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 microm in hybrid grafts vs. 24+/-7 microm in unsheathed grafts (P<0.001); 22+/-6 vs. 26+/-10 microm (P<0.001); 23+/-8 vs. 52+/-15 microm (P<0.001); 37+/-21 vs. 90+/-31 microm (P<0.001); 57+/-31 vs. 104+/-28 microm (P<0.001); 58+/-21 vs. 133+/-32 microm (P<0.001); and 72+/-22 vs. 244+/-100 microm (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.