Hrev_master Veins and Lymphatics 2018; volume 7:7280 [Veins and Lymphatics 2018; 7:7280] [page 29] The superficial venous pump Konstantin Mazayshvili Surgical Department, Surgut State University, Russia Abstract The present study has revealed the rela- tionship between the cross sectional area of the great saphenous vein and the degree of tension in the superficial fascia of the thigh. We conducted an ultrasound examination with 27 patients (54 lower limbs) in both standing and walking positions. With an increase and decrease in the degree of ten- sion of the superficial fascia, the blood is pushed to the sapheno-femoral junction. Nearly 200 mm3 of blood flows in, and is pushed out of, a 100-mm great saphenous vein segment in the thigh, towards the sapheno-femoral junction during a step cycle. As a result, the active function of the fascial compartment of the great saphenous vein has been found. We have called this mechanism the superficial venous pump. Introduction The main functions of the venous sys- tem are: to return blood to the heart, and to serve as a capacitance in order to maintain the filling of the heart. Motive forces in the venous return are common knowledge in medical literature, but are limited to respira- tion and skeletal muscle contractions of the extremities. Miller et al.1 determined that phasic blood flow coincides with breath. The respi- ratory modulation of venous return from the lower limb is dependent not only on the pressures produced by the respiratory and skeletal muscle pumps, but is also critically dependent upon the capacitance and com- pliance of the venous vasculature which separates them. The compliance is the ratio of the change in volume resulting from a change in transmural distending pressure. Because venous compliance is very high at low pressures, this is one of the main factors of the pumping mechanism itself. The peripheral venous pump is able to perform its main function of moving blood to the heart by the contraction of muscles in the foot, and the compression of the plantar vein when pressure is applied to the foot.2 Ricci et al.3 considered the compression of the deep plantar arch, located between the bone arch of the foot and the plantar aponeurosis, as foot systole. Elsner et al.4 have contributed data to the research of the venous pump function, namely that the medial outflow tract from the deep plantar venous plexus is fixed by fibrous bands connected to the first metatarsophalangeal joint. In addition, they were able to deduce that passive movements in the joint lead up to a 55 percent increase in blood flow; active movements result in an increase of up to 78 percent. In 1995, Staubesand et al. investigated the so-called ankle pump. With the aid of duplex ultrasound they measured the rate of blood flow in the GSV of the lower extrem- ity during a relaxed state, as well as during active and passive movements of the ankle joint. As a result of their observations, they reached the conclusion that movements in the ankle joint significantly increase the rate of blood flow in the GSV.5 During move- ment the muscles contract, resulting in blood being pushed away from the leg veins to the popliteal vein, which rapidly increas- es blood flow. As a result of the arising pressure gradient, distal valves in the deep and communicant veins close, thus prevent- ing backflow. When the muscles in the calf are relaxed, the pressure created within the deeper veins is less than that in the superfi- cial venous system, and blood repeatedly accumulates and leaves there through perfo- rating veins and muscular branches.6 The muscles of the venous pump also participate in preventing orthostatic intolerance by enhancing the venous return.7 The muscular venous pump in each of the lower extremity segments ensures significant acceleration of blood flow in the deep veins of the lower extremities. Meanwhile, little data is avail- able concerning the relation between the pumping mechanism and the variation of superficial venous outflow in the superficial GSV. The course of the GSV in a fascial canal derived from the deep fascia of the lower extremity is described.8,9 The fascial canal is a sheath surrounding the GSV, and is con- tinuous from the thigh to the leg (Figure 1). As described, it supports the vein from the hydrostatic pressure of the blood and pre- vents its dilation.8 The malfunction of this fascial envelope of the vein, in whole or in part, may be involved in the pathogenesis or complications in the varicosities, of the GSV. Ultrasonic examination of the GSV topography demonstrates that the GSV lies between sheets of saphenous fascia that are loosely adherent to its wall (Figure 2). Figure 2 shows that there is tissue space between the GSV and the sheets of saphe- nous fascia, and that the fascia rests on a small segment of the venous wall. This study aims at identifying mechanisms of effect of the saphenous fascia on the GSV diameter and, therefore, on expelling blood from the limb. This help understanding of how the venous vessel network can opti- mize blood flow in response to various mechanical forces. Materials and Methods Our investigation was approved by the local ethics committee the National Medical and Surgical Center, Russia. This study was performed in order to determine the role of the saphenous fascial compartment in the venous outflow of the GSV. We used duplex ultrasound to analyze types of GSV location in the thigh (I-type: a single GSV in the saphenous compartment without branching; h-type: GSV in the saphenous compartment with a tributary branching out of the com- partment; S-type: GSV is not visible, but there is a tributary vein which is not in the saphenous compartment)10 and the effect of saphenous fascia on the GSV diameter. For this study, linear transducers with a frequen- cy range of 7.5-13.0 MHz, were used. A total of 54 limbs in 27 consecutive patients (3 male and 24 female) were observed. All patients were Caucasians, with a mean age of 43.0 (SD 14.8) years. The CEAP clinical class for these patients was: С0 in 3 limbs, С1 in 28 limbs, С2 in 16 limbs, С3 in 3 limbs and С4 in 4 limbs. The data was analyzed with StatSoft’s Statistica 6.0, by using a dependent t-test for physical properties. A P value of less than 0.05 was considered statistically significant for all tests. A reflux in the thigh segment was found in 15 limbs; no reflux was found in 39 limbs. Reflux defined as retrograde flow lasting for more than 0.5 s, whereas less than 0.5 s is defined as normal or no Correspondence: Konstantin Mazayshvili, Surgical Department, Surgut State University, Russia. E-mail: nmspl322@gmail.com Key words: Superficial venous pump; great saphenous vein; venous outflow. Received for publication: 31 July 2017. Revision received: 28 November 2017. Accepted for publication: 28 November 2017. This work is licensed under a Creative Commons Attribution 4.0 License (by-nc 4.0). ©Copyright K. Mazayshvili, 2018 Licensee PAGEPress, Italy Veins and Lymphatics 2018; 7:7280 doi:10.4081/vl.2018.7280 No n- co mm er cia l u se on ly Article reflux11. Patients who participated in the study were asked to imitate walking move- ments during their examinations. In the first stage, the GSV diameter was measured in the standing position, with the knee fully extended; this produced the highest degree of tension in the saphenous fascia (Figure 3). The second stage of the patient exami- nation was carried out in the standing posi- tion, with the knee flexed (imitating walk- ing movement); this produced a relaxation of the fascial compartment (Figure 4). In order to replicate a working process, we asked the patients to lift one knee up until calf and thigh forms a right angle. After that, patients lowered that leg and repeated with the other leg. The effect of the saphenous fascia on the GSV diameter was analyzed during two different phases of the step cycle. The GSV diameter was measured at four different lev- els: at the sapheno-femoral junction (Level 1); in the lower third of the thigh (Level 2); in the upper third of the calf (Level 3); in the lower third of the calf (Level 4). The GSV diameter was measured in the vertical position, transversal to vein axis. The vein capacity was calculated with a theoretically selected GSV segment of 100 mm in the middle third of the thigh. To sim- plify the model, it was assumed that in such a segment of the GSV, differences in blood vessel configurations could be ignored. The selected vein segment for our purposes was considered to be cylindrical. The cross-sec- tional area of the GSV, and the volume of blood it contained, were calculated at two phases of the step cycle: i) during maximum tension of the saphenous fascia and, conse- quently, maximum compression of the GSV; ii) during maximum relaxation of the fascial compartment, when the GSV cross section assumed the form of a circle. The tension of the fascia was not measured itself. The assessment point of the SFJ was standardized according to Coleridge-Smith et al.12 The cross-sectional area of the blood vessel was calculated utilizing the basic for- mula to determine the area of an ellipse: (1) where S is the GSV cross sectional area; а is the minimum GSV diameter; b is the maxi- mum GSV diameter. The blood volume within the selected GSV segment was calculated utilizing the formula for the volume of a cylinder: V = S ⋅ H (2) Figure 1. Anatomic relationship between the GSV and the fascial compartment. Figure 2. Ultrasonic image of the GSV and its fascial compartment. Figure 3. Patient examination in the midstance position of the step cycle. [page 30] [Veins and Lymphatics 2018; 7:7280] No n- co mm er cia l u se on ly Article [Veins and Lymphatics 2018; 7:7280] [page 31] where V is the volume of the selected GSV segment; H is the length of the selected GSV segment; S is the GSV cross sectional area. Based on the previous two results, we calculated the blood volume forced out of the selected GSV segment during the step cycle, due to compression of the GSV by the walls of the fascial compartment. The calculations were based on the following formula: DV = V1 – V2 (3) where DV is the blood volume pushed out during the step cycle; V1 is the blood vol- ume in the GSV segment during maximum relaxation of the fascial compartment; V2 is the blood volume in the GSV segment dur- ing maximum tension of the fascial com- partment. Results and Discussion The results of this study show that max- imum fascial tension is reached during the midstance position of the step cycle, which results in GSV compression. This occurs because when tense, the sheets of saphe- nous fascia shift toward each other and cause compression of the GSV (Figure 5). As compression of the fascia compart- ment takes place, blood is simultaneously pushed out of the GSV segment towards the sapheno-femoral junction (Level 1). During the heel off position of the step cycle, fas- cial tension dissipates, and the saphenous fascia tissue no longer exerts pressure on the GSV (Figure 6); this results in the GSV assuming a form resembling a circle. The relaxing fascial compartment allows blood inflow from lower leg segments. Each process is repeated during subse- quent cycles of the step cycle. Changes in the GSV lumen size, in relation to the mid- stance and heel off positions of the step cycle, are shown in Figure 7. Formula 2, as previously discussed, was used to calculate the blood volume con- tained in a 100 mm segment of a theoreti- cally selected GSV, located in the middle of the thigh. Figure 8 shows these blood vol- umes in the midstance and step off positions of the step cycle. The calculation does not include the resting superficial vein flow and its velocity. Using this data in Formula 3, as previ- ously discussed, we obtain the following result: 198.8±31.2 mm3 of blood flows in, and is pushed out of, a 100 mm GSV seg- ment in the thigh, towards the sapheno- femoral junction (Level 1) during the step cycle. As a result of this research, we have obtained data proving an active function of the GSV fascial compartment, which is the main part of the active mechanism. One of its purposes is to form, together with the GSV trunk, a venous pump, or the superfi- cial venous pump of the lower extremities. The superficial venous pump was recently described. Franceschi and Zamboni distin- guished this mechanism and its place in venous outflow from the leg.13 Gianesini et al.14 determined the flow Figure 4. Patient examination in the heel off position of the step cycle. Figure 5. The sheets of saphenous fascia shift toward each other and cause compression of the GSV. No n- co mm er cia l u se on ly Article [page 32] [Veins and Lymphatics 2018; 7:7280] velocities along the venous segments of the lower limb in 26 healthy volunteers. The peak systolic velocity, average time velocity and diameter of the saphenous system were obtained. The investigation provides evi- dences of the superficial venous pump as the active mechanism of outflow with the Venturi effect as a potential factor in the flow aspiration from the superficial to the deeper veins. There was no difference in the results between the group patients with GSV reflux and does without. Different risks of its vari- cose transformation can be assumed depending on the types of GSV location in the thigh (I-type, h-type, S-type). In the h- type and S-type of GSV location, in which the trunk lies extrafascially, the sheets of saphenous fascia do not exert pressure on the vein. Meanwhile results of our investi- gation did not represent differences between the patients with different GSV location in the thigh. The pumping mechanism can lower the venous pressures and reduce the volume of blood contained within the superficial veins. The tributaries play the role of reser- voirs, from which blood enters the GSV. Because of the presence of valves, blood does not return to them during the tension of the saphenous fascia. However, when the valves in the tributaries are incompetent, at the time of compression of GSV in the fas- cial compartment the blood may overfill them. This can lead to their permanent over- stretch and varicose transformation. The h and s anatomical types of GSV location in the thigh also could impair this powerful pump and thus worsen venous return, caus- ing the development of varicose transfor- mation. The main limitations of the present study are represented by the exclusive focus on the mechanic aspects of venous return. Although this is the main hemodynamic component, the study does not take into account the effects of the vasoactive agents on the saphenous wall as well as the role of the inflammatory cascade on the veins and the surrounding tissues, including the super- ficial fascia.15-18 Figure 6. The saphenous fascia tissue no longer exerts pressure on the GSV this results in the GSV assuming a form resembling a circle. Figure 7. Changes in GSV lumen size in relation to measured positions of the step cycle. Positions of the step cycle: Stage 1 = midstance; Stage 2 = step off. Figure 8. Blood volumes in a theoretically selected GSV segment. Stage 1 = midstance; Stage 2 = step off. No n- co mm er cia l u se on ly Article [Veins and Lymphatics 2018; 7:7280] [page 33] Conclusions The conducted research has revealed an active function of the GSV fascial compart- ment in causing blood outflow. With the alternating tension and relaxation of the fas- cial compartment surrounding the GSV, blood is pushed out of the vein segment towards the sapheno-femoral junction, and then filled again, by a two-step process: i) when the saphenous fascia becomes tense, venous walls shift towards each other in the long segment, which leads to a rapid increase in blood flow; ii) when the sheets of saphenous fascia are relaxed, the vein, due to its elasticity, becomes round in its cross section. A concurrent increase in vein volume causes suction of blood to this seg- ment. One-way centripetal blood flow is provided by valves. We have called this mechanism the superficial venous pump. It plays the role of a peripheral superficial heart, which combined with venous valves serve to avoid gravitational reflux during fascial diastole. Finally this is a further argument in favor of saphenous vein spar- ing strategies.13,16,19 We are aware that the study was some- what biased. A wider range of patients might have provided a more precise under- standing of our research. Nevertheless, we hope that it will help in the further study of venous outflow from superficial structures. References 1. Miller JD, Pegelow DF, Jacques JA, Dempsey JA. Skeletal muscle pump versus respiratory muscle pump: modu- lation of venous return from the loco- motor limb in humans. J Physiol 2005; 563:925-43. 2. Uhl JF, Gillot C. Anatomy of the foot venous pump: physiology and influence on chronic venous disease. Phlebology 2012;5:219-30. 3. Ricci S, Moro L, Incalzi AR. The foot venous system: anatomy, physiology and relevance to clinical practice. Dermatol Surg 2014;40:225-33. 4. Elsner A, Schiffer G, Jubel A, et al. The venous pump of the first metatarsopha- langeal joint: clinical implications. Foot Ankle Int 2007;8:902-9. 5. Staubesand J, Heisterkamp T, Stege H. 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