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What Do We Learn From Explant Analysis Programs?

  • N. Chakfé
    Correspondence
    Corresponding author. Department of Vascular Surgery and Kidney Transplantation, Nouvel Hôpital Civil, BP 426, 67091 Strasbourg Cedex, France.
    Affiliations
    Groupe Européen de Recherche sur les Prothèses appliquées à la Chirurgie Vasculaire (GEPROVAS), France
    Department of Vascular Surgery and Kidney Transplantation, Les Hôpitaux Universitaires de Strasbourg, University of Strasbourg, Strasbourg, France
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  • F. Heim
    Affiliations
    Groupe Européen de Recherche sur les Prothèses appliquées à la Chirurgie Vasculaire (GEPROVAS), France
    Laboratoire de Physique et Mécanique Textile, ENSISA, Mulhouse, France
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Open ArchivePublished:June 30, 2017DOI:https://doi.org/10.1016/j.ejvs.2017.05.018
      In recent decades, vascular surgery has been marked by several technological breakthroughs with the successive introduction of vascular devices with improved performance. To treat vascular diseases more efficiently, vascular grafts, stents, and endografts were invented, developed, and used clinically. Each of these devices was considered to be a breakthrough technology invented by pioneers such as Voorheese for vascular grafts, Wallsten for stents, and Volodos and Parodi for endografts. These inventors had visions of the future of patient care in vascular surgery, paving the way for technological development, and introduced devices that were met with immediate enthusiasm not only by physicians but also by companies. However, for each of these new technological concepts, first generations of devices demonstrated questionable durability in humans and led to a considerable number of re-interventions and complications in patients. Consequently, Wesolowski,
      • Wesolowski S.A.
      A plea for early recognition of late vascular prosthetic failure.
      who wrote the paper entitled “A plea for early recognition of late vascular prosthetic failure,” should also be considered a pioneer with his interpretation of modern surgical practice.
      In this context, the first question is: what are the conditions for bringing a new device to clinical practice? At the beginning there is an idea, sometimes coming from genius physicians and scientists or most often from companies. At that early stage, one critical issue that must be considered is the updated scientific knowledge about the specific field for which the device should improve the physiological performance of the patient. But this is not sufficient, as the knowledge must be extended to all fields involved in the implantation environment, such as human anatomy and physiology, biology, and mechanical characteristics. The next development stage is the pre-market assessment of the device's performance. This step consists of performing tests as requested by the Council Directive 93/42/EEC of June 14, 1993 concerning medical devices. However, if following standards is absolutely necessary, one must bear in mind that these standards cannot be considered predictive of the long-term durability of the device. The main role of standards is to control that the characteristics as well as the performance of a device are always constant at manufacturing level, and are in accordance with clinical expectations. One limit of the approach is that existing standards may not be sufficiently documented with regard to new devices characterized by specific functionalities. However, we do know from daily clinical practice and from data in the literature that devices undergo failures, which occur even in the most recent product generations. It must be admitted that current pre-market tests are insufficient to predict the in vivo fate of implanted devices. A new approach is required to bridge the gap between the in vitro performances and the effective behavior of a device once it has been implanted. Explant analysis is likely to be the key to improve performances of future generations of devices.
      At this level, a second question arises: what do we learn from explant analysis programs? First, one can note that failures can actually occur in devices. There is no doubt that these failures are under-declared despite declaration being mandatory according to European rules. Reasons for reluctance to declare a failure are difficult to explain and are certainly multifactorial. Are failures considered to be a fatality? Do physicians consider these failures as a responsibility in which they don't want to be involved? Do physicians not want to be involved in a regulatory process they consider to be too demanding? Consequently, scientific societies are responsible for informing physicians about their duty in the field of failure declaration. The process should become part of their daily practice.
      Secondly, true epidemiological data could be collected, which, unfortunately, is not current practice. These epidemiological data could help in early detection of a specific device failure. They could help physicians in their practice choices. These data could be crossed with clinical variables to determine which are the best indications for use of a specific device. Moreover, epidemiological data are scientific data that counteract the development of rumors, which can be as harmful to physician practice as to companies. Explant analysis programs could be used to highlight major failures in devices that have been retrieved from the market without informing the vascular community towards recall of patients.
      • Georg Y.
      • Settembre N.
      • Marchand C.
      • Lejay A.
      • Thaveau F.
      • Durand B.
      • et al.
      Poor long-term stability of the Corvita abdominal stentgraft.
      Thirdly, retrieving explanted devices allows for valuable analyses on degradation phenomena. Analysis of only a few explants can be highly biased. However, analyzing a large number of explants of a specific device could help to distinguish a sporadic event from a general behavior, mainly by obtaining time related observations. Such analyses could help in setting up standardised classifications that enable objective comparisons between different models of devices.
      • Bussmann A.
      • Heim F.
      • Delay C.
      • Girsowicz E.
      • Del Tatto B.
      • Dion D.
      • et al.
      Textile aging characterization on new generations of explanted commercial endoprostheses.
      They could facilitate understanding of the in vivo behavior of devices and provide information on the mechanisms responsible for delayed degradation. They could help in improving the manufacturing process and the design of future generations of implants. As an example, it has previously been demonstrated that some longitudinal ruptures of knitted vascular grafts
      • Chakfé N.
      • Riepe G.
      • Dieval F.
      • Wang L.
      • Beaufigeau M.
      • Urban E.
      • et al.
      Longitudinal ruptures of polyester knitted vascular prostheses.
      can be related to the manufacturing process,
      • Dieval F.
      • Chakfé N.
      • Wang L.
      • Riepe G.
      • Thaveau F.
      • Heintz C.
      • et al.
      Mechanisms of longitudinal rupture of knitted polyester vascular prostheses: in vitro analysis of virgin prostheses.
      • Chaouch W.
      • Dieval F.
      • Le Nouen D.
      • Defoin A.
      • Chakfé N.
      • Durand B.
      1H-NMR spectroscopic study of the effect of aging vascular prostheses made of poly(ethylene terephthalate) on the macromolecular weight.
      and that parts of the lesions observed on first generations of endoprostheses
      • Riepe G.
      • Heilberger P.
      • Umscheid T.
      • Chakfé N.
      • Raithel D.
      • Stelter W.
      • et al.
      Frame dislocation of body middle rings in endografts tube grafts.
      • Riepe G.
      • Heintz C.
      • Kaiser E.
      • Chakfé N.
      • Morlock M.
      • Delling M.
      • et al.
      What can we learn from explanted endovascular devices.
      can be explained by inadequate choices of textile fabric.
      • Chakfé N.
      • Dieval 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.
      This is the only way in which to explain degradation mechanisms and set up tests to confirm hypotheses
      • Chenesseau B.
      • Heim B.
      • Pidancier C.
      • Lejay A.
      • Thaveau F.
      • Georg Y.
      • et al.
      How compression inside a delivery system can degrade the cover of aortic endografts: An experimental study.
      and evaluate trends in terms of behaviors.
      • Bussmann A.
      • Heim F.
      • Delay C.
      • Girsowicz E.
      • Del Tatto B.
      • Dion D.
      • et al.
      Textile aging characterization on new generations of explanted commercial endoprostheses.
      It is important to define how such a program should be run. Currently, in the absence of a dedicated program, explants are usually sent back to the manufacturer and no open data are available about the results. We strongly believe that explants should be sent to centralised centres dedicated to these issues.
      • Chong D.S.T.
      • Constantinou J.
      • Davis M.
      • Hamilton G.
      Calcification of a synthetic renovascular graft in a child.
      Ideally, such centres should be independent from the industry, must respect the confidentiality of manufacturers, and must work in total transparency regarding patients and physicians. Transparency should be based on establishing a strong link between the centres and major scientific societies that could report to health authorities. Such centres should be “information providers” for manufacturers allowing them early feedback on unexpected events and, in close partnership, setting up research programs to improve the durability of their products.
      In conclusion, developments in vascular surgery make it more and more necessary to draw inspiration on safety procedures from other industries, for example the aeronautics industry. Each of us wants to be sure that every part of the planes in which we travel worldwide to present our research results on vascular devices has been expertly characterized for a predetermined lifetime. In parallel, should we continue to implant vascular devices without systematic feedback on their durability? It is this kind of program that means we are no longer travelling in planes with square windows, which were identified as being responsible for the crashes of the de Havilland Comet in the 1950s.
      • Ministry of Transport and Civil Aviation
      Civil Aircraft Accident. Report of the Court of Inquiry into the Accidents to Comet G-ALYP on 10th January, 1954 and Comet G-ALYY on 8th April, 1954.
      We use more and more sophisticated devices incorporating different materials such as fabrics and metal, branches and modular connections, implanted in high stress areas. Therefore it is essential that we have closer and more systematic control on the durability of such complex devices.

      Acknowledgements

      We are grateful to the “ Société de Chirurgie Vasculaire et Endovasculaire de Langue Française ” and the “ European Society for Vascular Surgery ,” which support of the program of explants analysis.

      References

        • Wesolowski S.A.
        A plea for early recognition of late vascular prosthetic failure.
        Surgery. 1978; 84: 575-576
      1. http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A31993L0042.

        • Georg Y.
        • Settembre N.
        • Marchand C.
        • Lejay A.
        • Thaveau F.
        • Durand B.
        • et al.
        Poor long-term stability of the Corvita abdominal stentgraft.
        Eur J Vasc Endovasc Surg. 2014; 47: 160-163
        • Bussmann A.
        • Heim F.
        • Delay C.
        • Girsowicz E.
        • Del Tatto B.
        • Dion D.
        • et al.
        Textile aging characterization on new generations of explanted commercial endoprostheses.
        Eur J Vasc Endovasc Surg. 2017; ([in press])
        • Chakfé N.
        • Riepe G.
        • Dieval F.
        • Wang L.
        • Beaufigeau M.
        • Urban E.
        • et al.
        Longitudinal ruptures of polyester knitted vascular prostheses.
        J Vasc Surg. 2001; 33: 1015-1021
        • Dieval F.
        • Chakfé N.
        • Wang L.
        • Riepe G.
        • Thaveau F.
        • Heintz C.
        • et al.
        Mechanisms of longitudinal rupture of knitted polyester vascular prostheses: in vitro analysis of virgin prostheses.
        Eur J Vasc Endovasc Surg. 2003; 26: 429-436
        • Chaouch W.
        • Dieval F.
        • Le Nouen D.
        • Defoin A.
        • Chakfé N.
        • Durand B.
        1H-NMR spectroscopic study of the effect of aging vascular prostheses made of poly(ethylene terephthalate) on the macromolecular weight.
        J Biomed Mater Res A. 2009; 91: 939-952
        • Riepe G.
        • Heilberger P.
        • Umscheid T.
        • Chakfé N.
        • Raithel D.
        • Stelter W.
        • et al.
        Frame dislocation of body middle rings in endografts tube grafts.
        Eur J Vasc Endovasc Surg. 1999; 17: 28-34
        • Riepe G.
        • Heintz C.
        • Kaiser E.
        • Chakfé N.
        • Morlock M.
        • Delling M.
        • et al.
        What can we learn from explanted endovascular devices.
        Eur J Vasc Endovasc Surg. 2002; 24: 117-122
        • Chakfé N.
        • Dieval 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.
        Eur J Vasc Endovasc Surg. 2004; 27: 33-41
        • Chenesseau B.
        • Heim B.
        • Pidancier C.
        • Lejay A.
        • Thaveau F.
        • Georg Y.
        • et al.
        How compression inside a delivery system can degrade the cover of aortic endografts: An experimental study.
        Ann Vasc Surg. 2017; ([in press])
        • Chong D.S.T.
        • Constantinou J.
        • Davis M.
        • Hamilton G.
        Calcification of a synthetic renovascular graft in a child.
        Eur J Vasc Endovasc Surg Short Rep. 2016; 33: 13-15
        • Ministry of Transport and Civil Aviation
        Civil Aircraft Accident. Report of the Court of Inquiry into the Accidents to Comet G-ALYP on 10th January, 1954 and Comet G-ALYY on 8th April, 1954.
        Her Majesty’s Stationery Office, London1955

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