Effect of valve lesion on venous valve cycle: A modified immersed finite element modeling

The present study aimed to understand the effect of venous valve lesion on the valve cycle. A modified immersed finite element method was used to model the blood–tissue interactions in the pathological vein. The contact process between leaflets or between leaflet and sinus was evaluated using an adhesive contact method. The venous valve modeling was validated by comparing the results of the healthy valve with those of experiments and other simulations. Four valve lesions induced by the abnormal elasticity variation were considered for the unhealthy valve: fibrosis, atrophy, incomplete fibrosis, and incomplete atrophy. The opening orifice area was inversely proportional to the structural stiffness of the valve, while the transvalvular flow velocity was proportional to the structural stiffness of the valve. The stiffening of the fibrotic leaflet led to a decrease in the orifice area and a stronger jet. The leaflet and blood wall shear stress (WSS) in fibrosis was the highest. The softening of the atrophic leaflet resulted in overly soft behavior. The venous incompetence and reflux were observed in atrophy. Also, the atrophic leaflet in incomplete atrophy exhibited weak resistance to the hemodynamic action, and the valve was reluctant to be closed owing to the large rotation of the healthy leaflet. Low blood WSS and maximum leaflet WSS existed in all the cases. A less biologically favorable condition was found especially in the fibrotic leaflet, involving a higher mechanical cost. This study provided an insight into the venous valve lesion, which might help understand the valve mechanism of the diseased vein. These findings will be more useful when the biology is also understood. Thus, more biological studies are needed.

Platelets Drive Thrombus Propagation in a Hematocrit and Glycoprotein VI-Dependent Manner in an In Vitro Venous Thrombosis Model

OBJECTIVE

The objective of this study was to measure the role of platelets and red blood cells on thrombus propagation in an in vitro model of venous valvular stasis.

APPROACH AND RESULTS

A microfluidic model with dimensional similarity to human venous valves consists of a sinus distal to a sudden expansion, where for sufficiently high Reynolds numbers, 2 countercurrent vortices arise because of flow separation. The primary vortex is defined by the points of flow separation and reattachment. A secondary vortex forms in the deepest recess of the valve pocket characterized by low shear rates. An initial fibrin gel formed within the secondary vortex of a tissue factor-coated valve sinus. Platelets accumulated at the interface of the fibrin gel and the primary vortex. Red blood cells at physiological hematocrits were necessary to provide an adequate flux of platelets to support thrombus growth out of the valve sinus. A subpopulation of platelets that adhered to fibrin expose phosphatidylserine. Platelet-dependent thrombus growth was attenuated by inhibition of glycoprotein VI with a blocking Fab fragment or D-dimer.

CONCLUSIONS

A 3-step process regulated by hemodynamics was necessary for robust thrombus propagation: First, immobilized tissue factor initiates coagulation and fibrin deposition within a low flow niche defined by a secondary vortex in the pocket of a model venous valve. Second, a primary vortex delivers platelets to the fibrin interface in a red blood cell-dependent manner. Third, platelets adhere to fibrin, activate through glycoprotein VI, express phosphatidylserine, and subsequently promote thrombus growth beyond the valve sinus and into the bulk flow.

Aging of the venous valves as a new risk factor for venous thrombosis in the elderly: the BATAVIA study

Essentials Risk of venous thrombosis (VT) related to valve thickness and valvular reflux in unknown. Venous valves and reflux were measured by ultrasonography in cases and controls aged 70+. Risk of VT was associated with increased valve thickness and valvular reflux >1second. Thickening of valves is a generic process: there was no difference between right and left legs.

SUMMARY

Background Increasing age is the strongest risk factor for venous thrombosis (VT). Increasing age has been related to a thickening of the venous valves and a decreased valvular function. The association between valve thickness and the risk of VT is not known. Objectives To assess the association between increased valve thickness and valve closure time (VCT) and the risk of VT. Methods Analyses were performed in the BATAVIA study, including 70 cases aged 70 + with a first VT and 96 controls. We performed an ultrasound examination of the valves in the popliteal veins. The valves were imaged with a 9 MHz linear probe using B-mode ultrasonography. VCT was measured as an indicator for valve function using an automatic inflatable cuff. To estimate the risk of VT, valve thickness was dichotomized at the 90th percentile as measured in controls and VCT was dichotomized at 1 s. Results Mean valve thickness of controls was similar in the left (0.36 mm, 95% CI 0.34-0.37) and right (0.36 mm, 95% CI 0.35-0.38) leg. In 45 cases a valve was observed in the contralateral leg with a mean valve thickness of 0.39 mm (95% CI 0.36-0.42). Cases had an increased valve thickness compared with controls: mean difference 0.028 mm (95%CI 0.001-0.055). Valve thickness > 90th percentile increased the risk of VT 2.9-fold. Mean VCT in controls was 0.38 s, in contralateral leg of cases 0.58 s. VCT > 1 s increased the risk of VT 2.8-fold (95% CI 0.8-10.4). Conclusions Risk of VT was associated with increased valve thickness and valvular reflux of > 1 s.

[Possibilities of local phlebectomy in correction of pelvioperineal venous reflux]

The work was based on the results of examination and treatment of 43 female patients presenting with varicose transformation of pelvic, perineal, and lower-limb veins. The inclusion criteria were as follows: the presence of visually determined varicose transformation of the veins of the external genital organs, perineum, posterior surface of the thighs, as well as valvular insufficiency of the mentioned veins by the findings of ultrasonographic angioscanning (USAS). The following exclusion criteria were applied: the presence of pregnancy, symptoms of pelvic venous plethora (PVP), and varicothrombophlebitis. In 33 women correction of the pelvioperineal reflux (PPR) was performed with the help of local phlebectomy on the large pudendal lips and perineum, with the maximally possible mobilization of the vessel within the limits of the operative wound. Miniphlebectomy with the use of Varady phleboextractors was performed in 10 women presenting with isolated varicose transformation of the subcutaneous veins of the posterior femoral surface. The duration of follow up of patients amounted to 3 years. The criteria for efficiency of the carried out treatment were as follows: freedom from varicose syndrome both in the perineum and on the lower extremities, as well as no PVP symptoms during the whole term of follow up. Varicose syndrome of the external genital organs, perineum and posterior surface of the femurs was successfully eliminated in 100% of patients. Meticulous mobilization and removal of the veins of the labia majora, perineum and subcutaneous femoral veins is a reliable method of removing pathological reflux of blood from the intrapelvic to superficial veins of the perineum and lower limbs. 100% of our patients were found to be free from relapses of either vulvar or perineal varicosity, with no evidence of lower limb varicose veins. Local phlebectomy is an efficient method of elimination of varicose syndrome induced by PVP in patients with dilatation of intrapelvic, vulvar and perineal veins.

[Functional assessment of primary lesion of the great saphenous vein when deciding upon stripping]

The purpose of the study was to examine a possibility of functional assessment of the great saphenous vein (GSV) with the help of a day orthostatic loading test for prognosis of restoration of the function of the GSV afterremoving its varicose tributaries in patients with primary varicose veins. Our prospective study included a total of sixty-five 29-to-53-year-old patients (15 men and 50 women, mean age - 36.7 years). The total number of the lower limb examined amounted to 87. All patients underwent ultrasonographic examination (duplex scanning) prior to operation, 1 and 12 months thereafter. The study was carried out using a day orthostatic loading test consisting in duplex scanning performed twice during 24 hours: in the evening after 18:00 hours and in the morning before 10:00 hours after a good night's rest. It was demonstrated that the day orthostatic loading test characterized the degree of preservation of the muscular-tonic properties of the GSV, making it possible to predict reversibility of reflux along it after removing the varicose tributaries, hence it may be used as a criterion for individualization of the choice of the scope of surgical intervention. A high orthostatic gradient prior to operation suggests preservation of the potential of the muscular-tonic function of the GSV; its decrease after surgery demonstrates reduction of the volemic loading on the GSV.

[Chronic venous diseases: valvular function and leukocyte-endothelial interaction, possibilities of pharmacotherapy]

This article provides a review of the literature focusing on the data elucidating the pathogenesis of chronic venous diseases from the positions of macrohaemodynamic (venous valvular function) and microcirculatory impairments. Presented herein are confirmations of the interaction between two important mechanisms, as well as the literature data concerning the role of the venous microvalvular structures and possible haemodynamic impairments in functional venous insufficiency. Also presented are substantiations in confirmation of the theory of leukocyte-endothelial interaction, forming the basis for contemporary understanding of the pathogenesis of chronic venous diseases. This is followed by elucidating the role of venoactive drugs in conservative treatment of patients with chronic venous diseases, and, finally, touching upon current problems and promising approaches to solve them.

[Minimally invasive method of correction of valvular insufficiency of the femoral vein in various causes of its origin genesis]

Presented herein are the results of treatment of patients with chronic venous insufficiency and trophic ulcers of lower limbs on the background of varicose disease and postthrombophlebitic syndrome. The treatment consisted in removal of pathological deep vertical venous reflux by means of a modified method of dosed narrowing of the femoral vein according to P.G. Shvalb's technique [1]. The obtained outcomes confirmed the necessity of influencing the pathological vertical deep venous reflux in patients with severe forms of chronic venous insufficiency and pronounced retrograde shunt along deep veins.

Severity of chronic venous disease and anatomic distribution of valvular incompetence

AIM

The aim of the study was to examine the association between anatomical patterns of valvular incompetence and the severity of venous insufficiency in patients with chronic venous disease.

METHODS

A total of 211 consecutive patients (70% females) were referred from the vascular clinic to undergo a Doppler ultrasound examination. The extent and anatomical pattern of valvular incompetence was noted using CEAP criteria. Clinical classes C1-6 for each patient were expressed as a string of binary digits and translated into a clinical ordinal score. In this way, higher grade signs were not obscuring lower grade signs and non-parametric analysis could include a wider range of clinical data.

RESULTS

Varicose veins were the main complaint in 33% of the patients. 54% had at least one incompetent deep vein, 80% had incompetent perforators. Clinical severity increased with age, but was not related with gender. The presence of deep venous incompetence did not account for significant increase in signs. Superficial incompetence, especially if involving two or more segments, was most commonly seen in patients with severe signs. A linear regression model for clinical ordinal score identified non-saphenous superficial reflux and small saphenous vein reflux as the strongest predictors of clinical severity.

CONCLUSION

CEAP clinical classes can be translated into a clinical ordinal score, which is useful for data analysis. In a group with chronic venous disorders, clinical status is associated mostly with the condition of superficial and calf perforating veins.

[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).

[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.

A novel role for relaxin-2 in the pathogenesis of primary varicosis

Background

Varicose veins affect up to 40% of men and up to 51% of women. The pathophysiology of primary varicosis is poorly understood. Theories ranging from incompetence of the venous valves to structural changes in the vein wall have been proposed.

Methodology/Principal Findings

We analyzed the functional state of the intramural smooth muscle cells (n = 14 pairs matched for age and gender) and the expression of relaxin-2 and its receptors RXFP1 and RXFP2 in samples of varicose and healthy great saphenous veins (GSV) (n = 21 healthy GSV; n = 46 varicose GSV). Relaxin-2 and RXFP1 contents were determined in tissue samples (n = 9 samples per group). Pharmacological analyses were performed in a perfusion chamber. Morphometric determination of the nuclear size of the smooth muscle compartment yielded no significant difference in varicose GSV in comparison with the healthy controls. Relaxin-2 and its receptors were expressed in the muscular layer, endothelial cells and in blood vessels contained in the vein wall. Immunohistochemical expression of relaxin-2, RXFP1 and RXFP2 was significantly decreased in varicose GSV. Relaxin-2 and RXFP1 measured by ELISA and Western Blot were decreased in varicose GSV (relaxin-2 ELISA healthy vs. varicose GSV: 12.49±0.66 pg/mg versus 9.12±3.39 pg/mg of total protein; p = 0.01; Student's T-test). Contractions of vein samples induced by cholinergic or adrenergic stimulation were antagonized by relaxin-2.

Conclusions/Significance

We report that relaxin-2 and its receptors RXFP1 and RXFP2 are expressed in GSV and that their expression is significantly decreased in varicose GSV. Further, we were able to demonstrate a functional pharmacological relaxin-2 system in varicose GSV. Our results suggest a novel role for relaxin-2 in the pathogenesis of primary varicosis, rendering relaxin-2 a novel possible pharmacological agent for the treatment of this widely prevailing venous disease.

[State of crural perforating veins after sclerosurgical interventions for lower limb varicose disease]

Analysed herein are the findings obtained by comprehensive examination of 106 patients presenting with grade C3 chronic venous insufficiency according to the CEAP classification. Localization, intensity and extent of refluxes of blood in the venous system of the affected extremity were determined by means of ultrasonographic angioscanning. Based on the obtained results, the patients were subdivided into two groups. Group One was composed of 87 (82.1%) patients found to have their perforant venous insufficiency caused by superficial hypervolemia due to sharply pronounced varicosity of superficial veins. Group Two comprised 19 (17.9%) patients who had developed perforant insufficiency secondary to superficial and deep blood refluxes. In 82 (77.3%) Group One patients, the scope of the operations was limited to elimination of the superficial blood reflux, with only five (4.7%) patients at the second stage of management had their perforant blood reflux removed. Group Two patients were subjected to single-stage removal of both superficial and perforant blood refluxes. Excellent therapeutic outcomes were observed in 49.1% of cases, with good and satisfactory results obtained in 41.5% and 9.4% of patients, respectively.

What's new in veins?

Reflux cannot be interpreted without knowledge of the function of the calf muscle pump. The presence or absence of reflux alone has an insufficient predictive value for excellent functional treatment results. Valves are not simple moving slips but have an autonomous 4-step cycle movement that helps the calf muscle pump to be very effective. New calculations of the Starling equilibrium have shown that capillary filtration fraction returns mainly by the lymphatics. All these new findings help the phlebologist design a more precise and thus better treatment plan in phlebology practice.

Impact of venous thromboembolism, venous stasis syndrome, venous outflow obstruction and venous valvular incompetence on quality of life and activities of daily living: a nested case-control study

The role of venous stasis syndrome (VSS) mechanisms (i.e. venous outflow obstruction [VOO] and venous valvular incompetence [VVI]) on quality of life (QoL) and activities of daily living (ADL) is unknown. The objective of this study was to test the hypotheses that venous thromboembolism (VTE),VSS,VOO and VVI are associated with reduced QoL and ADL. This study is a follow-up of an incident VTE case-control study nested within a population-based inception cohort of residents from Olmsted County, MN, USA, between 1966 and 1990. The study comprised 232 Olmsted County residents with a first lifetime VTE and 133 residents without VTE. Methods included a questionnaire and physical examination for VSS; vascular laboratory testing for VOO and VVI; assessment of QoL by SF36 and of ADL by pertinent sections from the Older Americans Resources and Services (OARS) and Arthritis Impact Measurement Scales (AIMS2) questionnaires. Of the 365 study participants, 232 (64%), 161 (44%), 43 (12%) and 136 (37%) had VTE, VSS, VOO and VVI, respectively. Prior VTE was associated with reduced ADL and increased pain, VSS with reduced physical QoL and increased pain, and VOO with reduced physical QoL and ADL.VVI was not associated with QoL or ADL. In conclusion,VSS and VOO are associated with worse physical QoL and increased pain. VOO and VTE are associated with impaired ADL. We hypothesize that rapid clearance of venous outflow obstruction in individuals with acute VTE will improve their QoL and ADL.

Invasive treatment of deep venous disease. A UIP consensus

Deep venous disease includes primary and/or secondary pathological changes in the deep venous system. These may consist of valve insufficiency, complete or incomplete vein obliteration and/or functional impairment.

To what extent might deep venous thrombosis and chronic venous insufficiency share a common etiology?

According to the valve cusp hypoxia hypothesis (VCHH), deep venous thrombosis is caused by sustained non-pulsatile (streamline) venous blood flow. This leads to hypoxemia in the valve pockets; hypoxic injury to the inner (parietalis) endothelium of the cusp leaflets activates the elk-1/egr-1 pathway, leading to leukocyte and platelet swarming at the site of injury and, potentially, blood coagulation. Here, we propose an extension of the VCHH to account for chronic venous insufficiency. First, should the foregoing events not proceed to frank thrombogenesis, the valves may nevertheless be chronically injured and become incompetent. Serial incompetence in lower limb valves may then generate ''passive'' venous hypertension. Second, should ostial valve thrombosis obstruct venous return from muscles via tributaries draining into the femoral vein, as Virchow illustrated, ''active'' venous hypertension may supervene: muscle contraction would force the blood in the vessels behind the blocked ostial valves to re-route. Passive or active venous hypertension opposes return flow, leading to luminal hypoxemia and vein wall distension, which in turn may impair vasa venarum perfusion; the resulting mural endothelial hypoxia would lead to leukocyte invasion of the wall and remodelling of the media. We propose that varicose veins result if gross active hypertension stretches the valve ''rings'', rendering attached valves incompetent caudad to obstructed sites, replacing normal centripetal flow in perforating veins with centrifugal flow and over-distending those vessels. We also discuss how hypoxemia-related venous/capillary wall lesions may lead to accumulation of leukocytes, progressive blockage of capillary blood flow, lipodermosclerosis and skin ulceration.