Preserved endothelial function and morphology in canine arterial grafts under conditions of poor distal runoff

Late graft failure is still a significant problem particularly in vessels with poor runoff. In the present study, we examined whether poor runoff conditions contributed to either functional or morphological changes in experimental canine autogenous arterial grafts. Four weeks after grafting, isometric tension studies were performed on rings obtained from femoral arterial grafts with poor runoff and the findings were compared to rings from grafts with normal runoff. The flow rate and τ variation (wall shear stress variation) in the limbs with poor runoff (18.5 ± 4.2 ml/min, 52.9 ± 7.0 dyne/cm²) were significantly lower than those of the control limb (66.4 ± 9.2 ml/min, 201.1 ± 9.6 dyne/cm²). Acetylcholine (ACh), adenosine 5'- diphosphate (ADP), and A23187 (calcium ionophore) caused comparable endothelium-dependent relaxations in the two groups. Smooth muscle relaxation in response to sodium nitroprusside was also comparable in the two groups. No apparent intimal thickening of the arterial grafts was observed in the canine arterial grafts with normal or poor runoff. Scanning electron microscopy demonstrated mild endothelial cell damage in implanted autogenous arterial grafts. At 7 to 14 days after grafting, the endothelial cell layer in both groups of grafts appeared to be normal. These results are markedly different from our previous findings with vein grafts in which pronounced intimal thickening was associated with an impairment of the endothelium-dependent responses under conditions of poor runoff. Based on these findings, the intact endothelial function and the absence of intimal thickening under conditions of poor runoff may thus explain the improved patency of autogenous arterial grafts compared to the vein grafts in aortocoronary revascularization.