Rapid Valve Research Articles

Hypoxia-inducible factor prolyl hydroxylase inhibitor-induced thrombosis leading to transcatheter aortic valve dysfunction: a case report

Abstract Background Transcatheter aortic valve replacement (TAVR) is a well-established treatment option for patients with severe aortic valve stenosis; however, clinical valve thrombosis is a major challenge. Case summary A 92-year-old woman underwent TAVR for severe aortic stenosis. One month later, the patient developed acute heart failure. As the progression of anaemia due to renal anaemia seemed to cause acute heart failure exacerbation, we started an oral hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor. After 2 weeks, the patient redeveloped shortness of breath. Transthoracic echocardiography revealed that the mean aortic valve pressure gradient (ΔP) increased from 9 to 54 mmHg, and the aortic valve area decreased from 1.93 to 0.86 cm2. Blood work revealed a markedly elevated haemoglobin level from 8.0 to 13.2 g/dL, and transoesophageal echocardiography revealed markedly decreased left coronary and non-coronary cusp mobility. We diagnosed that the rapid increase in the haemoglobin level caused by the HIF-PH inhibitor was related to valve thrombosis and bioprosthetic dysfunction of the transcatheter aortic valve. The HIF-PH inhibitor was discontinued, and anticoagulation therapy was started. Transthoracic echocardiography at 16 days later revealed that the mean aortic valve ΔP improved by 15 mmHg, and the subjective symptoms resolved. Discussion This is the first report on a successful treatment of TAVR thrombosis formation associated with HIF-PH inhibitor use. When treating renal anaemia in patients undergoing TAVR, care should be taken to avoid rapid anaemia resolution and valve thrombosis development.

Offshore windfarm construction elevates metabolic rate and increases predation vulnerability of a key marine invertebrate

A global increase in offshore windfarm development is critical to our renewable energy future. Yet, widespread construction plans have generated substantial concern for impacts to co-occurring organisms and the communities they form. Pile driving construction, prominent in offshore windfarm development, produces among the highest amplitude sounds in the ocean creating widespread concern for a diverse array of taxa. However, studies addressing ecologically key species are generally lacking and most research is disparate, failing to integrate across response types (e.g., behavior, physiology, and ecological interactions), particularly in situ. The lack of integrative field studies presents major challenges to understand or mitigate actual impacts of offshore wind development. Here, we examined critical behavioral, physiological, and antipredator impacts of actual pile driving construction on the giant sea scallop (Placopecten magellanicus). Benthic taxa including bivalves are of particular concern because they are sound-sensitive, cannot move appreciable distances away from the stressor, and support livelihoods as one of the world's most economically and socially important fisheries. Overall, pile driving sound impacted scallops across a series of behavioral and physiological assays. Sound-exposed scallops consistently reduced their valve opening (22%), resulting in lowered mantle water oxygen levels available to the gills. Repeated and rapid valve adductions led to a 56% increase in metabolic rates relative to pre-exposure baselines. Consequently, in response to predator stimuli, sound-exposed scallops displayed a suite of significantly weaker antipredator behaviors including fewer swimming events and shorter time-to-exhaustion. These results show aquatic construction activities can induce metabolic and ecologically relevant changes in a key benthic animal. As offshore windfarm construction accelerates globally, our field-based study highlights that spatial overlap with benthic taxa may cause substantial metabolic changes, alter important fisheries resources, and ultimately could lead to increased predation.

Numerical modeling and simulation of water hammer phenomena using the MacCormack method

ABSTRACT Water hammer refers to pressure fluctuations caused by changes in fluid speed in hydraulic systems. This research proposes a model using the MacCormack method to study and control water hammer, specifically focusing on managing valve closure to reduce shock wave pressure during transient flow. Numerical simulations compare linear and quadratic closure laws for both rapid and gradual valve closure, with the goal of identifying the optimal laws. The findings show that with faster closure times, the overpressure at the valve section decreases linearly in the second quarter of the return period (t4). The application of the quadratic law results in reduced pressures at the valve compared to the linear law, with a maximum pressure difference of 0.05 bar between the highest and lowest values. When searching for the optimal valve closure law to mitigate overpressure, it is found that the exponent ‘m’ falls within the range of 1.117–1.599. As the slow closing time increases gradually, the range of variation for ‘m’ decreases. Furthermore, in the case of underpressure prevention, the exponent ‘m’ ranges from 0.95 to 1.419, and the range of ‘m’ remains relatively constant with the increase in closing time.

Comparison of apixaban versus aspirin for the prevention of latent bioprosthetic aortic valve thrombosis: study protocol for a prospective randomized trial.

The optimal antithrombotic strategy early after aortic valve replacement surgery with a biological valve remains controversial due to lack of high-quality evidence. Either oral anticoagulants or acetylsalicylic acid should be considered for the first 3 months. Hypo-attenuated leaflet thickening on cardiac computed tomography has been associated with latent bioprosthetic valve thrombosis and may be prevented with anticoagulation. We hypothesize that anticoagulation with apixaban is superior to single antiplatelet therapy with acetylsalicylic acid in reducing hypo-attenuated leaflet thickening of bioprosthetic aortic valve prostheses. In this prospective, open-label, randomized trial, patients undergoing isolated aortic valve replacement surgery with rapid deployment bioprosthetic valves will be randomized. The treatment group will receive 5 mg of apixaban twice a day for the first 3 months and 100 mg of acetylsalicylic acid thereafter. The control group will be administered 100 mg of acetylsalicylic acid once a day, indefinitely. After the 3-month treatment period, a contrast-enhanced electrocardiogram-gated cardiac computed tomography will be performed to identify hypo-attenuated leaflet thickening of the bioprosthetic valve. The primary objective of the study is to assess the impact of apixaban on the prevention of hypo-attenuated leaflet thickening at 3 months. The secondary and exploratory endpoints will be clinical outcomes and safety profiles of the two strategies. Antithrombotic therapy after aortic valve replacement is used to prevent valve thrombosis and systemic thromboembolism. Latent bioprosthetic valve thrombosis is a precursor of clinically significant prosthetic valve dysfunction or thromboembolic events. The hallmark feature of latent bioprosthetic valve thrombosis is hypo-attenuated leaflet thickening on cardiac computed tomography. Subclinical leaflet thrombosis occurs frequently in bioprosthetic aortic valves, more commonly in transcatheter than in surgical valves. There is no evidence on the effect of direct oral anticoagulants on the incidence of hypo-attenuated leaflet thickening after surgical aortic valve replacement with rapid deployment bioprostheses. ClinicalTrials.gov NCT06184113. Registered on December 28, 2023.

Performance evaluation of linear variable valve actuation for a linear engine generator

The Joule cycle Linear Engine Generator (LEG) is a promising power generation technology with the potential to achieve zero carbon emissions. However, the LEG expander valve actuation system presents unique challenges due to its lack of a traditional crankshaft, the need for swift valve lift and reversal, and variable lift. This paper presents a Linear Variable Valve Actuation (LVVA) system for a LEG prototype. The LVVA system is powered by voice coil motors. Rigorous experimental investigations were conducted to analyze crucial performance factors, including energy consumption, force balance, energy flow distribution, and the relationship between valve lift duration and energy consumption. The results show that the LVVA system can achieve the desired valve lift and timing, as well as very small variations in LEG performance compared to the model using an ideal lift curve. The LVVA accounts for approximately 3.59 % of the LEG power output. The energy consumption of 1.607 J per valve stroke provides a slight advantage over traditional actuation systems. The obtained optimal lift curves were used to refine the LEG model. The influence of valve lift curves on LEG performance was evaluated which reveals rapid valve openings and relatively short duration contributing to improved LEG performance.

Experimental Investigation of Column Separation Using Rapid Closure of an Upstream Valve

In this study, the phenomenon of column separation that occurs in the downstream pipeline of a rapid closure valve is experimentally investigated. Special attention is paid to the dynamic behavior of the formation, growth, and collapse processes of cavities, which are observed using a high-speed camera. Synchronized images of cavity patterns and measured pressure histories are analyzed to elucidate the process of water column separation, the mechanism of column separation events, and the influence of parameters on the transient flow. Experimental results indicate that during the collapse process of vapor cavities, a superposition phenomenon involving a positive pressure wave and collapse wave occurs, resulting in a nearly three times rise of Joukowsky pressure. In all test cases, the maximum pressure of the pipeline exceeded 150 times the reservoir static pressure. A new classification for a water hammer combined with cavitation (four types of pressure oscillation patterns) is proposed based on whether the duration of column separation decreases sequentially and the maximum pipeline pressure follows the first collapse of cavities at the valve. As the initial flow velocity increases, there is generally an increase in maximum pressure; however, this trend may be scattered under certain operation conditions.

Bicuspid Morphology and Rapid Deployment Valve Replacement: Is This Still a Contraindication?

When using rapid deployment surgical aortic valve replacement (RD SAVR) in treating bicuspid aortic valve morphology (BAV), several challenges are faced due to annular asymmetry. The Sievers classification has been traditionally used for the description of BAV morphology. In this study, we aimed to conduct a retrospective feasibility analysis of RD SAVR in relation to the Sievers classification. From January 2014 to March 2022, 31 patients with BAV morphology (15 patients with Sievers type 0 BAV and 16 with Sievers type 1 BAV) underwent RD SAVR. Specific surgical techniques were applied depending on the BAV morphology. Comparable clinical outcomes were observed. No paravalvular leaks and no valvular re-interventions occurred in either group. CPB and cross-clamping times, as well as the prosthesis sizes used, were also not significantly different. Postoperative mean gradients were comparable in both groups. No significant distinction was found between the groups in terms of postoperative pacemaker indication, postoperative stroke, or death. Annular symmetry can be adequately restored through precise prosthesis sizing and placement according to an individual’s valve morphology regardless of the Sievers classification of BAV by choosing a different landmark for the initial suture. RD SAVR seems to be a safe approach for any bicuspid morphology, with good hemodynamic results and time-saving potential in experienced hands.

Conduction Disorders after Surgical Aortic Valve Replacement Using a Rapid Deployment Aortic Valve Prosthesis: Medium-Term Follow-Up

We have previously reported that the incidence of postoperative conduction disorders, especially left bundle branch block (LBBB), after implantation of a rapid deployment Intuity™ Elite aortic valve prosthesis (Edwards Lifesciences, Irvine, CA, USA), was significantly increased compared with conventional aortic valve replacement. We were now interested in how these disorders behaved at intermediate follow-up. All 87 patients who had undergone surgical aortic valve replacement (SAVR) using the rapid deployment Intuity™ Elite prosthesis and were shown to have conduction disorders at the time of hospital discharge were followed up after surgery. These patients' ECGs were recorded at least 1 year after surgery, and the persistence of the new postoperative conduction disorders was assessed. At hospital discharge, 48.1% of the patients had developed new postoperative conduction disorders, with LBBB being the predominant conduction disturbance (36.5%). At medium-term follow-up (526 days, standard deviation (SD) = 169.6, standard error (SE) = 19.3 days, respectively), 44% of the new LBBB and 50% of the new right bundle branch block (RBBB) had disappeared. There was no new atrio-ventricular block III (AVB III) that occurred. One new pacemaker (PM) was implanted during follow-up because of AVB II Mobitz type II. At medium-term follow-up after the implantation of a rapid deployment Intuity™ Elite aortic valve prosthesis, the number of new postoperative conduction disorders, especially LBBB, has considerably decreased but remains high. The incidence of postoperative AV block III remained stable.

Aortic Valve Neocuspidization Procedure Provides Better Postoperative Outcomes When Compared to Rapid Deployement Aortic Valves

The aim of this study was to compare the early results of rapid deployment aortic valves (RD-AVR) and aortic valve neocuspidization (AVNeo) techniques. Between December 2019 to May 2022, 104 patients were operated on with aortic stenosis by RD-AVR (N = 52) and AVNeo (N = 52) techniques. Patients with isolated aortic valve stenosis and aortic stenosis concomittant with planned other cardiac surgeries were included. The mean age of patients in the RD-AVR and AVNeo groups were 67.4 ± 7.8 vs. 62.9 ± 8.7, respectively. Aortic cross-clamp time in the RD-AVR group was 56.7 ± 23.3 minutes, while it was 104.1 ± 27.9 minutes in the AVNeo group (P < 0.001). Cardiopulmonary bypass time in the RD-AVR group and in the AVNeo group was 89.8 ± 27.6 minutes and 141.8 ± 36.7 minutes, respectively (P < 0.001). Permanent pacemaker become necessary in four patients in the RD-AVR group secondary to type 2 AV block. Paravalvular leak was observed in six patients, who underwent RD-AVR, while grade 2 central aortic regurgitation was observed in one patient in the AVNeo group. Hospital mortality was 8% in the RD-AVR group and 6% in the AVNeo group (P = 0.696). AVNeo procedure is a feasible technique in all age groups of patients with successful hemodynamic results in the early postoperative period and with the advantage of not requiring anticoagulants. It also can be applied with other cardiac surgical interventions.

Research on an Off-Chip Microvalve for Pneumatic Control in Microfluidic Chips

A compact, rapid, and portable off-chip pneumatic control valve is significant for the miniaturization and integration of external pneumatic systems for microfluidic chips. In this work, an off-chip microvalve with a high-speed electromagnetic switch actuator and a polydimethylsiloxane (PDMS) material valve body has been designed to be easily encapsulated, simulated using MATLAB/Simulink software, and tested in a micromixer. Multi-physical coupling mathematical models are developed based on the elastic deformation force of the valve membrane, the driving force of the valve core, and the fluid force in the microchannel. Two single microvalves are used to form a three-way microvalve, which can control the air pressure in a pneumatic microchannel on the microfluidic chip. The relationship between the flow–duty cycle, the flow–pressure difference of the single electromagnetic microvalve, and the load pressure of the three-way microvalve is simulated and analyzed. Sample mixing performance controlled by the proposed off-chip three-way microvalve was tested to evaluate the pneumatic control capability, and the results show that the undertaking can fully satisfy the needs of a pneumatic microfluidic chip for most applications.

Large multinational evaluation of time to reintervention in patients undergoing bioprosthetic valve implantation during open heart surgery

Abstract Introduction Bioprosthetic valves are increasingly utilized during open heart surgery in favor of mechanical valves. These tissue valves are prone for structural valve degeneration and failure, especially in young patients. Transcatheter aortic valve implantation (TAVI) is an appealing approach in these patients. Purpose To describe independent correlates for early need for reintervention. Method We used a large multicenter registry of patients (&amp;gt;45 years of age) with failed bioprosthetic surgical valves undergoing TAVI valve-in-valve (VinV) in either aortic or the mitral positions. Early reintervention was (&amp;lt;5 years between open-heart surgery and VinV). Multi-variable properties that were included: patient gender, age at open-heart surgery, valve size, baseline renal failure, position of valve implantation, and bioprosthetic valve label size. Results A total of 3,324 patients were included in the study (age at the time of open heart surgery 68.9+7.9 years). Median time to TAVI was 9 years (IQR 6–13 years). A total of 632 (19%) patients experienced early valve degeneration with median time to TAVI of only 3 years [IQR 1–5]. Patients with early degeneration were older than those without early degeneration (mean age at surgery was 72.8±9 years vs. 68.9±8 years; p&amp;lt;0.001). in addition, significant linear relation between older patient age and early valve degeneration (p for trend &amp;lt;0.001). Re-intervention in the mitral position was more common in the group of patients with early degeneration (24.4% vs 18.2% without early degeneration; p&amp;lt;0.001) Patient age and mitral valve position were independently associated with increased rate of early degeneration (OR 1.09 [1.08–1.11], p&amp;lt;0.001; OR 1.62 [1.31–2.01]; p&amp;lt;0.001 respectively). Conclusions In this large multicenter analysis of patients undergoing TAVR for failed bioprosthetic valves we identified old patient age and mitral valve (vs. aortic) as independent correlates for early intervention. A discrepancy with known association of young age and rapid bioprosthetic valve degeneration is to be determined. Funding Acknowledgement Type of funding sources: None.

Comprehensive application analyses of elastic models and viscoelastic models in transient flows in polymeric pipelines

Abstract Based on the MOC (Method of Characteristics), the applicabilities of both the elastic models of the SF (Steady Friction), the CB-UF (Convolution-Based Unsteady Friction) and the MIAB-UF (Modified Instantaneous Acceleration-Based UF), and the viscoelastic models of the SF-VE (SF-Viscoelasticity), the CB-UF-VE (Convolution-Based Unsteady Friction-Viscoelasticity) and the MIAB-UF-VE (Modified Instantaneous Acceleration-Based UF-Viscoelasticity), are investigated for hydraulic transients induced by a downstream rapid valve closure in a polymeric pipeline. The predicted results by the elastic models are very different from the experimental data, whereas the predicted pressure peaks and phases by the viscoelastic models agree well with the experimental data because considering the pipe–wall creep effect, the CB-UF-VE and the MIAB-UF-VE generate better results than the SF-VE. The creep effects near the first pressure peak are captured well by the viscoelastic models. The analyses of the contributions of different factors to pressure attenuation show that for transient flows in polymeric pipelines, the effect of VE is greater than that of the CB-UF and MIAB-UF. The spectrum analyses show that the pressure amplitudes and harmonic frequencies by the elastic models match badly with the experimental data, whereas those by the viscoelastic models match well with the experimental data. The harmonic frequencies by the MIAB-UF-VE are the best, followed by the CB-UF-VE, and are worst by the SF-VE.

A pressure wire for rapid pacing, valve implantation and continuous haemodynamic monitoring during transcatheter aortic valve implantation procedures.

A pressure wire for rapid pacing, valve implantation and continuous haemodynamic monitoring during transcatheter aortic valve implantation procedures.

Nanoparticle-blockage-enabled rapid and reversible nanopore gating with tunable memory

Gated protein channels act as rapid, reversible, and fully-closeable nanoscale valves to gate chemical transport across the cell membrane. Replicating or outperforming such a high-performance gating and valving function in artificial solid-state nanopores is considered an important yet unsolved challenge. Here we report a bioinspired rapid and reversible nanopore gating strategy based on controlled nanoparticle blockage. By using rigid or soft nanoparticles, we respectively achieve a trapping blockage gating mode with volatile memory where gating is realized by electrokinetically trapped nanoparticles near the pore and contact blockage gating modes with nonvolatile memory where gating is realized by a nanoparticle physically blocking the pore. This gating strategy can respond to an external voltage stimulus (∼200 mV) or pressure stimulus (∼1 atm) with response time down to milliseconds. In particular, when 1,2-diphytanoyl-sn-glycero-3-phosphocholine liposomes are used as the nanoparticles, the gating efficiency, defined as the extent of nanopore closing compared to the opening state, can reach 100%. We investigate the mechanisms for this nanoparticle-blockage-enabled nanopore gating and use it to demonstrate repeatable controlled chemical releasing via single nanopores. Because of the exceptional spatial and temporal control offered by this nanopore gating strategy, we expect it to find applications for drug delivery, biotic-abiotic interfacing, and neuromorphic computing.

Concomitant use of Sapien 3 transcatheter valve for severe MAC with Intuity Elite rapid deployment valve for aortic stenosis

BackgroundConcomitant double valve pathology in the presence of severe MAC poses significant technical challenges when planning surgical intervention. With continued evolution of valve prosthesis, innovative techniques can be considered with the potential for additional therapeutic benefit.Case presentationWe present a novel technique of using a rapid deployment surgical aortic valve in combination with open surgical transcatheter mitral valve implantation (TMVI) for severe Mitral Annular Calcification (MAC). The Intuity Elite rapid deployment prosthesis (Edwards Lifesciences, Irvine, CA) was used concomitantly with the Sapien 3 (Edwards Lifesciences, Irvine, CA) transcatheter prosthesis trans-atrially on cardiopulmonary bypass in a patient with critical aortic stenosis and moderate-severe mixed mitral valve disease in the setting of severe MAC (off-label use).ConclusionsWe demonstrate how both technologies can, not only be accommodated, but indeed complement each other achieving an excellent outcome in a high-risk patient.

Hemodynamic study of the effect of the geometric height of leaflets on the performance of the aortic valve under aortic valve reconstruction

BackgroundAlthough aortic valve reconstruction has become an alternative treatment for aortic valve disease, the design of the geometric parameters of the reconstructed leaflet still mainly depends on the experience of doctors. The present study investigates the effects of the height of the leaflets on the performance and biomechanical states of the reconstructed aortic valve.MethodsThis numerical study was carried out using the finite element approach and the lattice Boltzmann method. The dynamic and biomechanical characteristics of the leaflets were evaluated by using the finite element approach, while the blood flow in the aortic sinus was evaluated by applying the lattice Boltzmann method. Three types of leaflets with different heights were designed. Then the dynamic characteristics, stress distribution, and effective orifice area (EOA) of the aortic valve and flow pattern were calculated as the indicators.ResultsThe results demonstrated that the height of the leaflets could indeed regulate the performance and the biomechanical states of the aortic valve. The rapid valve opening times of the 3 types of leaflets gradually reduced along with the decrease of the height ratio (HR_0.8: 120 ms vs. HR_1.0: 68 ms vs. HR_1.2: 31 ms), while the rapid valve closing times (RVCTs) of the 3 types of leaflets were similar to each other (approximately 75 ms). Moreover, the radial displacement of the leaflet at the fully open time increased along with the decrease of the HR of the leaflets (HR_0.8: 8 mm vs. HR_1.0: 6 mm vs. HR_1.2: 4 mm). In addition, the stress level of the leaflets also increased with the increase of the height of the leaflets (max stress, HR_0.8: 0.5 MPa, vs. HR_1.0: 1.1 MPa, vs. HR_1.2: 1.8 MPa). Similarly, the low velocity region near the ascending aortic wall and the wall shear stress (WSS) level on the ventricular side of the leaflets also increased along with the increase of the HR of the leaflets.ConclusionsIn short, the height of the leaflets mainly affects the opening performance of the reconstructed aortic leaflets. The HR of the reconstructed leaflets for adults should be less than 1.0 to balance the opening and closing performance of aortic leaflets.

RELAP5 application for water hammer analysis in different thermal-hydraulic systems

• Causes of water hammers: rapid valve operation, void-induced, condensation-induced. • RELAP5 code may represent water hammer due to valve operation and appearance of void. • The developed modelling recommendations are based on comparative analysis. • Water hammer in nuclear, fusion and district heating systems possible due to fast valve actions. • Integrity of pipelines in nuclear, fusion and district heating systems remain not violated. The water hammer phenomenon investigations employing RELAP5 code with one-dimensional two-fluid six-equation models of water and steam flow were performed and the main results shared in this paper. The capability of RELAP5 code to simulate transients leading strong pressure pulses was investigated employing the measurement results of three test facilities for different water hammer types: PPP at UMSICHT, CWHTF at FZR Dresden and PMK-2 at AEKI. Based on the benchmarking results the recommendations for the modelling of piping systems, which could be affected by different types of water hammer were developed and tested. The recommendations cover selection of thermal-hydraulic system conditions, parameters of modelling and RELAP5 code correlations. These recommendations have enabled to develop a detail RELAP5 models for the simulation of water hammer effects in further research works. The applications of RELAP5 code for water hammer analysis in different thermal-hydraulic systems (RBMK-1500 reactor main circulation loop, targets cooling/heating circuit in Wendelstein 7-X experimental stellarator facility and pipelines in district heating system) are presented in this paper. The performed analyses of transients demonstrated that the pressure pulsations could appear in all these systems as results of check valve closures. However, pressure surges are not so strong due to specific of such systems and integrity of pipelines remains not violated.

Age-related enhanced degeneration of bioprosthetic valves due to leaflet calcification, tissue crosslinking, and structural changes.

Bioprosthetic heart valves (BHVs), made from glutaraldehyde-fixed heterograft materials, are subject to more rapid structural valve degeneration (SVD) in paediatric and young adult patients. Differences in blood biochemistries and propensity for disease accelerate SVD in these patients, which results in multiple re-operations with compounding risks. The goal of this study is to investigate the mechanisms of BHV biomaterial degeneration and present models for studying SVD in young patients and juvenile animal models. We studied SVD in clinical BHV explants from paediatric and young adult patients, juvenile sheep implantation model, rat subcutaneous implants, and an ex vivo serum incubation model. BHV biomaterials were analysed for calcification, collagen microstructure (alignment and crimp), and crosslinking density. Serum markers of calcification and tissue crosslinking were compared between young and adult subjects. We demonstrated that immature subjects were more susceptible to calcification, microstructural changes, and advanced glycation end products formation. In vivo and ex vivo studies comparing immature and mature subjects mirrored SVD in clinical observations. The interaction between host serum and BHV biomaterials leads to significant structural and biochemical changes which impact their functions. There is an increased risk for accelerated SVD in younger subjects, both experimental animals and patients. Increased calcification, altered collagen microstructure with loss of alignment and increased crimp periods, and increased crosslinking are three main characteristics in BHV explants from young subjects leading to SVD. Together, our studies establish a basis for assessing the increased susceptibility of BHV biomaterials to accelerated SVD in young patients.

Transcatheter Aortic Valve Replacement Versus Sutureless and Rapid Deployment Surgical Aortic Valve Replacement: A Systematic Review and Meta-Analysis

Transcatheter aortic valve replacement (TAVR) and sutureless and rapid deployment (SURD) valves are alternatives to traditional surgical aortic valve replacement (AVR). However, there is a paucity of data comparing these newer techniques. We performed a systematic review and meta-analysis comparing clinical outcomes between TAVR and SURD valves.

Water Hammer and Harmonic Excitation Response With Fluid-Structure Interaction in Elbow Piping

Abstract This study focuses on the numerical analysis of a piping structure subjected to the water-hammer event caused by a rapid valve closure that is combined with external harmonic loading representing an idealized machine excitation. The fluid–structure interaction procedure applied to solutions involves the method of characteristic for the fluid equations with the finite element method for pipe structures, which are modeled as beams. Junction coupling at the pipe elbow governs the two-way coupled fluid–structure interaction, and both the friction and Poisson couplings are incorporated as well. There is an application on a piping structure that consists of a valve, tank, and elbow that are defined as boundary conditions. The solved result quantities include pressure and bending stress responses as well as dynamic displacement modes of the piping structure. Comparisons of the results show that water hammer loading combined with the mechanical excitation load induces significantly increased displacements and higher stress peaks when frequencies of the harmonic load and the acoustic natural mode of the piping system coincide. Additionally, the resulting mode of lateral structural vibration of the piping member closely resembles an analytically solved eigenmode of the beam. The conclusion is that dynamically changing flows due to a water hammer event can solely excite natural frequencies of the piping structure causing resonance in the system.