Valve Performance Research Articles

Static friction measurement methodology for the assessment of performance of industrial valves at high temperatures: Case study for a nickel-based alloy coating

High static friction between functional surfaces poses a serious challenge for industrial valves, particularly for those used in the advanced ultra-supercritical power generation industry that requires raising the steam temperature to 760 °C. In this context, we established the static friction measurement methodology by evaluating the effects of temperature, loading time, and number of static cycles on the evolution of the static coefficient of friction up to 800 °C. This methodology was applied on a nickel-based solid lubricant coating that appears an attractive candidate to withstand very harsh environments. The tribological behavior is explained in terms of a competition of three mechanisms governing the static friction processes: micro-welding or sintering of asperities, creep of asperities, and formation of lubricious oxides.

Consideration of Temperature Factors when Designing Butterfly Check Valves for Hazardous Production Facilities

The safety of hazardous production facilities is directly related to the reliability of pipeline systems, which must be ensured regardless of environmental conditions. Accidents on pipeline sections can have catastrophic consequences associated with damage to human health and the environment. Damage to the metal of pipeline elements during operation due to internal corrosion occurring under the influence of the working fluid is one of the main reasons for failure. This study aims to develop an improved butterfly check valve (BCV), which is a pipeline element. For this purpose, various structural materials used in the production of check valves were analyzed, and the changes in their mechanical properties under the influence of temperature were also considered. Based on this material, a butterfly check valve was developed. The stress-strain state of the developed structure was assessed using the finite element method (FEM). Strains, stresses, and displacements were calculated to evaluate valve performance. These calculations are necessary to determine the most loaded elements of the BCV at the maximum and minimum ambient temperatures. The following conclusions were obtained: X6CrNiTi18-10 stainless steel grade is the most suitable material for piping systems transporting liquids in production facilities. On the basis of the simulation results, the values of equivalent stresses, maximum strains, and displacements were obtained. The research results confirmed the performance of the improved design, the unhindered motion of the working fluid in the working direction, and the convenient connection to horizontal and vertical sections of the pipeline. Doi: 10.28991/CEJ-SP2023-09-020 Full Text: PDF

Design, modeling and experimental research of a multi-mode, fast-response piezoelectric control valve

To realize the precise regulation and fast response of the valve, a piezoelectric control valve with a simple and compact structure, and easy control is proposed. The control valve is divided into the valve core that consists of a sandwich piezoelectric transducer and a valve body. When a single excitation signal is applied to the transducer, the longitudinal vibration mode of the valve core is excited. The valve is opened due to the liner reciprocating motion of the end of the valve core. By adjusting the frequency of the excitation signal, the vibration mode of the transducer is switched between the first three modes of longitudinal vibration, which in turn adjusts the water output of the valve. Compared with the single-mode valve, the piezoelectric control valve has three working modes. Therefore, it has different adjustment precision and range for each mode. First, the electromechanical coupling model of the valve core and the mechanical model of the valve body are established by using the transfer matrix method. By analyzing the dynamic characteristics of the piezoelectric valve, the structure parameters of the valve core and valve body are optimized. Secondly, the prototype of piezoelectric valve is manufactured and assembled, and the validity of the proposed theoretical model is verified by the vibration measurement experiments. Finally, the flow performance and response speed of the piezoelectric valve are measured by experiments. The results show that the maximum pressure of the valve is 1 MPa when the assembly pre-pressure is 983 N. A sinusoidal-signal has the best excitation effect. Under the experimental conditions of sinusoidal excitation, a driving voltage amplitude of 250 V, and pressure of 1 MPa, the optimal driving frequencies of the piezoelectric valve in the first three operating modes are 33.8 kHz, 42.2 kHz, and 83 kHz, and the corresponding maximum flow rates are 3.3 mL/min, 1.15 ml/min, and 0.445 ml/min, respectively. The response performance of the piezoelectric valve is tested, indicating that the prototype can achieve stable operation within 3.5 ms after being powered on, and stop working within 5 ms after being powered off. The piezoelectric valve has good response characteristics and flow control ability, which has potential applications in the field of biomedicine.

Automated multi-functional system for the characterization of plate valves in reciprocating compressors

At present, there are two independent technologies and equipment for the test of the reciprocating compressor plate valve: the sealing test and blowing test. This method has single function and complicated test operation and may rely on theoretical calculations, which reduces the reliability of the test conclusion because the motion law of valve disk during opening and closing is extremely complicated. The existing test methods cannot meet the needs of more in-depth and accurate research, development and improvement of the plate valve. This study proposes a test device and method that can not only quantitatively test the performance of the plate valve but also qualitatively test the dynamic process of the suction valve plate, which can greatly reduce the testing time provide more intuitive and accurate valve plate motion tracks and valve paths. This paper takes the primary plate suction valve as the test object and adopts the automated multi-functional system to accurately obtain the valve’s sealing property, effective flow area, thrust coefficient, flow coefficient, drag drop, valve gap Mach number, initial opening pressure difference, maximum opening, and residence time of the valve plate on the valve lift guard to provide necessary data for valve design and performance evaluation. The test results of valve opening time are verified by industrial reciprocating compressor, which proves the accuracy and practicability of the system.

Impact of Multi-Grade Localized Calcifications on Aortic Valve Dynamics under Helical Inflow: A Comparative Hemodynamic Study

This study investigates the hemodynamic impacts of localized aortic valve calcification, utilizing immersed boundary-finite element (IBFE) method simulations with realistic inflow patterns of uniform and helical blood flow from the left ventricular outflow tract (LVOT). We modeled the aortic valve leaflets with varying grades of calcification, assessing their influence on valve performance, including transvalvular hemodynamics, wall shear stress (WSS) indices, and vortical structures. The findings highlighted that calcification significantly restricts leaflet motion, diminishes the orifice area, disrupts flow efficiency, and consequently increases the left ventricular workload. Advanced calcification resulted in elevated WSS, especially at the leaflet tips, which indicates a heightened risk of endothelial damage and further calcification. Asymmetrical calcifications redirect flow towards the ascending aorta wall, potentially inducing structural damage and increased stress on the remaining healthy leaflets. Calcification was also found to alter the naturally occurring helical blood flow patterns, affecting the system’s fluid transport efficiency and possibly contributing to cardiovascular disease progression. The study revealed a significant alteration in vortex formation, with calcification causing distorted and complex vortex structures, which may influence the dynamics of blood flow and valve function. These insights into the hemodynamic changes induced by calcification contribute to a better understanding of the progression of aortic valve diseases and could inform more effective diagnostic and treatment strategies.

Fluid–structure interaction modeling of bi-leaflet mechanical heart valves using smoothed particle hydrodynamics

Heart valves are essential for maintaining unidirectional blood flow, and their failure can severely affect cardiac functions. The use of artificial heart valves as replacement has proven to be a reliable and effective solution. Computational fluid dynamics has emerged as a powerful numerical tool for investigating the design, performance, and malfunctioning of mechanical heart valves without the need for invasive procedures. In this study, we employed smoothed particle hydrodynamics (SPH) in an open-source code “DualSPHysics,” to study the hemodynamics of a bi-leaflet mechanical heart valve (BMHV). The proposed SPH method was validated against the traditional finite volume method and experimental data, highlighting its suitability for simulating the heart valve function. The Lagrangian description of motion in SPH is particularly advantageous for fluid–structure interaction (FSI), making it well-suited for accurately modeling the heart valve dynamics. Furthermore, the SPH/FSI technique was applied to investigate the hemodynamic abnormalities associated with BMHV dysfunction. This work represents the first attempt to use SPH to model flow through a realistic BMHV by incorporating FSI. The normal and altered flow behavior and the movement dynamics of the BMHV under various blockage scenarios have also been investigated along with the potential risks of the blocked mechanical valve. The findings demonstrate that this SPH/FSI approach provides a unique, effective, and valuable tool for accurately capturing the transient hemodynamic behavior of bi-leaflet heart valves and its versatility enables the application to more complex patient-specific issues related to cardiovascular diseases.

Templated Assembly of Silk Fibroin for a Bio‐Feedstock‐Derived Heart Valve Leaflet

AbstractBioprosthetic valves are employed to replace defective heart valves. However, structural degeneration is prevalent in bioprosthetic valves because the heart valve leaflets are exposed to extreme and repetitive cardiovascular pressure. Herein, a silk fibroin‐based heart valve leaflet, which executes the physiological role of a heart valve, is developed. To this end, a templated assembly technology is developed. Notably, a physically optimal hierarchical structure for replacing the natural heart valve leaflet is realized by numerous firmly stacked β‐sheet crystals distributed within collective tyrosine‐reinforcing amorphous strands. Almost half (46.9%) of the silk fibroin‐based heart valve leaflet comprises strongly stacked β‐sheet crystals, leading to a 292% enhancement in stacking strength. The templated assembly results in the entanglement of amorphous strands, upregulating the non‐covalent interactions within the tyrosine. Consequently, the strength is enhanced by 1380% compared to native silk fibroin. Moreover, the templated assembly enhances the static and dynamic mechanical properties, thereby delivering a desirable performance for its use in heart valve replacement. Interestingly, the aortic valve composed of silk fibroin‐based leaflets does not fail under the cardiovascular pressure of 60–180 mmHg. Furthermore, the valve performance is satisfactory and surmounts the requirements of the industrial standard ISO 5840.

Vibration suppression of an armature assembly in hydraulic servo valve based on distributed parameters mathematical models

As a commonly used hydraulic control component, the nozzle-flapper servo valve has the advantages of small structure and sensitive dynamic response. Due to the small size and complex structure of the servo valve, the classical control methods based on various feedback information cannot effectively improve its performance. In order to effectively improve the performance of the servo valve, this paper implemented the feedforward control method to suppress the dynamic performance of the armature assembly of the servo valve. The distributed parameters mathematical models of the armature assembly are established and verified which can accurately predict the vibration of the armature assembly. With the mathematical model, the feedforward control signal is calculated based on the real-time velocity, acceleration, and deflection of the armature assembly, respectively. The applicability of different signals is analyzed and the signals calculated by velocity and deflection are verified which can effectively suppress the vibration amplitude of armature assembly. The numerical simulation and experimental methods are implemented to verify the performance of different control signals and the optimal feedforward control signal under different external loads is obtained.

Up to 6-year performance and clinical outcomes of balloon expandable transcatheter aortic valve according to the implantation strategy: insight from the DIRECTAVI trial

Abstract Background The randomized DIRECTAVI trial demonstrated safety and feasibility of transcatheter aortic valve implantation (TAVI) without balloon aortic valvuloplasty (BAV) using SAPIEN 3 balloon-expandable devices. Purpose To evaluate long-term clinical and hemodynamic results according to the implant strategy (direct TAVI versus BAV) with the SAPIEN 3 balloon-expandable device in patients included in the DIRECTAVI trial. Methods All patients included in the DIRECTAVI trial since 2016 were offered a clinical and echocardiographic follow-up until January 2023. We applied Valve Academic Research Consortium (VARC-3) criteria to define moderate/severe hemodynamic valve deterioration (HVD) as an increase in mean gradient ≥10 mm Hg resulting with a final mean gradient ≥20 mm Hg, or new/worsening aortic regurgitation (AR) of 1 grade resulting in ≥moderate AR. Survival until moderate/severe HVD between the 2 groups was the primary end-point and overall survival between direct TAVI and BAV were compared using logrank tests. Major clinical outcomes at latest follow-up were also assessed using Chi² or Fisher’s tests. Results Among 250 patients included in DIRECTAVI, 228 patients were followed-up during 4.5 ± 1.1 years. Mean age at follow-up was 87 ± 6.7 years. Incidence rates of moderate/severe HVD were similar in the 2 groups (1.45 versus 1.97 per 100 person-years, p=0.6) (Figure). Incidence rates for death were similar between groups (9.19 and 7.34 events per 100 persons-years for BAV and direct TAVI, respectively, p=0.4). No clinically significant differences in outcomes were observed at the latest follow-up, including major stroke (4.4% for BAV versus 2.6% for direct TAVI, p=0.7), hospitalizations for heart failure (15.8% for BAV group and 11.4% for direct TAVI group, p=0.3), permanent pacemaker implantation (37.7% for BAV and 31.6% for direct TAVI, p=0.3). Moderate/severe patient-prosthesis mismatch was also similar between groups (p=0.6). Conclusion Compared to systematic BAV, direct implantation of the SAPIEN 3 device was not associated with an increased risk of moderate/severe valve deterioration or adverse clinical events up to 6-year follow-up. These results encourage wide use of this simplified strategy with balloon-expandable devices, when possible.Survival without valve deterioration

A Review of Pilot-operated Hydraulic Valves – Development, Challenges, and a Comparative Study

Hydraulic systems have been widely used due to their high power-to-weight ratio. Despite the growing instances of being superseded by the electromechanical counterparts at low power levels, the market was incapable of presenting alternatives for large-size applications. Additionally, in recent years, the demand for more significant heavy machinery (Mobile & Industrial) has increased, which led to the necessity of even higher flow and pressure Pilot-operated valves, despite the fact that these valves have several issues. One might think the alternative could be developing a hydraulic system that does not rely on Pilot-operated valves, but after decades of research, these systems could not get close to the performance of Pilot-operated Multistage valves. The paper presents a comprehensive study of the progress accomplished from the year 2016 to early 2022 in hydraulic Pilot-operated valves; they are widely employed among ordinary valves, proportional valves, and state-of-the-art digital hydraulics. Higher efficiency will be a primary factor in the success of the new designs. The academia presented several studies to improve the Pilot valves’ performance, but still, they are limited. There are no dramatic developments, and there are only a few upgrades.

Recent progress in functional modification and crosslinking of bioprosthetic heart valves.

Valvular heart disease (VHD), clinically manifested as stenosis and regurgitation of native heart valve, is one of the most prevalent cardiovascular diseases with high mortality. Heart valve replacement surgery has been recognized as golden standard for the treatment of VHD. Owing to the clinical application of transcatheter heart valve replacement technic and the excellent hemodynamic performance of bioprosthetic heart valves (BHVs), implantation of BHVs has been increasing over recent years and gradually became the preferred choice for the treatment of VHD. However, BHVs might fail within 10-15 years due to structural valvular degeneration (SVD), which was greatly associated with drawbacks of glutaraldehyde crosslinked BHVs, including cytotoxicity, calcification, component degradation, mechanical failure, thrombosis and immune response. To prolong the service life of BHVs, much effort has been devoted to overcoming the drawbacks of BHVs and reducing the risk of SVD. In this review, we summarized and analyzed the research and progress on: (i) modification strategies based on glutaraldehyde crosslinked BHVs and (ii) nonglutaraldehyde crosslinking strategies for BHVs.

A synergistic strategy of dual-crosslinking and loading intelligent nanogels for enhancing anti-coagulation, pro-endothelialization and anti-calcification properties in bioprosthetic heart valves.

Currently, glutaraldehyde (GA)-crosslinked bioprosthetic heart valves (BHVs) still do not guarantee good biocompatibility and long-term effective durability for clinical application due to their subacute thrombus, inflammation, calcification, tearing and limited durability. In this study, double-modified xanthan gum (oxidized/vinylated xanthan gum (O2CXG)) was acquired from xanthan gum for subsequent double crosslinking and modification platform construction. Sulfonic acid groups with anticoagulant properties were also introduced through the free radical polymerization of vinyl sulfonate (VS) and vinyl on O2CXG. Taking advantage of the drug-loading function of xanthan gum, the treated pericardium was further loaded with inflammation-triggered dual drug-loaded nanogel (heparin (Hep) and atorvastatin (Ator)). Mechanical properties of O2CXG-crosslinked porcine pericardium (O2CXG-PP) were significantly improved via the first network formed by Schiff base bonds and the second C-C bonds network. Due to the presence of sulfonic acid groups as well as the dual drug release from nanogels under the stimulation of H2O2, the hemocompatibility, anti-inflammatory, pro-endothelialization and anti-calcification properties of the crosslinked pericardium modified with nanogels loaded with Hep and Ator (O2CXG+VS+(Hep+Ator) nanogel-PP) was significantly better than that of GA-crosslinked PP (GA-PP). The collaborative strategy of double crosslinking and sequential release of anticoagulant/endothelium-promoting drugs triggered by inflammation could effectively meet the requirement of enhanced multiple performance and long-term durability of bioprosthetic heart valves and provide a valuable pattern for multi-functionalization of blood contacting materials. STATEMENT OF SIGNIFICANCE: Currently, glutaraldehyde-crosslinked bioprosthetic heart valves (BHVs) are subject to subacute thrombus, inflammation, calcification and tearing, which would not guarantee good biocompatibility and long-term effective durability. We developed a cooperative strategy of double crosslinking and surface modification in which double-modified xanthan gum plays a cornerstone. The mechanical properties of this BHV were significantly improved via the first network formed by Schiff base bonds and the second C-C bonds network. Inflammation-triggered combination delivery of heparin and atorvastatin has been demonstrated to enhance anticoagulation, anti-inflammatory and pro-endothelialization of BHVs by utilizing local inflammatory response. The collaborative strategy could effectively meet the requirement of enhanced multiple performance and long-term durability of BHVs and provide a valuable pattern for the multi-functionalization of blood-contacting materials.

Valve Hemodynamics by Valve Size and 1-Year Survival Following Implantation of the Portico Valve in the Multicenter CONFIDENCE Registry

BackgroundThe CONtrolled delivery For ImproveD outcomEs with cliNiCal Evidence registry was initiated to characterize the clinical safety and device performance from experienced transcatheter aortic valve implantation (TAVI) centers in Europe and Australia that use the Portico valve to treat patients with severe aortic stenosis. We herein report for the first time the valve performance at 30-day across all implanted valve sizes and the 1-year survival from this registry. MethodsThis was a prospective, multicenter, single-arm observational clinical investigation of patients clinically indicated for implantation of a Portico valve in experienced TAVI centers. Patients were treated with a commercially available valve (size 23, 25, 27, or 29 mm) using either the first-generation delivery system (DS) (n = 501) or the second-generation (FlexNav) DS (n = 500). Adverse events were adjudicated by an independent clinical events committee according to Valve Academic Research Consortium-2 criteria. Echocardiographic outcomes were assessed at 30 days by an independent core laboratory, and a survival check was performed at 1 year. ResultsWe enrolled 1001 patients (82.0 years, 62.5% female, 63.7% New York Heart Association functional class III/IV at baseline) from 27 clinical sites in 8 countries across Europe and one site in Australia. Implantation of a single valve was successful in 97.5% of subjects. Valve hemodynamics at 30 days were substantially improved relative to baseline, with large aortic valve areas and low mean gradients across all implanted valve sizes (aortic valve areas were 1.7 ± 0.4, 1.7 ± 0.5, 1.8 ± 0.5, and 2.0 ± 0.5 cm2, and mean gradients were 7.0 ± 2.7, 7.5 ± 4.7, 7.3 ± 3.3, and 6.4 ± 3.3 mmHg for 23, 25, 27, and 29 mm valve sizes, respectively). Across all implanted valve sizes, most patients (77.1%) had no patient-prosthesis mismatch. Death from any cause within 1 year occurred in 13.7% of the patients in the first-generation DS group as compared with 11.0% in the second-generation DS group (p = 0.2). ConclusionsThe Portico valve demonstrated excellent hemodynamic performance across all valve sizes in a large cohort of subjects implanted in experienced TAVI centers. One-year survival rates were favorable when using both the first-generation and second-generation (FlexNav) DSs in this high-risk cohort. ClinicalTrials.gov IdentifierNCT03752866.

Effect of spool posture on control valve performance considering outlet shape and large fit clearance

The control valve serves as a crucial component of the downhole integrated water distributor in water injection oilfields, enabling waterflooding into oil reservoirs. However, the control valve opening cannot be adjusted in the practical environment, resulting in ineffective injection, which means that the spool is stuck. Furthermore, it is difficult to observe the details of the spool sticking and reproduce this phenomenon during testing. To reveal the mechanism of sticking, this paper establishes a CFD model, which considers the spool posture, large fit clearance and outlet shape, to study the spool performance. Additionally, the proposed model is demonstrated experimentally and theoretically. It is found that larger fit clearances result in significant distortion of the flow characteristic curve, with a flow regulation rate of only 90.87% observed when the fit clearance is 0.25 mm. Furthermore, the lateral outlet causes a reduction of 77.27% and 69.15% in radial forces for eccentricity or inclination angles changed from 0° to 180°, respectively. Sticking is strongly correlated with radial forces, the axial force is contingent upon the spool end face area. These findings provide crucial theoretical guidance for the design of control valves.

Bi-cuspid TAVR; bye or buy!

Key Points Mid term data of TAVR in stenotic bicuspid aortic valves is promising both in term of mortality and valve performance. Many factors should be considered before we generalize these results to all types of bicuspid native valves, TAVR valves, and patient populations. A randomized trial to SAVR versus TAVR remains the missing piece before we solve this complex clinical equation.

Balloon- vs Self-Expanding Transcatheter Valves for Failed Small Surgical Aortic Bioprostheses: 1-Year Results of the LYTEN Trial

BackgroundData comparing valve systems in the valve-in-valve transcatheter aortic valve replacement (ViV-TAVR) field have been obtained from retrospective studies. ObjectivesThe authors sought to compare the 1-year hemodynamic performance and clinical outcomes between balloon-expandable valves (BEV) SAPIEN 3/ULTRA (Edwards Lifesciences) and self-expanding valves (SEV) Evolut R/PRO/PRO+ (Medtronic) in ViV-TAVR. MethodsPatients with a failed small (≤23 mm) surgical valve undergoing ViV-TAVR were randomized to receive a SEV or a BEV. Patients had a clinical and valve hemodynamic (Doppler echocardiography) evaluation at 1-year follow-up. Study outcomes were defined according to VARC-2/VARC-3 criteria. Intended performance of the valve was defined as mean gradient <20 mm Hg, peak velocity <3 m/s, Doppler velocity index ≥0.25 and less than moderate AR. ResultsA total of 98 patients underwent ViV-TAVR (46 BEV, 52 SEV). At 1-year follow-up, patients receiving a SEV had a lower mean transaortic gradient (22 ± 8 mm Hg BEV vs 14 ± 7 mm Hg SEV; P < 0.001), and a higher rate of intended valve performance (BEV: 30%, SEV:76%; P < 0.001). There were no cases of greater than mild aortic regurgitation. There were no differences in functional status (NYHA functional class >II, BEV: 7.3%, SEV: 4.1%; P = 0.505) or quality of life (Kansas City Cardiomyopathy Questionnaire, BEV: 77.9 ± 21.2, SEV: 81.8 ± 14.8; P = 0.334). No differences in all-cause mortality (BEV: 6.5%, SEV: 3.8; P = 0.495), heart failure hospitalization (BEV: 6.5%, SEV: 1.9%; P = 0.214), stroke (BEV: 0%, SEV: 1.9%; P = 0.369), myocardial infarction (BEV: 0%, SEV: 1.9%; P = 0.347), or pacemaker implantation (BEV: 2.2%, SEV: 1.9%; P = 0.898) were found. ConclusionsIn patients who underwent ViV-TAVR for failed small aortic bioprostheses, those receiving a SEV exhibited a better valve hemodynamic profile at 1-year follow-up. There were no differences between SEV and BEV regarding functional status, quality of life, or clinical outcomes.

Neural network-based finite-time command-filtered adaptive backstepping control of electro-hydraulic servo system with a three-stage valve

This paper aims to improve the tracking control performance of the three-stage valve (TSV) controlled electro-hydraulic servo system (EHSS) with parameter uncertainties and other lumped unknown nonlinearities, including unknown dynamics and disturbances. A more accurate nonlinear model of the TSV-controlled EHSS is established and a neural network-based finite-time command-filtered adaptive backstepping control (NNFCABC) method is proposed for the EHSS. Adaptive control is used to deal with the system parameter uncertainties, and the radial basis function neural network (RBFNN) algorithm is introduced to approximate the lumped unknown nonlinearities. The prediction errors of serial-parallel estimation models (SPEMs) and the tracking errors are utilized together to design adaptive laws to estimate the system parameters and the weights of the RBFNNs. The entire control framework utilizes command-filtered control and backstepping techniques. By applying Levant differentiators as command filters and introducing fractional power terms into the virtual control laws and the SPEMs, the proposed NNFCABC theoretically guarantees the tracking performance of the closed-loop control system with finite-time convergence. Comparative simulations and experiments verify the feasibility and superiority of the proposed control scheme.

New Whole-Heart motion correction algorithm enables diagnostic CT of aortic valve and coronary arteries in systolic phase for transcatheter aortic valve implantation candidates

ObjectivesTo investigate the ability of new generation snapshot freeze (NGSSF) algorithm in improving diagnostic image quality of both aortic valve and coronary arteries for transcatheter aortic valve implantation (TAVI) candidates in TAVI planning CT. MethodsSixty-four TAVI candidates underwent TAVI planning CT were enrolled. Scans from coronary CT angiography were reconstructed at 20%, 30%, 40%, and 75% R-R cardiac phases with NGSSF and standard (STD) algorithm. In each phase, following parameters were compared: aortic valve measurements and their reproducibility; image quality of aortic valve and coronary arteries. The diagnostic accuracies of TAVI planning CT for coronary artery stenosis in 30% R-R phase with NGSSF and STD algorithms were calculated in 47out of 64 patients with invasive coronary angiography as reference standard. ResultsFor subjective image quality evaluation, the excellent rate for aortic valve improved from 25.0% to 93.8% and the interpretable rate for coronary arteries increased from 20.3% to 95.3% in the 30% phase images with NGSSF compared with images with STD. For the detection of > 50% coronary artery stenosis, the 30% phase images with NGSSF provided a sensitivity of 90%, specificity of 81.48%, negative predictive value of 91.7%, and positive predictive value of 78.3% on a per-patient basis; While images with STD, had a corresponding results of 95.0%, 33.33%, 90.0%, and 51.4%, respectively. ConclusionsNGSSF significantly improves image quality for both aortic valve and coronary arteries compared with STD for TAVI patients of all heart rates. NGSSF enables the accurate measurement for aortic valve and satisfactory diagnostic performance for coronary arteries stenosis in the same systolic phase for TAVI planning.

Leaflet thrombosis in transcatheter aortic valve intervention: mechanisms, prevention, and treatment options.

Transcatheter aortic valve intervention (TAVR) has emerged as a promising alternative to surgical aortic valve replacement for patients with severe aortic stenosis. However, leaflet thrombosis has raised concerns about the long-term durability and outcomes of TAVR. This study aims to provide an overview of the mechanisms, prevention strategies, and treatment options for leaflet thrombosis in TAVR. Leaflet thrombosis refers to the formation of blood clots on bioprosthetic valve leaflets, leading to impaired leaflet mobility, early valve degeneration and dysfunction, and potential clinical implications. While the mechanisms underlying thrombus formation on valve leaflets are not fully understood, several factors, such as altered blood flow patterns within valve neosinuses, prothrombotic surfaces, and patient-related causes, have been implicated. Two distinct entities have been identified, namely, hypoattenuated leaflet thickening and restricted leaflet motion. Their occurrence appears dynamic over time and is related to the valve type. Imaging, including transesophageal echocardiography and multidetector computed tomography, plays a crucial role in the diagnosis and follow-up of leaflet thrombosis. Preventing leaflet thrombosis requires a comprehensive and tailored approach involving identifying high-risk patients, close monitoring, and antithrombotic therapy. Antithrombotic therapy with dual antiplatelet agents or anticoagulation is commonly employed in TAVR patients, although the optimal regimen is yet to be defined. Novel antithrombotic agents, such as direct oral anticoagulants, are being investigated for their efficacy and safety in preventing leaflet thrombosis. When leaflet thrombosis is detected, treatment options include intensified antithrombotic therapy, valve-in-valve intervention, or balloon valvuloplasty. The long-term outcomes and impact of leaflet thrombosis on valve durability and patient prognosis are areas of ongoing research. Leaflet thrombosis in TAVR is a considerable complication affecting valve function and patient outcomes. Understanding the mechanisms underlying thrombus formation and implementing appropriate prevention strategies are essential for mitigating this risk. Treatment options aim to restore leaflet mobility and optimize valve performance. Further research is needed to establish standardized protocols for antithrombotic therapy, identify high-risk patient populations, and determine the long-term consequences of leaflet thrombosis on TAVR outcomes.

Left ventricular mass and valve performance after surgical and transcatheter aortic valve replacement: a single-center experience from Japan.

There are few reports on the postoperative left ventricular mass (LVM), aortic valve area (AVA), and pressure gradient (PG) after surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR) in Japan. We aimed to compare the postoperative LVM, AVA, stroke volume (SV), PG, and long-term outcomes between patients undergoing SAVR and TAVR procedures from single center in Japan. This was a retrospective cohort study. We included 107 patients who underwent simple SAVR between January 2012 and May 2022 (SAVR group, n=107) and 274 who underwent TAVR between January 2016 and May 2022 (TAVR group, n=274). The overall mean follow-up periods was 28.8±25.9 months (median: 24 months; range, 0.03-117 months). The aortic valve mean PG (mmHg) was significantly smaller in the TAVR group than in the SAVR group (P<0.001). The AVA index (cm2/m2) was significantly larger in the TAVR group than in the SAVR group (P<0.001). The SV index (mL/m2) was significantly smaller in the SAVR group than in the TAVR group (P=0.02). The LVM index (LVMI) (g/m2) was significantly smaller in the SAVR group than in the TAVR group (P<0.001). The incidence of mild or higher postoperative paravalvular leak (PVL) and pacemaker implantation were significantly higher in the TAVR group. The 5-year postoperative mortality, re-hospitalization, and major adverse cerebral and cardiovascular events (MACCEs) were significantly better in the SAVR group. The postoperative aortic valve PG, AVA, and SV were better in the TAVR group; however, LVM regression and postoperative outcomes were better in the SAVR group.