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J Thorac Cardiovasc Surg 2001;121:0290-0297
© 2001 The American Association for Thoracic Surgery

Surgery for Acquired Cardiovascular Disease

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

From the Department of Cardiac Surgery,^a Institute of Pathology,^b Department of Extra Corporeal Circulation,^c and Institute for Cardiovascular Research,^d "Vrije Universiteit," Amsterdam; Gaubius Laboratory,^e TNO-PG, Leiden; and the Department of Experimental Thoracic Surgery,^f University of Groningen, The Netherlands.

Received for publication April 28, 2000. Revisions requested June 14, 2000; revisions received July 25, 2000. Accepted for publication Sept 15, 2000. Address for reprints: W. Stooker, MD, Department of Cardiac Surgery L-325, University Hospital "Vrije Universiteit," PO Box 7057, 1007 MB Amsterdam, The Netherlands (E-mail: w.stooker{at}azvu.nl).

Background: Patency of vein grafts in coronary artery bypass grafting procedures is generally less favorable than those of selected arterial grafts. However, vein grafts still are needed in cardiac operations. It would be desirable to find measures to improve the patency of vein grafts next to antithrombotic regimens. Animal studies demonstrated that arterial pressure induces overdistention of the thin-walled vein grafts and that prevention of this overdistention with extravascular support ameliorates the arterialization process with, subsequently, more favorable patency. To evaluate whether perivenous stenting of the rather muscular human vein grafts is also beneficial, 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 perfused simultaneously with autologous whole blood, with a pressure of 60 mm Hg (nonpulsatile flow). After 30 minutes of perfusion, one segment, and after 60 minutes of perfusion, the remaining segment were taken for histologic and immunohistochemical examination. In the next experiments 7 segments of human vein graft were placed in the circuit and supported with a polytetrafluoroethylene 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 1 hour of perfusion. In the study vein grafts, with a perivenous polytetrafluoroethylene graft preventing overdistention (n = 7), the endothelium remained intact. Electron microscopic investigation of the media showed severe damage in the circular smooth muscle layer in the unstented group, whereas in the stented group almost no injury was found.
Conclusion: In our in vitro closed-loop model, reproducible vessel wall changes were observed in all human vein graft specimens studied. The beneficial effect of perivenous support could also be established for the human greater saphenous vein, providing a basis for clinical application.