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

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

OBJECTIVE

Ambulatory 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.

METHODS

Twelve 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).

RESULTS

ΔP 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.

CONCLUSIONS

During 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.

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

BACKGROUND

Column 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).

METHODS

A 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.

RESULTS

Thirty-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).

CONCLUSIONS

Obstruction 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.

Bidirectional perforators in the lower limb are not physiologically normal: A brief commentary

The suggestion that bidirectional flow is a normal feature seen in venous perforators of the lower leg has been a longstanding debate. Newer published evidence has changed the perspective on normal perforator flow and is presented here to resolve the misunderstandings and different viewpoints previously held.

Calf muscle pump pressure-flow cycle during ambulation

OBJECTIVE

Calf muscle pump (CMP) failure contributes to the severity and progression of chronic venous disease. Attempts to improve CMP function through resistance exercise have failed to improve chronic venous disease severity or quality of life, partially because the selection of the type of exercise was based on the assumption that the CMP ejects blood from the intramuscular venous sinuses (VSs), which has never been tested in humans. In the present study, we investigated the real-time changes in the pressure and size of the VS during the entire gait cycle of ambulation.

METHODS

We studied 12 lower extremities of nine healthy volunteers at rest and while walking on a treadmill at three different speeds (60, 90, and 120 steps/min). The changes in the VS cross-sectional area (CSA) and pressure were measured. Myography of the gastrocnemius muscle (GCM) and anterior tibial muscle (ATM) was used to register muscle activity. The relationship between the phases of the gait cycle and the measured parameters was analyzed using video records of all experiments.

RESULTS

The observed timing of events was consistent among all limbs studied. At rest, with the participants standing still, the VS pressure and CSA was 70.3 ± 4.2 mm Hg and 23.3 ± 14.6 mm2, respectively. During ambulation, at the first half of the stance, the GCM and ATM eccentrically contract, and the pressure is low (17 ± 8 mm Hg, 20 ± 12 mm Hg, and 29 ± 13 mm Hg at 1, 1.5, and 2 Hz, respectively), and the VS is collapsed. When the heel starts rising (the second half of the stance), the GCM concentrically contracts, the pressure increases, reaching its maximum value (143 ± 37, 134 ± 46, and 128 ± 41 mm Hg), and the VS opens, reaching its maximal size (1.8 ± 1.4 and 2.3 ± 2.2 mm2 at 1 and 1.5 Hz, respectively), followed by collapse of the VS. During the swing phase, the GCM relaxes, and the ATM concentrically contracts, resulting in a rapid decrease in pressure (2.6 ± 4.7, 1.1 ± 6.2, and -4.7 ± 3.2 mm Hg). The VS CSA remained negligible.

CONCLUSIONS

The GCM concentric contraction was associated with a simultaneous increase in VS pressure and CSA. GCM relaxation with ATM concentric contraction coincided with a decrease in VS pressure to negative values. The VSs do not fill but remain empty during the swing phase of ambulation, acting, not as a reservoir, but as a conduit, transferring blood from the network of intramuscular veins to the axial deep veins.

Effect of Lower Limb Venous Dilation on the Autonomic Cardiac Response among Healthy Young Men

Venous occlusion of the lower limbs, which simulates edema, can alter heart rate variability (HRV) by increasing feedback information from group III/IV sensory fibers. Our aim was to quantify this effect among healthy young men. The study group included 13 men (mean age, 20.4 years). Venous occlusion of the lower limbs was induced using a pressure cuff around both thighs. The effect of occlusion on autonomic cardiac response was quantified under occlusion pressures of 20, 60, and 100 mmHg. Compression was applied for 5 min. HRV was evaluated from changes in the low-frequency (LF) and high-frequency (HF) power of the electrocardiogram and the resulting LF/HF balance. Near-infrared spectroscopy of the leg was used to quantify the effects of occlusion on deoxyhemoglobin, measured as the area under the curve (HHb-AUC). The occlusion pressure of 100 mmHg induced a significant increase in the LF/HF ratio, compared to the baseline (p < 0.05). HHb-AUC was highest for the 100 mmHg occlusion pressure compared with the 20 and 60 mmHg pressures (p < 0.01). These findings indicate that venous dilation may elicit a shift towards sympathetic dominance in the autonomic balance.

Modified intraoperative distal compression method for lymphaticovenous anastomosis with high success and a low venous reflux rates

INTRODUCTION

For successful lymphaticovenous anastomosis (LVA), it is important to create anastomoses with high flow to maintain patency. To ensure that this can be achieved, we compared the efficacy of a modified intraoperative distal compression (IDC) technique with the conventional no compression (NC) method for lower limb lymphedema.

PATIENTS AND METHODS

In the IDC group, compression was applied to an area of the foot distal to the first LVA site. After completion of the first LVA, the distal compression was extended over the first LVA site to the distal end of the second LVA site.

RESULTS

There was no significant difference between the IDC (n = 25) and NC (n = 25) groups in detection rate. However, significant differences were observed in lymphatic vessel diameter and LVA success rate. No intraoperative anastomotic obstruction was seen at the conclusion of surgery. Intraoperative congestion with blood was detected in lymphatic vessels in 8 of 79 anastomoses (10.1%) in the NC group, but not in any cases in the IDC group (p = 0.002). There was a significant between-group difference in the rate of improvement in lymphedema between the IDC (16.1±3.6) and NC groups (14.0±3.4; p = 0.03).

DISCUSSION

IDC during LVA is thought to increase lymph flow in larger caliber lymphatics, leading to a high success rate and a low rate of venous reflux. IDC is beneficial when performing LVA.