Reduction of intimal and medial thickening in sheathed vein grafts

Background. Arterial pressures are described as an important factor in the development of graft degeneration and in reduced patency rate in vein bypass grafts. Sheathing of the graft with a pressure resistant mesh tubing might slow down this development. Methods. Saphenous vein grafts were implanted into the carotid arteries of five pigs in order to evaluate the influence on myointimal hyperplasia of a compliant Phynox mesh tubing (a wrought Cobalt-Chromium-Nickel-Molybdenum-Iron Alloy), which surrounded autologous vein grafts that were exposed to arterial pressure. Each pig was operated on using a sheathed vein graft (biocompound-graft, a hybrid vascular prosthesis) on one side and an untreated saphenous vein on the other. Results. After 4 weeks intimal hyperplastic changes were found in all histological sections. The wall thickness (medial and intimal layer) varied from 351 μm to 432 μm in the biocompound-graft and from 391 μm to 1196 μm in the native vein grafts (p< 0.05, n = 5). Severe myocytial and fibroblast proliferation was only found in the control grafts. Cellularity of the medial layer differed at sites of maximal cellular density and ranged from 11 to 12 cells in the biocompound-graft and from 17 to 18 cells per counting field in the native vein grafts (p< 0.05, n = 5). Conclusions. External support of vein grafts reduces intimal and medial layer proliferation. The findings of this study are in accordance with the results reported by other research groups.