A Numerical Tool for the Coupled Mechanical Assessment of Anastomoses of PTFE Arterio-venous Access Grafts
- 212 Downloads
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.
KeywordsArterio-venous access Haemodialysis Finite element method Computational fluid dynamics Fluid structure interaction
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.
- 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.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.
- 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.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
- 10.Gay, D., S. V. Hoa, and S. W. Tsai. Composite Materials: Design and Applications. Boca Raton: CRC Press, 2003.Google Scholar
- 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
- 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.Kundu, P. K., and I. M. Cohen. Fluid Mechanics (4th ed.). Amsterdam: Academic Press, 2008.Google Scholar
- 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.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
- 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.Rhoades, R. A., and D. R. Bell. Medical Physiology: Principles for Clinical Medicine (3rd ed.). Baltimore: Lippincott Williams and Wilkins, 2009.Google Scholar
- 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