The mechanism of venous valve closure in normal physiologic conditions

The purpose of this investigation was to study the mechanism of venous valve closure in physiologic conditions in situ, particularly the clarification of the role of reversed flow through the valve in the closure of the valve cusps. A second purpose was the study of temporal relations between movements of the valve cusps, changes in geometry of venous sinus, and blood flow.

Twelve healthy volunteers underwent examination with duplex ultrasound scanning. The time relationship between the flow and venous valve movements was analyzed on the basis of real time ultrasound scan records of the saphenofemoral junction. The size and shape of the common femoral vein and the proximal greater saphenous vein were measured with a planimeter.

Reverse flow below the valve was registered in only one of the 12 studied subjects. The maximum peak velocity of the reverse flow in this case was 0.8 cm/s and the duration was 0.2 seconds. The reverse flow was registered just before and just after valve closure. The mean duration of the outflow wave below the valve was 816 +/- 57 ms, which was not significantly different from the time of the valve cycle (819 +/- 55 ms; P =.864). The closure of the valve coincided with the decrease of the flow velocities. The first detectable movement of the valve cusps occurred 108 +/- 21 ms after the beginning of the flow deceleration. The mean time interval from the first cusp movement to the complete closure of the valve was 139 +/- 51 ms. Both the size and the shape of the sinus changed during the valve cycle. The size of the sinus increased as much as 127% of the baseline value (1.79 +/- 0.25 cm at baseline; 2.27 +/- 0.23 cm maximum; P =.02), and it became more spheric in shape. The changes in size and shape of the sinus coincided with the movements of the valve cusps. The first detectable change in the sinus size occurred 80 +/- 30 ms after the first detectable movement of the cusps toward closure.

Reverse flow through the valve is not necessary for the closure of the venous valve. The closure of the venous valve coincides with the decrease of the flow velocities and the ballooning of the sinus (increase of size and the curvature of the valve sinus).