Venous pressure gradients in the lower extremity and the hemodynamic consequences.
ABSTRACT Pressure differences play an important role in the hemodynamics of both arterial and venous circulation. Venous ambulatory pressure gradient of about 35 mm Hg arises during the activity of the calf muscle venous pump between the veins in the thigh and the lower leg; this is the initiator launching venous reflux in varicose vein patients. The hemodynamic consequence of venous reflux is interference with the physiological decrease in venous pressure in the lower leg and foot and the occurrence of ambulatory venous hypertension, the degree of which depends on the magnitude of refluxing blood. Pressure difference occurring between the femoral vein and the remnant of great saphenous vein after high ligation or crossectomy during calf pump activity may be the activator of the process leading to the building of new venous communicating channels, the consequence of which is recurrent reflux. Neovascularization is apparently triggered by this hemodynamic factor, not by the surgical procedure itself, because neovascularization does not occur after harvesting of the great saphenous vein in the groin in people without varicose veins. Venous pressure potentials developing in the lower leg during the calf pump activity force the blood to flow from deep into superficial veins during muscle contraction and in the opposite direction during muscle relaxation. An untoward event caused by venous pressure difference is presented - spontaneous bypassing of a competent valve in the saphenous remnant after crossectomy, which converted a favourable hemodynamic situation into a harmful one. Possible explanation of this undesirable event is offered.