The long-term fate of microvenous autografts.

Changes in length, external diameter, wall thickness, and morphology were examined in 60 intraarterial vein grafts and 30 intravenous vein grafts inserted in rabbit femoral vessels. Half of each graft type was explored at 6 or 12 months, giving four experimental groups. The overall patency for intraarterial grafts at exploration was 98 percent and for intravenous grafts 100 percent. In comparison with the initial graft length resected, all four groups were significantly shorter at the completion of anastomosis, and three of the four groups also were significantly shorter at exploration. The overall loss in length of grafts varied between 26 and 30 percent of original length. External diameter was significantly increased (from between 133 and 201 percent) in all four groups at exploration compared to the normal femoral vein. Intravenous grafts maintained normal vein morphology to 12 months. Intraarterial grafts were modified by the ingrowth of smooth-muscle cells from the recipient artery, thereby creating a neointima that significantly thickened their walls at both 6 and 12 months.