Pressure Gradient Research Articles

Abstract 4134273: Low 5-hydroxytryptamine levels are associated with adverse outcomes in patients with heart failure with preserved ejection fraction

Background: Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome and its pathophysiology is not fully understood. A monoamine, 5-hydroxytryptamine (5-HT), is involved in diverse biological functions and suggested to play a role in cardiovascular diseases. However, the clinical relevance of 5-HT in HFpEF remains unclear. Aims: This study aimed to elucidate the clinical significance and prognostic value of 5- HT in patients with HFpEF. Methods: We conducted a prospective study involving 240 consecutive hospitalized patients with HFpEF (mean age 72 years, 52% male). We measured circulating blood 5-HT levels using the enzyme-linked immunosorbent assay method. Clinical and outcome data were collected. Results: Correlation analysis revealed that 5-HT levels were negatively correlated with blood B-type natriuretic peptide concentration and tricuspid regurgitation pressure gradient. When patients were stratified into two groups based on the median 5-HT levels (90.5 ng/mL), Kaplan-Meier analysis showed that HFpEF patients with low blood 5-HT levels had lower event-free survival rates from the composite event of cardiac death and worsening heart failure over a median follow-up period of 725 days (Figure). In a multivariable Cox proportional hazard model adjusting for confounding variables, low levels of 5-HT were independently associated with increased risks of the composite of cardiac events (hazard ratio, 3.25; P < 0.01). Conclusion: Low 5-HT levels are associated with adverse outcomes in patients with HFpEF and 5-HT may serve as a useful biomarker for predicting prognosis in such patients.

Abstract 4138306: Impact of Early Menopause and Hormonal Replacement Therapy on Aortic Stenosis Progressio

Background: Early menopause is associated with an increased risk of cardiovascular disease and mortality in women. The present study aimed to examine the impact of early menopause and hormonal replacement therapy (HRT) on the progression of aortic stenosis (AS). Methods: Thirty-three postmenopausal women (mean age 65 ± 10 years) with mild or moderate AS prospectively recruited in the PROGRESSA study (NCT01679431) were included in this sub-analysis. All patients underwent multidetector computed tomography and Doppler-echocardiography at least twice during follow-up to assess both anatomic and hemodynamic AS severity, based on aortic valve calcification (AVC), mean pressure gradient (MG), and aortic valve area indexed to body surface area (AVA). Annualized changes in AVC, MG and AVAi were calculated between baseline and the last follow-up. Results: Over a median follow-up of 2 [1-4] years, early menopausal women had a faster progression rate of AVC, MG, and AVAi compared to other women: (100[58-130] vs. 23[2-71] AU/year, p=0.03); (2.37[0.82-3.61] vs. 0.31[0.01-1.78] mmHg/year, p=0.04); and (-0.12[-0.23-0.002] vs. -0.004[-0.07-0.08] cm 2 /m 2 /year, p=0.08) respectively. In multivariate analysis adjusted for age, AS severity at baseline, and comorbidities, early menopause remained significantly associated with faster AVC progression (p=0.003). Moreover, after comprehensive adjustment, women who received HRT (45%) had a slower progression rate of AVC (20[10-42] AU/year vs. 62[2-100], adjusted p=0.04). Conclusion: Early menopause is associated with faster progression of AS, both anatomically and hemodynamically. However, the use of HRT is associated with slower progression of AS. Integrating female-specific risk factors, particularly menopausal history and hormonal therapy status, into the clinical management of AS could enhance patient care.

Finite-beta turbulence in Wendelstein 7-X enhanced by sub-threshold kinetic ballooning modes

Abstract Magnetic fluctuations affecting turbulence and transport, which are manifest at finite normalized plasma pressure beta, pose a significant challenge to magnetic confinement fusion devices aiming to achieve high performance. Such regimes are not yet comprehensively understood in stellarator geometry. This work presents simulations of electromagnetic instabilities and high-beta turbulence in the Wendelstein 7-X (W7-X) stellarator, showing how ion-temperature-gradient-driven (ITG) turbulence is enhanced by unconventional kinetic ballooning modes well below the ideal MHD threshold. These sub-threshold KBMs (stKBMs) become strongly excited in the turbulent state and enable higher fluxes via zonal-flow erosion. The threshold of stKBM impact on turbulent fluxes is heavily dependent on the pressure gradient, evidenced here by the enhanced destabilization and fluxes resulting from the inclusion of an electron temperature gradient. Understanding and controlling these stKBMs will be paramount for W7-X and potentially other stellarators to achieve optimal performance.

3D CFD analysis of pressure, boundary layer and shear stresses on a gudgeon (Gobio gobio)

The fish’s mechanosensory lateral line system detects non-acoustic hydrodynamic stimuli required for feeding, schooling, predator avoidance and underwater object detection. Biological investigations have established that flow stimuli are detected through the boundary layer as pressure gradients by canal neuromasts and as shear stresses acting on the superficial neuromasts. Previous works have also shown that the spatial distribution of neuromasts is strongly correlated with the pressure coefficient. Despite these fundamental insights, substantial knowledge gaps persist in understanding how fish body geometry influences the boundary layer, the pressure distribution and shear stresses. To address these gaps, we provide a set of numerical models based on the open-source CFD toolkit OpenFOAM which are experimentally validated using velocity measurements obtained in a laboratory fish swim tunnel. Specifically, we investigate the mid dorsal-ventral planar flow fields around a 3D fish-shaped body of gudgeon (Gobio gobio), a common freshwater bottom-dwelling fish. The contributions of this work are two-fold: First, we provide a comparison of the boundary layer thicknesses and velocity profiles at flow velocities ranging from 0.25 to 1.25 m/s. Second, we qualitatively compare the spatial distributions of the pressure coefficient, dynamic pressure and shear stresses to biological observations of the neuromast locations of adult gudgeon.

TECHNICAL SOLUTIONS FOR DRILLING WELLS IN CHALLENGING CONDITIONS

Abstract. Drilling modern wells in difficult mining and geological conditions poses a number of tasks for engineers that require special solutions. These include instability of borehole walls in difficult geomechanical conditions, drilling of directional wells with long horizontal boreholes and their completion by multi-stage hydraulic fracturing, drilling in conditions of a narrow «window» of drilling mud density, as well as drilling of wells with extended reach from the vertical. The article describes the main difficulties and problems encountered in solving these problems, such as: wellbore collapse, absorption during drilling in difficult geomechanical conditions, the impossibility of running casing strings and liners into wells with a large deviation from the vertical by traditional methods, difficulties in cementing long horizontal liners, running completion for multi-stage hydraulic fracturing of a formation with packers in an open hole, difficulties in drilling in conditions of insignificant difference in pore pressure gradients and hydraulic fracturing. Certain proven solutions are offered to overcome such problems and difficulties, examples of solutions to the described problems are given. Among these solutions are geomechanical modeling with subsequent calculation of wellbore stability, as well as optimization of well trajectories, the product of multi-stage hydraulic fracturing by the Plug & Perf method of isolation and perforation in order to achieve a larger number of stages, as well as solutions for improving the quality of cementing horizontal liners. Pressure-controlled drilling technology and flotation of casing and liners into ERD wells will be considered. It concludes with conclusions about the relevance of the solutions described, the possibility of combining them to increase efficiency or under complex conditions, as well as aspects that require attention when choosing technologies and their implementation, such as the importance of risk assessment and the importance of technical integration of technologies, as well as preliminary calculations and analysis of technology implementation experience.

Dissipation in Skewed Boundary Layers

Abstract The entropy generation within a turbulent, collateral boundary layer is well understood and is characterised by a dissipation coefficient, Cd. However, it is common for the transverse pressure gradients in turbomachines to create highly skewed boundary layers, where the velocity varies in direction as well as magnitude. A combined experimental and high-fidelity computational approach is used to quantify the effect of skew on the dissipation coefficient for the first time. At a nominal condition of 14 degrees of skew and Reθ of 1000, the increase in dissipation coefficient is 20% as determined from direct numerical simulation, and 28% from experimental measurements, relative to the collateral boundary layer. Experimental data over a range of skew angles and Reθ values show that Cd increases approximately linearly with skew so that, at a skew of 25°, loss is 70% greater than in the collateral boundary layer. The implications for loss estimation are examined by evaluating boundary layer loss, in the Harrison turbine cascade, with and without the influence of skew on Cd. By accounting for the skew in the boundary layer, a new proposed model has been used to calculate the loss coefficient in the Harrison cascade to within 4% of the experimentally measured value.

High Compression in Palladium Alloy Metal Foil Pumps

Metal foil pumps (MFPs) are key components in the direct internal recycling inner fuel cycle loop for the recovery of hydrogen isotopes from deuterium-tritium fusion exhaust. Operating under vacuum conditions, they utilize superthermal hydrogen as the feed gas in a process called superpermeation. A notable feature of MFPs is their ability to pump against a pressure gradient. This study examines the compression capabilities of PdAg and PdCu MFPs at low temperatures with a constant feed pressure of 10 Pa. At 75°C, compression ratios exceeding 200 were readily achieved, with downstream pressures exceeding 4500 Pa using PdCu. For both alloys, net fluxes decreased by only ~15% at downstream pressures of 1000 Pa, which offers potential simplifications for the downstream pump train. Performance declined markedly when the temperature was elevated to 200°C. Pump curves were constructed and advocated as the most appropriate manner to assess MFP performance. Separate pressure-driven-permeation experiments at relevant conditions were conducted, providing a direct measurement of the hydrogen dissociation constant k d , which was found to be in good agreement with the previous literature. These measurements were used to predict pump curves and maximum compression ratios by balancing superpermeation with pressure-driven permeation, achieving excellent agreement with experiment. Last, experiments using asymmetric MFPs revealed the detrimental impact that surface impurities have on performance in this system.

Clinical assessment of patient outcomes post percutaneous pulmonary valve implantation: Insights from a single tertiary centre

Background: Percutaneous pulmonary valve implantation (PPVI) has emerged as a promising treatment for congenital right ventricular outflow tract (RVOT) dysfunction and restoring conduit graft viability. Methods: This is a single-centre retrospective study of 41 patients (18 men, 23 women; mean age 26.1±10.2 years) who underwent PPVI between December 2007 and November 2014 and were evaluated for right ventricular pressures and exercise tolerance. Results: PPVI significantly reduced mean baseline RVOT gradients across different pathologies: stenosis (45 vs 18.4 mmHg), regurgitation (19.2 vs 7.6 mmHg), and mixed disease (32.5 vs 12 mmHg). Furthermore, mean right ventricular (RV) systolic pressures decreased from 61.6±2.3 to 41.9±2 mmHg (p<0.001), while RV diastolic pressures decreased by about 60% from 14.3±1.1 to 8.6±1.4 mmHg (p<0.001). Echocardiography revealed significant improvements in pulmonary and tricuspid valve velocities (p for trend<0.01). Additionally, there was a consistent reduction in the main pulmonary artery maximum pressure gradient measured pre-procedure. No significant changes were observed in PR, QRS, or QTc interval duration on follow-up electrocardiograms. Similarly, no changes were noted in cardiopulmonary exercise test performance during follow-up. Conclusion: The study highlights the effectiveness of PPVI using Medtronic Melody and Edwards SAPIEN valves in patients with various pulmonary diseases. Immediate improvements in right ventricular pressures and functional outcomes suggest that PPVI is a valuable treatment option for individuals with RVOT dysfunction. Multi-centre collaborations are crucial for further elucidating the long-term effects of PPVI on cardiac function, exercise tolerance, and quality of life in RVOT dysfunction.

Evaluating the Diagnostic Potential of Four-Dimensional Flow Magnetic Resonance Imaging in Aortic Stenosis Diagnosis: A Systematic Review and Meta-Analysis.

This systematic review and meta-analysis evaluates the potential of four-dimensionalflow magnetic resonance imaging(4DFM) in assessing aortic stenosis (AS) compared to traditional imaging modalities like two-dimensional phase contrast MRI (2D MRI) and transthoracic echocardiography (TTE). AS is a common and severe valvular heart disease, particularly in older adults, requiring accurate diagnosis for proper clinical management. Conventional imaging methods have limitations in capturing complex flow dynamics, prompting the need for advanced modalities like 4DFM. The objectives of the review were to determine whether 4DFM offers superior diagnostic metrics, including peak aortic jet velocity, transvalvular pressure gradients, and aortic valve area (AVA), and to identify potential advantages of 4DFM in overcoming the limitations of traditional modalities. This review included six cohort studies with 285 participants, examining the diagnostic accuracy of 4DFM in terms of peak aortic jet velocity, transvalvular pressure gradients, and aortic valve area (AVA). Studies were selected from MEDLINE (PubMed), Cochrane Library, and Google Scholar databases between December 2010 and October 2024. The study pool was limited by stringent inclusion criteria focusing on cohort studies that directly compared 4DFM with TTE or 2D MRI for AS assessment. The National Institutes of Health Quality Assessment Tool and Cochrane ROBINS-I tool were used to assess bias. Quantitative results showed that 4DFM typically measured higher AVA values than TTE, with a mean difference of 0.48 cm² (95% CI: -0.16 to 1.12). For mean pressure gradients, 4DFM reported slightly higher measurements in individual studies, but pooled results showed no significant difference compared to TTE (mean difference: 3.32 mmHg, 95% CI: -2.30 to 8.93). In terms of peak aortic jet velocity, 4DFM demonstrated a pooled mean difference of -0.18 m/s (95% CI: -0.44 to 0.08) compared to TTE. High heterogeneity was observed across studies (e.g., I² = 97% for peak velocity, I² = 93% for AVA), likely due to differences in patient populations, imaging protocols, and software for data analysis.4DFM demonstrates potential as a complementary imaging tool, particularly in complex AS cases where conventional methods like TTE may provide inconclusive results. Its capacity to capture intricate flow dynamics and deliver high spatial resolution could inform clinical decision-making, potentially influencing practice guidelines to integrate 4DFM as a supplementary tool. Limitations such as high costs, specialized training requirements, and access challenges currently restrict widespread adoption. Limitations of this review include small sample sizes, high heterogeneity, and variability in patient populations and imaging protocols. Despite these challenges, 4DFMI demonstrated superior spatial resolution and complex cardiovascular flow assessment, suggesting it could serve as a valuable complement to TTE for more detailed AS evaluation, particularly in complex cases.Future studies should aim to standardize imaging protocols, incorporate larger and more diverse populations, and conduct cost-benefit analyses to support the integration of 4DFM into clinical practice, potentially shaping future diagnostic guidelines.

Optimal threshold of portal pressure gradient for patients with ascites after covered TIPS: a multicentre cohort study.

Transjugular intrahepatic portosystemic shunt (TIPS) is recommended for treating recurrent and refractory ascites. However, determining the target portal pressure gradient (PPG) has been inconclusive. This multicentre cohort study explored the post-TIPS PPG potential range associated with improving survival. The study enrolled 276 patients, all of whom underwent covered TIPS for ascites treatment across four medical centers. The cumulative incidences of clinical outcomes were compared among groups categorized by potential PPG thresholds. During the whole follow-up period with a medium follow-up of 21.6 (7.5, 41.6) months, 122 (44.2%) experienced liver-related death, and 73 (26.4%) patients experienced a recurrence of ascites. Multivariable analysis revealed PPG < 7mmHg (p = 0.007) and the recurrence of ascites (p = 0.033) are independent risk factors for survival, while the PPG ≥ 11mmHg was an independent risk factor for the recurrence of ascites (p = 0.012). Patients with ≥ 7mmHg had a lower rate of liver-related death than patients with post-TIPS PPG < 7mmHg (51.0% vs 66.6%, p = 0.004), while those with post-TIPS PPG ≥ 11mmHg exhibited a higher cumulative incidence of ascites compared to those with post-TIPS PPG < 11mmHg (44.6% vs 33.7%, p = 0.023). The robustness of the results was confirmed. Our study highlighted the existence of an optimal post-TIPS PPG range in patients with recurrent and refractory ascites. Patients may experience improved survival and ascites control with a post-TIPS PPG of 7-11mmHg.

Pressurised flow in cracks in embankment dam cores

A major hazard to embankment dams is internal erosion and piping arising from concentrated leaks through cracks in the core due to differential settlement. Previous work (Peirson et al., 2023) quantified the hydraulics of flow through near-surface transverse cracks subject to near-horizontal pressure gradients. This present short note extends the previous work to address pressurised flow through cracks that might occur deeper within the core. Water speeds, hydraulic shear stresses, flows are computed as a function of the applied hydraulic gradient. These results extend previous work addressing the hydraulics of very narrow cracks.

Developing a geomechanical model to predict breakdown pressure in a vertical borehole using failure analysis: a case study

Breakdown is an important process in geomechanics; a very complex process in hydraulic fracturing which has been the subject of extensive research in the literature. There exist several models in the literature for predicting the breakdown pressure. In this research, the breakdown pressure for hydraulic fracturing in a vertical borehole was modeled using 2D and 3D failure analysis. In the geomechanical model constructed in this case study, elastic moduli were obtained using petrophysical data as well as data extracted from core analysis. The in-situ stress state of the reservoir was obtained by poroelastic horizontal strain model and was then validated by field data. To test the accuracy of the horizontal strain model, several models were used to obtain the minimum horizontals stress. At the end, the induced principal stresses inside the borehole were modeled by Kirch Equations. Four failure criteria, namely Mohr–Coulomb, 2D Hoek–Brown, Hubbert-Willis and 3D Mogi-Coulomb were used to obtain the breakdown pressure for the target reservoir. Based on the prediction results of these failure criteria, it was obtained that 2D Hoek–Brown, Hubbert-Willis, and 3D Mogi-Coulomb criteria resulted in seemingly unrealistic breakdown pressures with respect to the minimum horizontal stress gradient. The Mohr–Coulomb criterion produced lower breakdown pressure gradients, yet closer to the minimum horizontal stress values, even though it neglects the effect of intermediate stress.

Intensification of an Autumn Tropical Cyclone by Offshore Wind Farms in the Northern South China Sea

AbstractThe rapid development of the wind industry is accompanied by increasing environmental impacts. Currently, there is a lack of research on the impacts of offshore wind farm (OWF) on tropical cyclone (TC) intensity, including the mechanisms involved. This research is carried out by using a coupled and an uncoupled numerical model to investigate the impact of OWF on an autumn TC in the northeastern South China Sea. The results show that the wind speed deficit caused by OWF leads to an increase in surface pressure on the inflow side. This causes the surface pressure in the TC periphery to increase by advection, even if the TC is some distance away from the OWF. The increase in pressure gradient from the periphery to the TC center enhances the TC secondary circulation, thereby intensifying the TC. When the TC enters the OWF, the above mechanisms weaken and the ocean dominates the TC intensification. This is because the reduction in wind speed caused by the OWF results in a weaker sea surface current velocity, which weakens the flow of upstream cold water into the OWF, warming the sea surface temperature (SST) within the OWF. This implies that the horizontal gradient of the local SST is an important factor to be considered in the development of OWF. Sensitivity experiments indicate that OWF can also intensify other types of TC, and that higher cut‐out wind speeds lead to stronger intensification effects. These results also provide a new perspective on TC intensity forecasts.

Cardiovascular sequelae in symptomatic SARS-CoV-2 infection survivors.

SARS-CoV-2 infection may lead to myocardial and endothelial damage. The present study sought to characterize the cardiovascular sequel in a large group of consecutive patients admitted for out-patient cardiovascular follow-up after a symptomatic COVID-19 infection. The aims of this study were as follows: to evaluate the presence of post-covid cardiovascular symptoms in an unselected population of outpatients referred to a post-COVID outpatient cardiology clinic and to characterize the long-term abnormalities associated with a more severe COVID-19 infection clinical course. A total of 914 patients were included in this single-center, observational, cross-sectional study, of which 163 were hospitalized and 149 required mechanical ventilation for COVID-19 pneumonia. Patients were analyzed at follow-up according to the care setting during the initial presentation. The median time to follow-up was 126 days. At that time, only 3.5% of patients reported no persistent dyspnea, chest pain, or fatigue on exertion. In a follow-up echocardiographic assessment, patients who required hospitalization showed slight alterations in the pulmonary acceleration time and the tricuspid regurgitation pressure gradient, as well as reduced exercise tolerance during treadmill exercise testing when compared to patients with a benign clinical course. 24-hour Holter EKG monitoring or 24-hour blood pressure monitoring did not identify significant differences between the analyzed subgroups. The current study reports on an association between COVID-19 severity and the presence of cardiovascular alterations at follow-up. A simple diagnostic protocol, comprising an exercise treadmill test and transthoracic echocardiography is useful in identifying patients who may benefit from regular, structured cardiovascular medical care.

Edemoascitis decompensation. Is it always liver cirrhosis?

Abstract Portal hypertension (PH) is a clinical syndrome characterized by an increase in the portal hepatic venous pressure gradient (HVPG), defined as the gradient between the portal vein and the inferior vena cava. When there is clinically significant PH, it is usually associated with clinical events such as the development of esophagogastric varices (EGV), oedemoascitic decompensation, encephalopathy... these being more frequent in the case of PH due to liver cirrhosis. In all etiologies of PH there is an increase in resistance to portal blood flow, followed by an increase in said flow. Depending on the location of the increased resistance, it will be classified as prehepatic, intrahepatic or posthepatic PH. Posthepatic portal hypertension occurs when there is a deterioration in hepatic venous outflow, increasing resistance at this level. We present the case of a patient where a striking portal dilation led to the diagnosis of posthepatic PH.

Calendering of non-isothermal viscoelastic sheets of finite thickness: A theoretical study

Abstract In this article, the sheeting of pseudoplastic material under non-isothermal conditions has been studied. It is an excellent forecasting instrument for sheeting, where the thickness of the sheet is relatively thin in relation to the roll size, according to theoretical study based on the lubrication theory. At the calendering process, the detachment point is determined by taking the material parameter’s impact into account. The governing equations are derived for the constitutive equation of the Carreau fluid with momentum and energy equations. Suitable non-dimensional parameters are used to develop the non-linear partial differential expressions into ordinary differential systems. The maximum pressure, roll separating force, normal stress effect, and power delivered to the fluid by rolls are among the engineering-relevant quantities that are determined. Moreover, a graphic analysis is conducted to examine the impact of different material parameters on the temperature profile, pressure gradient, velocity profile, and pressure distribution. The results specific mechanism is explained in depth.

Dynamic signatures: a mathematical approach to analysis

Abstract This study evaluates mathematical tools (principal component analysis, dynamic time warping, and the Kolmogorov–Smirnov hypothesis test) to analyse global and local data from dynamic signatures to reduce subjectivity and increase the reproducibility of handwriting examination using a two-step approach. A data set composed of 1800 genuine signature samples, 870 simulated signatures, and 60 disguises (30 formally similar or ‘autosimulated’ and 30 random but different from usual) provided by 30 volunteers was collected. The first step involved global data analysis using principal component analysis and a hypothesis test performed for 62 global characteristics, and associations of these characteristics were analysed through calculations of multivariate distance followed by a hypothesis test. The second step involved the analysis of local characteristics including vertical and horizontal positions, speed, pressure gradient, acceleration, and jerk point-to-point, by using dynamic time warping followed by a hypothesis test. Optimization of sensitivity and specificity metrics of the hypothesis test was explored by varying its stringency and observing accuracy rates for the simulated and genuine groups. A P-value threshold of 1 × 10−10 was found to be optimal, making the test more restrictive and yielding accuracy rates of 96.7% for genuine global data and 88.9% for simulated data. The same cutoff value for local characteristics provided an average accuracy rate of 95.4% for genuine samples and 94.7% for simulated samples, demonstrating high accuracy for both simulated and genuine samples. However, the method did not offer reasonable accuracy rates for disguises, consistent with observations in traditional handwriting examination. Our approach provided satisfactory results for forensic examination use. The visualization of graphs and signatures and analysis of all identifying elements of handwriting by the examining expert are still essential. In future studies, we plan to perform blind tests to validate our approach and propose a rigorous methodology.

Right ventricular outlet tract reconstruction for tetralogy of fallot: systematic review and network meta-analysis.

Concerns persist regarding pulmonary regurgitation after transannular patch repair (TAP) for Tetralogy of Fallot. Despite various architectural preservation techniques being introduced, the optimal strategy remains controversial. We aimed to compare different right ventricular outlet tract reconstruction techniques. PubMed, EMBASE and Cochrane Central were searched through March 2024 to identify comparative studies on right ventricular outlet tract reconstruction techniques (PROSPERO ID: CRD42024519404). The primary outcome was mid-term pulmonary regurgitation, with secondary outcomes including postoperative mortality, postoperative pulmonary regurgitation, length of intensive care unit stays, postoperative right ventricular outlet tract pressure gradient, and mid-term mortality. We performed a network meta-analysis to compare outcomes among TAP, valve-repairing (VR), TAP with neo-valve creation (TAPN), and valve-sparing (VS). Two randomized controlled studies and 32 observational studies were identified with 8,890 patients. TAP carried a higher risk of mid-term pulmonary regurgitation compared to TAPN (HR, 0.53; 95％CI [0.33; 0.85]) and VS (HR, 0.27; 95% CI [0.19; 0.39]), with no significant difference compared to VR. VS was also associated with reduced postoperative mortality compared to TAP (RR, 0.31; 95% CI [0.18; 0.56]), in addition to reduced ventilation time. TAP also carried an increased risk of postoperative pulmonary regurgitation compared to the other groups. The groups were comparable in terms of length of intensive care unit stay, right ventricular outlet tract pressure gradient, and mid-term mortality. VR was associated with a reduced risk of postoperative pulmonary regurgitation, while TAPN was associated with reduced risks of both postoperative and mid-term pulmonary regurgitation.

Incremental Prognostic Value of Left Ventricular and Left Atrial Strain in Moderate Aortic Stenosis.

Patients with moderate aortic stenosis (AS) show a poor prognosis if they have high-risk features. We investigated the incremental prognostic value of left ventricular (LV) and left atrial (LA) strain in patients with moderate AS. In a cohort of 923 patients with moderate AS (median age 74 years, men 55%, aortic valve area 1.18 [IQR 1.08-1.30] cm2, mean pressure gradient 25 [IQR 23-30] mmHg), LV global longitudinal strain (LV-GLS) and LA reservoir strain (LARS), were measured using speckle-tracking echocardiography. Absolute values of myocardial strain were used. The primary endpoint was a composite of all-cause mortality and heart failure hospitalization.During a median of 5.9 years, the primary endpoint occurred in 186 patients (20.2%). The median LV-GLS and LARS were 17.7% (IQR 14.8-19.7) and 24.5% (IQR 18.7-29.3). LV-GLS (adjusted HR 0.92, 95% CI 0.87-0.97) and LARS (adjusted HR 0.97, 95% CI 0.95-0.99) were significant predictors of the primary outcome, independent of clinical and echocardiographic variables including LV ejection fraction. Notably, the prognostic value of LV-GLS was stronger than that of LARS, remaining significant after further adjustment for LARS. LV-GLS<17% and LARS<22% were identified as optimal cutoffs for the primary outcome. Patients with both reduced LV-GLS and LARS had the worst outcome (log-rank p<0.001). LV-GLS<17% and LARS<22% had incremental prognostic value on top of other clinical and echocardiographic variables. In moderate AS, reduced LV-GLS and LARS have incremental prognostic value, and can refine risk stratification to identify high-risk patients.

A numerical investigation on rheological turbulent flow through a 90° mixing elbow

Mixing elbows are widely used in various industrial processes to mix two different Newtonian or non-Newtonian fluids under turbulent flow conditions. This study numerically investigates the fluid flow and mixing characteristics in 90-degree elbows with different bend curvatures (curvature ratios of 3, 6, and 9) and Reynolds numbers ranging from 1 × 104 to 5 × 105 for both fluid types. The Reynolds-Averaged Navier–Stokes equations are solved using the turbulent k-epsilon model in ANSYS Fluent. Results show that the bend curvature creates an adverse pressure gradient that drives secondary flows, which become more pronounced with higher Reynolds numbers and lower curvature ratios. Higher Reynolds numbers improve mixing quality, as indicated by velocity and temperature variations quantified using standard deviations. For Reynolds numbers in the range of 104, velocity fluctuations initially increase, but at higher values (~ 105), they decrease, even by up to 64% as the Reynolds number rises from 1 × 105 to 5 × 105. Similarly, increasing the curvature ratio enhances mixing efficiency, with a 32% reduction in velocity fluctuations when the curvature ratio increases from 6 to 9. Furthermore, shear-thinning fluids (n=0.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 0.6$$\\end{document}) exhibit superior mixing performance, with a standard deviation of velocity fluctuations at the outlet of 0.32, compared to 0.54 for shear-thickening fluids (n=1.4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 1.4$$\\end{document}). In terms of temperature fluctuations also, a similar trend is observed. These findings are valuable for optimizing mixing and fluid transport in industries such as chemical processing and food production, where effective mixing of complex fluids is critical. This study provides insights for improving the design of mixing systems that handle fluids with various rheological characteristics.