Aneurysm formation in human umbilical vein grafts used as arterial substitutes.

A series of 257 human umbilical vein grafts for femoropopliteal bypass in 203 patients, inserted between 1978 and 1984, is presented. The 6-year cumulative patency rate is 74% for above-knee and 44% for below-knee cases. Late complications, such as formation of aneurysms in the human umbilical vein graft, occurred in nine grafts, 21/2 to 6 years after implantation. This corresponds to 3.5% of the total number of 257 human umbilical vein grafts. Three of the grafts developed a second aneurysm at a later time, making a total of 12 aneurysms. The aneurysms were evident as a painful, pulsating mass. All patients were operated on, primarily by resection and interposition grafting. All aneurysms were saccular and false. Macroscopic and microscopic examination revealed that all aneurysms except four originated from a gap in the umbilical vein wall and the Dacron mesh. The adjacent graft wall had a completely normal architecture without biodegradation. The cause of the origin of the gap in the wall remains obscure. Four aneurysms were anastomotic and were located at the site of the suture line, placed at the factory, joining the two components of a composite human umbilical vein graft; these anastomotic aneurysms were caused by breaking of the Prolene suture.