Journal of Biomedical Engineering Research (대한의용생체공학회:의공학회지)

The Korean Society of Medical and Biological Engineering (대한의용생체공학회)
권호 표지

Hydrodynamic Characteristics of Self-expandable Graft Stents in Steady Flow

정상유동에서 자가팽창성 그래프트 스텐트의 수력학적 특성

  • 이홍철 (전북대학교 대학원 정밀기계공학과) ;
  • 김철생 (전북대학교 전자정보공학부 생체공학전공) ;
  • 박복춘 (전북대학교 기계항공시스템공학부) ;
  • 박복춘 (전북대학교 기계항공시스템공학부)
  • Published : 2003.02.01
Download PDF
⟨ Previous Next ⟩

Abstract

This experimental study is aimed at evaluating the hydrodynamic performance of newly designed self-expandable graft stents under steady flow condition. Two graft stents with different coating materials and a bare TiNi metallic stent for comparison test were used in the experiment. Pressure variation and velocity distribution at the upstream and downstream of the stents were measured at flow rates of 5, 10, and 15 l/min, respectively. Pressure loss due to insertion of the stent increased with increasing flow rate exponentially as expected. At a flow rate of 15 l/min, pressure loss of Polyure-thane(PU)-coated graft stent was 6 times higher than that of TiNi metallic stent, while the pressure loss of a porous Polytetrafluoroethylene(PTFE)-coated graft stent was comparable to a bare TiNi metallic stent. Velocity profiles of the porous PTFE-coated graft stent were similar to those of a bare TiNi metallic stent regardless of flow rate. Furthermore, the velocity profile of PU-coated graft stent revealed an asymmetrical and relatively low central velocity at a higher flow rate than 10 1/min, expecially, where the effects resulted in increases of wall shear stress and normal stress. The worse hydrodynamic behavior of PU-coated graft stent than the other two stents might be attributed to formation of folds due to poor flexibility of coated material when inserting the graft stent into the pipe with a more smaller size, which later gave rise non-symmetry of flow area, increase of surface roughness and jet flow via the crevice between the stent and cylinder wall.

본 실험연구에서는 정상유동상태에서 새롭게 설계된 자가팽창성 그래프트 스텐트의 수력학적 성능을 평가하고자 하였다. 코팅 재질이 다른 두 개의 그래프트 스텐트와 한 개의 타이티놀 금속스텐트가 실험에 사용되었으며, 유량이 가자 5, 10, 15 1/min에서 스텐트 전후에서의 압력변화 및 속도분포를 측정하였다. 스텐트 삽입에 의한 압력손실은 유량이 증가함에 지수적으로 증가하였다. 특히 15 1/min의 유량에서 다공성 PTFE 그래프트 스텐트와 TiNi 금속스텐트의 압력손실은 거의 동일하나 PU 그래프트 스텐트는 약 6배 이상의 현저한 증가를 보이고 있다. 스텐트 후류에서의 속도분포는 다공성 PTFE 그래프트 스텐트와 TiNi 금속스텐트는 유량에 관계없이 유사한 형태를 보여주고 있다. 그러나, PU 그래프트 스텐트에서는 특히 유량이 10 1/min 이상에서 속도분포가 비대칭적이고 관 중심에서의 상대적인 낮은 유속을 보여주고 있으며, 결과적으로 벽면전단응력 및 수직응력의 증가론 초래하고 있다. 이와같이 PU 그래프트 스텐트의 상대적으로 낮은 수력학적 성능은 스텐트가 보다 작은 관에 삽입되었을때 코팅재질의 낮은 유연성으로 인하여 스텐트의 표면에 주름이 발생하여 유동단면이 비대칭적으로 되고 벽면의 조도가 증가하며, 관벽과 스텐트와 틈새가 존재하여 제트류가 형성되기 때문으로 해석된다.

Keywords

References

  1. Proggress of Cardiovascular Disease v.39 Nonvascular stents Vanderburgh L.;Ho C. S. https://doi.org/10.1016/S0033-0620(96)80025-9
  2. Circulation v.83 no.SUP Ⅰ Intravascular stents: general principles and status of lower-extremity arterial applications Becker G. J
  3. Investigative Radiology v.4 Transluminally placed coilspring endoarterial tube graft: Long-term patency in canine popliteal artery Dotter C.T. https://doi.org/10.1097/00004424-196909000-00008
  4. Radiology v.156 Percutaneous endovascular stent: an experimental evaluation Wright K.C.;Wallace S;Charnsangavej C(et al.) https://doi.org/10.1148/radiology.156.1.4001423
  5. AJR v.150 Balloon-Expandable Intravascular Stent Palmaz J.C. https://doi.org/10.2214/ajr.150.6.1263
  6. Handbook of coronary stents(4th edition) Serruys P.W.;Rensing B.J.
  7. American J Cardiology v.81 Stent Grafts for Aortic Aneurysms: The next Interventional Challenge Barry T.K.;Gary J.B.;James F. B.;Gerald Z.
  8. Cardiovascular Surgery v.8 no.7 Clinical results of implantation of an endovascular covered stent graft via midsternotomy for distal aortic arch aneurysm Usui A;Ueda Y.;Watanabe T.(et al.) https://doi.org/10.1016/S0967-2109(00)00066-1
  9. J. of Biomechanics v.24 no.10 In vitro study of a physiological type flow in a bifurcated vascular prosthesis Rieu R.;Pelissier R. https://doi.org/10.1016/0021-9290(91)90170-R
  10. J. of Biomechanics v.31 Hemodynamics of endovascular prostheses S. Fabregues;K. Baijens;R. Rieu;P. Bergeron
  11. Investigative Radiology v.33 no.10 Visualization of flow patterns from stents and stent-grafts in an in vitro flowmodel Stefaller Muller-Hulsbeck;Helmut Schwarzenberg;Frank Wesner;Rainer Drost;Claus-Chistian Gluer;Martin Heller https://doi.org/10.1097/00004424-199810000-00008
  12. Annals of Biomedical Engineering v.28 Experimental and computational flow evaluation of coronary stents J.L. Berry;A. Santamarina;J.E. Moore Jr;S. Roychowdhury;W.D. Routh https://doi.org/10.1114/1.276
  13. J. Biomed. Eng. Res. v.17 no.1 Hydrodynamic investigation of a floating-type monoleaflet polymet valve under steady flow condition J.W. Kim;B.C. Pak;B.J. Baek;B.G. Min
  14. M.S. Thesis, Chonbuk National University Flow characteristics on down stream of expandable graft stents in a circular tube H.C. Lee
  15. J. Biomech. Mat. Res. v.8 Adhesion of Red Cells to Foreign Surfaces in the Presence of Flow Mohanda, N;Hochmuth, R.M.;Spaeth, E.E. https://doi.org/10.1002/jbm.820080203
  16. Circulation Res. v.22 Acute Vascular Endothelial Changes Associated with Increased Blood Velocity Gradient Fry, D.L. https://doi.org/10.1161/01.RES.22.2.165
  17. Proc. 6th Int. Conf. on Bio. Eng. Hemodynamics of Tilting Disc-type Prosthetic Heart Valves Modi, V.J.;Bishop, W.F.
  18. Biomechanics v.16 Laser Anemometry Measurements of Pulsatile Flow Past Aortic Valve Prostheses Chandran, K.B.;Cabell, G.N;Khalighi, B.;Chen, C.J. https://doi.org/10.1016/0021-9290(83)90011-8