Hemodynamic parameters of end to side anastomosis- experimental study

Objectives: Large number of prosthetic grafts is implanted worldwide, however, up to 50% of them fail by the end of tenth year. The principal cause of graft failure is a stenosis due to intimal hyperplasia. There exists well-known correlation between vessel wall biology and local flow pattern, with wall shear stress (WSS) being one of the most significant flow features.
Methods: Hemodynamic parameters of end to side anastomosis were investigated in several models with different connection angles (20°, 30°, 45° and 60°) at steady conditions experimentally and numerically. The models were made from plexiglass. 60% solution of sodium-iodine was used as a working fluid. The flow patterns were obtained from visualization. The flow fields in symmetry plain of model were measured by the Particle Image Velocimetry method. The numerical models were derived from experimental models. 3D flow fields were obtained from numerical solutions. Experimental and numerical results were compared.
Results: WSS values for anastomosis of various connection angles were related to baseline WSS of laminar flow in direct tube. For angles of 20°, 30°, 45°, 60° we found increase of baseline WSS of 130%, 200%, 250%, 300% respectively.
Conclusion: The most suitable hemodynamics in the end to side anastomosis is not in angle of 45° as generally recommended, but of 25°, when nearly laminar flow and minimal WSS is present. Achieving significantly lower WSS- especially at the bottom of anastomosis and its surroundings, we expect lower incidence of intimal hyperplasia and graft failure.Supported by grant of GACR 101/05/067