Answer:
The length of vein taken has not been shown to affect patency rates. However, with longer lengths, it has been clinically shown that the chances of thrombosis and kinking are increased given low flow rates in a longer graft. Choosing a vein for acceptable diameter is important. The discrepancy between two vessels in an anastomosis should not exceed a ratio of 2:1. Larger discrepancies lead to turbulence, thrombus formation, and subsequently lower patency rate and failure. Studies in rats have demonstrated that the patency rate of vessels is not affected by interposition grafting when the vein grafts and recipient vessels are of similar diameter.