3. Projects

Visualization of Fluid Dynamics in Vascular Prostheses and Anastomoses

Restenosis and occlusion of bypass grafts are one of the most important problems in vascular surgery. This restenosis is caused by neointimal growth (hyperplasia) and especially pronounced within artificial graft material and their connections to the original arteries. Numerous surgical and biomaterial approaches have been done to improve the outcome, but even the key factors promoting hyperplasia have not been undoubtfully identified. Beside material effects, disturbed flow patterns and changes in wall compliance and stress have been considered.

To study these problems, we have combined in-vivo experimental studies with flow visualization and numerical modelling (by Prof. Perktold, Graz). In one study with wrapped natural grafts we could show, that changes in vascular elasticity play a major role, compared to geometry influences (Trubel 1995). In a just finished study we compared different surgical techniques (Miller-Cuff, Linton patch, Taylor and conventional anastomoses) and found an explenation for the reported superior performance of the Miller anastomosis technique.

Schematic of the Miller cuff type anastomosis technique

3-dimensional calculation of the axial flow field component within the miller cuff (Calculated based on our cast models by Prof. Perktold, TU Graz, Austria)

Flow field during systole in the
Miller type Anastomosis

Cast of a Miller-Cuff anastomosis for grid digitalization

Acrylic model of an anastomosis cast, prepared for visualisation

Contact Persons:	Heinrich Schima
	Leopold Huber
	Wolfgang Trubel, MD
	Martin Czerny, MD

Cooperating Institutions:

Dept. of Vascular Surgery, Univ. of Vienna, Austria
Dept. of Cardiology, Univ. of Vienna, Austria
Dept. of Pathology, Univ. of Vienna, Austria Dept. of Mathematics, Techn. Univ. of Graz, Styria
Dept. of Biomedical Engineering, Univ. of Tel Aviv, Israel Dept. of Fluid Mechanics, Techn Univ. Athens, Greece

References:

Trubel W, Schima H, Czerny M, Perktold K, Schimek MG, Polterauer P.
Experimental comparison of four methods of end-to-side anastomosis with expanded polytetrafluoroethylene.
Br J Surg. 2004 Feb;91(2):159-67.

Schima H, Lackner B, Prosi M, Perktold K.
Numerical simulation of carotid hemodynamics in patients with rotary blood pump cardiac assist.
Int J Artif Organs. 2003 Feb;26(2):152-60.

Perktold K, Leuprecht A, Prosi M, Berk T, Czerny M, Trubel W, Schima H.
Fluid dynamics, wall mechanics, and oxygen transfer in peripheral bypass anastomoses.
Ann Biomed Eng. 2002 Apr;30(4):447-60.

Leuprecht A, Perktold K, Prosi M, Berk T, Trubel W, Schima H.
Numerical study of hemodynamics and wall mechanics in distal end-to-side anastomoses of bypass grafts.
J Biomech. 2002 Feb;35(2):225-36.

N. Noori, R. Scherer, K. Perktold, M. Czerny, G. Karner, W. Trubel, P. Polterauer, and H. Schima. Blood flow in distal end-to-side anastomoses with PTFE and a venous patch: Results of an in vitro flow visualisation study. Eur J Vasc Endovasc Surg 18:191-200, 1999.

K. Perktold, M. Hofer, G. Karner, W. Trubel, and W. Schima. Computer simulation of vascular fluid dynamics and mass transport: Optimal design of arterial bypass anastomoses. ECCOMAS:1-6, Wiley Publisher, 1998.

M. Hofer, G. Rappitsch, K. Perktold, W. Trubel, and H. Schima. Numerical study of wall mechanics and fluid dynamics in end-to-side anastomoses and correlation to intimal hyperplasia. J.Biomechanics 29:1297-1308, 1996.

W. Trubel, A. Moritz, H. Schima, F. Raderer, R. Scherer, R. Ullrich, U. Losert, and P. Polterauer.
Compliance and formation of distal anastomotic intimal hyperplasia in Dacron mesh tube constricted veins used arterial bypass grafts. ASAIO Journal 40/3:273-278, 1994.