Mechanism of venous valve closure and role of the valve in circulation: a new concept

Abstract

The valve cusps undergo the four phases constituting the valve cycle. The local hemodynamic events, such as flow separation and reattachment, and vortical flow in the sinus play important roles in the valve operation. In addition to prevention of retrograde flow, the valve acts as a venous flow modulator. The vortical stream behind the valve cusps participates in the operation of the valve, and prevents stasis inside the valve pocket. The central jet possibly facilitates outflow.

Computational Phlebology: The Simulation of a Vein Valve

“…where the summation is over all nearest- [10] and next-nearest- [11] neighbouring nodes of a simple square lattice. The difference between the position of node i and the neighbouring node j is r ij , and the equilibrium distance is r 0 ij .…”

“…The form chosen here simply allows the sinus region to expand as observed experimentally. In particular, the sinus region is considered to be between x = 4 cm and x = 6 cm (a sinus depth of 2 cm) and the force constant between x = 2 cm and x = 6 cm is chosen in order to qualitatively mimic experimental observations [11] …”

“…This is no longer thought to be the case, and the vein valves are now thought to respond to pressure gradients [9]. Significant insights into the physics of vein valves have been obtained through recent developments in ultrasound technology by Lurie et al [10][11][12]. They have been capable of visualising in situ both the vein valve cusps and the blood flow through the valve.…”

“…They have been capable of visualising in situ both the vein valve cusps and the blood flow through the valve. This led to the characterisation of four phases to the valve cycle: opening, equilibrium, closing and closed [12]. Interesting dynamic behaviour was observed during the equilibrium phase (when the valve is fully opened).…”

“…Interesting dynamic behaviour was observed during the equilibrium phase (when the valve is fully opened). The leading edges of the valve cusps were observed to flutter as the blood streamed past (much as a flag flutters in the wind) and vortical flow was observed behind the valve cusps in the valve sinuses [11]. It is this complex interaction between venous hemodynamics and valve solid mechanics that make modelling vein valves challenging.…”