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This consensus statement of Russian experts is based on a review of the relevant literature on the prevalence, diagnosis, and treatment of non-thrombotic and post-thrombotic venous obstruction, as well as management of patients after venous stenting. In the Part 1 we discussed the clinical manifestations of venous obstruction, the role of duplex ultrasound scan, CT venography, MR venography, direct venography, and intravascular ultrasound scan, as well as typical findings obtained by using these methods. The authors mentioned the functional assessment of venous outflow in healthy subjects and in those with obstruction and changes in them after the intervention. In conclusion, the authors formulated the suggestions for clinical recommendations on the diagnosis of chronic venous obstruction.

Objective Ultrasound-derived reflux volume (RV) has a low correlation with the clinical severity of chronic venous disease, as well as other hemodynamic parameters. The difference in methodology of measurements could be a possible explanation. The purpose of this study was to investigate the immediate effect of calf pump activity used in the functional methods on ultrasound-measured venous reflux parameters. Methods Patients with primary incompetence of the great saphenous vein (GSV) were recruited for the study. The diameter of the GSV, cross-sectional area in square centimeters, time average velocity in centimeters per second, and reflux duration (RT) in seconds were measured by duplex ultrasound examination. The RV flow rate (Q) in milliliters per second and RV in milliliters were calculated. The measurements were performed standing at rest before and 60 seconds after physical exercise (30 lifts to tiptoes at a frequency of 1 time per second). A decrease in the volume of reflux after exercise was calculated (DRV = RV [after] – RV [before]/RV [before] × 100%.) Automatic distal compression-decompression (120 mm Hg) was used as a provocation maneuver. Results There were 61 patients included in the study. Before exercise, reflux parameters were: RT = 4.85 seconds (interquartile range [IQR], 3.71-6.00 seconds); Q = 3.89 mL/second (IQR, 2.03-5.81 mL/second); and RV = 17.05 mL (IQR, 10.32-25.34 mL). After physical exercise, they changed to RT = 2.86 seconds (IQR, 2.14-3.33 seconds); Q = 3.61 mL/second (IQR, 2.06-6.37 mL/second); RV = 10.07 mL (IQR, 6.08-16.48 m:); and DRV = 40.9%. The changes in RT and RV values were statistically significant. DRV was inversely related to both the GSV diameter and the Venous Clinical Severity Score (r = −0.56, and r = −0.41, respectively; P Conclusions Venous reflux decreases within 1 minute after the end of the exercises. Reduction of the volume of retrograde flow occurs only owing to the shortening of reflux time, and not the flow rate, suggesting that venous reflux is influenced by exercise-induced changes in the volume of the venous reservoir.

This consensus statement of Russian experts is based on a review of the relevant literature on the prevalence, diagnosis, and treatment of non-thrombotic and post-thrombotic venous obstruction, as well as management of patients after venous stenting. In the Part 1 we discussed the clinical manifestations of venous obstruction, the role of duplex ultrasound scan, CT venography, MR venography, direct venography, and intravascular ultrasound scan, as well as typical findings obtained by using these methods. The authors mentioned the functional assessment of venous outflow in healthy subjects and in those with obstruction and changes in them after the intervention. In conclusion, the authors formulated the suggestions for clinical recommendations on the diagnosis of chronic venous obstruction.

Objective This study aimed to evaluate the impact of gravity, reservoir size, and competence of the ostial valve on venous reflux in different body positions. Methods Our study included 61 lower limbs with primary incompetence of the great saphenous vein (GSV). The diameter of the GSV and its cross-sectional area, time-averaged mean velocity (TAMEAN), and reflux time (RT) were measured with duplex ultrasound with pulsed wave Doppler. Reflux volume (RV) and reflux volume flow rate (Q) were calculated. The measurements were carried out in three body positions: horizontal, A; seated upright with stretched legs, B; and vertical, C. Distal automatic cuff compression-decompression (120 mm Hg) was used as a provocation maneuver. Results There was 100% occurrence of reflux in the patient positions B and C. Reflux was observed in 91.8% of cases in position A. All reflux parameters (TAMEAN, RT, Q, RV) and the size of the vein were significantly different in the three studied positions. The patient's height did not influence the magnitude of change in reflux parameters. All reflux parameters increased more significantly when the position changed from A to B than from B to C (TAMEAN, +103% and +37%; GSV diameter, +33% and +5%; RV, +408% and +65%, respectively). Conclusions Observed positional changes in reflux parameters suggest that gravitational forces are not a sole explanation for reflux flow in incompetent GSV. It is likely that the gravitational effect on venous flow is mediated by the changes in vein diameter and the total volume of the venous reservoir of the leg.

Objective Venous reflux is the sole pathophysiologic process in primary chronic venous disease and its progression. We hypothesize that the reflux volume (RV) increases along a great saphenous vein (GSV) in a distal direction. We aimed to compare simultaneously measured RV in the upper and lower GSV segments in a thigh. Methods Patients meeting the inclusion criteria were enrolled (70 limbs of patients with primary incompetence of the GSV) and consented to this participate in the single-center study. Patients were stratified into two groups: incompetent terminal valve and competent terminal valve. A cross-section area of the GSV was measured at the upper (CSA1, cm2) and distal (CSA2, cm2) points in a thigh. A cross-section area of each tributary that joined with the GSV between the points was measured, and their total cross-section area was calculated (CSAtrib). After a distal cuff compression-decompression maneuver, a time average mean velocity (cm/s) and reflux duration (seconds) were measured at both points simultaneously. The RV (mL) was calculated for each point (RV1 and RV2). The difference in absolute values of ΔRV (mL) and its relative changing (ΔRV, %) were calculated. Results The main result was RV increases caudally from saphenofemoral junction (SFJ) to the knee level (RV1 12.7 ± 8.4 and RV2 20.5 ± 14.0 mL; P Conclusions The RV in the GSV increases caudally from SFJ to the knee level. The observed RV was an aggregate of all GSV tributaries' flow and the flow via the SFJ if incompetent.

In physiological conditions, the cardiovascular system (CVS) is a closed circulatory system comprising a pump (the heart), a conduit system (vasculature), and a continuum media (blood) moving through the system. The heart is a major source of energy in this system. It pumps the blood through the two connected loops. From the mechanical point of view, CVS can be represented as a network of flexible tubes filled with a viscous incompressible fluid driven by a periodic energy source. The fluid dynamics are described by Navier-Stokes's equations, representing the fundamental physical principles of mass and momentum conservation. These equations allow computation of the blood velocity field and pressure depending on the forces exerted to the fluid's surface (surface forces) and to a unit portion of the fluid (mass forces). Equations of structural dynamics describe the motion of the vascular wall. The state-of-the-art models incorporate fluid and structure interaction (FSI). The blood flow in various parts of CVS has different features that must be considered during computational simulations. Elastic properties of the veins and arteries are different. The structural features of veins (valves) limit the backward flow. The geometry of venous cross-sections may be circular, elliptic, and dumbbell-shaped. It changes the flow characteristics. Blood rheology plays a significant role in venous flows. According to the mass conservation law, the work of the heart pump provides energy for the arterial flow and determines venous return to the heart atria. Venous hemodynamics comprises a lot of various processes with different physical and biological origins. Complex analysis of a patient requires computational simulations, which provide medical experts with a basis for prognosis and optimal surgical treatment. In this work, we review basic physical principles and modern mathematical models of venous hemodynamics. In conclusion, the blood flow in veins can be considered as a mechanical process. It obeys the fundamental physical principles and can be described by the well-known mathematical models of continuum mechanics. Thus, the flow characteristics can be simulated and predicted in various healthy and pathological conditions basing on the boundary conditions and material properties of the blood and veins.