Two-Year Results of a First-In-Human Study in Patients Surgically Implanted With a Bioprosthetic Venous Valve, the VenoValve in Patients With Severe Chronic Venous Insufficiency.

OBJECTIVE: Two-year follow-up results from a first-in-human study of patients implanted with the VenoValve are evaluated for supporting the long-term clinical safety and performance of the device. BACKGROUND: Chronic Venous Insufficiency (CVI) involves improper functioning of lower limb vein valves and inability of these valves to move blood back towards the heart. CVI symptoms include swelling, varicose veins, pain, and leg ulcers. Currently, there is no cure for this condition and treatment options are limited. This study provides 2-year outcomes for 8 patients who were implanted with the bioprosthetic VenoValve for treating severe CVI with deep venous reflux measured at the mid-popliteal vein. The 6-month and 1-year results were previously published. METHODS: Eleven patients with C5 & C6 CVI were implanted with VenoValve into the midthigh femoral vein and followed for 2 years. Assessed clinical outcomes include device-related adverse events, reflux time, disease severity, and pain scores. RESULTS: All 11 implant procedures were successful. Two-year follow-up data was obtained for 8 subjects: 1 patient died of non-device related causes, 1 was lost to follow-up, and 1 refused to follow-up due to the COVID-19 pandemic. No device-related adverse events occurred between the first and second years of follow-up. Reported 2-year clinical performance outcomes included significant decreases in mean reflux times of the mid-popliteal vein (61%), and significant improvements in mean scores for disease severity rVCSS (56%) and VAS pain (87%). CONCLUSIONS: Results from this study support long-term safety and effectiveness of the VenoValve for improving CVI severity by reducing reflux and thereby venous pressures in the lower extremities. With limited treatments for valvular incompetence involved in severe, deep venous CVI, the device may be considered as a novel therapy. A pivotal trial in the United States is currently being conducted to assess the device in a larger number of patients.

Has external banding become a historical technique during venous valve repair?

OBJECTIVE: In deep venous valve repair, transcommissural external valvuloplasty (TEV) is the commonly used technique. In some cases, external banding (EB) is combined with this procedure to improve the patency and durability of the surgical procedure. METHODS: We retrospectively analyzed patients who underwent deep venous valve repair from 1998 through 2018. Patients were divided according to the surgical procedure: Group A: TEV alone and Group B: TEV+EB. Early postoperative outcomes of the procedure were compared between the groups. RESULTS: There were 265 patients in Group A and 165 patients in Group B. The mean follow-up period was 4.2±3.7. The rate of recurrence of venous reflux, ulcer, and reoperation were 31.9 versus 30.9, 21.2 versus 21.8, and 16.7 versus 13.9 in Group A and Group B, respectively. There were 67 reoperations in the follow-up period. At reoperation, external valvuloplasty was performed in 64% of the reoperations in Group A, while this rate was 13% for Group B. CONCLUSIONS: There is no more need for EB during the venous valve repair with the increased experience of valvuloplasty techniques. TEV might be enough with acceptable long-term outcomes during deep venous reconstruction.

"Quality of Life after Varicose Vein Surgery in Patients with High-ligation and Stripping, External Valvuloplasty and Sapheno-femoral Redo Surgery".

BACKGROUND: High-ligation and stripping (HL/S) and external valvuloplasty (eVP) with the implantation of an external device to restore the valve's function, are surgical methods to eliminate reflux at the saphenofemoral junction. Furthermore, redo-surgery (RedoS) can be performed in terms of same side groin recurrences. It is unclear, if there is a difference in quality of life (QoL) between these 3 surgical treatment options. Therefore, it was the aim of our study to elucidate QoL in patients before and after surgical treatment at the saphenofemoral junction by comparing HL/S, eVP, and RedoS. METHODS: A total of 303 participants (156 HL/S, 81eVP, 64 RedoS) were recruited during the daily clinical routine. QoL was measured at admission and 6 weeks after the surgical procedure by means of SF-12 (12 item short form health survey) and Aberdeen Varicose Vein Questionnaire. RESULTS: The mean value of Aberdeen Varicose Vein Questionnaire was 14.5 (SD 2.1) preoperatively and 4.9 (SD 3.3) postoperatively in the HL/S group, 16.4 (SD 1.4) preoperatively and 6.8 (SD 2.5) postoperatively in the eVP group and 15.5 (2.2) preoperatively and 5.8 (SD 4.2) postoperatively in the RedoS group, which was statistically significant (P< 0.05) in all groups. Postoperatively, the mean values were statistically significant within the groups. Concerning physical aspects of the SF-12 we found a significant improvement in the RedoS group, while mental aspects were significantly better in the HL/S and eVP group postoperatively. Nevertheless, the clinical relevance of these SF-12 differences is questionable under consideration of the minimal important difference. CONCLUSIONS: Varicose vein surgery leads to a significant improvement of QoL in all groups. The implantation of an external patch could have a negative influence in QoL.

Prosthetic venous valves: Short history and advancements from 2012 to 2020.

Chronic Venous Disease is estimated at 83.6% of the global population. Patients experience pain, discomfort and severe complications with few effective therapies being available. Current strategies for the treatment of malfunctioning venous valves are invasive with a high recurrence rate. A prosthetic venous valve replacement is imminent, possibly providing better outcomes and improved general quality of life. In this review, prosthetic venous valves history is presented and assesses the advantages and disadvantages of developed venous valves. Articles that discussed potential designs of prosthetic venous valves were examined. A systematic search produced thirty-five papers fitting the inclusion criteria. Our understanding of the ideal abilities required in prosthetic valves has evolved. Developed valves are reported for regurgitation, migration and leakage. Issues have been resolved, but we are still away from the ideal valve. Improvements within the last eight years provided information on the importance of sinuses and prosthetic to venous wall-size mismatch.

Tissue-engineered transcatheter vein valve.

Chronic venous insufficiency affects over 2 million patients in the US alone, with severe cases involving thousands of patients with chronic leg ulcers and potential amputation. Current treatment options are limited, with surgical repair of vein valves being the most effective but challenging solution. A transcatheter vein valve made from a biologically-engineered matrix possessing the ability to regenerate has the potential to provide both valve function and long-term hemocompatibility and durability because the matrix becomes endothelialized and populated with host tissue cells. We have developed a novel tissue-engineered transcatheter vein valve (TEVV) on a Nitinol stent and demonstrated function and durability in vitro. Tissue was grown from fibroblasts in fibrin gel so as to embed the stent, with a tubular extension of the engineered tissue from one end of the stent that was stitched along opposite sides and everted into the stent to form a bileaflet valve. Following decellularization, to create an "off-the-shelf" TEVV comprised of the resulting collagenous matrix, it was tested in a pulse duplicator to evaluate hydrodynamic properties for a range of flow rates. The TEVV was shown to have forward pressure drops in the range of 2-4 mmHg, low closing volume, and nil regurgitation. Further hydrodynamic tests were performed after crimping and then again after 1 million cycle durability testing, showing no degradation of valve performance or any visual damage to the matrix. The TEVV held over 600 mmHg backpressure after the durability testing, ensuring the valve would withstand pressure spikes well outside of the normal in vivo range. Catheter-based delivery into the ovine iliac vein demonstrated TEVV closing 2 weeks p.o. and endothelialization without thrombosis 8 weeks p.o.

The influence of age on valve disease in patients with varicose veins analysed by transmission electron microscopy and stereology.

BACKGROUND: The aim of this study was to investigate the influence of age on the ultrastructure of venous valve morphology in patients with C2 classified chronic venous disorders according to the CEAP classification. PATIENTS AND METHODS: The study population consisted of 16 consecutive patients with varicose veins (C2). The mean age was 49.8 years (30-66). The (pre-) terminal valve including the vessel wall was harvested within the proximal 2 centimetres of the great saphenous vein. The mean thickness (volume-to-surface ratio = V/S ratio) of elastin, collagen, endothelium and of the entire valve was determined. A blinded morphologist performed the examination by transmission electron microscopy and stereology. Analyses by Pearson's product moment correlation, Kendall's tau and Spearman's rank correlation were performed to investigate whether there is a correlation between age and the ultrastructural morphology. RESULTS: Stereological analysis of the valves demonstrated a mean V/S ratio (signifying a thickness estimation) for elastin of 0.87 µm3/µm2, for collagen of 18.0 µm3/µm2, for endothelium of 0.65 µm3/µm2, and for the entire valve of 25.2 µm³/µm². Statistical analyses showed no statistically significant correlation between age and the ultrastructural morphology in this patient group. CONCLUSIONS: The ultrastructural morphology of the venous valves in chronic venous disorders may not depend on age in patients presenting with C2 disease. This conclusion may or may not apply to all C classes as we investigated a homogenous group of patients with C2 limbs.

Caval Valve Implantation.

Recently, transcatheter therapy has expanded the treatment options for patients with heart valve disease. With the growing understanding of tricuspid regurgitation and its natural history, it becomes increasingly obvious that this patient population is a heterogeneous cohort presenting for treatment in different stages of a continuous disease process. It is still unclear which interventional approach will result in functional and clinical success and in which subtype of patient population. This article reviews the pathophysiologic background and current evidence for caval valve implantation and examines the potential role of this approach for the treatment of severe tricuspid regurgitation.

Long-term results of the monocusp valve formation in the common femoral vein in patients with avalvular deep veins of the lower extremities.

BACKGROUND: Aim of the study was to evaluate the long-term results of the monocusp valve formation in the common femoral vein (CFV) in patients with avalvular deep veins (ADV) of the lower extremities. METHODS: A total of 36 patients (24 women and 12 men) at the age varying from 37 to 58 years old were given surgical treatment during the period from 2008 to 2014. Six patients presented with congenital ADV, while the remaining 30 ADV had a consequence of the post-thrombotic lesion in the valves with the complete recanalization and manifested deep venous axial reflux. In terms of CEAP clinical classification, the patients were categorized into the following groups: С4b (N.=11), C5 (N.=18), C6 (N.=7). All the patients underwent Duplex ultrasound (DUS) examination. Twelve patients were additionally examined by venography. Kistner grade IV reflux was diagnosed in all the patients. Twenty-eight patients had undergone surgical interventions on superficial and perforating veins before. The severe (C4b-C6) forms of chronic venous disease with manifested axial reflux in deep veins were regarded as an indication for surgery in the patients refractory to traditional treatment. The method described by Opie et al. was employed to construct the monocusp venous valve in the CFV. RESULTS: The long-term results of the treatment were evaluated in 26 patients followed up during the period from 18 to 48 (mean 29.5±8.2) months. Cumulative clinical success rate at four years was 76.5%. Freedom from ulcer recurrence at four years was 83.4% (C6 patients). Cumulative competence rate of the neovalve was accomplished in 70.6%. The evaluation in two years based on the VCSS revealed the reduction in the severity of the manifestations of chronic venous insufficiency (P<0.01). The quality of life was improved, its index decreased from 60.6±18.7 to 40.7±12.8 (P<0.05). The circumference of the narrowest segment of the tibia decreased from 271.1±4.7 to 256.8±5.7 mm (P<0.05). CONCLUSIONS: Formation of the monocusp valve in CFV makes it possible to eliminate pathological blood reflux from the inferior vena cava to deep veins of the lower extremities that is known to be one of the main factors in the appearance and progression of chronic venous insufficiency (CVI). The high effectiveness of this operation is confirmed by the well apparent clinical improvement in the state of the affected lower extremity and the quality of life of the patients.

Role of vessel-to-prosthesis size mismatch in venous valve performance.

BACKGROUND: Efforts to treat chronic venous insufficiency have focused on the development of prosthetic venous valves. The role of prosthetic valve-to-vessel size matching has not been determined. The purpose of this investigation was to assess the effect of size mismatching on venous valve function and to establish a mismatch limit that affects valve hemodynamic performance and venous wall stress to improve future valve designs and implants. METHODS: Flow dynamics of prosthetic venous valves were studied in vitro using a pulse duplicator flow loop. Valve performance based on flow rate and pressure measurements was determined at oversizing ratios ranging from 4.2% to 25%. Valve open area ratios at different size mismatching ratios were investigated by image analysis. Finally, a wall stress analysis was used to determine the magnitude of circumferential (hoop) stress in the venous wall at various degrees of oversizing. RESULTS: Our findings indicate that valve regurgitate volume, closing time, and pressure difference across the valve are significantly elevated at mismatch ratios greater than ∼15%. This is supported by increases in regurgitate velocity and open area relative to valves tested at near-nominal diameters. At this degree of size mismatch, the wall stress is increased by a factor of two to three times relative to physiologic pressures. CONCLUSIONS: These findings establish a relationship between valve size matching and valve hemodynamic performance, including vessel wall stress, which should be considered in future valve implants. The size of the prosthetic valve should be within 15% of maximum vein size to optimize venous valve hemodynamic performance and to minimize the hoop wall stress.

[Free autovenous graft with destructed valves in treatment of severe ischemia of lower extremities]. / Lechenie kriticheskoi ishemii nizhnikh konechnostei s ispol'zovaniem svobodnogo autovenoznogo transplantata s razrushennymi klapanami.

AIM: to improve treatment of patients with severe atherosclerotic lesion of lower extremities arteries followed by critical ischemia by optimization of femoropopliteal bypass surgery. MATERIAL AND METHODS: Treament and survey of 60 patients with severe atherosclerotic lesion of femoropopliteotibial segment and critical lower limb ischemia were analyzed. Patients were divided into 2 groups depending on technique of femoropopliteal bypass. Conventional in situ autovenous technique was used in group 1. In the second group we used original method of free autovenous graft with destructed valves. RESULTS: Technique of free autovenous graft with destructed valves decreases incidence of early postoperative complications by 13.3%, remote thrombosis of graft by 13.3%. Also it increases physical and mental components of health by 7.9% and 3.1% respectively. CONCLUSION: Use of free autovenous graft with destructed valves is reasonable and improves results of treatment.

[Perforating veins insufficiency in patients with varicose disease].

MATERIAL AND METHODS: It was analyzed the results of complex survey and treatment of 181 patients with varicose disease CEAP degrees C3-C6. Ultrasonic scanning was applied to define localization, severity and extension of blood reflux in venous system. RESULTS: Superficial reflux was revealed in all patients, perforating--in 59.7%, deep--in 22.8% of cases. We concluded that high-intensive total-subtotal blood reflux in superficial veins was main hemodynamic factor resulted perforating insufficiency in 42% of patients, high-intensive deep reflux--in 17.7% of cases additionally. In patients with subcompensated course of disease superficial reflux removal and large perforating veins (diameter 4.5±0.5 mm) ligation are advisable. Small perforating veins insufficiency (diameter 3.5±0.5 mm) is eliminated independently after superficial reflux removal. Two-staged treatment should be used in patients with decompensated course of disease and trophic disorders ofshin. Perforating veins sclerotherapy under ultrasonic control is advisable secondarily after superficial reflux removal.

Deep venous thrombosis and postthrombotic syndrome: invasive management.

Invasive management of postthrombotic syndrome encompasses the two ends of the deep vein thrombosis spectrum, patients with acute iliofemoral deep vein thrombosis and those with chronic postthrombotic iliofemoral venous obstruction. Of all patients with acute deep vein thrombosis, those with involvement of the iliofemoral segments have the most severe chronic postthrombotic morbidity. Catheter-based techniques now permit percutaneous treatment to eliminate thrombus, restore patency, potentially maintain valvular function, and improve quality of life. Randomized trial data support an initial treatment strategy of thrombus removal. Failure to eliminate acute thrombus from the iliofemoral system leads to chronic postthrombotic obstruction of venous outflow. Debilitating chronic postthrombotic symptoms of the long-standing obstruction of venous outflow can be reduced by restoring unobstructed venous drainage from the profunda femoris vein to the vena cava.

Surgery for deep venous incompetence.

BACKGROUND: Chronic deep venous incompetence (DVI) is caused by incompetent vein valves and/or blockage of large-calibre leg veins and causes a range of symptoms including recurrent ulcers, pain and swelling. Most surgeons accept that well-fitted graduated compression stockings (GCS) and local care of wounds serve as adequate treatment for most patients, but sometimes symptoms are not controlled and ulcers recur frequently, or they do not heal despite compliance with conservative measures. In these situations, in the presence of severe venous dysfunction, surgery has been advocated by some vascular surgeons. This is an update of the review first published in 2000. OBJECTIVES: To assess the effects of surgical management of deep venous incompetence in terms of ulcer healing, ulcer recurrence and alleviation of symptoms. SEARCH METHODS: For this update, the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched October 2014) and the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 9). SELECTION CRITERIA: Randomised controlled trials of surgical treatment for patients with DVI. DATA COLLECTION AND ANALYSIS: For this update, two review authors (RRG and SCH) extracted data independently. All included studies required full risk of bias assessment in line with current procedures of The Cochrane Collaboration. Two review authors (RRG and SCH) independently assessed risk of bias and consulted with a third review author (AA) when necessary. MAIN RESULTS: Four studies with 273 participants were included. All included studies reported clinical outcomes following valvuloplasty. We found no studies investigating other surgical procedures for the treatment of patients with DVI. All included studies investigated primary valve incompetence. We found no trials that investigated the results of surgery for secondary valvular incompetence or the obstructive form of DVI. Because different outcome measures were used, it was not possible to pool the results of included studies. The methodological quality of the included studies was low, mainly because information regarding randomisation and blinding was missing, or because data were incomplete or were presented poorly. Ulcer healing and ulcer recurrence were not reported in one study, and the remaining three studies did not include participants with ulcers or with active ulceration. Three studies reported no significant complications of surgery and no incidence of DVT during follow-up. One study did not report on the occurrence of complications. Clinical changes were assessed by subjective and objective measurements, as specified in the clinical, aetiological, anatomical, and pathophysiological (CEAP) classification score. This requires vascular laboratory measurements of lower limb haemodynamics before and after surgery. Tests include an overall evaluation of venous function with venous refilling time (VRT) or ambulatory venous pressure (AVP). Two small trials comparing external valvuloplasty using limited anterior plication in combination with ligation of incompetent superficial veins against ligation alone (L) showed that ligation plus limited anterior plication produced significant improvement in AVP: The mean difference was -15 mm Hg (95% confidence interval (CI) -20.9 to -9.0) at one year and -15 mm Hg (95% CI -21 to -8.9) at two years. Sustainable statistically significant improvement in AVP and VRT was achieved by ligation and limited anterior plication at 10 years in one study. However, AVP values after surgery remained relatively high, causing its benefit to be questioned. Similarly, another study including participants who were deteriorating preoperatively showed sustained mild clinical improvement for seven years in those subjected to valvuloplasty compared with participants undergoing superficial venous surgery alone. However, this benefit was lost when the condition of participants was stable preoperatively. One small study (n = 40) with grade 3 reflux and no participants with ulcers reported that external valvuloplasty of the femoral vein combined with surgical repair of the superficial venous system improved the haemodynamic status of the lower limbs, restored valvular function more effectively and achieved better outcomes than surgical repair of the superficial venous system alone. AUTHORS' CONCLUSIONS: No evidence was found for benefit or harm of valvuloplasty in the treatment of patients with DVI secondary to primary valvular incompetence. The individual trials included in this review were small; they used different methods of assessment and overall were of poor quality. They did not include participants with severe DVI. Trials investigating the effects of other surgical procedures on deep veins are needed. Until the findings of such trials become available, the benefit of valvuloplasty remains uncertain.

Characterization of a bioprosthetic bicuspid venous valve hemodynamics: implications for mechanism of valve dynamics.

BACKGROUND: Chronic venous insufficiency (CVI) of the lower extremities is a common clinical problem. Although bioprosthetic valves have been proposed to treat severe reflux, clinical success has been limited due to thrombosis and neointima overgrowth of the leaflets that is, in part, related to the hemodynamics of the valve. A bioprosthetic valve that mimics native valve hemodynamics is essential. METHODS: A computational model of the prosthetic valve based on realistic geometry and mechanical properties was developed to simulate the interaction of valve structure (fluid-structure interaction, FSI) with the surrounding flow. The simulation results were validated by experiments of a bioprosthetic bicuspid venous valve using particle image velocimetry (PIV) with high spatial and temporal resolution in a pulse duplicator (PD). RESULTS: Flow velocity fields surrounding the valve leaflets were calculated from PIV measurements and comparisons to the FSI simulation results were made. Both the spatial and temporal results of the simulations and experiments were in agreement. The FSI prediction of the transition point from equilibrium phase to valve-closing phase had a 7% delay compared to the PD measurements, while the PIV measurements matched the PD exactly. FSI predictions of reversed flow were within 10% compared to PD measurements. Stagnation or stasis regions were observed in both simulations and experiments. The pressure differential across the valve and associated forces on the leaflets from simulations showed the valve mechanism to be pressure driven. CONCLUSIONS: The flow velocity simulations were highly consistent with the experimental results. The FSI simulation and force analysis showed that the valve closure mechanism is pressure driven under the test conditions. FSI simulation and PIV measurements demonstrated that the flow behind the leaflet was mostly stagnant and a potential source for thrombosis. The validated FSI simulations should enable future valve design optimizations that are needed for improved clinical outcome.

More great saphenous vein valves - less varicose veins?

BACKGROUND: In patients with chronic venous disease (CVD) the number of venous valves and the degree of valve deterioration have not been extensively investigated and are poorly understood. The aim of this prospective study was to quantitatively and qualitatively investigate the venous valves in CVD patients in view of their clinical classification. PATIENTS AND METHODS: Within two years a consecutive series of 152 patients (223 limbs) undergoing primary surgery for great saphenous vein varicose veins was investigated. In all patients the 'C' class according to the basic CEAP-classification was registered preoperatively (C2 to C6) for each limb. Both the quantity and quality of venous valves were assessed in the GSV's after removal. Qualitative evaluation of the valves was based on macroscopic appearance using a classification from 0 to 5 and described as 'valve disease class'. RESULTS: A negative correlation between age and the number of valves was detected (p = 0.0035). There was an increase of C-class with increasing age. No significant correlation between the average number of valves per meter and the C-class was detected. For all C-classes an average of between four and five valves per meter was counted. Valve disease class was positively correlated with the C-class although the valve disease class was never higher than the C-class (p < 0.05). CONCLUSIONS: The valve disease class of the great saphenous vein correlates with the C-class of the CEAP-classification. The number of valves did not correlate with the 'C'-class. With each increase in the CEAP class the age increased as well.

[Restoration of valvular function of deep veins in lower-limb varicose disease].

The present work was based on analysing the results of a complex examination and surgical treatment of 16-to-78-year-old patients presenting with varicose disease during the period from 2006 to 2010. A total of 1,095 limbs were examined and operated on in 1,070 patients. Of these, 298 (29.6 %) were men, and 709 (70.4 %) women. The distribution of the patients according to the CEAP clinical classification was as follows: C1 - 3 patients, C2 - 215, C3 - 566, C4 - 203, C5 - 29, and C6 - 79 subjects. All patients underwent ultrasonic duplex scanning, with retrograde phlebography performed in 21 cases. 51.2% of patients were diagnosed as having pathological deep venous reflux. In the group of patients with valvular insufficiency of deep veins, a total of 93 operations aimed at correcting deep reflux were performed, including 12 interventions for congenital avalvulation of veins. The indications for restorative operations on the valvular apparatus of deep veins were determined in severe forms of chronic venous insufficiency combined with axial reflux along deep veins in cases of inefficiency of conventional methods of surgical and conservative treatment. The long-term outcomes of surgery were assessed after 18-48 months. The results were evaluated by means of clinical and instrumental methods of examination: the disease severity scale, patients quality of life questionnaire, ultrasonographic and roentgen contrast methods of examination, and legometry. The operations aimed at restoring the valvular function of the femoral veins turned out to be effective methods of correcting venous reflux and made it possible to restore the valvular function in 84% of cases. In the remote postoperative period valvular competence was observed in 74.6% of patients. Carrying out such operations significantly improve the course of the disease due to decreasing the malleolar volume (p<0.001), manifestations of symptoms of chronic venous insufficiency (p<0.001), and improving quality of life (p<0.001).

Role of sinus in prosthetic venous valve.

BACKGROUND: The majority of bioprosthetic venous valves do not have a sinus pocket and, in practice, they are often placed in non-sinus segments of the veins. The aim of this study is to investigate the effect of the sinus pocket on the flow dynamics in a prosthetic valve. METHODS: A bench top in vitro experiment was set up at physiological flow conditions to simulate the flow inside a venous system. Bicuspid bioprosthetic valves with different leaflet lengths (5 and 10 mm) were tested in tubes with and without a sinus pocket and the flows around the valve were visualized by particle image velocimetry (PIV). Velocity data measurements were made and the vorticity was calculated in the with- and without-sinus set-ups. RESULTS: PIV measurements showed that vortex structure was maintained by the sinus. For the 10-mm leaflet length design with sinus, the jet width at the exit of the valve was 59% of that without sinus. For the 5-mm design with sinus, the jet width was 73% of the valve without sinus. Flow from the sinus region was entrained into the main jet observed near the exit of the sinus and altered the flow at the near wall region. CONCLUSIONS: The sinus pocket alters the flow around the valve and functions as flow regulator to smooth the flow pattern around the valve. The vortical structure inside the sinus is maintained at the valve leaflet tip during the valve cycle. For the prosthetic valve designated to be placed without a sinus, a shorter leaflet length is preferable and performs more closely to the valve with sinus.

[Stages of development of surgical treatment for insufficiency of venous valves of lower limbs].

Insufficiency of the valvular apparatus of the lower-limb veins is one of the main causes of the development of chronic venous insufficiency. This disease is commonly prevalent in developed countries including Russia and is an urgent and socially significant problem. Insufficiency of the venous valves may be corrected by a wide variety of approaches and methods however they all are not universal or have low efficacy and in some cases cannot be applied at all. This article is dedicated to the review of the existing methods of surgical correction of valvular insufficiency of lower-limb veins, as well as a review of the studies of the most promising trend of this problem, i.e. prosthetic repair of venous valves.

Living-engineered valves for transcatheter venous valve repair.

BACKGROUND: Chronic venous insufficiency (CVI) represents a major global health problem with increasing prevalence and morbidity. CVI is due to an incompetence of the venous valves, which causes venous reflux and distal venous hypertension. Several studies have focused on the replacement of diseased venous valves using xeno- and allogenic transplants, so far with moderate success due to immunologic and thromboembolic complications. Autologous cell-derived tissue-engineered venous valves (TEVVs) based on fully biodegradable scaffolds could overcome these limitations by providing non-immunogenic, non-thrombogenic constructs with remodeling and growth potential. METHODS: Tri- and bicuspid venous valves (n=27) based on polyglycolic acid-poly-4-hydroxybutyrate composite scaffolds, integrated into self-expandable nitinol stents, were engineered from autologous ovine bone-marrow-derived mesenchymal stem cells (BM-MSCs) and endothelialized. After in vitro conditioning in a (flow) pulse duplicator system, the TEVVs were crimped (n=18) and experimentally delivered (n=7). The effects of crimping on the tissue-engineered constructs were investigated using histology, immunohistochemistry, scanning electron microscopy, grating interferometry (GI), and planar fluorescence reflectance imaging. RESULTS: The generated TEVVs showed layered tissue formation with increasing collagen and glycosaminoglycan levels dependent on the duration of in vitro conditioning. After crimping no effects were found on the MSC level in scanning electron microscopy analysis, GI, histology, and extracellular matrix analysis. However, substantial endothelial cell loss was detected after the crimping procedure, which could be reduced by increasing the static conditioning phase. CONCLUSIONS: Autologous living small-diameter TEVVs can be successfully fabricated from ovine BM-MSCs using a (flow) pulse duplicator conditioning approach. These constructs hold the potential to overcome the limitations of currently used non-autologous replacement materials and may open new therapeutic concepts for the treatment of CVI in the future.