DILATATION OF SAPHENOUS-VEIN GRAFTS BY NITRIC OXIDES

Objectives: To investigate firstly whether flow-dependent vasodilation is maintained vein grafts, and secondly whether nitric oxide donors d ilate vein grafts to improve the flow through graft stenoses. Design, materials and methods: The vasodilatation of mature patent vein grafts , in response to reactive hyperaemia and glyceryl trinitrate (GTN), ru ns assessed by the change in external diameter using duplex ultrasonog raphy. The severity (ratio of proximal systolic velocity, V1, to peak systolic velocity at the stenosis, V2, of vein graft stenoses was dete rmined by duplex ultrasonography before and after 24 h of local applic ation of GTN patches. Results: In post-occlusion hyperaemia the diamet er of patent distal vein grafts (n=7) increased to a maximum of 112+/- 1.9% of resting diameter after 2 min, p=0.026. The diameter increased further to 117+/-2.5% of the resting value 5 min after oral GTN (n=5), p=0.007. The velocity ratio, V2/V1, through graft stenoses (n=6) decr eased by 20+/-5% after application of GTN patches, principally as a re sult of reduction in V2, mean difference 0.8, p=0.15. The changes in r esponse to GTN were more evident for proximal than distal vein graft s tenoses.Conclusion: Flow-induced vasodilatation responses, which have been attributed to the endothelial release of nitric oxide, are mainta ined in patent vein grafts: the grafts dilate even further in response to GTN. The application of GTN patches close to a vein graft stenosis appears to reduce the velocity ratio through vein graft stenoses. GTN parches might be used to reduce the risk of graft occlusion when ther e is a delay between the detection and the treatment of haemodynamical ly significant graft stenoses.