Ambulatory Venous Pressure Research Articles

The human lower leg muscle pump functions as a flow diverter pump, maintaining low ambulatory venous pressures during locomotion

ObjectiveAmbulatory venous pressure (AVP) is the drop of pressure observed in the superficial veins of the lower leg during movement. This phenomenon has been linked to the function of the calf muscle pump (CMP) and the competence of venous valves. Nevertheless, the concept of the CMP function remains controversial. This study aimed to elucidate the association between lower leg muscles activity, changes in pressure in distinct venous segments, and lower extremity arterial blood supply in healthy subjects during various types and intensities of exercise. MethodsTwelve legs of nine healthy volunteers were enrolled in the study. Continuous pressure (intramuscular vein [IV] and three great saphenous vein [GSV] points) and surface electromyography data (gastrocnemius and anterior tibial [ATM] muscles) were recorded during treadmill walking, running, and plantar flexion exercises. The pressure gradient (ΔP, mmHg) between adjacent points of measurement was calculated. Minute unit power of muscle pump ejection and suction (NE, and NS, MPa/min) were calculated and compared with the arterial blood supply of the lower extremity (LBF, L/min). ResultsΔP demonstrated a consistent pattern of changes during walking and running. In GSV, the ΔP was observed to be directed from the thigh to the mid-calf (retrogradely) and from the ankle to the mid-calf (anterogradely) throughout the entire stride cycle. However, its value decreased with increasing stride cycle frequency. The dynamics of ΔP between the IV and GSV were as follows: It was directed from the IV to GSV during gastrocnemius contraction and was reversed during anterior tibial muscle contraction and gastrocnemius relaxation (swing phase). LBF, NE, and NS demonstrated similar exponential growth with increasing stride frequency during walking and running. ConclusionsDuring natural locomotion, the muscle pump acts as a flow diverter pump, redirecting the flow of blood from the superficial veins to the intramuscular veins via the perforating veins. During ambulation, the pressure in the superficial venous network depends upon the capacity of the muscle pump to provide output that matches the changes in arterial blood flow.

Improvements in edema and microcirculation in chronic venous insufficiency with Pycnogenol® or elastic compression.

Chronic venous insufficiency (CVI) is the consequence of venous valve reflux and/or venous flow obstruction and resulting venous hypertension in the lower extremities. The aim of this prospective supplement registry study was to evaluate the efficacy of compression stockings or Pycnogenol® in controlling symptoms and edema in CVI and their efficacy on microcirculatory parameters. Two comparable groups of 30 subjects with CVI were observed for 4 months. Elastic compression was less tolerated than Pycnogenol® with 12 subjects being unable to follow the compression routine. No side effects due to supplementation were observed; tolerability of the supplementation was optimal. Ambulatory venous pressure (AVP) and refilling time (RT) at inclusion indicated a significant increase in venous pressure and reflux (refilling time <16 seconds). AVP and RT did not change after 4 months. Microcirculatory and clinical measurements were comparable at inclusion between the 2 groups. After 4 months, skin resting flux (RF) and skin PO<inf>2</inf>-PCO<inf>2</inf> were significantly improved with Pycnogenol® compared to compression (P<0.05). The significant increase in skin PO<inf>2</inf> and the decrease in PCO<inf>2</inf> after Pycnogenol® intake were ascribed to the decrease in the abnormally high skin resting flux, a sign of better perfusion and skin nutritional supply. Pycnogenol® reduced leg volume, on average by 18.3% in the evening compared to 4.4% of reduction with compression (P<0.05) showing an important effect on edema. The venous Clinical Severity Score (VCSS) and the composite symptom score (CSS) decreased significantly in the Pycnogenol® group compared to compression, indicating a better improvement in microcirculatory perfusion and nutritional supply produced by the supplementation of Pycnogenol® in comparison with compression. Pycnogenol® significantly improved microcirculation and clinical symptoms in comparison with compression. The decrease in local oxidative stress (OS) at the distal perimalleolar region with Pycnogenol® was significant in comparison with compression (P<0.05). A lower local OS is an important metabolic indication of a better capillary perfusion with better nutritional exchanges. At the end of the registry study, four small ulcerations and skin breaks in four limbs (between 3 and 5 mm of maximum diameters) were observed in the compression group. No ulcerations or skin breaks were observed in the Pycnogenol® group. Pycnogenol® relieved edema, improved microcirculation in CVI patients and reduced stationary, interstitial fluid in comparison with compression. Most symptoms of CVI are associated with interstitial water retention; the presence of extra fluid in limb tissues alters perfusion and nutrient supply. Pycnogenol® supplementation reduced water and fluid accumulation in CVI limbs and improved microcirculation and local oxidative stress thus showing important anti-edema effects.

Noninvasive measurement of ambulatory venous pressure via column interruption duration in chronic venous disease

BackgroundColumn interruption duration (CID) is a noninvasive surrogate for venous refill time (VFT), a parameter used in ambulatory venous pressure measurement. CID is more accurate than invasive VFT measurement because it avoids errors involved with indirect access of the deep system through the dorsal foot vein. The aim of this retrospective single center study is to analyze the clinical usefulness of CID in assessment of chronic venous disease (CVD). MethodsA total of 1551 limbs (777 patients) were referred with CVD symptoms over a 5-year period (2018-2023); CID, air plethysmography, and duplex reflux data were analyzed. Of these limbs, 679 had supine venous pressure data as well. The pathology was categorized as obstruction if supine peripheral venous pressure was >11 mm Hg and as reflux if duplex reflux time in superficial or deep veins was >1 second. CID was measured via Doppler monitoring of flow in the great saphenous vein (GSV) and one of the paired posterior tibial (PT) veins near the ankle in the erect posture. The calf is emptied by rapid inflation cuff. CID is the time interval in seconds when cephalad venous flow in great saphenous vein and posterior tibial veins reappear after calf ejection. A CID <20 seconds in either vein is abnormal similar to the threshold used in VFT measurement. ResultsThirty-two percent of the limbs had obstruction, 17% had reflux, and 37% had a combination; 14% had neither. Higher clinical-etiology-anatomy-pathophysiology (CEAP) clinical classes (C4-6) were prevalent in 44% of pure reflux, significantly less (P < .0001) than in pure obstruction (73%) or obstruction plus reflux subsets (72%), partly reflecting distribution of pathology. There is a progressive increase in supine venous pressure and abnormal CID (P < .0001 and P < .0001, respectively) in successive CEAP clinical class. No such correlation between CEAP and any of the reflux severity grading methods (reflux segment score, Venous Filling Index, and Kistner axial grading) was observed. Abnormal CID (55%) was more prevalent in higher CEAP classes (>4) (P < .0001) than in lesser clinical classes (0-2) or limbs with neither obstruction nor reflux (P < .01). ConclusionsObstruction seems to be a more dominant pathology in clinical progression among CEAP clinical classes than reflux. CID is abnormal in both obstructive and refluxive pathologies and may represent a common end pathway for similar clinical manifestations (eg, ulcer). These data suggest a useful role for CID measurement in clinical assessment of limbs with CVD.

Venous dysfunction in obstructive hypertrophic cardiomyopathies: Results from the “HCM-Vein” pilot study

Hypertrophic cardiomyopathies (HCM) can be complicated by left ventricular outflow-tract obstruction (LVOTO) responsible for disabling exercise symptoms, a phenomenon influenced by hemodynamic factors including venous return. We aimed to evaluate venous dysfunction in obstructive HCM patients compared to healthy controls, and to investigate the relationship between venous dysfunction parameters and LVOTO in HCM. This is a clinical, monocentric, prospective, pilot study, in a tertiary care center. We investigated venous function using venous air plethysmography, and endothelial function. Among the 30 symptomatic obstructive HCM patients, 30% (n=9) presented abnormal venous residual volume fraction (RVFv) which translates in elevated ambulatory venous pressure vs. 0% in the 10 healthy controls (p<0.05). Comparing obstructive HCM patients with abnormal RVFv (n=9) to other obstructive HCM patients with normal RVFv (n=21), there were no significant differences in terms of age, sex (67% male), and classical echocardiographic parameters both at rest and during exercise, except for left ventricular end-diastolic volume index which was significantly lower in the group with abnormal RVFv compared to the other HCM patients (40.1±9.0ml/m2 vs. 50.2±10.6ml/m2, p=0.01). Fifty six percent of obstructive HCM patients with abnormal RVFv had an absolute increase in Willebrand factor (vs. 26% of other obstructive HCM patients, p<0.05). In this pilot monocentric study, venous insufficiency was observed in about 30% of symptomatic obstructive HCM patients. Patients with venous insufficiency had more frequently a smaller LV cavity volume. Due to the small sample size, this study is only hypothesis-generating, and further investigations are needed.

Narrative Review of the Pathogenesis of Stasis Dermatitis: An Inflammatory Skin Manifestation of Venous Hypertension.

Stasis dermatitis (SD), also known as venous dermatitis, is a form of inflammatory dermatitis of the lower extremities that typically occurs in older individuals and represents a cutaneous manifestation of venous hypertension. Venous hypertension (also known as sustained ambulatory venous pressure) is most often due to retrograde blood flow, which occurs due to calf muscle pump failure. This failure is most commonly secondary to incompetent venous valves, valve destruction, or obstruction of the venous system. Many of the common symptoms associated with SD are caused by inflammatory processes. This review summarizes the pathogenesis and key role of inflammation in SD by reviewing inflammatory biomarkers associated with SD. The literature was selected though a high-level PubMed search focusing on keywords relating to inflammation associated with SD. Venous reflux at the lower extremities causes venous hypertension, which leads to chronic venous insufficiency. High venous pressure due to venous hypertension promotes the local accumulation and extravasation of inflammatory cells across the vascular endothelium. Leukocyte trapping in the microcirculation and perivascular space is associated with trophic skin changes. Cell adhesion molecules are linked with the perpetuated influx of activated leukocytes into inflammatory sites. Here, inflammatory cells may influence the remodeling of the extracellular matrix by inducing the secretion of proteinases such as matrix metalloproteinases (MMPs). The increased expression of MMPs is associated with the formation of venous leg ulcers and lesions. Phosphodiesterase4 activity has also been shown to be elevated in individuals with inflammatory dermatoses compared to healthy individuals. Because inflammation is a key driver of the signs and symptoms of SD, several of the highlighted biomarkers of inflammation represent potential opportunities to target and interrupt molecular pathways of cutaneous inflammation and, therefore, remediate the signs and symptoms of SD. Understanding the pathogenesis of SD may help clinicians identify drivers of inflammation to use as potential targets for the development of new treatment options.

Clinical tolerance of untreated reflux after iliac vein stent placement

BackgroundWe have recently demonstrated in a large patient cohort that the prevalence and severity of reflux will improve in most limbs after stenting and that most limbs will not develop new-onset reflux. In the present report, we have focused on the long-term clinical outcomes associated with untreated reflux in the same patient cohort who had undergone iliofemoral venous stenting without correction of residual reflux. MethodsThe clinical outcomes data from 1379 limbs treated with only iliac vein stenting without correction of superficial or deep reflux from 1997 to 2018 were analyzed (23-year follow-up period). Of the 1379 limbs, 632 (46%) had had preexisting reflux before stenting and 747 (54%) had did not. The reflux data (reflux segmental score, air plethysmography, ambulatory venous pressure) for these patients have been previously reported in detail. The subsets were compared perioperatively with each other using the following variables: grade of swelling, visual analog scale for pain score, venous clinical severity score, venous stasis dermatitis, ulceration, and quality of life measures. ResultsBoth groups demonstrated improvements in the venous clinical severity score, grade of swelling, visual analog scale score, and quality of life. No differences were found in ulcer healing (5% vs 3% for limbs with and without prestent reflux, respectively) and resolution of dermatitis (6% vs 5% for limbs with and without prestent reflux, respectively) between the two groups. Of the 632 limbs with preexisting reflux, 218 (34%) had had axial reflux and 414 had had nonaxial reflux (66%). The clinical outcomes were similar between the two groups. Using a multisegment reflux score, the limbs with prestent reflux (n = 632) were divided into two groups. A segmental score of ≥3 indicated severe reflux and a score of <3 indicated moderate reflux. Of these 632 limbs, 161 (25%) had severe reflux and 471 (75%) had moderate reflux. The two groups demonstrated similar outcomes for most clinical parameters. The post-thrombotic limbs and nonthrombotic limbs also showed similar outcomes. ConclusionsThe long-term follow-up of patients after iliac vein stenting showed that uncorrected reflux is well tolerated by most patients across most clinical measures.

Long-term improvement of limb reflux prevalence and severity after iliac vein stent placement

BackgroundThe effect of iliac vein stenting on ipsilateral limb reflux is unknown and has remained a matter of speculation. It has been suggested that the propensity for reflux might worsen when proximal stenosis is corrected. This could allow for retrograde flow with coughing and the Valsalva maneuver, stressing the valve. We examined this hypothesis by an analysis of the long-term effects of iliac vein stenting on limb reflux using a single-center, retrospective analysis of prospectively collected data. MethodsReflux data from duplex ultrasound of 1387 limbs in 1228 patients who had undergone iliac vein stenting from 1997 to 2018 were analyzed. Of the 1387 limbs, 632 (46%) had had ipsilateral duplex ultrasound-determined valve reflux before stenting, and 747 limbs (54%) had not had reflux; data were missing for 8 limbs. Reflux status before and after stenting was available for seven individual segments for each limb in the database for analysis (total, 9653 segments). The stented patients were examined for reflux at least annually during the follow-up period (range, 1-26 years). Segmental reflux prevalence was detected using duplex ultrasound. We have referred to this as “duplex reflux” or simply “reflux.” Reflux severity was graded using (1) a reflux segmental score, assigning one point each for refluxing segments in the limb; (2) air plethysmography (venous filling index [VFI90]); and (3) ambulatory venous pressure (venous filling time [VFT]). ResultsPrestent duplex reflux was present in a combination of superficial, deep, and perforator segments. Reflux prevalence ranged from 7% of deep femoral segments to 51% at the popliteal segment. Post-stent reflux resolution varied from 21% at the femoral vein segment to 58% at the perforator segments. Reflux had completely resolved in 23% of the limbs. New-onset reflux was rare, with a median incidence of 7% for all segments at risk, with cumulative improvement (Kaplan-Meier curve) in reflux severity (segment score, VFI90, and VFT) for most limbs. These metrics were unimproved, with residual reflux in only 18%, 11%, and 6% (segment score, VFI90, and VFT, respectively) of the limbs at long-term follow-up. ConclusionsLong-term follow-up of limbs after iliac vein stenting has shown that the associated ipsilateral reflux prevalence and severity will improve in most limbs over time.

Ambulatory venous pressure studies and its correlation with CEAP grading of varicose veins

Ambulatory venous pressure studies and its correlation with CEAP grading of varicose veins

Venous Stasis Leg Ulcers: A Review

Chronic venous stasis ulcers (CVSU) of the lower extremity affect up to 5% of the population over 65 years and 1.5% of the general population. CVSU is caused by chronic venous disease produced by venous hypertension. Venous hypertension results from valvular incompetence within the deep venous system, or by the obstruction of venous outflow. Both of these mechanisms produce poor venous return. Additionally, poor mobility and decreased calf muscle pump function are thought to be contributing factors. Life-long use of compressive therapy is indicated in patients with chronic venous disease in lower extremities. It reduces ambulatory venous pressure. These include bandaging systems, garments (stockings), or devices.

Ambulatory venous pressure: new concepts

Background: The importance of the calf pump (the ‘peripheral heart’) in the lower limb venous circulation is well known. The ambulatory venous pressure (AMVP) is generally considered the quintessential functional test of calf pump function. However, much controversy exists on the basic hemodynamics of AMVP as well as its measurement. Recent work has helped to revise/clarify many of these controversies. Results from experimental simulations are used to illustrate key hemodynamic concepts. A multicameral model of calf pump Arnoldi popularized the notion that deep venous pressures can be monitored by inserting a needle in the dorsal foot vein (unicameral model). It has been shown recently that ambulatory venous pressures in the deep system is different from that in the dorsal foot vein and also the saphenous vein. AMVP profile in the three valved systems are different from each other (multicameral model). AMVP is traditionally monitored via % drop and also Venous refill time (VFT). Analysis of a large cohort of patients shows that VFT is more sensitive. % drop can be omitted as it is rare for it to be abnormal without concurrent abnormal VFT. AMVP is normal in venous obstruction, contradicting common belief. Ambulatory venous hypertension is a specific property of reflux, not obstruction. Supine venous pressure is elevated in obstruction but not reflux despite the suspected role of microvascular hypertension in reflux pathology. Role of calf capacitance &amp; compliance: While severe reflux can shorten VFT, reduced calf capacitance and compliance are more important as can be shown in experimental set ups and clinical analysis. Calf Pump failure: Like the heart, the calf pump can eject all the inflow presented to it (up to 3X normal). Thus the popular concept of ‘calf pump failure’ from reflux overload has little concrete evidence to support it. Column segmentation: It is commonly assumed that valve closure results in column segmentation. It can be shown in experimental settings that collapse of the venous segment below the valve closure is necessary for column segmentation. Furthermore a reconstruction of the events surrounding column restoration makes it clear that a closed valve above the calf pump cannot reopen with the hydrostatic pressure of the restored column height below the closed valve alone. Much higher pressures generated by inflow interacting with wall tension of the infra-valvular segment is necessary to reopen the closed valve and restore flow. AMVP does not reach resting levels in experimental models till wall tension is restored to resting levels. A full blown reflux through an open valve will not transmit column pressure when the calf pump is partially collapsed. A non-invasive replacement for AMVP: Prevailing clinical practice and recent guidelines emphasize duration of reflux at the proximal saphenous, femoral and popliteal valves for assessment of reflux severity. It has been shown that these proximal valves play no significant role in column segmentation. A group of valves in the posterior tibial vein and the great saphenous vein near the ankle are the critical players in column interruption duration (CID). CID can be measured non-invasively by duplex after calf ejection by pressurized cuffs. Conclusion: AMVP has declined in clinical use as duplex identification of reflux in proximal valves has become common practice. More useful information can be obtained by using Duplex to measure CID.

The hemodynamic impact of the bidirectional flow within calf perforators and conductive veins in varicose vein disease

The hemodynamic assessment of the bidirectional flow within calf perforators and in the conductive veins in varicose vein disease is presented. The bidirectional streaming within calf perforators is induced by the changing polarity of the systolic and diastolic pressure gradients arising during calf pump activity between the deep veins and the saphenous system of the lower leg, as documented by simultaneous pressure measurements in the posterior tibial vein and the great saphenous vein. This bidirectional flow makes the deep and superficial veins of the lower leg conjoined vessels. The vector of the bidirectional streaming in varicose vein patients is oriented inward, into the deep veins. The enlarged calf perforators are the consequence of the saphenous reflux; after elimination of saphenous reflux the diameter of calf perforators diminishes significantly. Results of venous pressure, plethysmographic and electromagnetic flow measurements rebut the still prevalent opinion that the outward flow within calf perforators is a reflux. There is an up-and-down flow in the conductive veins during calf pump activity with a prevailing systolic centripetal (orthograde) flow in the popliteal/femoral axis and a diastolic centrifugal (retrograde) flow in the incompetent great saphenous vein. The popliteal vein represents actually the drain pipe of the calf muscle pump. The ambulatory venous pressure gradient arising during the diastolic phase of the calf pump activity resembles the diastolic pressure difference between the aorta and the left ventricle.

Measurement of ambulatory venous pressure and column interruption duration in normal volunteers

BackgroundAmbulatory venous pressure (AMVP) measurement is considered the gold standard in evaluating calf pump function in chronic venous disease. The AMVP protocol was standardized in the 1970s with pressure monitoring through the dorsal foot vein. This technique was based on the belief that it represents calf venous pressure dynamics owing to rapid equilibration in the superficial and deep systems. This notion is subject to some doubt not only on theoretical grounds, but also owing to a lack of clinical correlation in a segment of the population with chronic venous disease. Our aims were to (1) examine if AMVP measured simultaneously through the dorsal foot vein (DFV) and the great saphenous vein (GSV) would be similar and (2) attempt to devise a noninvasive substitute via duplex measurement for the AMVP test. MethodsThe study was conducted in 76 limbs in 38 normal volunteers. Simultaneous AMVP measurements in DFV and GSV were made in 28 of these normal limbs. Column interruption duration (CID) after calf pump ejection was measured by monitoring duplex resumption of flow in the tibial veins and GSV after calf ejection. The return of AMVP back to baseline implies column restoration. The venous refill time therefore represents the CID via the pressure method. The pressure and duplex methods of CID were compared in the GSV. ResultsKey AMVP parameters (percent drop and venous refill time) significantly differed in DFV and GSV, showing a lack of pressure equilibration. CID measured by duplex in GSV was not significantly different from pressure-derived CID in the same vein. ConclusionsAMVP measured through the DFV does not reflect calf pump generated pressure events in GSV. A duplex method of measuring CID in GSV and posterior tibial vein is described. Duplex-derived CID is not significantly different from pressure-derived CID in the GSV.

Peripheral venous hypertension in chronic venous disease

BackgroundMicrovascular venous hypertension has emerged as a central feature of chronic venous disease (CVD). Yet, the incidence and severity of peripheral venous hypertension in the clinical setting have not been reported. This is an observational study of venous hypertension in the lower limb of a large cohort of patients with suspected CVD referred to a single referral center during a 16-year period. MethodsClinical and venous laboratory test data for 8868 limbs of 5792 patients with CVD symptoms seen from 1999 to 2015 were analyzed. Subset A limbs had a mix of obstruction/reflux or neither (n = 4132). These are limbs in which duplex ultrasound reflux (yes/no) status is known. The incidence and severity of obstruction in these limbs are unknown as tests of obstruction were not routinely performed. Subset B limbs had central obstruction (n = 159). These are limbs with intravascular ultrasound-proven stenosis in the iliac veins that was corrected by stent placement. Reflux was assessed by duplex ultrasound and air plethysmography (venous filling index [VFI90]). Pressure measurements included supine venous pressure, erect venous pressure, and ambulatory venous pressure (AMVP). Pressure measurements are categorized according to Clinical, Etiology, Anatomy, and Pathophysiology (CEAP) clinical class, reflux and obstruction with Venn distributions of prevalence. ResultsAll pressures (supine, erect, and ambulatory) trended worse in higher CEAP clinical classes. Supine foot venous pressures were elevated in 70% and 76% of subsets A and B, respectively. A positive association between elevated supine pressures and reflux could not be shown in this study. Supine foot venous pressure did not worsen with increasing reflux in the two subsets, but erect foot venous pressure did. Elevated supine pressures were associated with obstruction in subset B. AMVP worsened in most higher reflux categories. Ambulatory venous hypertension was dominantly associated (Venn distribution) with reflux, less commonly with obstruction. ConclusionsSupine venous hypertension is associated with obstruction and does not worsen with reflux. In contrast, erect foot venous pressure worsens in severe reflux categories. Ambulatory venous hypertension worsens in higher CEAP clinical classes. It worsens with increasing reflux. AMVP is dominantly associated (Venn distribution) with reflux, not obstruction.

Ambulatory venous pressure, air plethysmography, and the role of calf venous pump in chronic venous disease

BackgroundAmbulatory venous pressure (AMVP) records pressure dynamics with calf exercise. Air plethysmography (APG) measures related volume detail. APG has been suggested as a noninvasive surrogate for AMVP. We examine the correlations between APG and AMVP parameters and the role of “calf pump failure” in chronic venous disease (CVD). MethodsA total of 8456 limbs in 4610 patients investigated for CVD during a 20-year period were analyzed. APG and AMVP data were available in 4599 limbs for calculation of Pearson correlation coefficient; 1347 of these limbs had significant iliac vein stenosis, proven by intravascular ultrasound. Venn diagrams are used to explore overlapping incidence of APG and AMVP abnormalities. ResultsAPG calf volume and reflux (venous volume, venous filling index) showed progressively significant deterioration with advancing Clinical, Etiology, Anatomy, and Pathophysiology (CEAP) clinical class, anatomic extent of reflux (superficial, deep, perforator), and reflux severity (axial reflux, segmental score). Notably, calf ejection volume increased in a nearly linear fashion (R = 0.71) to venous volume such that residual volume fraction (RVF) remained normal even in the worst of these categories. AMVP too progressively deteriorated with clinical disease and reflux severity. Venous filling time was the key parameter as the pressure drop alone was abnormal in only 4% of the limbs analyzed. There was no correlation between RVF and AMVP (R = 0.22) or between AMVP and many other APG parameters. Venn distribution showed only minor overlap (30%) between AMVP and key APG abnormalities overall, but the overlap increases from 40% to 70% in advanced clinical and reflux categories. AMVP was rarely abnormal (7%) when APG was normal. Median AMVP was normal in calf pump failure categories, however defined (subnormal ejection fraction, RVF, or both). Median AMVP is normal in venous obstruction without reflux, while AMVP abnormalities are associated three to seven times more with reflux than with obstruction. ConclusionsAPG (venous filling index) is a useful index of reflux. Calf pump ejection is a powerful and plastic compensatory mechanism, and calf pump failure is rare. Ambulatory venous hypertension is dominantly associated with reflux and less with obstruction. AMVP too worsens with clinical and reflux severity categories. However, there is little correlation between APG and AMVP parameters as APG measures volume and AMVP measures pressure, each in its own domain, and the volume-pressure curve is nonlinear. AMVP may be omitted in routine clinical testing if APG is normal, as the yield (7%) will be very low. AMVP reflects venous hypertension, the end stage in CVD. AMVP should be used to identify such cases when APG is abnormal.

Pressure dynamics in chronic venous disease

Peripheral venous pressure is regulated by central and peripheral mechanisms. Peripheral venous hypertension is an important pathologic component of chronic venous disease and is present in about two-third of patients with chronic venous disease. It can result from reflux, obstructive lesions or high arterial inflow. The dominant influence in patients with peripheral venous hypertension appears to be obstruction rather than reflux. Reflux can be superficial or deep or both. In about 70% of patients with reflux, valvular incompetence is present in the superficial, deep and perforator systems in some combination. In an ex vivo experimental model, conduit pressure increased with smaller native or functional caliber, focal stenosis and increased post-capillary inflow. Venous pressure in the lower limb can be measured in a variety of ways: supine resting pressure, erect resting pressure and ambulatory venous pressure. These measurements are affected by factors such as intra-abdominal pressure, intra-thoracic pressure, gravity, venoarteriolar reflux, valve reflux and venous obstruction. Venous obstruction is associated with elevated supine pressures while reflux is associated with elevated erect resting and ambulatory venous pressures. Ambulatory venous pressure reflects venous hypertension in patients with advanced venous disease. However, our investigation has shown that ambulatory venous pressure hypertension is rarely present if air plethysmography testing is negative. Consideration maybe given to the omission of the ambulatory venous pressure testing if air plethysmography testing is normal.

Contribution of the calf pump and foot pump to the return of venous blood from the lower extremity

The anatomy and function of the calf pump and the foot pump as well as the interplay of their activity are described. The calf muscle pump constitutes an effective mechanism enhancing efficiently the return of venous blood toward the heart. During calf muscle contractions, the venous blood is ejected mainly into the popliteal vein, but a smaller part escapes through calf perforators into the saphenous system and streams further in the centripetal, i.e. physiological direction toward the heart. Calf muscle contractions induce marked increase in systolic pressure and calf muscle relaxations entail decrease of diastolic pressure both in deep and superficial veins of the lower leg. The systolic and diastolic pressure changes are produced in deep veins and are transmitted through calf perforators into the saphenous system, as documented by simultaneous pressure recordings in the posterior tibial and great saphenous veins. The systolic increase of pressure in the great saphenous vein is caused by the outward flow within calf perforators; competent valves in calf perforators would preclude any relevant pressure increase. Calf pump activity entails a distinct decrease of ambulatory venous pressure in lower leg veins, whereas in the thigh veins the pressure does not decrease; in this way, the ambulatory pressure gradient of 37.4 +- 6.4 mm Hg arises between thigh and lower leg veins and triggers the venous reflux in incompetent venous channels connecting both poles of the ambulatory pressure gradient. In contrast to the very efficient performance of the calf pump, the performance of the foot pump is hemodynamically unimportant. The ejection volume produced by the calf muscle pump comes at about 60 ml or more, whereas the blood volume ejected by the foot pump reaches a negligible value of 3-4 ml.

Venous compliance and clinical implications

Compliance is a characteristic of every deformable system. Compliance is very clear concept in physics and mechanics but in clinics, perhaps, is not the same. However, in veins compliance fits perfectly with the function of drainage of the venous system. Volumetric increase (dV) of the content is correlated with pressure increase (dP) inside the vein according to the equation C’= dV/dP. In humans 75% of the blood is located in the venous system, primarily because the molecular components of a vein media layer is significantly more compliant to that of arteries. This property is fundamental to understanding the change in blood volume in response to a change in posture. Measurements of venous compliance in clinical practice can be done by the means of ultrasound, as well as with the plethysmography. Ultrasound methods assimilate the cross sectional area to the volume of the vein, because it reflects the blood content. Changes in cross sectional area can be reliably measured in response to a change in posture, while pressure can be derived from the hydrostatic pressure changes. Venous compliance is of paramount importance also in pulsatile veins such as the inferior or superior vena cava and the jugular veins, where high resolution ultrasound may accurately derive the cross sectional area. Clinical implications of the mechanical properties of the venous wall are extensively discussed, including the need of dedicated venous stenting, which takes into account venous compliance as the main parameter of the venous function. In addition, venous compliance is the interpretative key for a better understanding of plethysmography curves, as well as of varicose veins and of their return to normal cross sectional area following ambulatory venous pressure reduction.

Randomised Controlled Trial: Potential Benefit of a Footplate Neuromuscular Electrical Stimulation Device in Patients with Chronic Venous Disease

Chronic venous disease (CVD) is common, affecting a quarter of the population. Current conservative methods of treatment aim to prevent progression of disease by reducing ambulatory venous pressure. Neuromuscular electrical stimulation (NMES) refers to the use of electrical impulses to elicit muscle contraction. This pilot randomised controlled trial investigates the effect of a footplate NMES device (REVITIVE) on venous flow parameters, limb oedema, and quality of life outcome measures in patients with CVD. Twenty-two patients with Clinical Etiological Anatomical and Pathophysiological (CEAP) clinical class C2–C4 venous disease were randomised to receive a sham or test device. The recommended duration of use was for 30 minutes daily for 6 weeks. Venous flow parameters (duplex ultrasound), limb volume (optoelectric volumeter), and quality of life outcome measures were measured at baseline and after 6 weeks. The mean age of participants was 62 years, body mass index 28.6, with a 15:7 female preponderance. There was a significant difference in the percentage change in femoral vein flow parameters (from baseline) between the test and sham group while using the device (Week 0 time-averaged mean velocity 102.4% vs. −9.1%, p < .0001; volume flow 107.9% vs. −3.7%, p < .0001; peak velocity 377.7% vs. −6.7%, p < .0001). Limb volume was observed to increase significantly in the sham group (2.0% at Week 0 and 1.2% at Week 6; p < .01). This was prevented in the test group (+0.8% at Week 0 and 1.0% at Week 6; p = .06). There was a significant difference in the Aberdeen Varicose Vein Questionnaire between the two groups over the 6 weeks. This trial demonstrated a significant difference in venous flow parameters and prevention of orthostatic limb oedema with NMES. There was a positive effect on quality of life. Larger studies are required to determine the clinical significance of this in patients with venous disease.

Stasis Dermatitis: Pathophysiology, Evaluation, and Management.

Stasis dermatitis commonly occurs in older age. It is caused by venous hypertension resulting from retrograde flow due to incompetent venous valves, valve destruction, or obstruction of the venous system. Further tissue changes arise from an inflammatory process mediated by metalloproteinases, which are up-regulated by ferric ion from extravasated red blood cells. Stasis dermatitis presents initially as poorly demarcated erythematous plaques of the lower legs bilaterally, classically involving the medial malleolus. It is one of the spectrum of cutaneous findings that may result from chronic venous insufficiency. Its mimics include cellulitis, contact dermatitis, and pigmented purpuric dermatoses. Duplex ultrasound is useful in demonstrating venous reflux when the clinical diagnosis of stasis dermatitis is inadequate. Conservative treatment involves the use of compression therapy directed at improving ambulatory venous pressure. Interventional therapy currently includes minimally invasive techniques such as endovenous thermal ablation and ultrasound-guided foam sclerotherapy, which have supplanted the use of open surgical techniques.

Randomised Controlled Trial: Potential Benefit of a Footplate Neuromuscular Electrical Stimulation Device in Patients with Chronic Venous Disease

Chronic venous disease (CVD) is common, affecting a quarter of the population. Current conservative methods of treatment aim to prevent progression of disease by reducing ambulatory venous pressure. Neuromuscular electrical stimulation (NMES) refers to the use of electrical impulses to elicit muscle contraction. This pilot randomised controlled trial investigates the effect of a footplate NMES device (REVITIVE) on venous flow parameters, limb oedema, and quality of life outcome measures in patients with CVD. Twenty-two patients with Clinical Etiological Anatomical and Pathophysiological (CEAP) clinical class C2-C4 venous disease were randomised to receive a sham or test device. The recommended duration of use was for 30minutes daily for 6 weeks. Venous flow parameters (duplex ultrasound), limb volume (optoelectric volumeter), and quality of life outcome measures were measured at baseline and after 6 weeks. The mean age of participants was 62 years, body mass index 28.6, with a 15:7 female preponderance. There was a significant difference in the percentage change in femoral vein flow parameters (from baseline) between the test and sham group while using the device (Week 0 time-averaged mean velocity 102.4% vs.-9.1%, p<.0001; volume flow 107.9% vs.-3.7%, p<.0001; peak velocity 377.7% vs.-6.7%, p<.0001). Limb volume was observed to increase significantly in the sham group (2.0% at Week 0 and 1.2% at Week 6; p<.01). This was prevented in the test group (+0.8% at Week 0 and 1.0% at Week 6; p=.06). There was a significant difference in the Aberdeen Varicose Vein Questionnaire between the two groups over the 6 weeks. This trial demonstrated a significant difference in venous flow parameters and prevention of orthostatic limb oedema with NMES. There was a positive effect on quality of life. Larger studies are required to determine the clinical significance of this in patients with venous disease.