A new outside stent – does it prevent vein graft intimal proliferation?

Objective: The saphenous vein subjected to arterial pressure stretches to its elastic limits and constitutes intimal hyperplasia. Sheathing of the vein graft with pressure-resistant tubing might prolong vein graft patency. Methods: Twenty-one sheep received radial vein grafts or hybrid grafts composed of radial vein, collagen fibrin glue and highly flexible torlen/dacron mesh tubing transplanted into the carotid artery position. Veins were examined with the use of light and electron microscopy. Proliferating cell antigen (Ki-67) stains served as markers of proliferation. Results: The mean wall thickness of both intimal and medial layers was evaluated. The mean intimal wall thickness was 19 ^ 11 mm in hybrid grafts vs. 24 ^ 7 mm in unsheathed grafts (P , 0:001); 22 ^ 6 vs. 26 ^ 10 m m( P , 0:001); 23 ^ 8 vs. 52 ^ 15 mm (P , 0:001); 37 ^ 21 vs. 90 ^ 31 m m( P , 0:001); 57 ^ 31 vs. 104 ^ 28 m m( P , 0:001); 58 ^ 21 vs. 133 ^ 32 m m( P , 0:001); and 72 ^ 22 vs. 244 ^ 100 m m( P , 0:001) after respectively 5 days, 9 days, 4 weeks, 6 weeks, 8 weeks, 10 weeks and 12 weeks from implantation. Electronic microscope examination of hybrid grafts revealed a smooth endothelial layer with intact nuclei and an intima composed of layers of collagen and muscle fibers. In unsheathed grafts endothelial edema and nuclear destruction were observed. Conclusions: The external vein graft support with mesh tubing reduces intimal and medial layer thickening and cell proliferation in composite vein grafts transplanted in the arterial position. q 2002 Elsevier Science B.V. All rights reserved.