Valvular obstruction of blood flow through saphenous veins.

To measure effects of vein valves upon blood flow through venous bypass conduits, 15 human saphenous veins (mean length 40.6 cm, 5.3 valves/vein) were perfused with normal saline at constant pressure (100 mm Hg). Flow through vein was measured before and after valve bisection. Vein valves were bisected using Leather's techniques. After valve bisection, flow in antegrade and retrograde directions was measured in seven veins. These data were analyzed using paired t tests. Antegrade flow through seven veins with intact valves averaged 317.1 cc/min. With valve bisection this increased significantly (P less than 0.001) to 474.3 cc/min. Retrograde flow through veins with valves bisected increased significantly (P less than 0.0001) to 428.3 cc/min. Eleven veins (mean length 42.2 cm, 5.6 valves/vein) perfused simulated capillary beds with banked blood using pulsatile flow (mean pressure 92 mm Hg). Flow, again, was measured before and after valve bisection. Data were analyzed using the paired t test. Antegrade flow increased from 124.4 cc/min in veins with valves intact to 142.5 cc/min once valves were bisected (P = 0.02). These data demonstrate that saphenous vein valves cause significant obstruction to blood flow under conditions similar to those in the arterial system. Bisection of vein valves significantly increases flow through vein. Improved patency of vein grafts using valve bisection techniques may be explained by increased blood flow alone.