A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pr...A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body,a cooling structure is set on the valve seat.This can significantly reduce the temperature of the valve body and valve seat.The effects of its structure on the cooling characteristics and stress of the valve seat are studied,and six main parameters that can completely describe the geometry of the cooling structure are proposed.The central composite design method is used to select sample points,and the multi-objective genetic algorithm(MOGA)method is used for optimal structural design.A modification method according to the main parameters for the valve seat is proposed.The results show that the cooling structure weakens the pressure-bearing capability of the valve seat.Among the six main parameters of the valve seat,the distance from the end face of the lower hole to the Z-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat.An optimum design value is proposed.This work can provide a reference for the design of high-temperature and high-pressure valves.展开更多
The finite element method （FEM） and particle image velocimetry （PIV） technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at th...The finite element method （FEM） and particle image velocimetry （PIV） technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at three different valve openings. For FEM numerical simulation, the stream function ψ-vorticity ω forms of continuity and Navier-Stokes equations are employed and FEM is applied to discrete the equations. Homemade simulation codes are executed to compute the values of stream function and vorticity at each node in the flow domain, then according to the correlation between stream function and velocity components, the velocity vectors of the whole field are calculated. For PIV experiment, pulse Nd： YAG laser is exploited to generate laser beam, cylindrical and spherical lenses are combined each other to produce 1.0 mm thickness laser sheet to illuminate the object plane, Polystyrene spherical particle with diameter of 30-50 μm is seeded in the fluid as a tracing particles, Kodak ES 1.0 CCD camera is employed to capture the images of interested, the images are processed with fast Fourier transform （FFT） cross-correlation algorithm and the processing results is displayed. Both results of numerical simulation and PIV experimental show that there are three main areas in the spool valve where vortex is formed. Numerical results also indicate that the valve opening have some effects on the flow structure of the valve. The investigation is helpful for qualitatively analyzing the energy loss, noise generating, steady state flow forces and even designing the geometry structure and flow passage.展开更多
AIM To determine whether the need for additional tricuspid valve repair is an independent risk factor when surgery is required for a left-sided heart disease.METHODS One hundred and eighty patients(68 ± 12 years,...AIM To determine whether the need for additional tricuspid valve repair is an independent risk factor when surgery is required for a left-sided heart disease.METHODS One hundred and eighty patients(68 ± 12 years,79 males) underwent tricuspid annuoplasty.Cox proportionalhazards regression model for multivariate analysis was performed for variables found significant in univariate analyses.RESULTS Tricuspid regurgitation etiology was functional in 154 cases(86%),organic in 16 cases(9%),and mixed in10 cases(6%),respectively.Postoperative mortality at 30 days was 11.7%.Mean follow-up was 51.7 mo with survival at 5 years of 73.5%.Risk factors for mortality were acute endocarditis [hazard ratio(HR) = 9.22(95%CI:2.87-29.62),P < 0.001],ischemic heart disease requiring myocardial revascularization [HR = 2.79(1.26-6.20),P = 0.012],and aortic valve stenosis [HR = 2.6(1.15-5.85),P = 0.021].Significant predictive factors from univariate analyses were double-valve replacement combined with tricuspid annuloplasty [HR = 2.21(1.11-4.39),P = 0.003] and preoperatively impaired ejection fraction [HR = 1.98(1.04-3.92),P = 0.044].However,successful mitral valve repair showed a protective effect [HR = 0.32(0.10-0.98),P = 0.046].Additionally,in instances where tricuspid regurgitation required the need for concomitant tricuspid valve repair,mortality predictor scores such as Euroscore 2 could be shortened to a simple Euroscore-tricuspid comprised of only 7 inputs.The explanation may lie in the fact that significant tricuspid regurgitation following leftsided heart disease represents an independent risk factor encompassing several other factors such as pulmonary arterial hypertension and dyspnea.CONCLUSION Tricuspid annuloplasty should be used more often as a concomitant procedure in the presence of relevant tricuspid regurgitation,although it usually reveals an overly delayed correction of a left-sided heart disease.展开更多
Poppet valves are basic components of many manufacturing operations and industrial processes. The valve plug will withstand unbalanced pressure during the switching process due to the complex fluid-structure interacti...Poppet valves are basic components of many manufacturing operations and industrial processes. The valve plug will withstand unbalanced pressure during the switching process due to the complex fluid-structure interaction(FSI) in the local flow condition, especially with the occurrence of cavitation, which results in a convoluted generation and propagation of mechanical and fluid-dynamic vibrations. In the present work, computational fluid dynamics(CFD) approaches are proposed to model the flow-driven movement of the disc, in consideration of the valve stem rigidity, for a cryogenic poppet valve with liquid nitrogen as the working fluid. Cavitation effects are included in the CFD simulations. The relationship between the displacement of the disc and the resistance of the stem is obtained in advance using the finite element method(FEM), and implemented in CFD calculations based on the user-defined functions(UDFs). The disc vibration is realized using the dynamic mesh technology according to the resultant flow field force and resistance of the stem determined in the UDF. The vibration characteristics of the valve disc, including velocity and vibration frequency, are presented. The temporal evolutions of cavitation behavior due to the vibration are also captured. Comparisons of results between cavitation and non-cavitation conditions are made, and spectral analysis of the transient pressure fluctuations reveals that the presence of cavitation induces transient unbalanced loads on the valve disc and generates instantaneous tremendous pressure fluctuations in the flow field. Various pressure differences between the inlet and outlet as well as valve openings are modeled to probe the influences of FSI on valve disc vibration mechanisms.The consequent analysis gives deeper insights and improves understanding of the mechanism of the complicated interaction between the cavitating flow and the vibration of the valve disc.展开更多
A new flow field mathematical model is proposed to describe accurately the flow field structure and calculate the static characteristics of the pilot stage in a deflector jet servo valve(DJSV). The flow field is divid...A new flow field mathematical model is proposed to describe accurately the flow field structure and calculate the static characteristics of the pilot stage in a deflector jet servo valve(DJSV). The flow field is divided into five regions, a 3D turbulent jet is adopted to describe the free jet region, and a velocity distribution expression of the jet is proposed. The jet entrainment model is put forward in the pressure recovery region to describe the coupling relationship between the pressure in the receiving chamber and the jet flow. The static characteristics, including pressure-flow characteristics, pressure characteristics,and flow characteristics of the pilot stage are obtained. The flow field structure and the static characteristics are verified by finite element analysis(FEA) and experiment, respectively, and the mathematical model results are in good agreement with the experimental and simulation results.展开更多
AIM:To assess the incidence of mitral valve prolapse in patients with newly diagnosed primary open angle glaucoma.METHODS:The study included 12 patients without any other comorbidities or taking any general or local m...AIM:To assess the incidence of mitral valve prolapse in patients with newly diagnosed primary open angle glaucoma.METHODS:The study included 12 patients without any other comorbidities or taking any general or local medications.Each patient underwent a full ophthalmological examination with visual field assessment and optical computed tomography of the macula and optic nerve head.Carotid Doppler ultrasound was performed to exclude impaired blood flow in this region and transthoracic echocardiography with assessment of the function and morphology of the heart valves.RESULTS:In the study group,mitral valve prolapse was found in seven patients(58.3%),while mitral valve regurgitation in 11 patients(91.7%).One case of normal pressure glaucoma and four cases of juvenile glaucoma were diagnosed.There were also other risk factors for glaucoma:myopia(58.3%),migraine headaches(41.7%),a positive family history of glaucoma(16.7%).CONCLUSION:Mitral valve prolapse could be indicated as a new risk factor for glaucoma.It seems reasonable to conduct screening tests for glaucoma in patients with mitral valve prolapse in the course of echocardiography.展开更多
Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their oper...Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their operational performance to satisfy the technical specification of project related.Test facilities for operational tests of thyristor valves are supposed to enable to undertake more severe electrical stresses than those being applied in the thyristor valves under test(test objects).On the other hand,the stresses applied into the test objects are neither higher nor lower than specified by the specification,because inappropriate stresses applied would result in incorrect evaluation of performance on the test objects,more seriously,would cuase the damage of test objects with expensive cost losing.Generally,the process of operational tests is complicated and performed in a complex synthetic test circuit(hereafter as STC),where there are a lot of sensors used for measuring,monitoring and protection on line to ensure that the test circuit functions in good condition.Therefore,the measuring systems embedded play a core role in STC,acting like "eyes".Based on the first project of building up a STC in China,experience of planning measuring systems is summarized so as to be referenced by related engineers.展开更多
Valvular heart disease is a pathologic process involving one or more of the four valves(aortic,pulmonary,mitral and tricuspid)of the heart typified by stenosis or regurgitation and leading to patient symptoms.The most...Valvular heart disease is a pathologic process involving one or more of the four valves(aortic,pulmonary,mitral and tricuspid)of the heart typified by stenosis or regurgitation and leading to patient symptoms.The most common causes are tissue degeneration,rheumatic fever and congenital heart diseases.Aortic valve replacement(AVR)using either mechanical or bioprosthetic(tissue)valves via open-heart surgical展开更多
Between August 1976 and May 1988,43 patients had their heart valve prostheses replaced.The total mortality was as high as 25.6%,but the operative mortality was reduced to 6.25%in the last 16 cases.The indications,main...Between August 1976 and May 1988,43 patients had their heart valve prostheses replaced.The total mortality was as high as 25.6%,but the operative mortality was reduced to 6.25%in the last 16 cases.The indications,main risk factors and surgical techniques are discussed.展开更多
Background There is scarce data about comparisons between geriatric assessment tools in patients with aortic stenosis(AS).We aimed to describe the geriatric profile of patients with AS undergoing transcatheter aortic ...Background There is scarce data about comparisons between geriatric assessment tools in patients with aortic stenosis(AS).We aimed to describe the geriatric profile of patients with AS undergoing transcatheter aortic valve implantation(TAVI)and to analyze the ability of different tools for predicting clinical outcomes in this context.Methods This was a single center retrospective registry including patients with AS undergoing TAVI and surviving to hospital discharge.The primary endpoint was all-cause mortality or need for urgent readmission one year after TAVI.Results A total of 377 patients were included(mean age of 80.4 years).Most patients were independent or mildly dependent,with an optimal cognitive status.The proportion of frailty ranged from 17.6%to 49.8%.A total of 20 patients(5.3%)died and 110/377 patients(29.2%)died or were readmitted during follow up.Overall,most components of the geriatric assessment showed an association with clinical outcomes.Disability for instrumental activities showed a significant association with mortality and a strong association with the rate of mortality or readmission.The association between frailty and clinical outcomes was higher for short physical performance battery(SPPB),essential frailty toolset(EFT)and the frailty index based on comprehensive geriatric assessment(IF-VIG)and lower for Fried criteria and FRAIL scale.Conclusions AS patients from this series presented a good physical performance,optimal cognitive status and a reasonably low prevalence of frailty.The best predictive ability was observed for disability for instrumental activities and frailty as measured by the EFT,SPPB and the IF-VIG.展开更多
BACKGROUND Valvular heart disease affects more than 100 million people worldwide and is associated with significant morbidity and mortality.The prevalence of at least moderate valvular heart disease is 2.5%across all ...BACKGROUND Valvular heart disease affects more than 100 million people worldwide and is associated with significant morbidity and mortality.The prevalence of at least moderate valvular heart disease is 2.5%across all age groups,but its prevalence increases with age.Mitral regurgitation and aortic stenosis are the most frequent types of valvular heart disease in the community and hospital context,res-pectively.Surgical valve replacement(or mitral valve repair)is the standard of care for treating heart valve disease.However,the replacement of a prosthetic heart valve can lead to complications,either in the peri-procedural phase or in the long-term follow-up period.CASE SUMMARY We present a case of a 71-year-old female patient with a history of mitral valve replacement and warfarin anti-coagulation therapy.She was admitted to the intensive care unit due to spontaneously reperfused ischemic stroke of probable cardioembolic etiology.A dysfunctional mitral prosthesis was identified due to malfunction of one of the fixed discs.Furthermore,a possible microthrombotic lesion was suspected.Therefore,systemic thrombolysis was performed with subsequent normalization of mitral disc opening and closing.CONCLUSION This case underscores the critical importance of a multidisciplinary approach for timely decision-making in critically ill patients with prosthetic valve complications.展开更多
BACKGROUND The management of severe symptomatic aortic stenosis has been revolutionized by transcatheter aortic valve replacement(TAVR),offering a minimally invasive alternative to surgical aortic valve replacement(SA...BACKGROUND The management of severe symptomatic aortic stenosis has been revolutionized by transcatheter aortic valve replacement(TAVR),offering a minimally invasive alternative to surgical aortic valve replacement(SAVR).However,the compara-tive safety and efficacy of these interventions remain subjects of ongoing investigation.AIM To compare the clinical outcomes and safety of TAVR vs SAVR in patients with severe symptomatic aortic stenosis.METHODS A systematic review and meta-analysis were conducted according to PRISMA guidelines.Randomized controlled trials(RCTs)comparing TAVR and SAVR were identified from databases including PubMed,Scopus,and Web of Science up to May 31,2024.Data were extracted on clinical outcomes,including mortality,procedural compli-cations,and post-procedure adverse events.Risk ratios(RRs)with 95%CIs were calculated using a random-effects model.RESULTS A total of 10 RCTs were included.TAVR demonstrated a significantly lower risk of acute kidney injury(RR:0.33;95%CI:0.25–0.44),major bleeding(RR:0.37;95%CI:0.30–0.46),and new-onset atrial fibrillation(RR:0.44;95%CI:0.34–0.57)compared to SAVR.However,TAVR was associated with higher risks of new permanent pacemaker implantation(RR:3.49;95%CI:2.77–4.39),major vascular complications(RR:2.47;95%CI:1.91–3.21),and paraval-vular leaks(RR:4.15;95%CI:3.14–5.48).Mortality at 30 days was comparable(RR:0.95;95%CI:0.78–1.15),but long-term mortality was slightly higher with TAVR in some analyses(RR:1.23;95%CI:1.01–1.49).Rates of stroke(RR:0.97;95%CI:0.81–1.17)and myocardial infarction(RR:0.91;95%CI:0.67–1.24)were similar between the groups.CONCLUSION TAVR offers a less invasive option with significant benefits in reducing acute kidney injury,major bleeding,and new-onset atrial fibrillation,making it particularly advantageous for high-risk surgical candidates.However,higher risks of permanent pacemaker implantation,vascular complications,and paravalvular leaks highlight the need for individualized patient selection and shared decision-making to optimize outcomes.展开更多
Gifford-McMahon-type pulse-tube cryocoolers(GM-PTCs)working at liquid helium temperatures are promising in quantum technology and cryogenic physics for their high reliability and minimal vibration.These features stem ...Gifford-McMahon-type pulse-tube cryocoolers(GM-PTCs)working at liquid helium temperatures are promising in quantum technology and cryogenic physics for their high reliability and minimal vibration.These features stem from the fact that there are no extra moving parts introduced into the system.The rotary valve is a key component in GM-PTCs that transfers the output exergy from the compressor to the cold head.Because a low Carnot efficiency of 1.58%is achieved at liquid helium temperatures,optimizing the rotary valve is crucial for improving the efficiency of GM-PTCs.In this regard,an exergy-loss analysis method is proposed in this paper to quantitatively obtain the leakage loss and viscosity loss of a rotary valve by experimental measurements.The results show that viscosity loss accounts for more than 97.5%of the total exergy loss in the rotary valve,and that it is possible to improve the structure of the rotary valve by expanding the flow area by 1.5 times.To verify the method,the cooling temperature and power of a remote two-stage GM-PTC were monitored,with original or optimized rotary valves installed.The experimental results show that compared to the original rotary valve,the optimized rotary valve can improve the cooling efficiency of a GM-PTC by 16.4%,with a cooling power of 0.78 W at 4.2 K.展开更多
Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibra...Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.展开更多
Pediatric heart valve replacement(PHVR)remains a challenging procedure due to the uniqueanatomical and physiological characteristics of children,including growth and development,as well asthe long-term need for durabl...Pediatric heart valve replacement(PHVR)remains a challenging procedure due to the uniqueanatomical and physiological characteristics of children,including growth and development,as well asthe long-term need for durable valve function.This review provides an overview of both surgical andtranscatheter options for aortic,mitral,pulmonary,and tricuspid valve replacements in pediatric patients,highlighting the indications,outcomes,and advancements in technology and technique.Surgical valvereplacement traditionally involves the implantation of biological or mechanical prosthetic valves,withbiologicalvalves beingpreferred in children to reduce the need for lifelong anticoagulation therapy.However,the limitation ofbiological prostheses,nanely their inability to grow with the child,necessitates the frequentneed for reoperations.Recent innovations in valve engineering,such as the development of tissue engineeredand expandable valves,aim to address these issues.Transcatheter valve replacement(TVR)has emergedas a promising alternative,particularly for patients with complex anatomy or those who are high-risk fortraditional surgery.While the use of transcatheter devices in children remains limited due to the smallervascular size and limited long-termn data,several studies have demonstrated the feasibility and safety ofthe procedure in certain patient populations.Despite these advancements,challenges related to valvesize,durability,and the need for individualized treatment planning persist.The future of pediatric heartvalve replacemnent will likely involve a multidisciplinary approach combining surgical,transcatheter,andregenerative medicine strategies,aimed at optimizing outcomes,reducing the need for reinterventions,andimproving long-term quality of life for pediatric patients with valvularheart disease.This article discussesall options availab le for patients with valvular dysfunction,making it easy for parents/patients to go to as areference source of information.展开更多
Valvular Heart Disease(VHD),including stenosis and regurgitation,is a significant contributor to global cardiovascular morbidity.Current prosthetic solutions mechanical and bioprosthetic heart valves each present majo...Valvular Heart Disease(VHD),including stenosis and regurgitation,is a significant contributor to global cardiovascular morbidity.Current prosthetic solutions mechanical and bioprosthetic heart valves each present major limitation.Mechanical valves require lifelong anticoagulation due to thrombogenicity,while bioprosthetic valves suffer from structural degeneration and limited durability.Polymeric Heart Valves(PHVs)have emerged as promising alternatives,aiming to integrate the mechanical resilience of synthetic materials with the biocompatibility and hemodynamic performance of natural valves.Recent studies have explored advanced polymers such as Polyhedral Oligomeric Silsesquioxane–Polycarbonate–Urea–Urethane(POSS-PCU),Silicone–Polyurethane Urea(SiPUU),and nanocomposites like Polyvinyl Alcohol(PVA)and SIBS for their enhanced thromboresistance,calcification resistance,and long-term mechanical durability.Complementary to material innovation,fabrication methods such as 3D printing,Melt Electrospinning Writing(MEW),and Focused Rotary Jet Spinning(FRJS)offer patient-specific designs and microstructural control.This review systematically compares traditional and next-generation prostheses,examines mechanical and biological performance,and discusses critical design challenges including porosity,thrombogenicity,and leaflet calcification.Finite Element Analysis(FEA)and Computational Fluid Dynamics(CFD)are highlighted for optimizing design and simulating physiological conditions.By presenting recent preclinical progress and manufacturing strategies,this review outlines a translational roadmap toward clinically viable,biomimetic polymeric heart valves capable of addressing the needs of both adult and pediatric patients.Compared to traditional bioprosthetic tissues,advanced polymers offer better resistance to calcification,reduced thrombogenicity,and tunable mechanical properties.展开更多
Background Transcatheter Aortic Valve Implantation(TAVI)has changed the treatment paradigm of the aortic stenosis(AS).It has become the treatment of choice in patients with symptomatic AS and surgical high risk,and a ...Background Transcatheter Aortic Valve Implantation(TAVI)has changed the treatment paradigm of the aortic stenosis(AS).It has become the treatment of choice in patients with symptomatic AS and surgical high risk,and a valid alternative to surgical aortic valve replacement in patients with low and medium surgical risk.Despite numerous evidence on clinical results,indications and benefits,only a few studies analyse it from patient's perspective and the impact of TAVI on them.The objective of this study is to evaluate the experience of patients undergoing TAVI.Methods Cross-sectional,descriptive observational study in two Spanish hospitals,with a establish Nurse TAVI program,with100 patients undergoing TAVI.A specific questionnaire was designed(VALVEX questionnaire)and a pilot study was conducted by a multidisciplinary team of doctors,nurses and patients.The questionnaire was given to patients at 30 days after TAVI procedure during the follow up at the TAVI nurse clinic.Results The study demonstrated a mean satisfaction of 9 for the TAVI program,with 96%of patients that would recommend TAVI to other patients.Patients scored a high satisfaction on the information received prior to the procedure.During the procedure and admission,the satisfaction was high in relation to the care received.During the follow up,satisfaction was high in relation to the role of the TAVI nurse,for the information and continuation of care during the procedure,in reducing anxiety,organising their admission and understanding the process.However,questions with less scores were related to hospital catering,delay between diagnosed and treatment,and patient decision-making process.Conclusion The evaluation of patient experience allows us to improve the information given to the patient during their TAVI process and it can also allow patients to be more relax,aware and prepared for the procedure.Continuous follow up enables monitoring of patient recovery and helps to discuss any doubts improving patient's satisfaction.The use of PREMs and PROMs associated to TAVI pathway combined with an active participation of the patient on the design of the questionnaire is essential for keeping the patient in the centre of the TAVI pathway.展开更多
Aortic stenosis(AS)is the most common valvular heart disease,with a prevalence of over 4%among octogenarians.[1]The prevalence of autopsy-confirmed wild-type transthyretin cardiac amyloidosis(ATTRwt-CA)increases with ...Aortic stenosis(AS)is the most common valvular heart disease,with a prevalence of over 4%among octogenarians.[1]The prevalence of autopsy-confirmed wild-type transthyretin cardiac amyloidosis(ATTRwt-CA)increases with age,accounting for 25%of patients aged 85 years and older in Europe and 12%of patients older than 80 years in Japan.[2,3]Recent studies have reported that ATTRwt-CA coexists in 11%-16%of older patients with AS undergoing transcatheter aortic valve replacement(TAVR).[1,4,5]In a metaanalysis by Ho et al.,[6]the prevalence rates of cardiac amyloidosis,predominantly ATTRwt-CA,in patients with AS and those referred for TAVR or surgical aortic valve replacement(SAVR)were 14.4%and 15.2%,respectively.Conversely,the prevalence of AS in patients with cardiac amyloidosis is 8.7%.Owing to the high surgical risk in patients with both AS and ATTRwt-CA,TAVR may be preferred over SAVR.展开更多
Severe aortic stenosis has increased exponentially as a result of the aging of the population.Transcatheter aortic valve replacement(TAVR)procedures increase by 20%-30%per year in Spain.Referred patients are increasin...Severe aortic stenosis has increased exponentially as a result of the aging of the population.Transcatheter aortic valve replacement(TAVR)procedures increase by 20%-30%per year in Spain.Referred patients are increasingly older,have comorbidities,and frailty.TAVR cardiac rehabilitation(CR)programs significantly improve both functional capacity and quality of life of patients.However,there are no guidelines on how to carry out them and few elderly patients are referred to CR.Furthermore,mortality in women who undergo TAVR is higher than in men and even fewer are referred to CR programs.Multidisciplinary patient care,including comorbidities and frailty,is essential.It is necessary to ensure exquisite continuity of care during TAVR,CR,and the rest of the patient's life.Telerehabilitation could be an option in some lower-risk patients to include more patients in CR programs after TAVR,given the high demand.This article reviews the evidence on why CR should be performed in post-TAVR patients and proposes a practical and novel approach to the care process and the recommended aspects and components of the CR program.展开更多
Particularly commendable is the important work of Calvo,et al.[1]in comparing geriatric assessment tools to predict mortality and readmissions in elderly patients undergoing transcatheter aortic valve implantation(TAV...Particularly commendable is the important work of Calvo,et al.[1]in comparing geriatric assessment tools to predict mortality and readmissions in elderly patients undergoing transcatheter aortic valve implantation(TAVI).Their efforts underscore the growing importance of frailty assessment in cardiovascular risk stratification.We would like to respectfully highlight several areas that,if addressed in future studies(Figure 1),could further enhance the utility and inclusivity of these assessments.展开更多
基金supported by the National Natural Science Foundation of China(No.52175067)the Zhejiang Key Research&Development Project(No.2021C01021)+1 种基金the Natural Science Foundation of Zhejiang Province(No.LY20E050016)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(CPSF)(No.GZC20241478)。
文摘A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body,a cooling structure is set on the valve seat.This can significantly reduce the temperature of the valve body and valve seat.The effects of its structure on the cooling characteristics and stress of the valve seat are studied,and six main parameters that can completely describe the geometry of the cooling structure are proposed.The central composite design method is used to select sample points,and the multi-objective genetic algorithm(MOGA)method is used for optimal structural design.A modification method according to the main parameters for the valve seat is proposed.The results show that the cooling structure weakens the pressure-bearing capability of the valve seat.Among the six main parameters of the valve seat,the distance from the end face of the lower hole to the Z-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat.An optimum design value is proposed.This work can provide a reference for the design of high-temperature and high-pressure valves.
文摘The finite element method （FEM） and particle image velocimetry （PIV） technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at three different valve openings. For FEM numerical simulation, the stream function ψ-vorticity ω forms of continuity and Navier-Stokes equations are employed and FEM is applied to discrete the equations. Homemade simulation codes are executed to compute the values of stream function and vorticity at each node in the flow domain, then according to the correlation between stream function and velocity components, the velocity vectors of the whole field are calculated. For PIV experiment, pulse Nd： YAG laser is exploited to generate laser beam, cylindrical and spherical lenses are combined each other to produce 1.0 mm thickness laser sheet to illuminate the object plane, Polystyrene spherical particle with diameter of 30-50 μm is seeded in the fluid as a tracing particles, Kodak ES 1.0 CCD camera is employed to capture the images of interested, the images are processed with fast Fourier transform （FFT） cross-correlation algorithm and the processing results is displayed. Both results of numerical simulation and PIV experimental show that there are three main areas in the spool valve where vortex is formed. Numerical results also indicate that the valve opening have some effects on the flow structure of the valve. The investigation is helpful for qualitatively analyzing the energy loss, noise generating, steady state flow forces and even designing the geometry structure and flow passage.
文摘AIM To determine whether the need for additional tricuspid valve repair is an independent risk factor when surgery is required for a left-sided heart disease.METHODS One hundred and eighty patients(68 ± 12 years,79 males) underwent tricuspid annuoplasty.Cox proportionalhazards regression model for multivariate analysis was performed for variables found significant in univariate analyses.RESULTS Tricuspid regurgitation etiology was functional in 154 cases(86%),organic in 16 cases(9%),and mixed in10 cases(6%),respectively.Postoperative mortality at 30 days was 11.7%.Mean follow-up was 51.7 mo with survival at 5 years of 73.5%.Risk factors for mortality were acute endocarditis [hazard ratio(HR) = 9.22(95%CI:2.87-29.62),P < 0.001],ischemic heart disease requiring myocardial revascularization [HR = 2.79(1.26-6.20),P = 0.012],and aortic valve stenosis [HR = 2.6(1.15-5.85),P = 0.021].Significant predictive factors from univariate analyses were double-valve replacement combined with tricuspid annuloplasty [HR = 2.21(1.11-4.39),P = 0.003] and preoperatively impaired ejection fraction [HR = 1.98(1.04-3.92),P = 0.044].However,successful mitral valve repair showed a protective effect [HR = 0.32(0.10-0.98),P = 0.046].Additionally,in instances where tricuspid regurgitation required the need for concomitant tricuspid valve repair,mortality predictor scores such as Euroscore 2 could be shortened to a simple Euroscore-tricuspid comprised of only 7 inputs.The explanation may lie in the fact that significant tricuspid regurgitation following leftsided heart disease represents an independent risk factor encompassing several other factors such as pulmonary arterial hypertension and dyspnea.CONCLUSION Tricuspid annuloplasty should be used more often as a concomitant procedure in the presence of relevant tricuspid regurgitation,although it usually reveals an overly delayed correction of a left-sided heart disease.
基金supported by the National Natural Science Foundation of China(Nos.51636007 and 51976177)the Key Research and Development Plan of Zhejiang Province(No.2020C01029),China。
文摘Poppet valves are basic components of many manufacturing operations and industrial processes. The valve plug will withstand unbalanced pressure during the switching process due to the complex fluid-structure interaction(FSI) in the local flow condition, especially with the occurrence of cavitation, which results in a convoluted generation and propagation of mechanical and fluid-dynamic vibrations. In the present work, computational fluid dynamics(CFD) approaches are proposed to model the flow-driven movement of the disc, in consideration of the valve stem rigidity, for a cryogenic poppet valve with liquid nitrogen as the working fluid. Cavitation effects are included in the CFD simulations. The relationship between the displacement of the disc and the resistance of the stem is obtained in advance using the finite element method(FEM), and implemented in CFD calculations based on the user-defined functions(UDFs). The disc vibration is realized using the dynamic mesh technology according to the resultant flow field force and resistance of the stem determined in the UDF. The vibration characteristics of the valve disc, including velocity and vibration frequency, are presented. The temporal evolutions of cavitation behavior due to the vibration are also captured. Comparisons of results between cavitation and non-cavitation conditions are made, and spectral analysis of the transient pressure fluctuations reveals that the presence of cavitation induces transient unbalanced loads on the valve disc and generates instantaneous tremendous pressure fluctuations in the flow field. Various pressure differences between the inlet and outlet as well as valve openings are modeled to probe the influences of FSI on valve disc vibration mechanisms.The consequent analysis gives deeper insights and improves understanding of the mechanism of the complicated interaction between the cavitating flow and the vibration of the valve disc.
基金supported by the National Natural Science Foundation of China (Nos. 51775383 and 52175059)。
文摘A new flow field mathematical model is proposed to describe accurately the flow field structure and calculate the static characteristics of the pilot stage in a deflector jet servo valve(DJSV). The flow field is divided into five regions, a 3D turbulent jet is adopted to describe the free jet region, and a velocity distribution expression of the jet is proposed. The jet entrainment model is put forward in the pressure recovery region to describe the coupling relationship between the pressure in the receiving chamber and the jet flow. The static characteristics, including pressure-flow characteristics, pressure characteristics,and flow characteristics of the pilot stage are obtained. The flow field structure and the static characteristics are verified by finite element analysis(FEA) and experiment, respectively, and the mathematical model results are in good agreement with the experimental and simulation results.
文摘AIM:To assess the incidence of mitral valve prolapse in patients with newly diagnosed primary open angle glaucoma.METHODS:The study included 12 patients without any other comorbidities or taking any general or local medications.Each patient underwent a full ophthalmological examination with visual field assessment and optical computed tomography of the macula and optic nerve head.Carotid Doppler ultrasound was performed to exclude impaired blood flow in this region and transthoracic echocardiography with assessment of the function and morphology of the heart valves.RESULTS:In the study group,mitral valve prolapse was found in seven patients(58.3%),while mitral valve regurgitation in 11 patients(91.7%).One case of normal pressure glaucoma and four cases of juvenile glaucoma were diagnosed.There were also other risk factors for glaucoma:myopia(58.3%),migraine headaches(41.7%),a positive family history of glaucoma(16.7%).CONCLUSION:Mitral valve prolapse could be indicated as a new risk factor for glaucoma.It seems reasonable to conduct screening tests for glaucoma in patients with mitral valve prolapse in the course of echocardiography.
基金Project Supported by National Development and Reform Commission(No.[2006]2709)
文摘Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their operational performance to satisfy the technical specification of project related.Test facilities for operational tests of thyristor valves are supposed to enable to undertake more severe electrical stresses than those being applied in the thyristor valves under test(test objects).On the other hand,the stresses applied into the test objects are neither higher nor lower than specified by the specification,because inappropriate stresses applied would result in incorrect evaluation of performance on the test objects,more seriously,would cuase the damage of test objects with expensive cost losing.Generally,the process of operational tests is complicated and performed in a complex synthetic test circuit(hereafter as STC),where there are a lot of sensors used for measuring,monitoring and protection on line to ensure that the test circuit functions in good condition.Therefore,the measuring systems embedded play a core role in STC,acting like "eyes".Based on the first project of building up a STC in China,experience of planning measuring systems is summarized so as to be referenced by related engineers.
基金supported by the Department of Anesthesiology and Pain Medicine,University of California Davis Health
文摘Valvular heart disease is a pathologic process involving one or more of the four valves(aortic,pulmonary,mitral and tricuspid)of the heart typified by stenosis or regurgitation and leading to patient symptoms.The most common causes are tissue degeneration,rheumatic fever and congenital heart diseases.Aortic valve replacement(AVR)using either mechanical or bioprosthetic(tissue)valves via open-heart surgical
文摘Between August 1976 and May 1988,43 patients had their heart valve prostheses replaced.The total mortality was as high as 25.6%,but the operative mortality was reduced to 6.25%in the last 16 cases.The indications,main risk factors and surgical techniques are discussed.
文摘Background There is scarce data about comparisons between geriatric assessment tools in patients with aortic stenosis(AS).We aimed to describe the geriatric profile of patients with AS undergoing transcatheter aortic valve implantation(TAVI)and to analyze the ability of different tools for predicting clinical outcomes in this context.Methods This was a single center retrospective registry including patients with AS undergoing TAVI and surviving to hospital discharge.The primary endpoint was all-cause mortality or need for urgent readmission one year after TAVI.Results A total of 377 patients were included(mean age of 80.4 years).Most patients were independent or mildly dependent,with an optimal cognitive status.The proportion of frailty ranged from 17.6%to 49.8%.A total of 20 patients(5.3%)died and 110/377 patients(29.2%)died or were readmitted during follow up.Overall,most components of the geriatric assessment showed an association with clinical outcomes.Disability for instrumental activities showed a significant association with mortality and a strong association with the rate of mortality or readmission.The association between frailty and clinical outcomes was higher for short physical performance battery(SPPB),essential frailty toolset(EFT)and the frailty index based on comprehensive geriatric assessment(IF-VIG)and lower for Fried criteria and FRAIL scale.Conclusions AS patients from this series presented a good physical performance,optimal cognitive status and a reasonably low prevalence of frailty.The best predictive ability was observed for disability for instrumental activities and frailty as measured by the EFT,SPPB and the IF-VIG.
文摘BACKGROUND Valvular heart disease affects more than 100 million people worldwide and is associated with significant morbidity and mortality.The prevalence of at least moderate valvular heart disease is 2.5%across all age groups,but its prevalence increases with age.Mitral regurgitation and aortic stenosis are the most frequent types of valvular heart disease in the community and hospital context,res-pectively.Surgical valve replacement(or mitral valve repair)is the standard of care for treating heart valve disease.However,the replacement of a prosthetic heart valve can lead to complications,either in the peri-procedural phase or in the long-term follow-up period.CASE SUMMARY We present a case of a 71-year-old female patient with a history of mitral valve replacement and warfarin anti-coagulation therapy.She was admitted to the intensive care unit due to spontaneously reperfused ischemic stroke of probable cardioembolic etiology.A dysfunctional mitral prosthesis was identified due to malfunction of one of the fixed discs.Furthermore,a possible microthrombotic lesion was suspected.Therefore,systemic thrombolysis was performed with subsequent normalization of mitral disc opening and closing.CONCLUSION This case underscores the critical importance of a multidisciplinary approach for timely decision-making in critically ill patients with prosthetic valve complications.
文摘BACKGROUND The management of severe symptomatic aortic stenosis has been revolutionized by transcatheter aortic valve replacement(TAVR),offering a minimally invasive alternative to surgical aortic valve replacement(SAVR).However,the compara-tive safety and efficacy of these interventions remain subjects of ongoing investigation.AIM To compare the clinical outcomes and safety of TAVR vs SAVR in patients with severe symptomatic aortic stenosis.METHODS A systematic review and meta-analysis were conducted according to PRISMA guidelines.Randomized controlled trials(RCTs)comparing TAVR and SAVR were identified from databases including PubMed,Scopus,and Web of Science up to May 31,2024.Data were extracted on clinical outcomes,including mortality,procedural compli-cations,and post-procedure adverse events.Risk ratios(RRs)with 95%CIs were calculated using a random-effects model.RESULTS A total of 10 RCTs were included.TAVR demonstrated a significantly lower risk of acute kidney injury(RR:0.33;95%CI:0.25–0.44),major bleeding(RR:0.37;95%CI:0.30–0.46),and new-onset atrial fibrillation(RR:0.44;95%CI:0.34–0.57)compared to SAVR.However,TAVR was associated with higher risks of new permanent pacemaker implantation(RR:3.49;95%CI:2.77–4.39),major vascular complications(RR:2.47;95%CI:1.91–3.21),and paraval-vular leaks(RR:4.15;95%CI:3.14–5.48).Mortality at 30 days was comparable(RR:0.95;95%CI:0.78–1.15),but long-term mortality was slightly higher with TAVR in some analyses(RR:1.23;95%CI:1.01–1.49).Rates of stroke(RR:0.97;95%CI:0.81–1.17)and myocardial infarction(RR:0.91;95%CI:0.67–1.24)were similar between the groups.CONCLUSION TAVR offers a less invasive option with significant benefits in reducing acute kidney injury,major bleeding,and new-onset atrial fibrillation,making it particularly advantageous for high-risk surgical candidates.However,higher risks of permanent pacemaker implantation,vascular complications,and paravalvular leaks highlight the need for individualized patient selection and shared decision-making to optimize outcomes.
基金supported by the National Key Research&Development Program of China(No.2023YFF0721304)the Key Research&Development Program of Jiangsu Province(No.2021015-4),China。
文摘Gifford-McMahon-type pulse-tube cryocoolers(GM-PTCs)working at liquid helium temperatures are promising in quantum technology and cryogenic physics for their high reliability and minimal vibration.These features stem from the fact that there are no extra moving parts introduced into the system.The rotary valve is a key component in GM-PTCs that transfers the output exergy from the compressor to the cold head.Because a low Carnot efficiency of 1.58%is achieved at liquid helium temperatures,optimizing the rotary valve is crucial for improving the efficiency of GM-PTCs.In this regard,an exergy-loss analysis method is proposed in this paper to quantitatively obtain the leakage loss and viscosity loss of a rotary valve by experimental measurements.The results show that viscosity loss accounts for more than 97.5%of the total exergy loss in the rotary valve,and that it is possible to improve the structure of the rotary valve by expanding the flow area by 1.5 times.To verify the method,the cooling temperature and power of a remote two-stage GM-PTC were monitored,with original or optimized rotary valves installed.The experimental results show that compared to the original rotary valve,the optimized rotary valve can improve the cooling efficiency of a GM-PTC by 16.4%,with a cooling power of 0.78 W at 4.2 K.
基金The Fundamental Research Funds for the Central Universities(JD2423)。
文摘Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.
文摘Pediatric heart valve replacement(PHVR)remains a challenging procedure due to the uniqueanatomical and physiological characteristics of children,including growth and development,as well asthe long-term need for durable valve function.This review provides an overview of both surgical andtranscatheter options for aortic,mitral,pulmonary,and tricuspid valve replacements in pediatric patients,highlighting the indications,outcomes,and advancements in technology and technique.Surgical valvereplacement traditionally involves the implantation of biological or mechanical prosthetic valves,withbiologicalvalves beingpreferred in children to reduce the need for lifelong anticoagulation therapy.However,the limitation ofbiological prostheses,nanely their inability to grow with the child,necessitates the frequentneed for reoperations.Recent innovations in valve engineering,such as the development of tissue engineeredand expandable valves,aim to address these issues.Transcatheter valve replacement(TVR)has emergedas a promising alternative,particularly for patients with complex anatomy or those who are high-risk fortraditional surgery.While the use of transcatheter devices in children remains limited due to the smallervascular size and limited long-termn data,several studies have demonstrated the feasibility and safety ofthe procedure in certain patient populations.Despite these advancements,challenges related to valvesize,durability,and the need for individualized treatment planning persist.The future of pediatric heartvalve replacemnent will likely involve a multidisciplinary approach combining surgical,transcatheter,andregenerative medicine strategies,aimed at optimizing outcomes,reducing the need for reinterventions,andimproving long-term quality of life for pediatric patients with valvularheart disease.This article discussesall options availab le for patients with valvular dysfunction,making it easy for parents/patients to go to as areference source of information.
文摘Valvular Heart Disease(VHD),including stenosis and regurgitation,is a significant contributor to global cardiovascular morbidity.Current prosthetic solutions mechanical and bioprosthetic heart valves each present major limitation.Mechanical valves require lifelong anticoagulation due to thrombogenicity,while bioprosthetic valves suffer from structural degeneration and limited durability.Polymeric Heart Valves(PHVs)have emerged as promising alternatives,aiming to integrate the mechanical resilience of synthetic materials with the biocompatibility and hemodynamic performance of natural valves.Recent studies have explored advanced polymers such as Polyhedral Oligomeric Silsesquioxane–Polycarbonate–Urea–Urethane(POSS-PCU),Silicone–Polyurethane Urea(SiPUU),and nanocomposites like Polyvinyl Alcohol(PVA)and SIBS for their enhanced thromboresistance,calcification resistance,and long-term mechanical durability.Complementary to material innovation,fabrication methods such as 3D printing,Melt Electrospinning Writing(MEW),and Focused Rotary Jet Spinning(FRJS)offer patient-specific designs and microstructural control.This review systematically compares traditional and next-generation prostheses,examines mechanical and biological performance,and discusses critical design challenges including porosity,thrombogenicity,and leaflet calcification.Finite Element Analysis(FEA)and Computational Fluid Dynamics(CFD)are highlighted for optimizing design and simulating physiological conditions.By presenting recent preclinical progress and manufacturing strategies,this review outlines a translational roadmap toward clinically viable,biomimetic polymeric heart valves capable of addressing the needs of both adult and pediatric patients.Compared to traditional bioprosthetic tissues,advanced polymers offer better resistance to calcification,reduced thrombogenicity,and tunable mechanical properties.
基金funded by a IBYE23_0002 grant supported by Instituto de investigación biom-édica de Salamanca IBSAL,Castilla y León (Spain) and by a GRS 2860/A1/2023 by Gerencia Regional de Salud o f Castilla y León (Spain)。
文摘Background Transcatheter Aortic Valve Implantation(TAVI)has changed the treatment paradigm of the aortic stenosis(AS).It has become the treatment of choice in patients with symptomatic AS and surgical high risk,and a valid alternative to surgical aortic valve replacement in patients with low and medium surgical risk.Despite numerous evidence on clinical results,indications and benefits,only a few studies analyse it from patient's perspective and the impact of TAVI on them.The objective of this study is to evaluate the experience of patients undergoing TAVI.Methods Cross-sectional,descriptive observational study in two Spanish hospitals,with a establish Nurse TAVI program,with100 patients undergoing TAVI.A specific questionnaire was designed(VALVEX questionnaire)and a pilot study was conducted by a multidisciplinary team of doctors,nurses and patients.The questionnaire was given to patients at 30 days after TAVI procedure during the follow up at the TAVI nurse clinic.Results The study demonstrated a mean satisfaction of 9 for the TAVI program,with 96%of patients that would recommend TAVI to other patients.Patients scored a high satisfaction on the information received prior to the procedure.During the procedure and admission,the satisfaction was high in relation to the care received.During the follow up,satisfaction was high in relation to the role of the TAVI nurse,for the information and continuation of care during the procedure,in reducing anxiety,organising their admission and understanding the process.However,questions with less scores were related to hospital catering,delay between diagnosed and treatment,and patient decision-making process.Conclusion The evaluation of patient experience allows us to improve the information given to the patient during their TAVI process and it can also allow patients to be more relax,aware and prepared for the procedure.Continuous follow up enables monitoring of patient recovery and helps to discuss any doubts improving patient's satisfaction.The use of PREMs and PROMs associated to TAVI pathway combined with an active participation of the patient on the design of the questionnaire is essential for keeping the patient in the centre of the TAVI pathway.
文摘Aortic stenosis(AS)is the most common valvular heart disease,with a prevalence of over 4%among octogenarians.[1]The prevalence of autopsy-confirmed wild-type transthyretin cardiac amyloidosis(ATTRwt-CA)increases with age,accounting for 25%of patients aged 85 years and older in Europe and 12%of patients older than 80 years in Japan.[2,3]Recent studies have reported that ATTRwt-CA coexists in 11%-16%of older patients with AS undergoing transcatheter aortic valve replacement(TAVR).[1,4,5]In a metaanalysis by Ho et al.,[6]the prevalence rates of cardiac amyloidosis,predominantly ATTRwt-CA,in patients with AS and those referred for TAVR or surgical aortic valve replacement(SAVR)were 14.4%and 15.2%,respectively.Conversely,the prevalence of AS in patients with cardiac amyloidosis is 8.7%.Owing to the high surgical risk in patients with both AS and ATTRwt-CA,TAVR may be preferred over SAVR.
文摘Severe aortic stenosis has increased exponentially as a result of the aging of the population.Transcatheter aortic valve replacement(TAVR)procedures increase by 20%-30%per year in Spain.Referred patients are increasingly older,have comorbidities,and frailty.TAVR cardiac rehabilitation(CR)programs significantly improve both functional capacity and quality of life of patients.However,there are no guidelines on how to carry out them and few elderly patients are referred to CR.Furthermore,mortality in women who undergo TAVR is higher than in men and even fewer are referred to CR programs.Multidisciplinary patient care,including comorbidities and frailty,is essential.It is necessary to ensure exquisite continuity of care during TAVR,CR,and the rest of the patient's life.Telerehabilitation could be an option in some lower-risk patients to include more patients in CR programs after TAVR,given the high demand.This article reviews the evidence on why CR should be performed in post-TAVR patients and proposes a practical and novel approach to the care process and the recommended aspects and components of the CR program.
文摘Particularly commendable is the important work of Calvo,et al.[1]in comparing geriatric assessment tools to predict mortality and readmissions in elderly patients undergoing transcatheter aortic valve implantation(TAVI).Their efforts underscore the growing importance of frailty assessment in cardiovascular risk stratification.We would like to respectfully highlight several areas that,if addressed in future studies(Figure 1),could further enhance the utility and inclusivity of these assessments.
