Venous Hemodynamics Research Articles

Extracellular Fluid Content in the Legs of Patients with Chronic Venous Disease

This study aimed to determine the factors that affect the extracellular fluid (ECF) content in the legs of patients with chronic venous disease (CVD). Bioimpedance analysis and air plethysmography (APG) were performed in 79 patients with CVD who visited our clinic between September 2016 and March 2019. The normal right legs (N) of 14 healthy volunteers were also reviewed for comparison. The ratio of ECF resistance (Re) of the leg to that of the arm (ReL/ReA) was used to express the ECF content in the tested leg. The severity of CVD was expressed using the clinical, etiological, anatomical, and pathophysiological (CEAP) classification. The ReL/ReA decreased as the CEAP class increased (N: median; 0.81 [range 0.66-0.95], C0-1: 0.79 [0.60-0.98], C2: 0.77 [0.56-1.08], C3: 0.67 [0.57-0.85], C4: 0.64 [0.44-0.89]). Older age, female sex, and CEAP class affected the ReL/ReA, but body mass index did not. The ReL/ReA did not correlate with the parameters that were derived from APG, including the venous filling index. We found that the ECF content in legs of patients with CVD might be primarily affected by patient-related factors and CEAP class, as opposed to venous hemodynamics.

Influence of Superficial Venous Ablation on Deep Venous Dilation and Reflux in Patients With Saphenous Varicose Veins.

To investigate the influence of superficial venous ablation on deep venous dilation and reflux in patients with saphenous varicose veins, and to elucidate the association between superficial venous reflux and deep venous morphology and hemodynamics. The data of 154 patients with 223 limbs, who underwent endovenous radiofrequency ablation (RFA) of the great saphenous vein for primary varicose veins between September 2014 and March 2016 in Eniwa Midorino Clinic, were retrospectively analyzed. Overall venous hemodynamics of the leg, including functional venous volume (VV) and venous filling index (VFI), was assessed using air-plethysmography. Saphenous and deep vein reflux and diameter were evaluated with duplex scanning. Hemodynamic and morphologic changes were evaluated before and 1 month after RFA. The VV and VFI were significantly decreased in postoperative values than in preoperative values (P < .001). Limbs with deep venous reflux significantly decreased postoperatively than preoperatively (P < .001). There were significant differences in the diameter of the common femoral vein (CFV) and popliteal vein (PV) between the preoperative and postoperative values (P < .001). There were strong to moderate correlations between the VV and the diameter of the CFV or PV (CFV, r = 0.47, P < .001; PV, r = 0.35, P < .001), while there were moderate to weak correlations between the VFI and the diameter of the CFV or PV (CFV, r = 0.23, P < .001; PV, r = 0.33, P <.001). Superficial venous ablation significantly reduced deep venous dilation and reflux in patients with saphenous varicose veins. Significant correlations existed between the VV or VFI, which reflected superficial venous reflux, and the diameter of the deep veins. These findings reveal that volume overload due to superficial venous reflux is associated with deep venous morphology and hemodynamics.

Association between vein diameters, reflux characteristics, and clinical severity in patients with chronic venous insufficiency in Northwest China

ObjectiveOur goal was to summarize the relationship between vein diameters, reflux characteristics, and clinical severity in consecutive patients with chronic venous insufficiency (CVI) in Northwest China. MethodsWe evaluated 531 consecutive patients with CVI (249 women) who presented to the Department of Ultrasound of Xijing Hospital from September 2017 to July 2019. Reflux times and the mean diameters of the great saphenous, the small saphenous, and the calf perforator veins based on duplex ultrasound scans obtained in the standing position were recorded. Venous-specific assessment tools—the Heaviness, Achiness, Swelling, Throbbing, Itching (HASTI) score, the Venous Clinical Severity Score (VCSS), and the Clinical, Etiological, Anatomical, Pathophysiological (CEAP) class—were analyzed. Regression analysis was used to investigate the relationship between the clinical scores, vein diameters, and reflux times. A P value of less than .05 was considered statistically significant. ResultsWe analyzed 531 consecutive patients with 728 limbs. The mean age was 55.24 ± 11.38 years; the mean body mass index (BMI) was 24.75 ± 3.49 kg/m2. Three hundred thirty-four patients (62.9%) presented with unilateral limb findings and 197 (37.1%), with bilateral limb involvement. No significant changes were noted in age and BMI across CEAP classes (F = 2.322 and F = 3.917, respectively; P > .05 for both). Both the HASTI score (r2 = 0.8741; P < .001) and the VCSS (r2 = 0.9257; P < .001) correlated with the CEAP class. The HASTI score strongly correlated with the mean diameters of the great saphenous and small saphenous veins (r2 = 0.9252, r2 = 0.6304, respectively; P < .001 for both) similarly to VCSS (r2 = 0.9396, r2 = 0.7195, respectively; P < .001 for both). The HASTI score and VCSS correlated equally with the mean diameters of the calf perforator veins (r = 0.7773 and r = 0.7781, respectively; P < .001 for both). In those with C6, both great saphenous vein (F = 4.608; P < .001) and small saphenous vein reflux times (F = 14.97; P < .001) were significantly higher than those in C1. Both the HASTI score and VCSS strongly associated with the reflux times of the great saphenous (r2 = 0.7706 and r2 = 0.8181, respectively; P < .001 for both) and small saphenous veins (r2 = 0.6470 and r2 = 0.7865, respectively; P < .001 for both). ConclusionsThis analysis is one of the few epidemiologic studies of patients with CVI in Northwest China. Age and BMI did not correlate with CEAP class. Both the HASTI score and VCSS correlated strongly with the CEAP classification; vein diameters and reflux time in both the great saphenous vein and the small saphenous vein, indicating the validity of these outcome tools to venous hemodynamics and to CVI in general.

Portal venous hemodynamics as predictors for the development and grades of esophageal varices in Post‐HCV cirrhotic patients: An Egyptian center study

AbstractThere is no consensus regarding the precise predictive role of portal vein hemodynamics for the prediction of esophageal varices. We performed the current prospective work to assess the diagnostic ability of portal vein hemodynamics for the prediction and grading of esophageal varices. The present work is a prospective one performed in the period from April 2014 till September 2017. Two hundred patients with HCV‐related cirrhosis with esophageal varices were enrolled in the present work as case group (group I). In addition, 100 cirrhotic cases, with no esophageal varices, were included in the work as control arm (group II). Doppler ultrasound (US) and upper endoscopy were performed to all patients. Case group were further subdivided according grades of esophageal varices into four grades. These grades were correlated to splenic size, portal vein velocity, portal vein caliber, and hepatic artery resistivity index. Cases in group I had significantly larger spleen &amp; portal vein diameter and higher hepatic artery resistivity index than cases in group II (P &lt; .001). The portal vein caliber had the highest diagnostic performance for the detection of esophageal varices with cut‐off values of ≥12.5 mm (sensitivity = 99% and specificity = 94%). Patients with grade IV varices had significantly elevated values of splenic diameter, portal vein caliber, and hepatic artery resistivity index; and lower portal vein velocity than other patients with lower grades (P &lt; .001). The same findings were observed with other esophageal varices grades. In conclusion, non‐invasive portal hemodynamic parameters are good indicators for the prediction and severity of esophageal varices.

Doppler characteristics of hepatic venous hemodynamics in adult healthy camels (Camelus dromedarius)

Abstract The present study was designed to describe the Doppler measurements of hepatic venous blood flow in camels (Camelus dromedarius). A total number of 9 adult healthy camels underwent hepatic Doppler examinations on the right side between the 11th and 9th intercostal spaces. The splenic and cranial mesenteric veins showed turbulent blood flows at their fusion to form the main portal trunk. At porta hepatis, the main portal vein exhibited turbulent blood flows and the mean velocities ranged from 21 to 28 cm/sec. In contrast, the intrahepatic branches of portal veins revealed smooth laminar spectral patterns with low blood velocities ranged from 12 to 22 cm/sec. In addition, hepatic veins and caudal vena cava have laminar blood flows. In conclusion, as a non-invasive clinical tool, Doppler ultrasonography is a simple and easy applicable method for assessment of hepatic hemodynamics in camels (Camelus dromedaries). The present findings have the potential to serve as references for evaluating the health status of the liver from camels. Therefore; a further research study, including comparative evaluation of Doppler findings in camels with various hepatic diseases, may be required.

Surgical thrombectomy for iliofemoral deep vein thrombosis: Patient outcomes at 8.5 years.

IntroductionDeep vein thrombosis (DVT) is a frequent burden and a post-thrombotic syndrome (PTS) can be a serious long-term consequence. Iliofemoral DVT should be associated with severe forms of PTS. Therefore an early thrombus removal has been recommended in specific conditions. The aim of this study was to find out both, the long-term results after surgical thrombectomy of iliofemoral DVT in respect of the development of PTS as well as the venous hemodynamics after surgery concerning venous reflux and venous obstruction.MethodsSixty-seven patients who underwent surgical thrombectomy between the years 2000 and 2014 were included in this study; iliofemoral DVT was present in 52 of these patients. 35 patients could be reinvestigated after a mean follow-up of 8.5 years. CEAP (Clinical-Etiological-Anatomical-Pathophysiological) and Villalta scores were recorded in order to describe and assess PTS. Follow-up examinations included a detailed duplex mapping. Venous hemodynamics were measured by digital photoplethysmography and venous occlusion plethysmography.ResultsThe primary patency rate of the iliofemoral segment was 88% after 8.5 years. 48% of all patients showed reflux in deep vein segments. Mild or moderate PTS occurred in 57% of all patients. Notably, there was no patient with an active ulcer or severe PTS. The mean venous outflow volume of all patients in the treated legs was 66.1 ml/100ml/min and significantly less than in the controlled contralateral non-treated legs (p<0.05). The mean venous refilling time was 16.3 seconds, while the mean value of the non-treated contralateral legs was 25.6 seconds and therefore significantly higher (p<0.05).ConclusionEven though venous hemodynamics are significantly inferior in the treated legs, this study demonstrates excellent patency rates and good clinical outcome after surgical thrombectomy of iliofemoral veins.

Effects of ankle pump exercise frequency on venous hemodynamics of the lower limb.

The purpose of this study was (1) to compare the effects of ankle pump exercise(APE) frequency on hemodynamics of the common femoral vein(CFV) and (2) to analyse the relationship between APE duration and lower limb fatigue. Twenty-seven males and thirty-three females performed APE. Among them, there were thirty participants with non-lower limb fracture (N-LLF) and thirty participants with lower limb fracture (LLF).The colour doppler ultrasound was used to record the time-averaged mean velocity (TAMV) of common femoral venous flow when the participants at rest and move at different frequencies of 6 times/min, 10 times/min, 30 times/min, 60 times/min. The ratings of perceived exertion (RPE) was used to assess the lower limb fatigue of the participants when performing APE at the frequency of 60 times/min after 1 min, 2 mins, 3 mins, 4 mins and 5 mins. With the increase of frequency, TAMV increased significantly in both the participants with N-LLF and LLF (p < 0.01). The TAMV were 19.82±3.86, 33.78±8.76, 37.06±8.67, 43.82±10.40, 52.18±10.53, respectively in the participants with N-LLF and 16.98±3.01, 22.20±4.96, 24.01±5.78, 29.20±7.05, 35.75±9.28, respectively in the injured limb of patients with LLF when at rest and moving at the frequency of 6 times/min, 10 times/min, 30 times/min, 60 times/min. There was a positive correlation (p < 0.01) between lower limb fatigue and exercise duration.When the RPE was 16 points (the corresponding fatigue degree is "tired"), the exercise duration of the participants with N-LLF was 3 mins and that of the injured limb of patients with LLF was 2 mins. Both fast and slow-frequency APE can promote venous blood return in the lower limb. Despite of the equivalent APE duration, fast-frequency APE can promote venous blood return more effectively. When the frequency of APE was 60 times/min, participants with N-LLF can exercise for 3 mins, and the injured limb of patients with LLF can exercise for 2 mins.

An Experimental Investigation of White Matter Venous Hemodynamics: Basic Physiology and Disruption in Neuroinflammatory Disease.

The white matter is highly vascularised by the cerebral venous system. In this paper, we describe a unique blood oxygen-level dependent (BOLD) signal within the white matter using functional MRI and spatial independent components analysis. The signal is characterized by a narrow peak frequency band between 0.05 and 0.1 Hz. Hypercapnia, induced transient increases in white matter venous BOLD that disrupted the oscillation indicative of a vasocontractile mechanism. Comparison of the white matter venous BOLD oscillations between 14 healthy subjects and 18 people with perivenular inflammation due to multiple sclerosis (MS), revealed loss of power in the white matter venous BOLD signal in the peak frequency band (patients = 6.70 ± 0.94 dB/Hz vs. controls = 7.64 ± 0.71 dB/Hz; p = 0.006). In MS, lower power was associated with greater levels of neuroinflammatory activity (R = −0.64, p = 0.006). Using a signal modeling technique, we assessed the anatomical distribution of white matter venous BOLD signal abnormalities and detected reduced power in the periventricular white matter, a region of known venous damage in MS. These results demonstrate a novel link between neuroinflammation and vascular physiological dysfunction in the cerebral white matter, and could indicate enduring loss of vascular compliance associated with imperfect repair of blood-brain barrier damage after resolution of acute neuroinflammation.

Bioelectrical impedance analysis of leg edema and its association with venous functions in patients with saphenous varicose veins.

To quantitatively evaluate edema of the lower legs in patients with saphenous varicose veins, and to determine the association between leg edema and venous hemodynamics of the lower legs. The data of 140 patients with saphenous varicose veins in Eniwa Midorino Clinic from April 2018 to November 2019 were retrospectively analyzed. Body composition values, including Body Mass Index, extracellular water/total body water (ECW/TBW) ratio of each leg, and skeletal muscle mass of each leg, were measured by segmental multi-frequency bioelectrical impedance analyzer. Overall venous hemodynamics of the leg, including functional venous volume, venous filling index (VFI), and ejection fraction, were assessed using air-plethysmography. Saphenous and deep vein reflux were evaluated by duplex scan. A total of 140 patients (58 men and 82 women) with a mean age of 66.0 years (range, 21 to 84 years) were analyzed. On visual inspection, 204 legs had saphenous-type varicose veins, while 76 legs did not. The legs were divided into two groups according to the presence or absence of leg edema, which was defined as ECW/TBW ≥0.390 and <0.390, respectively; 178 legs had leg edema and the remaining 102 legs had no leg edema. In univariate analysis, there were significant differences in age, sex, the presence of saphenous varicose veins, hypertension, and VFI between legs with edema and those without edema. Multivariable logistic regression analysis for leg edema detected age, female, and VFI as an independent risk factor for leg edema. Leg edema was objectively evaluated by bioelectrical impedance analysis in patients with saphenous varicose veins. Older age, female, and increased venous reflux were identified as independent risk factors for leg edema.

Состояние артериальной и венозной церебральной гемодинамики у пациентов с различными видами головной боли

Состояние артериальной и венозной церебральной гемодинамики у пациентов с различными видами головной боли

Fluid-Structure Coupling Model and Experimental Validation of Interaction Between Pneumatic Soft Actuator and Lower Limb.

Pneumatic soft actuators (PSAs) are components that produce predesigned motion or force in different end-use devices. PSAs are lightweight, flexible, and compatible in human-machine interaction. The use of PSAs in compression therapy has proven promising in proactive pressure delivery with a wide range of dosages for treatment of chronic venous insufficiency and lymphedema. However, effective design and control of PSAs for dynamic pressure delivery have not been fully elaborated. The purpose of this study is to explore interactive working mechanisms between a PSA and lower limbs through establishing fluid-structure coupling models, an intermittent pneumatic compression (IPC) testing system, and conducting experimental validation. The developed IPC testing system consisted of a PSA unit (multichambered bladders laminated with an external textile shell), a pneumatic controller, and various real-time pressure monitoring sensors and accessory elements. The established coupling model characterized the dynamic response process with varying design parameters of the PSA unit, and demonstrated that the design of initial thickness, stiffness, and air mass flow of the PSA, as well as stiffness of limb tissues of the users, influenced PSA-lower limb interactions and resultant pressure dosages. The simulated results presented a favorable agreement with the experimental data collected by the IPC testing system. This study enhanced understanding of PSA-lower limb interactive working mechanisms and provided an evidence-based technical guidance for functional design of PSA. These results contribute to improving the efficacy of dynamic compression therapy for promotion of venous hemodynamics and user compliance in practice.

VENOUS BLOOD INDICES AFTER CAVAPLICATION IN PATIENTS WITH THROMBOSIS OF THE VENA CAVA INFERIOR

Summary. Despite reports of plication with inferior vena cava thrombosis, the venous hemodynamics before and after hardware cavaplication has been not evaluated.&#x0D; The aim of research. Estimate the changes of the venous blood flow indices after complication in patients with vena cava inferior thrombosis.&#x0D; Materials and methods. Quantitative assessment of venous blood flow was performed in 34 patients with inferior vena cava thrombosis before and after incomplete hardware cavaplication. Cavaplication was performed in 11 (32.4 %) patients with non-tumor and in 23 (67.6 %) patients with tumors of the vena cava inferior. For selecting the site of cavaplication, the infrarenal branch of the vena cava inferior directly below the renal veins was prevailed – in 29 (85.3 %) patients, the plication of vena cava inferior lower or higher hepatic veins in 4 (11.8 %) and 1 (2.9 %) patients were performed respectively.&#x0D; Results. Increases of following indices of central and regional hemodynamics after hardware cavaplication were observed, in particular, volume (by 56.5 %) and the linear rate of blood flow (by 40.4 %), minute volume of blood flow (by 16.2 %), cardiac index (by 8.8 %), systolic volume (by 6 %), end-systolic volume index (by 4.5 %), end-diastolic volume index (by 3.9 %) and ejection fraction (by 2.1 %). Instead, the pressure in the inferior vena cava (by 18.2 %) and stroke volume (by 8.9 %) decreased, which, however, was also considered as a positive result of thrombectomy from the vena cava inferior and hardware cavaplication.&#x0D; Conclusions. Within a year after inferior vena plication, indicators of central and peripheral hemodynamics were within the physiological norm and collateral pathways during radioisotope phleboscintigraphy weren`t determined. At the same time, the lumen of the vena cava inferior was completely restored, after 12-18 months, in all cases after plication.

CHIVA to Treat Saphenous Vein Insufficiency in Chronic Venous Disease: Characteristics and Results

There is considerable debate in the literature with relation to the best method to treat patients with chronic venous disease (CVD). CHIVA is an office-based treatment for varicose veins performed under local anesthesia. The aim of the technique is to lower transmural pressure in the superficial venous system and avoid destruction of veins. Recurrence of varicosities, nerve damage, bruising and suboptimal aesthetic results are common to all treatments for the disease. This paper evaluates and discusses the characteristics and results of the CHIVA technique. We conclude that CHIVA is a viable alternative to common procedures that is associated with less bruising, nerve damage, and recurrence than stripping saphenectomy. The main advantages are preservation of the saphenous vein, local anesthesia, low recurrence rates, low cost, low pain, and no nerve damage. The major disadvantages are the learning curve and the need to train the team in venous hemodynamics.

Influence of operative treatment of variсocele on the development of arterial hypertension

Purpose of the research. To assess the incidence of arterial hypertension in men with varicocele and to identify the relationship between increased blood pressure and surgical treatment of varicocele.&#x0D; Material and methods. A survey of 412 men receiving treatment for arterial hypertension, 482 men previously operated on for varicocele and 68 patients with varicocele who had no surgical treatment was conducted.&#x0D; Results. Varicose veins of the spermatic cord in patients with arterial hypertension were detected in 44.6% of cases, which exceeds the incidence of varicocele occurrence in men of a comparable age category by 1.52 times. Surgical treatment of the left spermatic cord varicocele is combined with the development of arterial hypertension in 51.2% of patients, which is three times higher than the incidence of hypertension in men who didnt undergo surgical treatment for varicocele and twice the frequency of hypertension in the general population of men of comparable age. The more frequent occurrence of renal arterial hypertension in patients who underwent surgical treatment for varicocele may indicate an adverse effect of occlusion of the internal spermatic vein on the state of renal venous hemodynamics.&#x0D; Conclusion. Varicocele should be considered as a compensatory process for renal venous hypertension due to obstruction of blood flow through the renal vein, and elimination of compensatory blood flow can lead to renal venous hypertension, hypoxia and the development of arterial hypertension.

Impact on venous haemodynamics after treatment of great saphenous vein incompetence using plethysmography and duplex ultrasound

To evaluate postoperative venous haemodynamics and quality of life after treatment of great saphenous vein (GSV) incompetence. Radiofrequency ablation and high ligation and stripping were performed in 62 patients (65 limbs) and 58 (65 limbs), respectively. Phlebectomies were performed in both modalities. Strain-gauge plethysmography on the foot combined with superficial venous occlusion was used to measure refilling time after knee bends. Strain-gauge plethysmography, duplex ultrasound and quality of life were assessed before and one month after treatment. Duplex ultrasound displayed successful intervention in all but two limbs. Refilling time increased similar in radiofrequency ablation and high ligation and stripping after treatment (p < 0.001). Postoperatively, strain-gauge plethysmography detected remaining reflux in 71% of the patients. Multivariate analysis showed that two or more incompetent calf branches were associated with remaining reflux (OR 4.82 (95% CI: 1.33-17.5), p = 0.02). No difference in quality of life was seen in patients with remaining reflux. Despite successful treatment, a majority of the limbs showed remaining reflux, in which incompetent calf branches appear to play an important role.Clinicaltials.gov: Lower Limb Venous Insufficiency and the Effect of Radiofrequency Treatment Versus Open Surgery. Nr: NCT02397226.

Fundamental physiologic concepts of venous hemodynamics and systemic venous return

Understanding the nominal venous anatomy and venous hemodynamics is the first and fundamental step in understanding the pathophysiology of venous disorders. Over the last two decades, significant effort has gone into improving the management of chronic venous disorders resulting in substantial improvement in the management of patients affected by venous insufficiency. Given the continuity of the venous system especially pertinent to the relationship between thoracic, abdominal, pelvic, and infrainguinal venous anatomy, combined with the increasing knowledge we gained regarding hemodynamics of the venous system it is imperative that a comprehensive approach to venous disorders is undertaken that evaluates venous system as a continuum rather than an approach that would evaluate only isolated venous territory affected by a specific venous disorder. Understanding of venous anatomy and physiology, as the basic components for venous hemodynamics, is an essential step to gain insights into venous return concepts, initially described by Dr. Guyton. Dr. Guyton's model represents a fundamental and one of the most significant advancements in our understanding of venous return. This manuscript details essential domains of hemodynamics, which can be useful for validation of our current understanding of systemic venous return.

The Feasibility of Underwater Computerised Strain Gauge Plethysmography and the Effects of Hydrostatic Pressure on the Leg Venous Haemodynamics

BackgroundStrain gauge plethysmography (SGP) is employed to evaluate venous drainage of the lower leg.MethodsIn this study, SGP was used to evaluate the effects of the hydrostatic pressure (HP) of water on venous volume (VV), expelled volume, and ejection fraction (EF) in 22 healthy legs before and during immersion in water.ResultsHP reduced VV by 100% and even more during underwater (UW) exercise, making calculation of the UW EF possible.DiscussionUW SGP is feasible and indicates that HP improves venous haemodynamics. This study suggests that including UW leg exercise in the rehabilitation protocols of patients with chronic venous disease may be useful.KeywordsStrain gauge plethysmography, Underwater compression, Underwater ejection fraction, Underwater venous volume.

Physical principles of venous hemodynamics and its mathematical modeling

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.

Invitation Letter to the Project on systemic and local venous return

Project: Systemic and local venous return Subtitle: Old and new concepts in venous hemodynamics and new interesting hypotheses Issue Editor: Prof. BB Lee Co-Editors: Dr. F Passariello, Prof. N Labropoulos, Dr. S. Ricci

Anatomy and venous hemodynamics of gait phases

The Valve-Muscular Pump (MVP) of the lower limb, a kind of peripheral heart, is principally activated during walking, by the succession of gait phases. The pump has three parts, which work in a coordinated way. The foot pump, due to the compression of the predominating lateral plantar vein during the contact on the ground (40% of gait event), “eject” 20-30 cm3 of blood into the posterior tibial vein and, in alternative, in the anterior tibial, peroneal and saphenous veins connected by perforators. The distal calf pump, activated during dorsiflexion of the ankle (passive 20% and active 40% of gait event), when the calf muscles are stretched and their distal part descends within the fascial sheath. This movement acts like a piston which expels venous blood in proximal direction. The proximal calf muscle pump due to sural and gastrocnemius muscles rich in venous sinuses that are strongly squeezed during the impulse phase of the step. During dorsiflexion of the ankle (passive or active) space is given to the blood coming from the foot pump (due to weight bearing), that will feed in prevalence the posterior tibial veins. These two systems are “in series”: the foot pump cannot expel the blood into the deep veins if these are not regularly emptied. The proximal pump, at the opposite, is very strong and can void a high volume of blood in the popliteal vein, even in the absence of a favourable gradient as it works “in parallel”.