrence of any damage associated with the cleaning process. After cleaning, the stentgraft was extensively evaluated, and the images of all of the primary points of interest were captured using a camera (Nikon D5100) and a digital microscope (Keyence VHX-600).
      We observed the fragmentation of the PCU membrane primarily at the extremities of each of the three components. This membrane comprises layers of PCU filaments with a helicoidal orientation of approximately 55°.
      We observed two modes of degradation of the PCU membrane (Fig. 3):
      • -
        Degradation initiated at the middle of each cell, as defined by the braided stent structure, and extending to the edges (Fig. 3A, B, C).
      • -
        The detachment of PCU membrane fragments, initiating at the periphery of the cells (Fig. 3D).
      Figure thumbnail gr3
      Figure 3Modes of degradation of the fabric (Keyence VHX 600). Degradation, initiated at the middle of each cell, was defined by the braided stent structure, extending to the edges (A, B, and C), and the detachment of fabric fragments at the size of a cell of the braided structure with light degeneration of the filaments (D).
      Filament fractures of the braided stent structures were observed at the conical extremity of the bifurcated segment (Fig. 4).
      Figure thumbnail gr4
      Figure 4Lesions of the braided stent structure in the conical region of the body. Microscopic views of the stent fractures (Keyence VHX 600).

      Discussion

      The CSG was one of the first generation stentgraft models proposed in the 1990s for the treatment of AAA. The first generation stentgrafts were disappointing in terms of stability
      • Chakfé N.
      • Diéval F.
      • Riepe G.
      • Mathieu D.
      • Zbali I.
      • Thaveau F.
      • et al.
      The influence of the textile structure on aortic endoprostheses degradation. Evaluation of explanted grafts.
      • Heintz C.
      • Riepe G.
      • Birken L.
      • Kaiser E.
      • Chakfé N.
      • Morlock M.
      • et al.
      Nitinol wire corrosion of explanted endovascular grafts used for AAA repair. An important failure mechanism?.
      and have subsequently been retrieved from the market. Therefore, it might be important to report this case for the following reasons. First, although this device has been retrieved from the market, there is no available information concerning the reasons for retrieval. The CSG has been used for the treatment of peripheral aneurysms, and cases of “cigar-shape” deformation have been reported after a few months of implantation.
      • Sanchez L.A.
      • Veith F.J.
      • Ohki T.
      • Suggs W.D.
      • Bakal C.
      • Cynamon J.
      • et al.
      Early experience with the Corvita endoluminale graft for treatment of arterial injuries.
      • Sitsen M.E.
      • Ho G.H.
      • Blankensteijn J.D.
      Deformation of self-expanding stent-grafts complicating endovascular peripheral aneurysm repair.
      The only clinical evaluation reported in the literature offered encouraging medium-term results.
      • Dereume J.P.
      • Ferreira J.
      • Dehon P.
      • Cavenaile J.C.
      • Le Minh T.
      • Motte S.
      • et al.
      Treatment of abdominal aortic aneurysm by application of a Corvita endoprosthesis. Medium term results of a feasibility study.
      However, no evidence of the durability of this device has been reported, and to the best of our knowledge, this case is the first instance of explant analysis reported since the extensive analysis of explants using other first generation devices retrieved from the market. The second reason is the specificity of the fabric that has been used in this device. The first-generation devices extensively used polyethylene terephthalate (PET) woven fabrics; thus, in the present study, we used porous spun PCU liners. The choice of polyurethane was questionable because of the lack of data concerning the long-term stability of this material in vivo. The same membrane was used to construct a vascular graft, but a PET external mesh was added to reinforce this structure. This prosthesis has been studied in animal models,
      • Xie X.
      • Eberhart A.
      • Guidoin R.
      • Marois Y.
      • Douville Y.
      • Zhang Z.
      Five types of polyurethane vascular grafts in dogs: the importance of structural design and material selection.
      demonstrating the degradation of the melted adhesive between the external PET mesh and the underlying PCU membrane after 6 months. Another animal model study of the PCU vascular graft showed adequate biostability with only minor hydrolysis after 3 years.
      • Seifalian A.M.
      • Salacinski H.J.
      • Tiwari A.
      • Edwards A.
      • Bowald S.
      • Hamilton G.
      In vivo biostability of a poly(carbonate-urea)urethane graft.
      In conclusion, this study aimed to provide data to the medical community regarding the long-term durability of a particular model of the vascular device. Although this device is no longer available on the market, the knowledge of this report provides evidence for the control of the stentgraft in patients potentially lost to follow-up and should be helpful for designing future devices. One of the biases of such a retrieval programme is that we only analysed devices presenting complications and requiring open reintervention, and we are aware that we cannot firmly confirm the obligatory degradation of all devices or sporadic cases of degradation in this particular case.

      Acknowledgements

      The authors would like to thank the “Société de Chirurgie Vasculaire de Langue Française” and the “European Society for Vascular Surgery” for financially supporting our explant analysis programme.

      Conflict of Interest

      None.

      Funding

      None.

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