FLOW WAVE-FORM EFFECTS ON END-TO-SIDE ANASTOMOTIC FLOW PATTERNS

Purpose: Restenosis due to distal anastomotic intimal hyperplasia, a l eading cause of arterial bypass graft failure, is thought to be promot ed by hemodynamic effects, specifically 'abnormal' wall shear stress p atterns. The purpose of this study was to quantify the effects of flow waveform on peri-anastomotic flow and wall shear stress patterns. Met hods: Blood flow and wall shear stress patterns were numerically compu ted in a representative three-dimensional anastomosis using femoral, i liac and coronary flow waveforms suitable for humans at rest. Numerica l results were validated against experimental data. Results: Peri-anas tomotic wall shear stress patterns were influenced by a complex interp lay between secondary flow effects and unsteadiness. Peripheral flow w aveforms (iliac, femoral) produced large temporal and spatial wall she ar stress gradients on the host artery bed. In comparison, the coronar y flow waveform produced normalized bed wall shear stress gradients th at were a factor of 2-3 less than for the peripheral waveforms, even t hough average bed wall shear stress magnitudes were similar for the tw o waveforms. Conclusions: If anastomotic intimal hyperplasia is promot ed by large spatial and/or temporal gradients of wall shear stress, as has been proposed, this study predicts that there will be markedly le ss intimal hyperplasia on the host artery bed of coronary bypass graft s than for peripheral bypass grafts. This information, in conjunction with a comparative histopathologic study of intimal hyperplasia distri bution, could help determine specific wall shear stress factors promot ing intimal hyperplasia. (C) 1998 Elsevier Science Ltd. All rights res erved.