Conception of the venous hemodynamics in the lower extremity

Contradictory reports on the significance of several hemodynamic phenomena, such as femoral vein incompetence and incompetent calf perforators, impede orientation in venous hemodynamics. Venous pressure difference arising between the popliteal and the posterior tibial vein during the activity of the calf muscle venous pump was reported for the first time about 50 years ago, but regrettably, this important discovery continues to be unrespected. The venous pressure difference has since been termed ambulatory pressure gradient and seems to be the key factor triggering the venous reflux in the lower limb as well as the process leading to varicose vein recurrence. On the other hand, simultaneous recordings of the mean venous pressure in the posterior tibial and long saphenous veins demonstrated that the pressure curves have been identical at rest, during ambulation, and in the recovery period, a finding typical of conjoined vessels. Bidirectional flow within calf perforators taking place both in healthy subjects and in patients with varicose veins enables a quick equilibration of pressure changes between deep and superficial veins of the lower leg. Reflux disturbing the venous hemodynamics is in various degrees dependent on the quantity of retrograde flow; abolition of reflux restores normal venous hemodynamics. Reflux in superficial veins, if large enough, may cause the most severe form of chronic venous insufficiency. Femoral vein incompetence and incompetent calf perforators per se do not produce ambulatory venous hypertension and do not cause hemodynamic disturbance. This study discusses the controversial issues, tries to define and appraise the principal hemodynamic phenomena (ambulatory venous hypertension, ambulatory pressure gradient, venous reflux, superficial and deep vein incompetence, incompetent perforators), mentions a possible relation between deep vein incompetence and varicose veins, and attempts to present, based on proved facts, a comprehensive picture of the venous hemodynamics in the lower extremity.