Hemodynamic coupling of a pair of venous valves.

BACKGROUND In vivo studies have shown that valves in veins are paired in an orthogonal configuration. The aim of this study is to characterize the flow interaction of paired valves under controlled in vitro bench conditions. METHODS A bench top in vitro experiment was set up at physiological flow conditions to simulate the flow inside a venous valve. Two bicuspid bioprosthetic valves paired in 0° and 90° orientations were tested in a 12-mm-diameter tube, and the two-dimensional velocity fields around the valve were measured by particle image velocimetry. The distance between the two valves was varied from 3 to 5 cm, and the corresponding velocities and vorticities were determined. RESULTS Velocity field shows the flow exit from the orthogonal valve-pairing configurations forced the main jet stream to turn to the outer region of the tube. Flow patterns between the valves show significantly less stagnation region from the 90° valve pairing over a 0° valve pairing case. The variation in valves distance shows that the coupling effect of the two valves extends to a range beyond four times of the tube diameter, albeit the ability to alter the flow decreases at larger distances. CONCLUSIONS The findings suggest that the 90° valve pairing configuration regulates the flow between the valves, and the separation distance affects the hemodynamic efficiency of the two valves by reducing the total reverse flow volume.