Successful Reproduction of In-Vivo Fracture of an Endovascular Stent in Superficial Femoral Artery Utilizing a Novel Multi-loading Durability Test System

Kiyotaka Iwasaki, S. Tsubouchi, Y. Hama, Mitsuo Umezu

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    Aim: High rates of stent fracture have been reported in the treatment of diseased superficial femoral artery (SFA). Understanding of in-vivo mechanical-loading environments, therefore, draws serious attention. We have developed a novel multi-loading durability tester which can apply cyclic twist and stretch on stents. Here, in-vitro stent fracture patterns were compared with stent fracture observed in vivo. Methods: The angle of cyclic twist as well as cyclic stretch exerted to the stents was regulated to physiologic conditions by utilizing referenced data of MR angiography of SFAs obtained in the spine and fetal position. Stiffness of the silicone vessel models were regulated to that of SFAs. As the SFAs are intrinsically stretched in vivo, stents were tested not only in the nonstretched vessel model but also in the 50% pre-stretched vessel model, respectively. The simultaneous cyclic multi-loads were exerted to the stents under the mean luminal pressure of 100mmHg at 60 cycles per minute. Considering the data that average Japanese walk 7378 steps per day, the cyclic numbers of the in-vitro durability tests were converted to the equivalent durability in vivo. Results: Only minor fracture was observed at the stent strut after one-year-equivalent duration when the stents were tested using the non-stretched vessel models. However, employment of the novel pre-stretched vessel model resulted in complete stent fractures in the middle of longitudinal direction in 2-months-equivalent duration. Moreover, the fracture pattern was clearly coincident with the stent fracture in vivo. Conclusions: This is the first demonstration that the pre-stretch of vessel model is a requisite condition in durability tests of stents for SFA. Moreover, these results indicated that reproduction of multi-loading environments including cyclic twist and stretch is of great significance in order to obtain reliable durability data of endovascular stents for SFA.

    Original languageEnglish
    Title of host publicationIFMBE Proceedings
    Pages1443-1446
    Number of pages4
    Volume23
    DOIs
    Publication statusPublished - 2009
    Event13th International Conference on Biomedical Engineering, ICBME 2008 -
    Duration: 2008 Dec 32008 Dec 6

    Other

    Other13th International Conference on Biomedical Engineering, ICBME 2008
    Period08/12/308/12/6

    Fingerprint

    Stents
    Durability
    Angiography
    Struts
    Silicones
    Demonstrations

    Keywords

    • Accelerated durability test
    • Endovascular stent
    • Regulatory science
    • Stent fracture
    • Superficial femoral artery

    ASJC Scopus subject areas

    • Biomedical Engineering
    • Bioengineering

    Cite this

    Successful Reproduction of In-Vivo Fracture of an Endovascular Stent in Superficial Femoral Artery Utilizing a Novel Multi-loading Durability Test System. / Iwasaki, Kiyotaka; Tsubouchi, S.; Hama, Y.; Umezu, Mitsuo.

    IFMBE Proceedings. Vol. 23 2009. p. 1443-1446.

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Iwasaki, K, Tsubouchi, S, Hama, Y & Umezu, M 2009, Successful Reproduction of In-Vivo Fracture of an Endovascular Stent in Superficial Femoral Artery Utilizing a Novel Multi-loading Durability Test System. in IFMBE Proceedings. vol. 23, pp. 1443-1446, 13th International Conference on Biomedical Engineering, ICBME 2008, 08/12/3. https://doi.org/10.1007/978-3-540-92841-6_356
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    abstract = "Aim: High rates of stent fracture have been reported in the treatment of diseased superficial femoral artery (SFA). Understanding of in-vivo mechanical-loading environments, therefore, draws serious attention. We have developed a novel multi-loading durability tester which can apply cyclic twist and stretch on stents. Here, in-vitro stent fracture patterns were compared with stent fracture observed in vivo. Methods: The angle of cyclic twist as well as cyclic stretch exerted to the stents was regulated to physiologic conditions by utilizing referenced data of MR angiography of SFAs obtained in the spine and fetal position. Stiffness of the silicone vessel models were regulated to that of SFAs. As the SFAs are intrinsically stretched in vivo, stents were tested not only in the nonstretched vessel model but also in the 50{\%} pre-stretched vessel model, respectively. The simultaneous cyclic multi-loads were exerted to the stents under the mean luminal pressure of 100mmHg at 60 cycles per minute. Considering the data that average Japanese walk 7378 steps per day, the cyclic numbers of the in-vitro durability tests were converted to the equivalent durability in vivo. Results: Only minor fracture was observed at the stent strut after one-year-equivalent duration when the stents were tested using the non-stretched vessel models. However, employment of the novel pre-stretched vessel model resulted in complete stent fractures in the middle of longitudinal direction in 2-months-equivalent duration. Moreover, the fracture pattern was clearly coincident with the stent fracture in vivo. Conclusions: This is the first demonstration that the pre-stretch of vessel model is a requisite condition in durability tests of stents for SFA. Moreover, these results indicated that reproduction of multi-loading environments including cyclic twist and stretch is of great significance in order to obtain reliable durability data of endovascular stents for SFA.",
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    AU - Iwasaki, Kiyotaka

    AU - Tsubouchi, S.

    AU - Hama, Y.

    AU - Umezu, Mitsuo

    PY - 2009

    Y1 - 2009

    N2 - Aim: High rates of stent fracture have been reported in the treatment of diseased superficial femoral artery (SFA). Understanding of in-vivo mechanical-loading environments, therefore, draws serious attention. We have developed a novel multi-loading durability tester which can apply cyclic twist and stretch on stents. Here, in-vitro stent fracture patterns were compared with stent fracture observed in vivo. Methods: The angle of cyclic twist as well as cyclic stretch exerted to the stents was regulated to physiologic conditions by utilizing referenced data of MR angiography of SFAs obtained in the spine and fetal position. Stiffness of the silicone vessel models were regulated to that of SFAs. As the SFAs are intrinsically stretched in vivo, stents were tested not only in the nonstretched vessel model but also in the 50% pre-stretched vessel model, respectively. The simultaneous cyclic multi-loads were exerted to the stents under the mean luminal pressure of 100mmHg at 60 cycles per minute. Considering the data that average Japanese walk 7378 steps per day, the cyclic numbers of the in-vitro durability tests were converted to the equivalent durability in vivo. Results: Only minor fracture was observed at the stent strut after one-year-equivalent duration when the stents were tested using the non-stretched vessel models. However, employment of the novel pre-stretched vessel model resulted in complete stent fractures in the middle of longitudinal direction in 2-months-equivalent duration. Moreover, the fracture pattern was clearly coincident with the stent fracture in vivo. Conclusions: This is the first demonstration that the pre-stretch of vessel model is a requisite condition in durability tests of stents for SFA. Moreover, these results indicated that reproduction of multi-loading environments including cyclic twist and stretch is of great significance in order to obtain reliable durability data of endovascular stents for SFA.

    AB - Aim: High rates of stent fracture have been reported in the treatment of diseased superficial femoral artery (SFA). Understanding of in-vivo mechanical-loading environments, therefore, draws serious attention. We have developed a novel multi-loading durability tester which can apply cyclic twist and stretch on stents. Here, in-vitro stent fracture patterns were compared with stent fracture observed in vivo. Methods: The angle of cyclic twist as well as cyclic stretch exerted to the stents was regulated to physiologic conditions by utilizing referenced data of MR angiography of SFAs obtained in the spine and fetal position. Stiffness of the silicone vessel models were regulated to that of SFAs. As the SFAs are intrinsically stretched in vivo, stents were tested not only in the nonstretched vessel model but also in the 50% pre-stretched vessel model, respectively. The simultaneous cyclic multi-loads were exerted to the stents under the mean luminal pressure of 100mmHg at 60 cycles per minute. Considering the data that average Japanese walk 7378 steps per day, the cyclic numbers of the in-vitro durability tests were converted to the equivalent durability in vivo. Results: Only minor fracture was observed at the stent strut after one-year-equivalent duration when the stents were tested using the non-stretched vessel models. However, employment of the novel pre-stretched vessel model resulted in complete stent fractures in the middle of longitudinal direction in 2-months-equivalent duration. Moreover, the fracture pattern was clearly coincident with the stent fracture in vivo. Conclusions: This is the first demonstration that the pre-stretch of vessel model is a requisite condition in durability tests of stents for SFA. Moreover, these results indicated that reproduction of multi-loading environments including cyclic twist and stretch is of great significance in order to obtain reliable durability data of endovascular stents for SFA.

    KW - Accelerated durability test

    KW - Endovascular stent

    KW - Regulatory science

    KW - Stent fracture

    KW - Superficial femoral artery

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