Acceleration of impairment of endothelium-dependent responses under poor runoff conditions in canine autogenous vein grafts

Objectives: To assess the effects of changes in shear stress on endothelium-dependent responses. Materials and methods: Autologous vein grafts were implanted in poor or normal distal runoff limbs of 10 mongrel dogs. Six weeks after grafting the vein grafts were removed, cut into rings, and suspended in organ chambers for isometric tension recording. Results: The average value of intimal thickening teas 110.7 +/- 45.2 mu m in poor runoff limbs and 65.5 +/- 27.9 mu m in central limbs, respectively. There was a significant difference between the two groups. Acetylcholine caused comparable endothelium-independent contractions in both groups. In the control group, adenosine diphosphate, thrombin and A23187 caused endothelium-dependent relaxations. In the poor runoff group, the endothelium-dependent relaxations caused by adenosine diphosphate and thrombin were impaired, while A23187 caused comparable endothelium-dependent relaxations. Direct relaxations in response to sodium nitroprusside were comparable between the two groups. Conclusions: This dysfunction of the endothelium under conditions of abnormal flow mall accelerate intimal thickening of the vein graft and result in late graft failure.