Proximal Valve Research Articles

Types of peripherally inserted central catheters and the risk of unplanned removals in patients: A prospective cohort study

BackgroundPeripherally inserted central catheters are widely used in clinical practice. Despite the many advantages of peripherally inserted central catheters, unplanned removals can occur owing to irreversible complications and may have adverse consequences for patients. However, the relationship between peripherally inserted central catheter type and the incidence of unplanned removal is unclear. ObjectiveTo investigate the association between the type of peripherally inserted central catheter and unplanned catheter removal. DesignA multicenter prospective cohort study. SettingsSixty hospitals located in 30 cities across seven provinces in China. ParticipantsThree thousand two hundred and twenty-two patients aged 18 years or older with one peripherally inserted central catheter inserted for treatment were enrolled, and 3166 (98.3 %) patients with follow-up data were included in the final analysis. MethodsThe included participants had peripherally inserted central catheters that either had a proximal valve (n = 2436) or were open-ended (n = 730). A competing risk Cox regression model was used, and both univariate and multivariate analyses were conducted. A sub-distribution hazard model was applied to test the validity of the results. ResultsOf the 2436 peripherally inserted central catheters with a proximal valve and 730 that were open-ended, 272 (11.2 %) and 46 (6.3 %) were removed unplanned, respectively. The whole incidence of unplanned removal was 10.04 %; multivariate Cox regression was conducted and it was determined that unplanned removal was statistically significantly associated with the proximal valve peripherally inserted central catheter type (hazard ratio: 1.86, 95 % confidence interval: 1.28 to 2.70, p = 0.001). In patients without cancer, the risk of unplanned removal of peripherally inserted central catheters with a proximal valve was 8.14 times higher than that of open-ended peripherally inserted central catheters (p < 0.001). ConclusionsIn this study, peripherally inserted central catheters with a proximal valve had a higher risk of unplanned removals, especially in patients without cancer. The peripherally inserted central catheter type should be considered in advance, and clinical staff should take appropriate measures to prevent unplanned removals after insertion.

Influence of Peripherally Inserted Central Catheters With Proximal Valves on Red Blood Cell Hemolysis During Transfusion.

The aim of this study was to verify the occurrence of hemolysis after infusion of packed red blood cells (PRBCs) in 12 peripherally inserted central catheters (PICCs) with a proximal valve, according to size and infusion rate. This was an experimental in vitro study performed under laboratory-controlled conditions, and the sample was composed of 12 PICCs with proximal valves (3F and 4F catheter). Twelve type A+ aliquots from 10 PRBCs were analyzed preinfusion and postinfusion according to PICC size and infusion rate. Hemolysis markers, total hemoglobin (g/dL), hematocrit (%), free hemoglobin (g/dL), potassium (mmol/L), lactate dehydrogenase (U/L), and rate of hemolysis (%) were studied. Data were analyzed using analysis of variance and Bonferroni multiple comparison tests. After the infusions in 3F PICCs, an increase was seen in rate of hemolysis (P = .003) and free hemoglobin (P = .014), in addition to a reduction in total hemoglobin (P = .002), with significant influence of minimum and maximum flow rates on the rate of hemolysis. The study finding indicated that the smaller catheter size and the infusion rate influenced variations in some hemolysis markers, but the alterations observed in the hemolysis markers would not contraindicate the infusion of PRBCs by 3F and 4F PICCs with proximal valves.

Proximal Aortic Dilatation and Pulmonary Valve Replacement in Patients with Repaired Tetralogy of Fallot: Is There a Relationship? A Cardiac Magnetic Resonance Imaging Study.

Aortopathy is a known complication whose incidence is growing within the population of tetralogy of Fallot (TOF) patients. Its pathology and relationship with other comorbidities remain unclear. This study was designed to determine the prevalence and predictors of proximal aortic dilatation after TOF repair. We retrospectively investigated all patients who underwent follow-up cardiac magnetic resonance imaging (CMR; at least 4 years after TOF repair) between March 2004 and December 2019. The dimensions at the ascending aorta (AAo) and sinus of Valsalva (SoV) levels were measured. Aortic dilatation was defined as an internal aortic diameter that was >2 standard deviation of the previously published normal values. We included 77 patients (mean age 28.9 ± 10.5 years, 41.5% female, mean follow-up of 24.5 ± 8.1 years). AAo and SoV were dilated in 19 (24.6%) and 43 (55.8%) patients, respectively. Patients with dilated AAo and SoV were older during the corrective surgery (p < 0.001 and p = 0.004, respectively) and during CMR (p = 0.002 and 0.024, respectively) than patients without AAo and SoV dilatation. Patients of the dilated AAo group were more likely to have prior palliative shunt (p = 0.008), longer shunt duration (p = 0.005), and a higher degree of aortic valve regurgitation (AR) fraction (p < 0.001) and to undergo pulmonary (PVR) and/or aortic valve replacement (p < 0.001 and p = 0.013, respectively). PVR (p = 0.048, odds ratio = 6.413, and 95% CI = 1.013–40.619) and higher AR fraction (p = 0.031, odds ratio = 1.194, and 95% CI = 1.017–1.403) were independent predictors for AAo dilatation. Aortopathy is a common progressive complication that may require reintervention and lifelong follow-up. Our study shows that proximal aortic dilatation may be attributed to factors that increase the volume overload across the proximal aorta, including late corrective surgery and palliative shunt. We also found that PVR and higher AR fraction are independent predictors of AAo dilatation.

Comparative analysis of laparoscopic proximal gastrectomy plus semi-embedded valve anastomosis with laparoscopic total gastrectomy for adenocarcinoma of the esophagogastric junction: a single-center retrospective cohort study

BackgroundWe invented a new antireflux anastomosis method for use in proximal gastrectomy for adenocarcinoma of the esophagogastric junction (AEG) and named it semi-embedded valve anastomosis (SEV). This study was conducted to compare and analyze the short-term efficacy and long-term prognosis of this anastomosis reconstruction method versus laparoscopic total gastrectomy (LTG).MethodsWe retrospectively analyzed the general data and surgical outcomes of patients with AEG who underwent three united laparoscopic proximal gastrectomy plus semi-embedded valve anastomosis (TULPG-SEV, N = 20) and LTG (N = 20) at our hospital from January 2015 to September 2017 and investigated the incidence of postoperative reflux esophagitis and postoperative nutritional status between the two groups. Survival analysis was also performed.ResultsThe operative time (178.25 ± 15.41 vs 196.5 ± 21.16 min) and the gastrointestinal reconstruction time (19.3 ± 2.53 vs 34.65 ± 4.88 min) of the TULPG-SEV group were significantly less than that of the LTG group. There was no difference in intraoperative blood loss, length of hospital stay, and postoperative complications. There was no difference in the scores on the postoperative reflux disease questionnaires (RDQs) conducted 1 month (P = 0.501), 3 months (P = 0.238), and 6 months (P = 0.655) after surgery between the TULPG-SEV group and LTG group. Gastroscopy revealed 2 cases of reflux esophagitis (grade B or higher) in each group. The postoperative hemoglobin level was better in the TULPG-SEV group than in the LTG group, and the difference was most noticeable at 1 month after surgery (P = 0.024) and 3 months after surgery (P = 0.029). The levels of albumin and total protein were not significantly different between the groups. There were more patients with weight loss over 5 kg after surgery in the LTG group than in the TULPG-SEV group (P = 0.043). There was no significant difference in the 3-year overall survival rate between the two groups (P = 0.356).ConclusionSEV has a certain antireflux effect and can reduce the anastomosis time. Proximal gastrectomy may be better than total gastrectomy for maintaining postoperative hemoglobin levels and reducing weight loss.

Validation of New Real-Time Three-Dimensional Transesophageal Echocardiographic Scoring System in Prediction of Immediate and Long-term Outcome After Percutaneous Balloon Mitral Valvuloplasty

Dear Editor,The guidelines recommend percutaneous mitral balloon commissurotomy (PMBC) as the first choice therapy for symptomatic patients with moderate or severe mitral stenosis (MS) with favorable valve morphology and for asymptomatic MS patients with pulmonary hypertension (1). Echocardiography is the main diagnostic imaging method for assessing mitral valve stenosis and evaluating the severity and hemodynamic consequences of MS as well as valve morphology and disease extension (2). The main predictor of successful BMV is mitral valve morphology. Therefore, the MV scoring system using echocardiography is very important. Several two-dimensional echocardiographic scoring systems have been proposed to evaluate MV morphology, the severity of which is related to immediate and long-term outcome (3). Most cardiologists use the Wilkins score for evaluation of MV anatomy. Although, none of the available 2DE scores have not been shown to be superior to any of the other scores (4). The evaluation of the MV Wilkins score depends on the assessment of four parameters, which include: leaflets mobility, thickness, calcification, and subvalvular involvement. Each parameter is given a score of 1-4 and by calculating its sum, the total score of 1-16/16 (mild involvement = 1-4/16, moderate involvement = 5-8/16, and severe involvement &gt; 8/16) is obtained (3). The ideal echocardiographic scoring system should have the following characteristics:Quantitative and qualitative evaluation of each component of the MV apparatus separately to determine the deformity in a specific portionThe inclusion of all the points that have been proven through a large study affects the BMV resultEasy to use and interpretable by most cardiologists at a reasonable timeHigh reliability and reproducibility (4)In recent years, real-time three-dimensional echocardiography technology has evolved rapidly. RT3DE provides detailed morphologic display and analysis of the mitral valve structure. Improving the RT3DE probe technology, especially transesophageal probes, highlights the need to introduce a RT3DE scoring system (5). Anwar et al. introduced the first scoring system using real-time three-dimensional transthoracic echocardiography (RT3D-TTE) in patients with mitral valve stenosis candidate BMV, and compared the new score with the Wilkins score in predicting outcome after BMV. In the new RT3DE score, each leaflet was divided into three scallops (anterolateral A1-P1, middle A2-P2, and posteromedial A3-P3) and each scallop was scored separately for thickness, calcification, and mobility, as follows: 0 for normal thickness and mobility, 1 for abnormal thickness and restricted mobility, and for scoring calcification: 0 for the absence of calcification, 1 for calcification of middle scallop (A2 or P2) and 2 if there is calcification of commissural scallops (A1, A3-P1, P3). For scoring subvalvular apparatus, the anterior and posterior chordae were scored at three levels as follows: proximal (valve level), middle, and distal (papillary muscle level). Each level was scored separately for thickness and separation in between as follows: 0 for normal thickness, 1 for abnormal thickness, also 0 in case of normal chordal separation (distance in between &gt;5 mm), 1 in case of partial separation (distance in between &lt;5 mm) and 2 in case of absence separation. From the sum of these points, a total score of 0-31/31 (mild MV involvement &lt;8, moderate MV involvement 8-13, and severe MV involvement &gt;14) is obtained (6). 3D-Anwar score is complex and time consuming. This is due to the many anatomical and morphological components to achieve an accurate assessment. The available 3D score is highly selective for optimal BMV result, which leads to more patients being referred for surgery (5). So we decided to introduce a three-dimensional transesophageal (3D-TEE) echocardiographic scoring system that meets the criteria of an ideal echocardiographic scoring system, and evaluate the validity of the new score in predicting the immediate and long-term outcome of patients after BMV. We also believe that many studies are needed to achieve an ideal RT3DE scoring system.

Double trouble: diagnostic dilemma in a rare association of proximal ureteric valve with orthotopic ureterocele\u2014case report

BackgroundAssociation of the ureterocele and proximal ureteral valve is a rare congenital anomaly which can lead to quick detoriation of renal function due to double obstruction. Though ureteral valves have been associated with other ureteral anomalies, this specific association is extremely rare.Case presentationA 7-month-old boy was referred to us for antenatally detected hydronephrosis. Provisional diagnosis of orthotopic ureterocele with pelviureteric junction (PUJ) obstruction was made based on preoperative imaging. Endoscopic incision of ureterocele was done and retrograde pyelography showed tight obstruction at PUJ which necessitated a pyeloplasty. Examination of resected specimen confirmed a ureteral valve. Postoperatively, the patient had good improvement in kidney function.ConclusionTo conclude, congenital ureteral valves are a rare cause of ureteric obstruction and its association with ureterocele is rarer still. Identification of an ureterocele should not deter us from searching for an associated pathology like a ureteric valve when imaging shows more severe hydronephrosis suggestive of more proximal obstruction.

A comparison of hydrophobic polyurethane and polyurethane peripherally inserted central catheter: results from a feasibility randomized controlled trial

BackgroundTo evaluate the feasibility of an efficacy trial comparing a hydrophobic polyurethane peripherally inserted central catheter (PICC) with a standard polyurethane PICC.MethodsThis pilot randomised controlled trial (RCT) was conducted between May 2017 and February 2018. Adult participants (n = 111) were assigned to hydrophobic polyurethane PICC with proximal valve (intervention) or a polyurethane PICC with external clamp (standard care). Primary outcome was trial feasibility including PICC failure. Secondary outcomes were central line-associated bloodstream infection, local infection, occlusion, thrombosis, fracture and dislodgement, phlebitis, local or systemic allergic reaction, and PICC dwell time.ResultsAll feasibility outcomes were achieved, apart from eligibility criteria. In total, 338 patients were screened, 138 were eligible (41%), and of these 111 were randomised (80%). Patients received the allocated PICC in 106 (95%) insertions. No patients withdrew from the study and there was no missing data. PICC failure was 24% (13/55) in the intervention group and 22% (12/55) in the standard care group (p = 0.820). PICC failure per 1000 PICC days was 16.3 in the intervention group and 18.4 in the control group (p = 0.755). The average dwell time was 12 days in the intervention and 8 days in the control group.ConclusionsThis study demonstrates the feasibility of an efficacy trial of PICC materials in an adult population, once adjustments were made to include not only in-patients, but also patients being discharged to the Hospital in the Home service.Trial registrationAustralia and New Zealand Clinical Trials Registry ACTRN12616001578493. Prospectively registered on 16 November 2016. The trial protocol was published a priori (Kleidon et al., Vasc Access 3:15–21, 2017).

Possible Assessment of Calf Venous Pump Efficiency by Computational Fluid Dynamics Approach.

Three-dimensional simulations of peripheral, deep venous flow during muscular exercise in limbs of healthy subjects and in those with venous dysfunction were carried out by a computational fluid-dynamics (CFD) approach using the STAR CCM + platform. The aim was to assess the effects of valvular incompetence on the venous calf pump efficiency. The model idealizes the lower limb circulation by a single artery, a capillary bed represented by a porous region and a single vein. The focus is on a segment of the circuit which mimics a typical deep vein at the level of the calf muscle, such as the right posterior tibial vein. Valves are idealized as ball valves, and periodic muscle contractions are given by imposing time-dependent boundary conditions to the calf segment wall. Flow measurements were performed in two cross-sections downstream and upstream of the calf pump. Model results demonstrate a reduced venous return for incompetent valves during calf exercise. Two different degrees of valvular incompetence are considered, by restricting the motion of one or both valves. Model results showed that only the proximal valve is critical, with a 30% reduction of venous return during calf exercise in case of valvular incompetence: the net flow volume ejected by the calf in central direction was 0.14 mL per working cycle, against 0.2 mL for simulated healthy limbs. This finding appeared to be consistent with a 25% reduction of the calf ejection fraction, experimentally observed in chronic venous disease limbs compared with healthy limbs.

A Novel Dual Non-Invasive Ventilator Continuous Positive Airway Pressure Non-Aerosolization Circuit for Emergency Use in the COVID-19 Pandemic

The COVID-19 pandemic is a public health emergency of unprecedented scale. The surge in clinical cases of patients with severe respiratory illness has overwhelmed the traditional capacity of healthcare systems worldwide. Continuous Positive Airway Pressure (CPAP) delivered through Non-Invasive Ventilation (NIV) has been shown to be useful in caring for patients with COVID-19. In particular patients with early stage milder acute hypoxemic respiratory failure can benefit from NIV CPAP therapy, though there is an acknowledged risk of COVID-19 aerosolization with traditional circuit use. Furthermore, given the surge in clinical care demand, there is an acute global shortage of ventilators, including NIV devices and therefore innovative methods are needed to increase NIV capacity and ameliorate infectious aerosolization. This paper outlines an emergency use modified dual NIV CPAP Circuit that uses a 3D printed splitter designed to work with traditional international NIV CPAP tubing standards and a 3D printed respiratory face mask knuckle to allow for distal expiratory breath exhalation through a viral filter rather than through an open to air proximal valve, which is the traditional NIV CPAP configuration. We expect that this work will increase global NIV CPAP capacity and ameliorate aerosolization of COVID-19 in patients undergoing therapy in an emergency scenario.

The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Rectal Cancer.

The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Rectal Cancer.

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 &amp; 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.

Morphometric characteristics of competent proximal valves of the great saphenous vein and superficial femoral vein in vivo according to ultrasound angioscanning data

Introduction. It seems relevant to study the ultrasound anatomy and physiology of the proximal valve segments of the superficial femoral vein (SFV) and the great saphenous vein (GSV) to develop effective reconstructive surgical interventions on venous valves in chronic vein diseases.The aim of the survey was to study the ultrasound anatomy of the venous wall, the size and shape of the proximal SFV and GSV valves are normal at rest and during the functional test Valsalva.Material and methods. Proximal valve SFV studies were performed in 144 lower limbs in 115 people (mean age 51.1 ± 14.4 years, 60 women and 55 men), proximal GSV valves studies - in 82 lower limbs in 67 persons (average age 45, 1 ± 13.3 years, 33 women, 34 men). A longitudinal and transverse ultrasound scanning of the femoral vein bifurcation and safenofemoral junction areas were performed, the structures of the proximal SFV and GSV valves were visualized, the valve shape was measured and the diameter of the veins was measured at the level valves at the base of the valves (inlet diameter), at the point of maximum ectasia (diameter of ectasia), at the upper border of the valve (diameter of the outlet), as well as measuring the length of the valve a (length to ectasia, the total length of the valve). The degree of ectasia over the valve was judged by calculating the relative venous diameter change (RVDC).Results. the average diameter of the SFV at the level of the lower boundary of its first valve was 10.01 ± 1.44 mm. The average diameter of the SFV at the level of the maximum ectasia of its first valve was 13,1±2 mm. The average value of the index of RVDC for SFV was 31%±10,4%. An increase in the diameter of the vein in the zone of supravalvular ectasia up to 20% corresponded to the spindle-shaped valve, more than 20% - to the clavate form, which was noted in the majority of the examined. The change in the relative venous diameter of the SFV on the Valsalva test was 38,2%±12,4%. The average diameter of the GSV at the base of the first valves was 6,07±1,25 mm. The average diameter of the GSV at the level of the maximum ectasia of the osteal valve was 9,44±1,69 mm. The average RVDC for GSV was 58%±24%.Conclusion. the natural form of proximal SFV and GSV valves is clavate with presence of the significant supravalvular ectasia, which was noted in the majority of the subjects alone and in all during the performance of the Valsalva functional test.

Biaxial Mechanical Behavior of Bovine Saphenous Venous Valve Leaflets

Chronic venous disease is caused by chronic venous insufficiency (CVI), which results in significant symptoms such as venous ulcers, ankle eczema, leg swelling, etc. Venous valve incompetence is a major cause of CVI. When the valves of veins in the leg become incompetent (i.e., do not close properly), blood is able to flow backwards (i.e., reflux), which results in blood pooling in the lower extremities, distal venous hypertension, and CVI. Current clinical therapies, such as surgical venous valve reconstruction and bioprosthetic venous valve replacement, are highly invasive and only moderately successful. This is due, in part, to the scanty information available about venous valve leaflet structure and mechanical properties. To date, only one previous study by our research group has reported on the mechanical properties of venous valve leaflet tissue, and specifically in the case of jugular vein valves. In this study, we conducted equibiaxial tensile tests on bovine saphenous vein valve leaflet tissues to better understand their nonlinear, anisotropic mechanical behavior. By stretching the valvular tissues to 60% strain in both the circumferential and radial directions, we generated stress-strain curves for proximal (i.e., those closest to the heart) and distal (i.e., those furthest from the heart) valve leaflets. Histology and collagen assays were also conducted to study corresponding leaflet microstructures and the biochemical properties of the tissues. Results showed: (1) saphenous venous valve tissues possessed overall anisotropic properties. The tissues were stiffer in the circumferential direction than in the radial direction (p<0.01), and (2) saphenous venous valve tissues from the proximal end showed nonlinear isotropic mechanical properties, while those from the distal end showed nonlinear anisotropic mechanical properties. (3) Distal saphenous venous valve tissues appeared to be stiffer than proximal ones in the circumferential direction, p=0.04 (i.e., inter-valvular variability), and (4) the collagen concentration showed a decreasing trend from the proximal to the distal end. This study focuses on highly relevant animal (bovine) tissues to develop test protocols, establish biomechanical structure-function correlations, and to provide data critical to the design of clinical prosthetic venous valves. To the best of the author's knowledge, this is the first study reporting the biaxial mechanical properties of saphenous venous valve leaflet tissues and thus contributes toward refining our collective understanding of valvular tissue biomechanics.

Biaxial mechanical properties of bovine jugular venous valve leaflet tissues.

Venous valve incompetence has been implicated in diseases ranging from chronic venous insufficiency (CVI) to intracranial venous hypertension. However, while the mechanical properties of venous valve leaflet tissues are central to CVI biomechanics and mechanobiology, neither stress-strain curves nor tangent moduli have been reported. Here, equibiaxial tensile mechanical tests were conducted to assess the tangent modulus, strength and anisotropy of venous valve leaflet tissues from bovine jugular veins. Valvular tissues were stretched to 60% strain in both the circumferential and radial directions, and leaflet tissue stress-strain curves were generated for proximal and distal valves (i.e., valves closest and furthest from the right heart, respectively). Toward linking mechanical properties to leaflet microstructure and composition, Masson's trichrome and Verhoeff-Van Gieson staining and collagen assays were conducted. Results showed: (1) Proximal bovine jugular vein venous valves tended to be bicuspid (i.e., have two leaflets), while distal valves tended to be tricuspid; (2) leaflet tissues from proximal valves exhibited approximately threefold higher peak tangent moduli in the circumferential direction than in the orthogonal radial direction (i.e., proximal valve leaflet tissues were anisotropic; [Formula: see text]); (3) individual leaflets excised from the same valve apparatus appeared to exhibit different mechanical properties (i.e., intra-valve variability); and (4) leaflets from distal valves exhibited a trend of higher soluble collagen concentrations than proximal ones (i.e., inter-valve variability). To the best of the authors' knowledge, this is the first study reporting biaxial mechanical properties of venous valve leaflet tissues. These results provide a baseline for studying venous valve incompetence at the tissue level and a quantitative basis for prosthetic venous valve design.

Valsalva maneuver in phlebologic practice.

Forced expiration against an airway obstruction was originally described as a method for inflating the Eustachian tubes and is accredited to Antonio Maria Valsalva (1666-1723). The Valsalva maneuver is commonly applied for different diagnostic purposes. Its use for phlebologic diagnosis is the object this review. Venous reflux is the most frequent pathophysiologic mechanism in chronic venous disease. Reflux is easily visualized by duplex ultrasound when properly elicited, in standing position. A simple way to elicit reflux is the so-called "compression-release maneuver": by emptying the muscle reservoir, it determines a centrifugal gradient, dependent on hydrostatic pressure, creating an aspiration system from the superficial to the deep system. The same results are obtained with dynamics tests activating calf muscles. The Valsalva maneuver elicits reflux by a different mechanism, increasing the downstream pressure and, thus, highlighting any connection between the source of reflux and the refluxing vessel. The Valsalva maneuver is typically used to investigate the saphenofemoral junction. When the maneuver is performed correctly, it is very useful to analyse several conditions and different hemodynamic behaviours of the valvular system at the saphenofemoral junction. Negative Valsalva maneuver always indicates valvular competence at the saphenofemoral junction. Reverse flow lasting during the whole strain (positive Valsalva maneuver) indicates incompetence or absence of proximal valves. Coupling Valsalva maneuver to compression-release maneuver, with the sample volume in different saphenofemoral junction sections, may reveal different hemodynamic situations at the saphenofemoral junction, which can be analysed in detail.

ИЗУЧЕНИЕ РАБОТЫ ПРОКСИМАЛЬНОГО КЛАПАНА СОБСТВЕННОЙ БЕДРЕННОЙ ВЕНЫ И ВЛИЯНИЕ ФАКТОРОВ VIS A TERGO И VIS A FRONTE НА ЕГО РАБОТУ

Objective: A study of the femoral vein proximal valve function and the influence of vis a tergo and vis a fronte factors to it work. Methods: The study has done on 22 volunteers at the age of 18-80 years without signs of chronic venous diseases. It was conducted a comparison of vein diameter on the level of the intercuspidal incisura in patients with the proximal valve work and the absence of it. Results: It was fixed that the functions of the valves in 9 patients, and degree of lumen reduction of significant variation from 35.5% to 55.4%. Functioning of the valves was not detected in 7 patients, however the grade of vein diameter composed from 27% to 62.5%. In patients with presence of cycle functioning valves, it was strictly corresponded to the act of breathing – factor vis a fronte. The 6 patients were examined for the studying the influence of the phases of cardiac cycle to the valve functions, to whom were received the conservative treatment in the department of vascular surgery. Within 2-3 days the valve cycle was detected in all patients as a result of the conducted therapy; it was strictly correlated with breathing and was not synchronized with ECG. To exclude the factor of vis a fronte the examination was performed during breath hold. The functioning of the valves was detected in all patients and closure of the valves occurred strictly following the phase of ventricular systole displayed on ECG; that is not effect of direct factor vis a tergo – the kinetic energy of the blood flow in cardiac ejection but effect of its main part-potential energy of vascular wall deformation. Conclusion: The main mechanism of venous outflow in lower limbs are calm – the direct factor of vis a tergo. The main mechanism of lower limbs are not enough in blood volume expansions in venous system, includes the additional mechanism of venous back out in the following way of vis a fronte, the arteriovenous pump. Keywords: Functioning of vein valve, vis a tergo, vis a fronte.

The effect of pathologic venous valve on neighboring valves: fluid-structure interactions modeling.

Understanding the hemodynamics surrounding the venous valve environment is of a great importance for prosthetic valves design. The present study aims to evaluate the effect of leaflets' stiffening process on the venous valve hemodynamics, valve's failure on the next proximal valve hemodynamics and valve's failure in a secondary daughter vein on the healthy valve hemodynamics in the main vein when both of these valves are distal to a venous junction. Fully coupled, two-way fluid-structure interaction computational models were developed and employed. The sinus pocket region experiences the lowest fluid shear stress, and the base region of the sinus side of the leaflet experiences the highest tissue stress. The leaflets' stiffening increases the tissue stress the valve is experiencing in a very low fluid shear region. A similar effect occurs with the proximal healthy valve as a consequence of the distal valve's failure and with the mother vein valve as a consequence of daughter vein valve's failure. Understanding the described mechanisms may be helpful for elucidating the venous valve stiffness-function relationship in nature, the reasons for a retrograde development of reflux and the relationship between venous valves located near venous junctions, and for designing better prosthetic valves and for improving their positioning.

Familial Hypercholesterolemia: new therapeutic approaches

Familial Hypercholesterolemia (FH) is caused by a mutation in the gene that encodes the low-density lipoprotein (LDL) receptor, resulting in very high levels of circulating LDL-cholesterol and endothelial damage during time. Apoprotein B, activated by LDL receptor, and PCSK9 (proprotein convertase subtilisin / kexin type 9 serine Protease), that impairs the clearance of LDL receptors, are important additional mechanisms that lead to increase LDL-cholesterol. The prevalence of Homozigous form (HoFH) is estimated to be 1 per 1 million individuals and, if untreated, proximal coronary disease or aortic valve disease frequently occurs during childhood and most affected patients suffer from fatal coronary disease before the age of 30. Heterozygous condition (HeFH) occurs in about 1/380-500 individuals. The levels of LDL-cholesterol in this form may greatly vary but the disease is always asymptomatic until adult age when there is a high risk of early cardiovascular disease. Lifestyle intervention and maximal statin therapy are the mainstays of treatment. In patients that not achieve LDL-C targets, primarly HoFH patients, adjunctive lipoprotein apheresis is recommended where available. Biological agents represents to date a new therapeutic approach for this not so rare condition. The PCSK9 pathway is one of the best examples of how genetics has led to identification of a new target for cholesterol management. Different PCSK9 inhibitors (alirocumab, evolocumab) are now available [1]. Mipomersen is an antisense oligonucleotide (ASO) that targets apoliporotein B-100 mRNA and disrupts its function: it is distributed mainly to the liver where it silences apoB mRNA, thereby reducing hepatic apoB-100 and giving rise to reductions in plasma total cholesterol, LDL-cholesterol, and apoB concentrations [2]. Lomitapide is a microsomal triglyceride transfer protein (MTP) inhibitor. MTP resides in the lumen of the endoplasmic reticulum, thereby preventing the assembly of apo B–containing lipoproteins in enterocytes and hepatocytes. This inhibition leads to a reduction in the synthesis of chylomicrons and very low–density lipoprotein, resulting in a reduction in plasma LDL levels [3].

Evaluation of Acquired Valvular Heart Disease by the Pediatrician: When to Follow, When to Refer for Intervention? Part II.

Lesions of the heart valves are the commonest acquired cardiac abnormalities seen in pediatric age group. Aortic regurgitation (AR) results from abnormality of the valve leaflets or of the aortic root. Mitral valve lesion may be associated in patients with rheumatic heart disease (RHD). Left ventricle dilates and may develop dysfunction in advanced states. Coronary perfusion also tends to suffer in severe AR. The symptoms develop later and include dyspnea and palpitations. An early diastolic, high pitched murmur, best heard at base of the heart is the hallmark of AR. All symptomatic patients with severe AR and those with left ventricular dysfunction should undergo surgical intervention. Aortic stenosis (AS) is often due to congenitally bicuspid or unicuspid valve. RHD rarely results in AS; associated AR is common in such cases. The most common cause of tricuspid valve involvement is secondary to dilatation of right ventricle and tricuspid annulus resulting in tricuspid regurgitation (TR). Rarely RHD affects the tricuspid valve directly; resulting in stenosis with TR. Involvement of both mitral and aortic valves is almost pathognomonic of RHD etiology. Severity of individual lesions may be difficult to ascertain as proximal valve lesion tends to modify the assessment of the distal valve lesion. It is important to understand that all valvular lesions do not require surgery. Regular secondary prophylaxis with long acting penicillin (for patients with RHD) may retard further progression of valve lesion and must be emphasized to the family. For mild and asymptomatic moderate valvular lesions, periodic monitoring with clinical examination and echocardiography is sufficient. No guidelines are available for timing of intervention in such children; data may have to be extrapolated from published guidelines for adult patients. Various types of surgical options are available for regurgitant valves, but none is ideal. The pediatricians are required to have knowledge of valvular diseases so as to refer the patient at an appropriate time for intervention or further evaluation. His/ her role is also crucial in follow up of post operated patients, especially those on oral anticoagulation.

Percutaneous pulmonary valve implantation with the Venus P-valve: clinical experience and early results.

At present, the exclusion for percutaneous pulmonary valve implantation for free pulmonary regurgitation after tetralogy of Fallot repair includes an unfavourably large right ventricular outflow tract. To report feasibility and early experience with a recently developed transcatheter heart valve, Venus P-valveTM, implanted in six patients with severe pulmonary regurgitation with large right ventricular outflow tracts. Patients There were two female patients and four male patients. The median age of the patients was 18.5 years, and the mean body weight was 53.8 kg. All the patients were in NYHA class II and had severe pulmonary regurgitation after previous transannular patch repair of tetralogy of Fallot. The median time after the last surgical operation was 13.5 years. The Venus P-valveTM was successfully implanted in all the patients with implanted valve diameters ranging from 24 to 32 mm. The mean fluoroscopy time was 29.8 minutes. None of the patients had significant outflow tract gradient or pulmonary regurgitation immediately after valve implantation. Only one patient had unexpected mild proximal valve migration to the right ventricular body during withdrawal of the delivery system. It caused mild paravalvar leak and significant tricuspid regurgitation. At 6 months follow-up, the median of right ventricular end-diastolic volume indices decreased from 146 to 108 ml/m2 (p-value=0.046). The Doppler systolic peak gradient across the valve ranged from 4 to 40 mmHg, and there was no evidence of stent fracture on fluoroscopy or structural valve failure. The Venus P-valveTM can be implanted successfully and effectively in patients with severe pulmonary regurgitation and a large right ventricular outflow tract. The early results with this valve are encouraging.