A numerical study of blood flow patterns in anatomically realistic and simplified end-to-side anastomoses

Purpose: Recently, some numerical and experimental studies of blood flow in large arteries have attempted to accurately replicate in vivo arterial geo metries, while others have utilized simplified models. The objective of thi s study was to determine how much an anatomically realistic geometry can be simplified without the loss of significant hemodynamic information. Method: A human femoral-popliteal bypass graft was used to reconstruct an a natomically faithful finite element model of an end-to-side anastomosis. No nideal geometric features of the model were removed in sequential steps to produce a series of successively simplified models. Blood flow patterns wer e numerically computed for each geometry, and the flow and wall shear stres s fields were analyzed to determine the significance of each level of geome tric simplification. Results: The removal of small local surface features and out-of-plane curva ture did not significantly change the flow and wall shear stress distributi ons in the end-to-side anastomosis. Local changes in arterial caliber playe d a more significant role, depending upon the location and extent of the ch ange. The graft-to-host artery! diameter ratio was found to be a strong det erminant of wall shear stress patterns in regions that are typically associ ated with disease processes. Conclusions: For the specific case of an end-to-side anastomosis, simplifie d models provide sufficient information for comparing hemodynamics with qua litative or averaged disease locations, provided the primary" geometric fea tures are well replicated The ratio of the graft-to-host artery diameter wa s shown to be the most important geometric feature. ''Secondary" geometric features such as local arterial caliber changes, out-of-plane curvature, an d small-scale surface topology are less important determinants of the wall shear stress patterns. However, if patient-specific disease information is available for the same arterial geometry, accurate replication of both prim ary and secondary geometric features is likely required.