THE EFFECT OF WALL DISTENSIBILITY ON FLOW IN A 2-DIMENSIONAL END-TO-SIDE ANASTOMOSIS

The development of intimal hyperplasia at the distal anastomosis is th e major cause of long-term bypass graft failure. To evaluate the suspe cted role of hemodynamic factors in the pathogenesis of distal intimal hyperplasia, an understanding of anastomotic flow patterns is essenti al. Due to the complexity of arterial flow, model studies typically ma ke simplifying assumptions, such as treating the artery and graft wall s as rigid. In the present study this restriction is relaxed to consid er the effects of vessel wall distensibility on anastomotic flow patte rns. Flow was simulated in an idealized 2-D distensible end-to-side an astomosis model, using parameters appropriate for the distal circulati on and assuming a purely elastic artery wall. A novel numerical approa ch was developed in which the wall velocities are solved simulataneous ly with the fluid and pressure fields, while the wall displacements ar e treated via an iterative update. Both the rigid and distensible case s indicated the presence of elevated temporal variations and low avera ge magnitudes of wall shear stress at sites known to be susceptible to the development of intimal hyperplasia. At these same sites, large sp atial gradients of wall shear stress were also noted. Comparison betwe en distensible- walled and corresponding rigid-walled simulations sho wed moderate changes in wall shear stress at isolated locations, prima rily the bed, toe and heel. For example, in the case of a distensible geometry and a physiologic pressure waveform, the heel experienced a 3 8 percent increase in cycle-averaged shear stress, with a correspondin g 15 percent reduction in shear stress variability, both relative to t he corresponding values in the rigid-walled case. However, other than at these isolated locations, only minor changes in overall wall shear stress patterns were observed. While the physiological implications of such changes in wall shear stress are not known, it is suspected that the effects of wall distensibility are less pronounced than those bro ught about by changes in arterial geometry and flow conditions.