Perivenous support reduces early changes in human vein grafts: Studies in whole blood perfused human vein segments

Background: Patency of vein grafts in coronary artery bypass grafting proce dures is generally less favorable than those of selected arterial grafts. H owever, vein grafts still are needed in cardiac operations. It would be des irable to find measures to improve the patency of vein grafts next to antit hrombotic regimens. Animal studies demonstrated that arterial pressure indu ces overdistention of the thin-walled vein grafts and that prevention of th is overdistention with extravascular support ameliorates the arterializatio n process with, subsequently, more favorable patency. To evaluate whether p erivenous stenting of the rather muscular human vein grafts is also benefic ial, we designed an in vitro model to study the early effects of perivenous support in human vein grafts. Methods: Seven paired segments of human vein graft obtained during coronary artery bypass grafting procedures were placed in a perfusion circuit and p erfused simultaneously with autologous whole blood, with a pressure of 60 m m Hg (nonpulsatile flow). After 30 minutes of perfusion, one segment, and a fter 60 minutes of perfusion, the remaining segment were taken for histolog ic and immunohistochemical examination. In the next experiments 7 segments of human vein graft were placed in the circuit and supported with a polytet rafluoroethylene graft to prevent overdistention with 7 unstented segments as controls. Results: In unsupported vein grafts perfused with autologous blood under a pressure of 60 mm Hg, a complete de-endothelialization was shown after I ho ur of perfusion. In the study vein grafts, with a perivenous polytetrafluor oethylene graft preventing overdistention (n = 7), the endothelium remained intact. Electron microscopic investigation of the media showed severe dama ge in the circular smooth muscle layer in the unstented group, whereas in t he stented group almost no injury was found. Conclusion: In our in vitro closed-loop model, reproducible vessel wall cha nges were observed in all human vein graft specimens studied. The beneficia l effect of perivenous support could also be established for the human grea ter saphenous vein, providing a basis for clinical application.