Functional aspects of the veins of the leg

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.

Plethysmographic features of calf pump failure in chronic venous obstruction and reflux

BACKGROUND

Calf pump failure (CPF) is a common concept in chronic venous disease. Dorsal vein pressures were originally used to define the pathophysiology. More recently, an abnormal ejection fraction (EF) and residual volume fraction (RVF) with air plethysmography (APG) have been substituted for its diagnosis. The relationship between reflux and calf pump function has been studied extensively. Reflux is thought to be the main cause of CPF, although other mechanisms may play a secondary role. Data mining in our dataset revealed that CPF is frequently found in nonrefluxive limbs-an unexpected finding. We analyzed the APG features of CPF in nonrefluxive limbs of a large cohort of patients investigated for chronic venous disease in our clinic. Data from refluxive limbs (control) seen over the same period was included for comparison. Venous obstructive pathology was variably present in both subsets. Iliac vein stent outcome in CPF limbs from both subsets is included. The role of obstruction in CPF is currently unknown.

METHODS

Records of 13,234 limbs in 8813 patients evaluated for suspected chronic venous disease over a 22-year period were analyzed. Prestent and poststent data in 406 CPF limbs (129 nonrefluxive; 277 refluxive) that underwent iliac vein stenting to correct associated stenosis are included. This is a single-center retrospective analysis of prospectively collected data. Duplex and APG data were available for included limbs. A RVF of more than 50% was defined as CPF. A reflux time of greater than 1 second elicited with automated cuffs in the erect position was defined as reflux.

RESULTS

There were 7780 (59%) limbs with reflux and 5454 (41%) that were nonrefluxive. Supine venous pressure, an index of venous obstruction, was elevated in both subsets. The incidence of CPF was 25% in refluxive limbs and 16% in nonrefluxive limbs totaling 2790 limbs. Venous volume and venous filling index were significantly elevated (P = .0001) in refluxive limbs compared to nonrefluxive limbs. The EF was diminished (<50%) in all CPF limbs except in a small fraction (n = 427 [3%]). Stent correction of iliac vein stenosis corrected CPF, normalizing the RVF in both subsets.

CONCLUSIONS

CPF frequently occurs in nonrefluxive limbs with incidence only slightly less than in refluxive limbs. An RVF of more than 50% seems to be a practical definition of a CPF; an EF of less than 50% is associated with a RVF of greater than 50% in 97% of analyzed limbs. Prospective identification of CPF in limbs with chronic venous disease may allow more detailed investigation of its cause (preload, afterload, neuromuscular pathology or joint immobility, etc) and direct more targeted treatment than currently practiced.

Extension of Iliac Vein Stent into the Profunda Femoral Vein for Salvage

BACKGROUND

Extension of iliac vein stents into the common femoral vein is often required to correct stenoses found at or near the inguinal ligament. Very rarely, extension of the iliac stent into the profunda femoris vein may be required because of severe disease at the femoral trijunction. Profunda extension of iliac vein stents is a rare but useful technique for salvage. Our experience with extensions of iliac vein stents into the profunda femoris vein is described. Methods PATIENTS: Search of our Electronic medical records (EMR) identified 20 limbs (0.75%) among a total of 2641 stented limbs (years 2006-2017) in whom the iliac vein stent was extended into the profunda femoris vein. Patients had been followed at 6 weeks, 3 months, 6 months and yearly thereafter following the index procedure. Routine follow up consisted of detailed clinical evaluation including venous clinical severity score, visual analogue pain assessment, and edema grading by physical examination. Stent surveillance was performed at follow up visits.

TECHNIQUE

The iliac vein stent was declotted if needed and then extended into the profunda femoris vein at the same sitting. Antegrade access of the profunda femoris vein was preferred by direct puncture near the lesser trochanter or through a popliteal approach when a profunda-popliteal connection was present. An internal jugular access was used when an antegrade approach failed.

RESULTS

Stent extension into the profunda was a secondary procedure after the initial iliac-common femoral vein stent failed in 17/20 (85%) limbs. In 3 (15%) limbs, profunda extension was carried out at the initial iliac vein stent procedure as there was severe stenosis at the femoral confluence. One or more reinterventions after profunda extension were required in 50% of the limbs to maintain secondary patency or functionality. Fifteen of twenty(75%) limbs with profunda extensions remained patent on long term follow up. The median duration of secondary patency of stents that remained patent, those that occluded and overall were 23 months, 3 months, and 10 months respectively. Thirty percent of stents remained patent at 5 years.

CONCLUSION

Extension of an iliac vein into the profunda femoris vein is a rarely required but useful procedure for stent salvage and symptom relief. Corrective reinterventions are often required but can result in long term patency extending to many years.

Cardiovascular Response to Posture Changes: Multiscale Modeling and in vivo Validation During Head-Up Tilt

In spite of cardiovascular system (CVS) response to posture changes have been widely studied, a number of mechanisms and their interplay in regulating central blood pressure and organs perfusion upon orthostatic stress are not yet clear. We propose a novel multiscale 1D-0D mathematical model of the human CVS to investigate the effects of passive (i.e., through head-up tilt without muscular intervention) posture changes. The model includes the main short-term regulation mechanisms and is carefully validated against literature data and in vivo measures here carried out. The model is used to study the transient and steady-state response of the CVS to tilting, the effects of the tilting rate, and the differences between tilt-up and tilt-down. Passive upright tilt led to an increase of mean arterial pressure and heart rate, and a decrease of stroke volume and cardiac output, in agreement with literature data and present in vivo experiments. Pressure and flow rate waveform analysis along the arterial tree together with mechano-energetic and oxygen consumption parameters highlighted that the whole system approaches a less stressed condition at passive upright posture than supine, with a slight unbalance of the energy supply-demand ratio. The transient dynamics is not symmetric in tilt-up and tilt-down testing, and is non-linearly affected by the tilting rate, with stronger under- and overshoots of the hemodynamic parameters as the duration of tilt is reduced. By enriching the CVS response to posture changes, the present modeling approach shows promise in a number of applications, ranging from autonomic system disorders to spaceflight deconditioning.

Flick-Spin Methodology for Improving Cannulation Success in Tortuous and Valve-Rich Peripheral Veins

Peripheral veins often contain tortuosities and valves that hinder the effective passage of intravenous catheters to the full extent of catheter length. This report describes a methodology termed flick-spin that has proven efficacious for venous catheter passage in tortuous and valve-rich peripheral veins. The method relies on (1) applying longitudinal tension to the vessel in an attempt to straighten it, (2) rotating or spinning the catheter along its longitudinal axis, and (3) flicking the skin or visible vein just beyond the catheter tip, all during catheter advancement. Additionally, lateral pressure may also be applied to the vessel—ie, proximal to the catheter tip and during catheter advancement—to fine-tune catheter tip direction. The report contains multiple illustrations to communicate the anatomic, physiologic, and technical underpinnings of the technique, as well as instructions for troubleshooting common problems.

A Study of Venous Return from the Leg during Exercise

Bi-directional ultrasound velocity detector tracings were made of venous blood flow through the popliteal vein in the following situations: (1) walking normally; (2) walking in place; (3) sitting, foot on floor, with rhythmic plantar and dorsi-flexion; (4) sitting, foot on a treadle device requiring 20 degrees of plantar-flexion and 20 degrees of dorsi-flexion to complete a cycle; (5) using the treadle device while in recumbent position, and (6) pushing the foot in plantar flexion against a pedal equipped with a spring resistance.

These studies show that active walking, which consists of both plantar flexion and dorsi-flexion, produces cephalad return of venous blood from the foot and leg. When the walking cycle is accompanied by weight bearing, plantar flexion produces a greater blood velocity. However, when there is no weight bearing, dorsi-flexion produces a greater blood velocity than plantar flexion.

Therefore, when not bearing weight on the foot, a full range of dorsi-flexion as well as a full range of plantar flexion is essential to utilizing maximum efficiency of the lower extremity muscle pump.

Evaluation of the Time Course of Vascular Responses to Venous Congestion in the Human Lower Limb

This study examined the time course of changes in blood flow to the lower leg in response to venous distension--the veni-arteriolar vasoconstrictor response--in 31 healthy males. During a 5-min period of venous distension (thigh cuff pressure 50 mm Hg), calf blood flow (venous occlusion plethysmography) decreased more rapidly (within 30 s) compared to skin perfusion (after 2 min, Laser Doppler flowmetry), consistent with disparate filling times of superficial and deeper veins and a greater increase in deep vein volume. On completion of venous filling, vascular resistance in the skin was unchanged from baseline, implying that the reduction in perfusion was solely the result of reduced perfusion pressure. For the whole calf, vascular resistance was unchanged after 1 min but decreased thereafter by 35-45% from baseline, indicating adjustment of pre- or post-capillary resistances to maintain flow. Repeated plethysmographic flow measurements assisted the decrease in resistance, most likely by intermittent compression of the thigh cuff acting to displace blood volume centrally and alleviate congestion. These findings do not support an active veni-arteriolar vasoconstrictor mechanism in response to venous distension alone in the lower leg, and provide evidence of dynamic flow adjustments that should be acknowledged during procedures that involve prolonged periods of venous congestion.

Cardiovascular response to passive cycle exercise

PURPOSE

Cardiovascular response of trained males (N = 20) and fit but untrained controls (N = 10) were examined during rest and passive cycle exercise (PCE).

METHODS

Heart rate (HR), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and mean arterial pressure (MAP) were measured during PCE for 6 min at intensities of 30 and 60 rpm. Also vagal influence on the heart was assessed through time series analysis of heart period variability (HPVts) at high and medium frequencies. Electromyography (EMG) was used to monitor muscle activity during PCE.

RESULTS

During PCE no differences in cardiovascular response were found between the trained and untrained groups; thus groups were combined for the remainder of the analysis. Results indicated that during light and medium PCE all subjects combined showed a significant increase in HR, CO, and MAP and a significant decrease in HPVts (P < 0.001).

CONCLUSION

The increase in HR during passive exercise may be a result of the stimulation of mechanoreceptors. The small and similar SV response during PCE of both groups suggests that the muscle pumps may not be effective during this form of passive exercise.

Venous outflow of the leg: anatomy and physiologic mechanism of the plantar venous plexus

PURPOSE

Mechanisms of venous outflow from the leg and foot have not been clearly defined. The purpose of this study was to evaluate the anatomy and physiologic mechanism of the plantar venous plexus and its impact on venous drainage from the tibial veins.

METHODS

Fifty phlebograms that contained complete foot and calf films were reviewed. On lateral films, the number of veins in the plantar venous plexus and its tibial outflow tract were counted. The length and diameter of the longest vein in the plantar venous system and the length of the foot arch were measured. The ratio of the length of the plantar venous plexus to the arch length was calculated. The presence or absence of valves within the plexus was recorded. Plantar venous plexus outflow was evaluated by an duplex ultrasonographic scan of the posterior tibial, anterior tibial, and peroneal veins during intermittent external pneumatic compression of the plantar surface of the foot.

RESULTS

The plantar venous plexus was composed of one to four large veins (mean, 2.7 veins) within the plantar aspect of the foot. The diameter of these veins was 4.0 +/- 1.2 mm. The veins coursed diagonally from a lateral position in the forefoot to a medial position at the level of the ankle, spanning 75% of the foot arch. Prominent valves were recognized within the plantar veins in 22 of 50 patients. The plexus coalesced into an outflow tract of one to four veins (mean, 2.5 veins) that flowed exclusively into the posterior tibial venous system. Small accessory veins that drained the plantar surface of the forefoot flowed into either the posterior tibial or peroneal veins. This pattern of selective drainage of the plantar venous plexus was confirmed by duplex imaging. Mechanical compression of the plantar venous plexus produced a mean peak velocity in the posterior tibial veins of 123 +/- 71 cm/sec, in the anterior tibial veins of 24 +/- 14 cm/sec, and in the peroneal veins of 29 +/- 26 cm/sec.

CONCLUSIONS

The plantar venous plexus is composed of multiple large-diameter veins that span the arch of the foot. Compression of the plantar venous plexus, such as that which occurs during ambulation, is capable of significantly increasing flow through the posterior tibial venous system into the popliteal vein. Its function may be integral to venous outflow from the calf and priming of the more proximal calf muscle pump.

Venous pressure in the saphenous vein near the ankle during changes in posture and exercise at different ambient temperatures

The venous pressure in the saphenous vein at the ankle was measured in ten healthy subjects (5 men, 5 women) aged 19-33 years during supine posture, orthostasis and cycle ergometer exercise (50 W, 50 rpm). Measurements were made at 20, 28 and 36 degrees C at 50% relative humidity. A custom-built setup consisting of two pressure transducers and a differential amplifier was used to compensate for the hydrostatic effects, temperature influences and movement artefacts that disturbed the pressure measurements. Pressure was lowest in the supine position and varied only slightly with the ambient temperature. The mean pressures were 7 (SEM 1) mmHg [0.9 (SEM 0.13) kPa], 7 (SEM 1) mmHg [0.9 (SEM 0.13) kPa], 4 (SEM 1) mmHg [0.5 (SEM 0.13) kPa] at 20, 28 and 36 degrees C. The venous pressure increased when the subjects were passively tilted from a supine to an upright posture. The rate of the increase was smaller at 20 degrees C than at 28 degrees and 36 degrees C. The final level the pressure reached during motionless standing differed slightly. The mean pressures were 76 (SEM 2) mmHg [10.1 (SEM 0.27) kPa], 79 (SEM 7) mmHg [10.5 (SEM 0.93) kPa] and 75 (SEM 3) mmHg [10.0 (SEM 0.40)] at the three temperatures. When starting exercising, venous pressure decreased within the 1st min to a level which remained virtually constant until the end of exercise. However, this level was found to be temperature dependent. It was lowest at 20 degrees C (26 (SEM 3) mmHg [3.5 (SEM 0.40) kPa]) and increased with temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Repair and replacement of deep vein valves in the treatment of venous insufficiency

Venous insufficiency is a widespread condition, the prevalence of venous ulceration being 0.5-1.0 per cent in Western populations. A principal abnormality causing venous insufficiency is deep venous reflux, usually resulting from post-thrombotic valve destruction. Patients undergoing treatment for venous insufficiency should have all venous abnormalities investigated, defined and corrected where possible. Although treatment for superficial and communicating vein incompetence is available, correction of deep vein reflux has been neglected until recently. Deep vein valve physiology, the selection of patients for deep vein valve surgery and methods of valve repair and replacement are reviewed.

Effect of vein pump activation upon muscle blood flow and venous pressure in the human leg

The effect of vein pump activation upon superficial venous pressure and blood flow in human skeletal muscle tissue was studied in 7 healthy subjects. Blood flow was measured in the anterior tibial muscle by the local 133Xe washout technique. The subjects were placed on a steeply tilted couch in nearly erect position. The vein pump in gastrocnemius-soleus muscles was activated by heel-raisings, and the anterior tibial muscle remained relaxed during this procedure. Blood flow in the resting anterior tibial muscle was constant before, during and after 20 heel-raisings per min. A more heavy exercise with 40 heel-raisings per min increased blood flow about 100%. This increase in blood flow was absent during venous stasis (40 mmHg), and in areas infiltrated with lidocaine. It is concluded, that intense dynamic exercise in gastrocnemius-soleus muscles, in erect humans, increased blood flow considerably in another crural muscle remaining in the resting state. The present study strongly suggests, that the observed increase in blood flow, was associated with a decrease in regional subfascial venous pressure to below the threshold level of the local sympathetic veno-arteriolar reflex.

Femoral vein pressure measurements for evaluation of venous function in patients with postthrombotic iliac veins

Fifty patients with postthrombotic disease were examined by phlebography and by bilateral femoral vein pressure measurements. The degree of obstruction to venous flow was best evaluated by measuring the pressure elevation and pressure difference after exercise and the time required for these parameters to return to pre-exercise levels; pressures during rest and exercise were less conclusive indicators of obstruction. Good correspondence was found between femoral vein pressure and the severity of postthrombotic symptoms, while phleboraphy provided largely morphologic, rather than functional, information. We, therefore, consider it important to determine femoral vein pressure during and after exercise to evaluate the significance of postthrombotic iliac vein disease.

Muscle Pumping in the Dependent Leg

Since the exercising dependent leg displaces blood toward the heart, against a potential gradient, it must perform useful circulatory work. We studied the peripheral circulation in healthy, sedentary males by measuring calf circumference (using mercury-in-Silastic strain gages), muscle pump ejection velocity (using a transcutaneous Doppler flowmeter), intrathoracic and intra-abdominal pressures (through catheters in the esophagus and rectum) and power of the leg muscle pump (product of blood flow and the upstream-downstream venous pressure difference). Measurements of pressure, flow velocity, and volume changes in the dependent venous beds of healthy young men demonstrated that during running in place, (1) the abdominal contraction necessary to fix the pelvis raised inferior caval pressure and impeded venous outflow from the legs, but that, (2) the leg muscles themselves were capable of effectively pumping blood past this functional obstruction. By doing so, these peripheral pumps contributed more than 30% of the energy required to circulate blood during running.