On the Conditions for the Venous Return From the Lower Leg in Healthy Subjects and in Patients With Chronic Venous Insufficiency

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Abstract
By the action of the normal venous pump, the blood volume in the veins of the lower leg decreases. The systolic and diastolic pressures in the veins of the ankle region fall as the veins are emptied. The rich network of muscular veins in the calf seems to act as a heart-chamber that receives the blood from the lower leg during diastole and from which the blood is expelled towards the thigh during systole with a force comparable to the systolic pressure in the heart and great arteries. The end result of this action is a fall in pressure in all veins of the lower leg to new and lower levels, favorable for the flow from the capillaries and for the absorption of interstitial fluids. The low pressure is maintained for some time after the end of all muscular activity. The action of the venous pump in patients with incompetence of the valves of the subcutaneous, deep, and communicating veins can bring the pressure in all veins of the lower leg down from values near the calculated hydrostatic pressure to a pressure level that is about as low as that found in the normal extremity after muscular exercise. It cannot, however, maintain a low pressure after muscular exercise for more than a few sec. The flow from the capillaries in the upright position towards the veins will therefore meet a greater resistance than in normal cases. The rapid rise in pressure after muscular exercise seems to be due to an almost instantaneous filling of the deep and superficial veins, during diastole. The blood which leaves the deep veins of the lower leg during systole is quickly replaced by a flow from the superficial varicosities through the wide incompetent communicating veins and, in the patients with deep valvular insufficiency, by a back flow from the veins of the thigh. What is lost from the lower parts of the saphenous veins during diastole is replaced by a back flow from above through the incompetent saphenofemoral junction. The maintained high blood volume in all the veins of the lower leg prevents the fall in systolic pressure in the saphenous veins and in the lower posterior tibial vein that is observed in healthy subjects during rhythmic muscular exercise. Common for both groups of patients was the presence of large, incompetent ankle perforators, which allowed the constantly high systolic pressure in the lower posterior tibial vein to be freely transmitted to the subcutaneous veins of the ulcer region.