Popliteal Valve Research Articles

New perspectives for prevention of the post-thrombotic syndrome

While on conventional anticoagulation, up to 50% of patients with one or more episodes of proximal deep vein thrombosis (DVT) can develop post-thrombotic (PTS) manifestations. The potential strategies for PTS prevention are the treatment of acute DVT with catheter-directed thrombolysis (CDT), the use of elastic compression stockings (ECS) and that of the direct oral anticoagulants (DOAC) in place of vitamin K antagonists (VKA) for the initial and long-term treatment of DVT. Based on the results of three randomized clinical trials, CDT cannot be recommended on a routine basis because of its invasiveness, the associated risk of major bleedings and the uncertainty about its efficacy. According to the results of a placebo-controlled randomized clinical trial, ECS are no longer recommended for PTS prevention on a routine basis. However, based on the results of a recent subanalysis of a prospective cohort study, patients with residual vein thrombosis and/or popliteal valve reflux at three months are likely to benefit from ECS for at least six months. Finally, following the demonstration that the inadequacy of VKA therapy plays a key role in the PTS development, several retrospective and prospective studies have shown that the use of DOACs for the initial and long-term treatment of DVT in place of VKAs reduces the risk of PTS by approximately 50%. In conclusion, the availability of DOACs and the potential of ECS in selected patients with proximal DVT are expected to play a key role for decreasing the rate and the severity of PTS in the forthcoming years.

Elastic compression stockings for prevention of the post-thrombotic syndrome in patients with and without residual vein thrombosis and/or popliteal valve reflux.

Not available.

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 & 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.

A new ultrasonographic technique for diagnosing deep venous insufficiency—imaging and functional evaluation of venous valves by ultrasonography with improved resolution

This is to demonstrate a new 2D-ultrasonographic technique which enabled clear resolution of deformed valves, visualization of venous reflux and quantitation of valve incompetence. In a 59-year-old Japanese female patient, ultrasonography was done using Aplio, Toshiba Medical Systems Co., Japan, equipped with 8 MHz linear probe capable of differential tissue harmonic imaging to diagnose the cause of her leg edema. Venous ultrasonography using this device at the popliteal venous valve in this patient demonstrated clear view of deformed venous valve and valve separation at one end of valvular agger while the other part of the valve is closed. Color Doppler failed to show venous reflux due to its low velocity. However, the appearance and disappearance of a thrombus-like echo could be imaged using 2D-ultrasonography. In addition, we were able to demonstrate the time-course change of valve opening and closing, and quantitate the valve incompetence using M-mode ultrasonography.

Haemodynamic significance of incompetent calf perforating veins

A total of 149 consecutive unselected patients (221 limbs) who presented with signs and symptoms of chronic venous problems (varicose veins with or without ankle oedema, skin changes and leg ulcers) have been studied by clinical examination, ascending deep to superficial venography, Doppler ultrasound and ambulatory venous pressure measurements. Of the limbs, 180 (82 per cent) had varicose veins without obstruction in the deep veins or reflux in the popliteal or femoral veins while 41 (18 per cent) had deep venous disease. Of the 180 limbs with 'primary' varicose veins 110 (60 per cent) did not have incompetent calf perforating veins (group A) while 70 (40 per cent) did (group B). On the basis of the ambulatory venous pressure after calf muscle exercise and the refilling time, the incompetent calf perforating veins of limbs in group B belonged to three subgroups of different haemodynamic significance. In 20 limbs (30 per cent) they were found to be of no haemodynamic significance, in 25 (35 per cent) of moderate haemodynamic significance and in 25 (35 per cent) of major haemodynamic significance. The last were, on clinical examination, indistinguishable from limbs with deep venous disease although they had patent deep veins with competent popliteal valves.

Hemodynamic and clinical impact of ultrasound-derived venous reflux parameters

Purpose This study was undertaken to assess which ultrasound-derived parameter was superior for measuring venous reflux quantitatively and to evaluate the importance of popliteal vein valve reflux. Patients and methods A retrospective analysis was performed of 244 refluxive limbs in 182 patients who underwent ultrasound scanning, venous pressure measurement, air plethysmography, and clinical classification of severity according to the CEAP score. Reflux time (RT, s), peak reflux velocity (PRV, m/s), time of average rate of reflux (TAF, mL/min), absolute displaced volume retrogradely (ADV, mL) were compared to clinical class, ambulatory venous pressure (% drop), venous filling time (s), and venous filling index (mL/s) using nonparametric statistical tests. A P value of <.05 was considered significant. Limbs were divided into 3 groups: (A) axial great saphenous vein reflux only (n = 68); (B) axial deep reflux including popliteal vein incompetence with or without concomitant gastrocnemius or great or small saphenous vein reflux (all ultrasound reflux parameters of each refluxive vein added at the knee level) (n = 79); and (C) all limbs with popliteal vein reflux (the ultrasound data of the refluxive popliteal vein exclusively was used in comparison regardless of concomitant associated reflux) (n = 103). Limbs were also stratified into limbs with skin changes and ulcer (C-class 4-6) and those without (C-class 1-3) and subsequently compared. Results No meaningful significant correlation was found between RT and the clinical and hemodynamic results in groups A and B. The PRV and TAF correlated significantly with the hemodynamic parameters. The PRV and TAF and clinical severity trended towards correlation in group A ( P = .0554 and P = .0998, respectively), but was significantly correlated in group B. The poor hemodynamic condition in the subset of C-class 4-6 limbs in groups A and B was reflected in a greater PRV, TAF, and ADV in this subset as compared with the limbs in C-class 1-3. RT was not significantly different in the subsets of limbs, further suggesting that RT is not related to hemodynamic or clinical state of the limbs. No meaningful correlations were found in group C. Although the hemodynamic data were significantly poorer in the subset of limbs with C-class 4-6 than in C-class 1-3, the ultrasound-derived parameters were not significantly different. Conclusion The duration of valve reflux time (or valve closure time) cannot be used to quantify severity of reflux and is purely a qualitative measurement. The PRV and the rate of reflux appeared to better reflect the magnitude of venous incompetence. In the presence of axial reflux, it appeared logical and physiologically correct to sum up these reflux parameters for each venous segment crossing the knee. The popliteal valve reflux (the “gatekeeper” function) was not in itself an important determinant of venous hemodynamics and clinical severity. Additional reflux in other venous segments must be taken into account.

Late results of iliofemoral venous thrombectomy.

Although anticoagulation therapy for iliofemoral venous thrombosis prevents pulmonary embolism, it is not designed to avoid the postthrombotic syndrome. Mechanical removal of the thrombus in the form of venous thrombectomy should yield better long-term results. The purpose of our study was to analyze the clinical outcome and venous valvular function of limbs 5 to 13 years after iliofemoral venous thrombectomy. Seventy-seven lower extremities underwent venous thrombectomy for acute iliofemoral venous thrombosis and were monitored for a mean follow-up of 8 1/2 years (range, 5 to 13 years). Patency of the iliofemoral venous system, competence of the femoral popliteal valves, and clinical signs and symptoms of chronic venous insufficiency were evaluated in each case. Subsequent to early perioperative failure, patency remained stable over time at 84%. Valvular competence was preserved in 80% at 5 years; however, it decreased to 56% at 10 years. It is important that more than 90% of the limbs had no symptoms or mild symptoms of chronic venous insufficiency. Venous thrombectomy should be considered for primary treatment in selected cases of early iliofemoral venous thrombosis.

Asymptomatic Popliteal Vein Aneurysms

Popliteal vein aneurysms represent a rare vein abnormality. There is agreement on the etiology, symptomatology (thromboembolism), and diagnosis (color duplex scanning). Surgery is the treatment of choice in symptomatic cases, but management in asymptomatic cases remains uncertain. Seven cases (5 women and 2 men with a mean age of fifty-nine years) of asymptomatic popliteal vein aneurysms are presented. The diagnosis and follow-up were made by color flow duplex imaging (CFDI). All aneurysm were of a saccular type, fully compressible, without evidence of thrombus in the sac, and with a maximal diameter ranging from 2.0 to 2.8 cm. In all but 1 case the popliteal valve was located in the aneurysmal sac and minor reflux was detected. Superficial vein incompetence was found in 6 patients, whereas in the seventh patient reflux was found in the superficial femoral vein. No treatment was offered and close surveillance with CFDI every four months was performed. So far, all patients remain asymptomatic over a period of two months to two years. Asymptomatic cases may remain without treatment under close surveillance with CFDI and regular clinical follow-up.

Observations on the calf venous pump mechanism: Determinants of postexercise pressure

Purpose: We investigated the factors determining postexercise pressure and the relationship of venous valve closure and venous column segmentation to ambulatory venous pressure changes.Methods: Valve closure and venous segmentation were observed during dynamic ascending phlebography in 40 nonrefluxive limbs and by duplex imaging in 25 normal limbs in healthy volunteers. Simultaneous volume (air plethysmography) and pressure studies during calf exercise were also carried out. Some studies used a simple mechanical model comprised of a collapsible latex tube (“calf pump”) and a graduated “popliteal” valve.Results: The femoropopliteal venous column above the popliteal valve remains unsegmented and continuous during ambulatory venous pressure changes in response to calf muscle contraction. Therefore ambulatory venous pressure changes cannot be explained purely on the basis of hydrostatic column pressure changes. Postexercise pressure appears to be determined by a complex set of factors: (1) physical segmentation of the venous column below the popliteal valve (i.e., tibial valve closure); (2) tube collapse below the closed valve, which further aids in the breakup of the hydrostatic column pressure and dampens the effect of any reflux through or around the closed valve; (3) ejection fraction, which influences the degree of tube collapse; and (4) the interaction of the resultant pressure forces with the wall properties of the venous pump.Conclusions: The mechanism of ambulatory venous pressure reduction is complex and multifactorial. The importance of venous wall characteristics as a determinant of postexercise pressure has not been previously appreciated. Changes in venous wall property after a thrombotic process, for example, could conceivably influence ambulatory venous pressure and recovery time in the absence of reflux.

The relation of venous ulceration with ambulatory venous pressure measurements

Two hundred thirty-six limbs of 220 unselected patients who were admitted with venous problems (83 with ulcers) were studied with continuous-wave Doppler ultrasonography, duplex scanning, and ambulatory venous pressure measurements. Patients with evidence of deep venous disease because of reflux or obstruction in the deep veins on Doppler and duplex ultrasonic examination or with an ambulatory venous pressure greater than 45 mm Hg despite the ankle cuff had venography. One hundred fifty-three limbs had superficial venous disease (reflux in the superficial veins with competent popliteal valves), and 83 limbs had deep venous disease (popliteal reflux on duplex examination or deep venous obstruction on venography). No ulceration occurred in limbs with ambulatory venous pressure <30 mm Hg, and there was a 100% incidence with ambulatory venous pressure >90 mm Hg. A linear increase occurred from 14% in limbs with ambulatory venous pressure between 31 and 40 mm Hg to 100% in limbs with ambulatory venous pressure greater than 90 mm Hg (r = 0.79). In the groups studied, an increased incidence of ulceration was associated with an increase in ambulatory venous pressure irrespective of whether the venous problem was the result of superficial or deep venous disease. Ambulatory venous pressure has both diagnostic and prognostic significance in patients with venous disease.

Popliteal Valvular Construction Using a Silastic Sling (Technique II) for Deep Venous Insufficiency of the Lower Limb

Objective: To establish the safety and efficacy of a silastic sling procedure for reconstructing popliteal vein. Design: Prospective survey of patients undergoing surgical treatment for popliteal vein reflux. Setting: Department of Surgery, County Hospital, Bad Karlshafen, Germany. Patients: 209 patients undergoing surgery for popliteal vein incompetence. Interventions: Silastic sling procedure (Technique II) for correction of popliteal vein incompetence. Main outcome measures: Continuous wave Doppler ultrasound examination of popliteal vein, ambulatory foot vein pressure measurements, lower limb venography. Results: One week following surgery 202 patients (of 209) reported relief of pain and reduction of limb oedema. 77 patients with ulcers (of 85) healed following the surgical procedure. Ambulatory venous pressure improved from 71 SD 11 mmHg to 36 SD 17 mmHg. There was prolongation of the venous refilling time from 9 SD 5 seconds to 27 SD 17 seconds. Postoperative phlebography in 92 patients was performed on the tenth post-operative day and in no patient was deep vein thrombosis observed. In 82 of these patients phlebography demonstrated that the constructed popliteal valve was patent. Conclusions: Construction of a popliteal valve using the author's silastic sling technique is a satisfactory method for managing patients with otherwise uncontrolled popliteal vein reflux due to either primary valvular failure or previous deep vein thrombosis.

Venous ulceration: factors influencing recurrence after standard surgical procedures

Ninety patients with chronic venous ulceration were investigated to determine the extent of the incompetence of the venous valves. They were then treated by established surgical methods to control reflux. All wore fitted compression stockings and were regularly followed up. Forty-two patients had valvular incompetence confined to the perforating and superficial veins. All their ulcers healed and only one developed a minor recurrence during the three year follow-up. Nineteen patients had additional but limited incompetence of the deep veins; all their ulcers healed, but three developed a recurrence. Twenty-nine patients had extensive deep vein valvular incompetence including incompetence of the popliteal valve; in 12 of these patients either the ulcer failed to heal or the patient developed a recurrent ulcer within 18 months. Thirty-two other patients developed further venous reflux from the opening of new channels, including the perforating veins of the foot, and required sclerosants or local ligation. It was concluded that established surgical techniques, thoroughly performed, were very effective for the treatment of chronic venous ulceration provided the popliteal valves were competent. When the popliteal valves were incompetent the recurrence rate was unacceptably high and additional methods, including vein valve transplants, excision of the ulcer with skin grafting and lumbar sympathectomy, were considered. Nine of 11 patients who received a vein valve transplant had falls in their ambulant venous pressures, improvement in the nutrition of their skin and healing of their recurrent ulcers.

The value of dynamic venous pressure measurements.

AbstractThis article describes the technique of measuring ambulatory venous pressures and their value in the diagnosis and assessment of the severity of venous hypertension as well as their contribution toward our understanding of venous hemodynamics and the pathophysiology of venous disorders. It demonstrates that ambulatory venous pressures are not only of diagnostic significance, but also of prognostic significance. Competent popliteal valves will protect the leg from venous hypertension despite proximal (iliofemoral) occlusion. Although the measurement of ambulatory venous pressures is the “gold standard,” it is invasive and cannot be repeated frequently nor can it be used as a screening test. It has been employed in the validation of a number of noninvasive tests now used for the routine screening of patients. Nevertheless, ambulatory venous pressure measurements are essential if the beneficial hemodynamic effect of surgical reconstructive procedures is to be convincingly demonstrated.

Late hemodynamic sequelae of deep venous thrombosis.

Twenty-nine limbs in 19 patients who had deep venous thrombosis documented by phlebography were studied by hemodynamic techniques 2 to 13 years later (mean, 7 years). Two limbs were found to be "normal." Nine limbs were hemodynamically obstructed; the remaining 18 limbs had developed reflux abnormality. All of the nine limbs with obstruction demonstrated symptoms of severe swelling or ulceration. In contrast, limbs with valve reflux were either asymptomatic or had only mild to moderately severe symptoms. Correspondingly, the reflux hemodynamic derangement was also mild, with reflux confined to a single level (commonly the popliteal valve). The implications of the differences in clinical presentation and hemodynamic profile between this group with post-thrombotic valve reflux and the typical patient with stasis caused by chronic venous insufficiency are explored. The natural history of stasis sequelae of deep venous thrombosis has apparently changed somewhat since the introduction of anticoagulation therapy.

Late hemodynamic sequelae of deep venous thrombosis

Twenty-nine limbs in 19 patients who had deep venous thrombosis documented by phlebography were studied by hemodynamic techniques 2 to 13 years later (mean, 7 years). Two limbs were found to be “normal.” Nine limbs were hemodynamically obstructed; the remaining 18 limbs had developed reflux abnormality. All of the nine limbs with obstruction demonstrated symptoms of severe swelling or ulceration. In contrast, limbs with valve reflux were either asymptomatic or had only mild to moderately severe symptoms. Correspondingly, the reflux hemodynamic derangement was also mild, with reflux confined to a single level (commonly the popliteal valve). The implications of the differences in clinical presentation and hemodynamic profile between this group with postthrombotic valve reflux and the typical patient with stasis caused by chronic venous insufficiency are explored. The natural history of stasis sequelae of deep venous thrombosis has apparently changed somewhat since the introduction of anticoagulation therapy.

Venous function after fracture of the lower extremity. A 9-year follow-up of 150 cases.

One hundred and fifty patients were examined 8-10 years after a fracture of the lower limb to evaluate whether the frequency of deep venous insufficiency (DVI) was influenced by the type of fracture. The evaluation included clinical examination, subjective complaints, venous pressure, plethysmography and doppler sonography. Symptoms and signs of DVI were more common in the fractured than in the uninjured limbs, while objectively diagnosed DVI did not differ between the groups. Only minor differences were present in the development of DVI between limbs with various types of fracture (hip fractures were not included in the study). High age and incompetence of the popliteal valves were more important in the development of DVI than the earlier fracture. The frequency of objectively measured DVI in the fractured limbs was 35 per cent and in the uninjured limbs 30 per cent.

Significance of popliteal reflux in relation to ambulatory venous pressure and ulceration.

Fifty-one patients (55 limbs) who had had deep venous thrombosis (DVT) extending into the femoral or iliofemoral segment three to five years earlier and ten limbs of ten healthy volunteers were studied. The ambulatory venous pressure (AVP) was measured by inserting a needle in a vein on the foot; the presence of reflux in the popliteal vein was determined by a directional Doppler ultrasonic blood velocity detector. All patients had ascending venography. The results suggest that the most important factor in determining the AVP and ulceration in postthrombotic limbs is the condition of the popliteal valves. Ulceration does not occur even in the presence of occlusion if the popliteal valves are competent. The extent of DVT and recanalization or the failure of recanalization is of secondary importance.