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Cardiovascular Engineering and Technology

, Volume 2, Issue 3, pp 160–172 | Cite as

A Numerical Tool for the Coupled Mechanical Assessment of Anastomoses of PTFE Arterio-venous Access Grafts

  • M. N. Ngoepe
  • B. D. Reddy
  • D. Kahn
  • C. Meyer
  • P. Zilla
  • T. FranzEmail author
Article

Abstract

The anastomotic angle is assumed to affect the performance of arterio-venous (AV) access grafts by altering wall shear stress (WSS) and wall tension. The objective of this study was to develop a coupled numerical tool to assess fluid and structural anastomotic mechanics of a straight upper arm access graft. 3D computational fluid dynamics (CFD) and finite element (FE) models were developed for arterial and venous anastomoses with different graft attachment angles. The fluid simulations were executed using flow velocity profiles for anastomotic inlets obtained from a whole-graft CFD model. A mesh adaptation algorithm was developed to couple CFD and FE meshes and capture fluid structure interactions. The coupling algorithm enabled transfer of blood pressure (BP) and WSS predicted with the CFD models to the FE models as loadings. The deformations induced in the FE models were used to update the CFD geometries after which BP and WSS were recalculated and the process repeated until equilibrium between fluid and solid models. Maximum BP in the vein was 181 mmHg. WSS peaked at 2.3 and 0.7 Pa and the structural wall stress reached 3.38 and 3.36 kPa in arterial and venous anastomosis. Since flow-induced wall tension has been identified as a contributor to access graft failure along with WSS, the computational tool will be useful in studying the coupled mechanics in these grafts. Initial investigations of arterial and venous anastomotic end-to-side configuration indicated a slightly better performance of the 90° configuration over 135° arterial and 45° venous configurations.

Keywords

Arterio-venous access Haemodialysis Finite element method Computational fluid dynamics Fluid structure interaction 

Notes

Acknowledgments

B.D.R. acknowledges the support for the South African Research Chair in Computational Mechanics by the Department of Science and Technology and the National Research Foundation.

References

  1. 1.
    Aguirre, A., M. Oliva, R. Schoephoerster, and V. Kasyanov (eds.). Static and dynamic mechanical testing of a polymer with potential use as heart valve material. In: Summer Bioengineering Conference, 2003, Key Biscayne, FL. New York: ASTM, 2003.Google Scholar
  2. 2.
    B. Braun vascular systems: Vascugraft (http://www.Aesculap-extra.Net/public/frame_doc_index.Html?Med_id=100051022). Berlin: B. Braun Melsungen AG; 2010. p. 8.
  3. 3.
    Cacho, F., M. Doblare, and G. A. Holzapfel. A procedure to simulate coronary artery bypass graft surgery. Med. Biol. Eng. Comput. 45(9):819–827, 2007.CrossRefGoogle Scholar
  4. 4.
    Chen, J., X.-Y. Lu, and W. Wang. Non-newtonian effects of blood flow on hemodynamics in distal vascular graft anastomoses. J. Biomech. 39(11):1983–1995, 2006.CrossRefGoogle Scholar
  5. 5.
    Cole, J. S., J. K. Watterson, and M. J. O’Reilly. Numerical investigation of the haemodynamics at a patched arterial bypass anastomosis. Med. Eng. Phys. 24(6):393–401, 2002.CrossRefGoogle Scholar
  6. 6.
    Dobrin, P. B., F. N. Littooy, and E. D. Endean. Mechanical factors predisposing to intimal hyperplasia and medial thickening in autogenous vein grafts. Surgery 105(3):393–400, 1989.Google Scholar
  7. 7.
    Ethier, C. R., and C. A. Simmons. Introductory Biomechanics: From Cells to Organisms. Cambridge Texts in Biomedical Engineering. Cambridge: Cambridge University Press, 2007.Google Scholar
  8. 8.
    Fisher, R. K., T. V. How, T. Carpenter, J. A. Brennan, and P. L. Harris. Optimising miller cuff dimensions. The influence of geometry on anastomotic flow patterns. Eur. J. Vasc. Endovasc. Surg. 21(3):251–260, 2001.CrossRefGoogle Scholar
  9. 9.
    Garcia-Pajares, R., J. R. Polo, A. Flores, E. Gonzalez-Tabares, and J. V. Solis. Upper arm polytetrafluoroethylene grafts for dialysis access. Analysis of two different graft sizes: 6 mm and 6–8 mm. Vasc. Endovasc. Surg. 37(5):335–343, 2003.CrossRefGoogle Scholar
  10. 10.
    Gay, D., S. V. Hoa, and S. W. Tsai. Composite Materials: Design and Applications. Boca Raton: CRC Press, 2003.Google Scholar
  11. 11.
    Golledge, J. Vein grafts: haemodynamic forces on the endothelium—a review. Eur. J. Vasc. Endovasc. Surg. 14(5):333–343, 1997.CrossRefGoogle Scholar
  12. 12.
    Golledge, J., R. J. Tumer, S. L. Harley, D. R. Springall, and J. T. Powell. Development of an in vitro model to study the response of saphenous vein endothelium to pulsatile arterial flow and circumferential deformation. Eur. J. Vasc. Endovasc. Surg. 13(6):605–612, 1997.CrossRefGoogle Scholar
  13. 13.
    Holzapfel, G. A., T. C. Gasser, and R. W. Ogden. A new constitutive framework for arterial wall mechanics and a comparative study of material models. J. Elasticity 61(1–3):1–48, 2000.MathSciNetzbMATHCrossRefGoogle Scholar
  14. 14.
    Kanterman, R. Y., T. M. Vesely, T. K. Pilgram, B. W. Guy, D. W. Windus, and D. Picus. Dialysis access grafts: anatomic location of venous stenosis and results of angioplasty. Radiology 195(1):135–139, 1995.Google Scholar
  15. 15.
    Kharboutly, Z., V. Deplano, E. Bertrand, and C. Legallais. Numerical and experimental study of blood flow through a patient-specific arteriovenous fistula used for hemodialysis. Med. Eng. Phys. 32(2):111–118, 2010.CrossRefGoogle Scholar
  16. 16.
    Kharboutly, Z., M. Fenech, J. M. Treutenaere, I. Claude, and C. Legallais. Investigations into the relationship between hemodynamics and vascular alterations in an established arteriovenous fistula. Med. Eng. Phys. 29(9):999–1007, 2007.CrossRefGoogle Scholar
  17. 17.
    Kim, Y. H., K. B. Chandran, T. J. Bower, and J. D. Corson. Flow dynamics across end-to-end vascular bypass graft anastomoses. Ann. Biomed. Eng. 21(4):311–320, 1993.CrossRefGoogle Scholar
  18. 18.
    Koch, T. M., B. D. Reddy, P. Zilla, and T. Franz. Aortic valve leaflet mechanical properties facilitate diastolic valve function. Comput. Methods Biomech. Biomed. Eng. 13(2):225–234, 2010.CrossRefGoogle Scholar
  19. 19.
    Kohler, T., T. Kirkman, and A. Clowes. The effect of rigid external support on vein graft adaptation to the arterial circulation. J. Vasc. Surg. 9(2):277–285, 1989.Google Scholar
  20. 20.
    Kundu, P. K., and I. M. Cohen. Fluid Mechanics (4th ed.). Amsterdam: Academic Press, 2008.Google Scholar
  21. 21.
    Lee, S. W., P. F. Fischer, F. Loth, T. J. Royston, J. K. Grogan, and H. S. Bassiouny. Flow-induced vein-wall vibration in an arteriovenous graft. J Fluids Struct. 20(6):837–852, 2005.CrossRefGoogle Scholar
  22. 22.
    Lee, S.-W., D. S. Smith, F. Loth, P. F. Fischer, and H. S. Bassiouny. Importance of flow division on transition to turbulence within an arteriovenous graft. J. Biomech. 40(5):981–992, 2007.CrossRefGoogle Scholar
  23. 23.
    Li, X.-M., and S. Rittgers. Computational simulation of biomechanics in e-PTFE and venous miller’s cuffs: implications for intimal hyperplasia. J. Med. Eng. Technol. 29(4):187–196, 2005.CrossRefGoogle Scholar
  24. 24.
    Li, L., C. M. Terry, Y. T. Shiu, and A. K. Cheung. Neointimal hyperplasia associated with synthetic hemodialysis grafts. Kidney Int. 74(10):1247–1261, 2008.CrossRefGoogle Scholar
  25. 25.
    Longest, P. W., and C. Kleinstreuer. Numerical simulation of wall shear stress conditions and platelet localization in realistic end-to-side arterial anastomoses. J. Biomech. Eng. 125(5):671–681, 2003.CrossRefGoogle Scholar
  26. 26.
    Loth, F., P. F. Fischer, N. Arslan, C. D. Bertram, S. E. Lee, T. J. Royston, et al. Transitional flow at the venous anastomosis of an arteriovenous graft: potential activation of the erk1/2 mechanotransduction pathway. J. Biomech. Eng. 125(1):49–61, 2003.CrossRefGoogle Scholar
  27. 27.
    Malik, J., V. Tuka, and V. Tesar. Local hemodynamics of the vascular access for hemodialysis. Kidney Blood Press Res. 32(1):59–66, 2009.CrossRefGoogle Scholar
  28. 28.
    Martinez, R., C. Fierro, P. Shireman, and H.-C. Han. Mechanical buckling of veins under internal pressure. Ann. Biomed. Eng. 38(4):1345–1353, 2010.CrossRefGoogle Scholar
  29. 29.
    Mitrovic, I. Cardiovascular disorders: vascular disease. Chapter 11. In: Pathophysiology of Disease: An Introduction to Clinical Medicine, 6th ed., edited by S. J. McPhee and G. D. Hammer. McGraw-Hill, 2010.Google Scholar
  30. 30.
    Morinaga, K., H. Eguchi, T. Miyazaki, K. Okadome, and K. Sugimachi. Development and regression of intimal thickening of arterially transplanted autologous vein grafts in dogs. J. Vasc. Surg. 5(5):719–730, 1987.Google Scholar
  31. 31.
    O’Callaghan, S., M. Walsh, and T. McGloughlin. Numerical modelling of Newtonian and non-newtonian representation of blood in a distal end-to-side vascular bypass graft anastomosis. Med. Eng. Phys. 28(1):70–74, 2006.CrossRefGoogle Scholar
  32. 32.
    Ogden, R. W. Large deformation isotropic elasticity—on the correlation of theory and experiment for incompressible rubberlike solids. Proc. R. Soc. Lond. Math. Phys. Sci. 326(1567):565–584, 1972.zbMATHCrossRefGoogle Scholar
  33. 33.
    Politis, A. K., G. P. Stavropoulos, M. N. Christolis, F. G. Panagopoulos, N. S. Vlachos, and N. C. Markatos. Numerical modeling of simulated blood flow in idealized composite arterial coronary grafts: steady state simulations. J. Biomech. 40(5):1125–1136, 2007.CrossRefGoogle Scholar
  34. 34.
    Porter, K. E., S. Nydahl, P. Dunlop, K. Varty, A. J. Thrush, and N. J. London. The development of an in vitro flow model of human saphenous vein graft intimal hyperplasia. Cardiovasc. Res. 31(4):607–614, 1996.Google Scholar
  35. 35.
    Rhoades, R. A., and D. R. Bell. Medical Physiology: Principles for Clinical Medicine (3rd ed.). Baltimore: Lippincott Williams and Wilkins, 2009.Google Scholar
  36. 36.
    Schiller, N. K., T. Franz, N. S. Weerasekara, P. Zilla, and B. D. Reddy. A simple fluid–structure coupling algorithm for the study of the anastomotic mechanics of vascular grafts. Comput. Methods Biomech. Biomed. Eng. 13(6):773–781, 2010.CrossRefGoogle Scholar
  37. 37.
    Schwartz, L. B., M. K. O’Donohoe, C. M. Purut, E. M. Mikat, P. O. Hagen, and R. L. McCann. Myointimal thickening in experimental vein grafts is dependent on wall tension. J. Vasc. Surg. 15(1):176–186, 1992.CrossRefGoogle Scholar
  38. 38.
    Su, C. M., D. Lee, R. Tran-Son-Tay, and W. Shyy. Fluid flow structure in arterial bypass anastomosis. J. Biomech. Eng. 127(4):611–618, 2005.CrossRefGoogle Scholar
  39. 39.
    Van Doormaal, J. P., and G. D. Raithby. Enhancements of the simple method for predicting incompressible fluid flows. Numer. Heat Transfer 7(2):147–163, 1984.zbMATHCrossRefGoogle Scholar
  40. 40.
    Van Tricht, I., D. De Wachter, J. Tordoir, and P. Verdonck. Hemodynamics and complications encountered with arteriovenous fistulas and grafts as vascular access for hemodialysis: a review. Ann. Biomed. Eng. 33(9):1142–1157, 2005.CrossRefGoogle Scholar
  41. 41.
    Van Tricht, I., D. De Wachter, J. Tordoir, and P. Verdonck. Comparison of the hemodynamics in 6 mm and 4–7 mm hemodialysis grafts by means of CFD. J. Biomech. 39(2):226–236, 2006.CrossRefGoogle Scholar
  42. 42.
    Vazquez, M. A. Vascular access for dialysis: recent lessons and new insights. Curr. Opin. Nephrol. Hypertens. 18(2):116–121, 2009.CrossRefGoogle Scholar
  43. 43.
    Winsor, T., and G. E. Burch. Use of the phlebomanometer: normal venous pressure values and a study of certain clinical aspects of venous hypertension in man. Am. Heart J. 31(4):387–406, 1946.CrossRefGoogle Scholar
  44. 44.
    Zilla, P., M. Wolf, N. Rafiee, L. Moodley, D. Bezuidenhout, M. Black, et al. Utilization of shape memory in external vein-graft meshes allows extreme diameter constriction for suppressing intimal hyperplasia: a non-human primate study. J. Vasc. Surg. 49(6):1532–1542, 2009.CrossRefGoogle Scholar
  45. 45.
    Zwolak, R., M. Adams, and A. Clowes. Kinetics of vein graft hyperplasia: association with tangential stress. J. Vasc. Surg. 5(1):126–136, 1987.Google Scholar

Copyright information

© Biomedical Engineering Society 2011

Authors and Affiliations

  • M. N. Ngoepe
    • 1
  • B. D. Reddy
    • 1
  • D. Kahn
    • 2
  • C. Meyer
    • 1
  • P. Zilla
    • 3
  • T. Franz
    • 1
    • 3
    • 4
    Email author
  1. 1.Centre for Research in Computational and Applied MechanicsUniversity of Cape TownRondeboschSouth Africa
  2. 2.Transplant Unit & Division of General SurgeryUniversity of Cape TownObservatorySouth Africa
  3. 3.Chris Barnard Division of Cardiothoracic SurgeryUniversity of Cape TownObservatorySouth Africa
  4. 4.Cardiovascular Research Unit, Faculty of Health SciencesUniversity of Cape TownObservatorySouth Africa

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