Valve Surgery Research Articles

The improvement effects of TAVR on cardiac electrical remodeling of patients with severe aortic stenosis

Objectives: To assess the effectiveness of transcatheter aortic valve replacement (TAVR) on electrocardiographic remodeling in patients with severe aortic stenosis (AS), and identify its influencing factors. Methods: A cohort study was conducted on patients with a confirmed diagnosis of severe AS who successfully underwent TAVR at the Second Affiliated Hospital of Dalian Medical University between June 2018 and March 2023. Data, including standard 15-lead electrocardiograms and echocardiograms, were collected before the operation, 1 week after the operation, and 3 months after the operation. The average degree of ST-segment depression in the lateral wall leads of the electrocardiograms, and the amplitude of the T-wave were measured and calculated. The changes of electrocardiograms indexes were observed, and Spearman correlation analysis was used to explore the correlation between each index of electrocardiograms and each index of echocardiography. Multiple linear regression analysis was used to determine the influencing factors of the improvement of electrocardiographic remodeling in patients with severe AS after TAVR. Results: A total of 33 patients with severe AS, aged (73±9) years, were included in the study. Among them there were 15 (45%) males. The degree of ST-segment depression, supra-aortic flow velocity, peak transaortic pressure, and mean transaortic pressure exhibited significant improvement at 1 week post-TAVR (all P<0.05). Similarly, significant improvements in T-wave hypoplasia or inversion, left ventricular mass, and left ventricular mass index were observed at 3 months post-TAVR (all P<0.05). The degree of ST-segment depression was found to be correlated with supra-aortic flow velocity, peak transaortic pressure, and mean transaortic pressure (all P<0.05). Additionally, a correlation was observed between T-wave amplitude and left ventricular mass, left ventricular mass index, left ventricular end-diastolic internal diameter, and left ventricular ejection fraction (all P<0.05). Multiple linear regression analysis revealed that supra-aortic flow velocity was an independent influencing factor of the level of ST-segment depression (β=-0.156, P=0.007), while left ventricular mass index was identified as an independent influencing factor of T-wave amplitude (β=-2.007, P=0.001). Conclusion: The improvement in electrocardiographic remodeling could be observed after TAVR in patients with severe AS, which may be due to enhanced cardiac perfusion and regression of left ventricular hypertrophy subsequent to aortic valve opening.

Aortic Valve Surgery in Patients Over 75 Years Old: Early Results and Predictors of Hospital Mortality

Background: Aortic valve surgery is the most essential part of worldwide heart valve surgery. In recent decades, the patient profile has changed even in our country, with the age of patients undergoing aortic valve surgery increasing significantly. The primary objectives of this study are the early results of aortic valve replacement surgery in patients over 75 years old and the negative predictors that affect hospital mortality. Materials and Methods: This is a retrospective study of 73 patients over 75 who underwent aortic valve surgery in 2014-2021 in our Cardiac Surgery Service, University Hospital Center “Mother Theresa” in Tirana. The patients' data regarding demographic, preoperative, operative, and postoperative variables were collected from the hospital's medical records. The data are presented in mean values and standard deviation. T-test and chi-squared test are also used. Results: This study involved 73 patients, 50 males and 23 females. The age range was 75-85, averaging 77.12±2.31 years. Hospital mortality was 4.1%. The incidence of major perioperative complications such as low cardiac output, stroke, respiratory problems, bleeding, atrial fibrillation, wound infection, and conduction disturbances was 6.8%, 2.7 %, 4.1%, 2.7 %, 21.9 %, 2.6%, and 4.2 %. Conclusions: Aortic valve surgery for elderly patients over 75 can be performed well. Concomitant procedures, prolonged extracorporeal circulation, and emergency intervention expose the patient to a high operative risk.

Selection of Prosthesis in Aortic Valve Surgery: Short Review and Trend in our Practice in 10 Years

Introduction: In our country, the predominant condition treated in aortic valve surgery in its early stages was aortic valve disease of rheumatic origin, primarily in patients under the age of 60. In recent decades, due to lifestyle changes, increased average lifespan, and a shift in surgical treatment concepts among the elderly, there has been a noticeable trend towards atherosclerotic aortic valve disease treated surgically. This condition poses challenges in selecting the type of prosthesis for surgical replacement—either bioprosthetic or mechanical. The replacement of the aortic valve, aside from its undeniable benefits for patients, also introduces various complications, such as bleeding related to anticoagulation, thromboembolism, prosthetic endocarditis, and structural degeneration of the prosthesis. These complications vary between the two main groups of prostheses: bioprosthetic and mechanical. In this context, we are confronted with the challenge of selecting the type of prosthesis suitable for each patient. This paper presents current issues regarding selecting aortic valve prostheses, considering factors related to the prosthesis and the patient. We will also discuss the trends in prosthesis usage in our country over the past decade. Materials and Methods: We reviewed the types of mechanical and bioprosthetic valves used over the past ten years at our clinic, the Cardiac Surgery Service of the University Hospital Center "Mother Teresa.” We consulted articles, studies, and guidelines for managing heart valve diseases from European and American cardiology associations. Conclusion: The choice of prosthesis for aortic valve replacement remains a current issue, involving considerations of patient-related and prosthesis-related factors. The decision is based on guidelines recommendations, surgical team judgment, and patient preference, following a detailed explanation of the benefits and risks associated with each type of prosthesis.

Redo Aortic Valve Replacement After Prior Transcatheter versus Surgical Aortic Valve Replacement: Insights from Western Experience

Introduction: The demand for reoperation on the aortic valve in Albania is rising, mirroring the increasing average age of the population and the subsequent rise in patients requiring aortic valve surgery. This trend underscores the need for this informative article, which aims to provide insights into the risks and outcomes of aortic valve reoperations, particularly in light of efforts by interventional cardiologists to expand the indications for TAVR to younger and lower-risk patients. Data from the Society of Thoracic Surgeons (STS) National Database reveal results that warrant attention, with concerns over reoperations after TAVR growing, mainly due to the uncertain feasibility of repeat TAVR. This article presents a novel perspective on the risks associated with surgical aortic valve replacement (SAVR) after prior TAVR or SAVR. It underscores the urgent need to develop an optimal strategy for managing these patients and offers fresh insight. Material and Methods: Our research, based on a comprehensive analysis of data from the Society of Thoracic Surgeons in the USA's 10-year database, included individuals who underwent bioprosthetic SAVR following prior TAVR and/or SAVR. Our analyses, which included total and isolated SAVR groups, focused on the primary outcome of operative mortality, ensuring the reliability and thoroughness of our study. Results: The study included 31,106 patients who underwent SAVR. Among them, 1,126 had prior TAVR (TAVR-SAVR), 674 had undergone SAVR followed by TAVR and SAVR (SAVR-TAVR-SAVR), and 29,306 had undergone prior SAVR (SAVR-SAVR). Matched analysis for isolated SAVR cases showed a 1.74-fold higher operative mortality for TAVR-SAVR than SAVR-SAVR (P = 0.020). In our center, 5 cases have been performed in the last two years with excellent results, no losses, and operating times close to the first-time interventions. Conclusions: This study's findings significantly contribute to the field. They could influence clinical practice, particularly for patients with longer life expectancies and anatomy unsuitable for TAVR. They suggest an initial SAVR approach may provide better results even in necessary surgical re-interventions on the aortic valve.

Minimally Invasive Mitral Valve Surgery: Initial One-team Experience and Short Review.

Introduction: Minimally invasive mitral valve surgery (MIMVS) is now a widely accepted and more frequently utilized method for patients needing mitral valve surgery. The promoted advantages are less trauma, less bleeding, less pain, and fewer wound infections, allowing faster postoperative and decreased healthcare costs. Material and Methods: This is a single-center retrospective study. We have collected the records of patients who underwent MIMVS by one team at the Cardiac Surgery Service, UHC” Mother Theresa” Hospital. The patients' data regarding demographic, preoperative, operative, and post-operative variables were collected from the medical records in the hospital. All statistical analyses were performed using IBM SPSS version 24.0 software (SPSS, Inc., Chicago, IL, USA). Results: Surgical technique includes mitral valve repair or replacement through right lateral mini-thoracotomy, through a small 5-7cm incision in the 4th–5th right intercostal space under direct vision Seldinger technique under transesophageal echocardiogram guidance is used for cannulation, first 3 cases of MIMVS was performed with 2 venous cannulas – one percutaneous jugular cannula and femoral one, 8 cases underwent single two-stage femoral venous cannulation for venous drainage, femoral arterial cannulation and vacuum assisted cardiopulmonary by-pass(CPB). Conclusion: Minimal-invasive mitral valve surgery is as safe as the standard approach and allows faster recovery with a shorter length of hospitalization, resulting in decreased healthcare costs. We need a more extensive study to confirm the other advantages, but minimal-invasive should be pushed to become a standard approach for mitral valve surgery. An adequate learning curve is mandatory for all the operative teams to achieve all the benefits for the patients.

The effect of power-based control on the haemodynamics and valve function of the biventricular assist circulation system.

Biventricular assist devices (BiVAD) are capable of providing mechanical support to the left and right ventricles to improve blood supply in heart failure, thereby maintaining patients' lives and improving their quality of life. But there is evidence that the incidence of aortic valve incompetence and other valvular pathologies is related to BiVAD support. Such as constant speed (CS) control may cause the valve to close completely and lose its normal valve function. The valve function is related to the percentage of valve opening which is approximately 30% of the cardiac cycle. This study developed a power-based control model for BiVAD that could regulate motors' speed by altering the power to satisfy objectives of keeping valve function and restoring physiologic perfusion. The effects of the power-based controller on the hemodynamics and valve function were investigated by simulating BiVAD under constant power and variable power controls. Different heart failure and activity levels were also mimicked under variable power control to obtain the BiVAD's critical parameters and the assist ratios. The results show that the power-based control can help the BiVAD to assist a patient with heart failure, and the power settings should comprehensively consider objectives of valve function and physiologic perfusion.

Impact of Dialysis Modality on Mortality and Complications in Cardiovascular Surgery

Background: Patients receiving maintenance dialysis face high mortality and complication rates following cardiovascular (CV) surgery. With the growing utilization of peritoneal dialysis (PD), it is important to understand the impact of modality (PD vs. center-based hemodialysis [HD]) on outcomes following CV surgery. Methods: This retrospective cohort study used data from the National Inpatient Sample (2016-2020) to compare outcomes of PD and HD patients undergoing coronary artery bypass grafting and surgical valve procedures. Multivariable logistic regression, negative binomial regression, and linear regression models were used, adjusting for demographic factors, comorbidities, and hospital characteristics. The primary outcome was in-hospital mortality, and secondary outcomes included prolonged ventilation, length of stay, and hospital charges. Results: A total of 30,155 patients were included in the study, with 28,015 (92.9%) receiving HD and 2,140 (7.1%) receiving PD. Compared to HD, PD was associated with lower in-hospital mortality (OR 0.61, 95% CI 0.38-0.97), reduced prolonged ventilation (OR 0.51, 95% CI 0.32-0.81), shorter length of stay (IRR 0.85, 95% CI 0.80-0.91), and decreased hospital charges (mean difference -$87,172 USD, 95% CI -$113,523 to -$60,820) compared to HD. Among PD patients, post-operative transition to HD was associated with worse outcomes. Conclusions: Maintaining PD during the perioperative period may confer benefits over HD, including lower hospital charges and improved patient outcomes. Careful consideration of dialysis modality in the management of CV surgery patients is needed to optimize clinical outcomes and reduce healthcare costs.

Design of Combined Rainwater-Harvesting and Stormwater-Detention System with Passive Release for New Buildings in Taiwan

Taiwan experiences abundant rainfall, but faces significant water shortages, making rainwater harvesting (RWH) a potential alternative water source. Additionally, extreme rainfall events strain urban flood control systems, highlighting the need for integrated stormwater management. To address these challenges, Taiwan mandates stormwater detention (SWD) in new buildings. However, the current RWH and SWD systems are designed independently, with no combined design guidelines available. This study proposes three combined RWH and SWD systems, series, parallel, and enhanced parallel with a valve using a passive release mechanism. System performance was evaluated through short-term and long-term simulations. Short-term simulations were conducted to ensure the system’s compliance with the domestic flood control design standards. These simulations assessed the peak flow mitigation and lag times for 5-, 10-, and 25-year design storms under four scenarios. Long-term simulations used historical rainfall data to analyze the differences in the combined systems and operational plans for continuous rainfall events. Three performance indicators—volumetric reliability, the stormwater retention ratio, and the stormwater detention ratio—were employed to assess water supply and the stormwater detention performance. The short-term simulation results revealed that the system performance was sensitive to the initial conditions. The series and parallel systems performed well, while the enhanced parallel system outperformed the others under specific initial conditions and valve operations. In contrast, long-term simulations revealed that the series and parallel systems achieved higher stormwater retention and a more stable performance than the enhanced parallel system. Among the three systems, the parallel system offers reduced installation space, lower costs, and easier maintenance, making it the recommended option for Taiwan. This study provides valuable guidance for designing combined RWH and SWD systems.

Atrioventricular Septal Defect (AVSD) in a 44-Year-Old Male Incidentally Detected by CTA prior to Mitral Valve Surgery

Atrioventricular Septal Defect (AVSD) in a 44-Year-Old Male Incidentally Detected by CTA prior to Mitral Valve Surgery

Prevalence and predictors of left atrial thrombus in patients with rheumatic atrial fibrillation undergoing cardiac surgery: a cross-sectional study

BackgroundUnlike non-rheumatic atrial fibrillation (AF), where left atrial thrombus (LAT) is predominantly confined to the left atrial appendage (LAA), a significant proportion of LAT in rheumatic AF occurs within the left atrial cavity (LAC). However, LAC thrombosis in rheumatic AF has not been extensively studied. This study aimed to evaluate the prevalence of LAT and its subtypes and identify potential predictors of LAT.MethodsThis retrospective study included adult patients with rheumatic AF who underwent open-heart surgery for mitral valvular abnormalities between January 2019 and December 2020. LAT was identified through intraoperative inspection and categorized as either LAC thrombus or LAA thrombus. The prevalence of LAT and its subtypes was calculated, and logistic regression analysis was performed to identify predictors of LAT.ResultsA total of 530 patients (mean age: 59.7 ± 9.5 years; male: 29.8%) with a predominance of mitral stenosis (59.6%) were included. LAT was identified in 82 patients (15.5%), including 44 (8.3%) with LAA thrombus and 38 (7.2%) with LAC thrombus. In the multivariable logistic regression model, coronary artery disease (OR: 6.35, 95% CI: 2.79–14.46, p < 0.001), larger left atrial diameter (OR: 1.31 per 10 mm increase, 95% CI: 1.02–1.68, p = 0.03), and moderate-to-severe mitral stenosis (OR: 1.77, 95% CI: 1.00–3.13, p = 0.05) were independently associated with an increased risk of LAT, whereas moderate-to-severe mitral regurgitation was independently associated with a decreased risk of LAT (OR: 0.21, 95% CI: 0.11–0.43, p < 0.001).ConclusionIn patients with rheumatic AF undergoing open-heart mitral valve surgery, LAT can be located in either the LAA or LAC. The presence of LAT was independently associated with coronary artery disease, left atrial enlargement, and mitral valvular abnormalities. Timely screening and management of LAT are crucial to mitigate potentially fatal thromboembolic events.

Performance Analysis of a Waste-Gated Turbine for Automotive Engines: An Experimental and Numerical Study

In this article, the results of an experimental investigation and a 1D modeling activity on the steady-state performance of a wastegated turbocharger turbine for spark ignition engines are presented. An experimental campaign to analyze the turbine performance for different waste-gate valve openings was conducted at the test bench for components of propulsion systems of the University of Genoa. Thanks to the experimental activity, a 1D model is developed to assess the interaction between the flow through the impeller and the by-pass port. Advanced modeling techniques are crucial for improving the assessment of turbocharger turbines performance and, consequently, enhancing the engine–turbocharger matching calculation. The initial tuning of the model is based on turbine characteristic maps obtained with the by-pass port kept closed. The study then highlights the waste-gate valve behavior considering its different openings. It was found that a more refined model is necessary to accurately define the mass flow rate through the waste-gate valve. After independently tuning the 1D models of the turbine and the waste-gate valve, their behavior is analyzed in parallel-flow conditions. The results highlight significant interactions between the two components that must be taken into account to reduce inaccuracies in the engine-turbocharger matching calculation. These interactions lead to a reduced swallowing capacity of the turbine impeller. This reduction has an impact on the power delivered to the compressor, the boost pressure, and, consequently, the engine backpressure. The results suggest that methods generally adopted that consider the by-pass valve and the turbine as two nozzles working in parallel under the same thermodynamic condition could be insufficient to accurately assess the turbocharger behavior.

Effect of Blade Number on Internal Flow and Performance Characteristics in Low-Head Cross-Flow Turbines

Cross-flow turbines are widely used in microhydropower systems because of their cost-effectiveness, environmental sustainability, adaptability, and robust design. However, their relatively lower efficiency than other turbine types limit their application in large-scale projects. Previous studies have identified poor flow profiles as a significant factor contributing to inefficiency, with the number of blades playing a critical role in the flow behavior, efficiency, and structural stability. This study employed numerical simulations to analyze how varying the number of blades affects the internal flow characteristics and performance of the turbine at, and off, its best operating points. Configurations with 16, 20, 24, 28, 32, 36, 40, and 44 blades were investigated under constant low-head conditions, fully open valve settings, and varying runner speeds. Simulations were performed using ANSYS CFX, incorporating steady-state conditions, a two-phase flow model with a movable free surface, and a shear stress turbulence model. The results indicate that the 28-blade configuration achieved a maximum hydraulic efficiency of 83%, outperforming the preset 24-blade setup by 6%. Flow profiles were examined using pressure and velocity gradients to identify regions of adverse pressure. Due to the impulse nature of the turbine, the flow profile is more sensitive to changes in the flow speed than to pressure. The flow trajectory showed stability in the first stage but exhibited discrepancies in the second stage, which were attributed to turbulence, recirculation, and shaft flow impingement. The observed performance improvements were linked to reduced hydraulic losses due to flow separation and friction, emphasizing the significance of the number of blades and the regions of optimal efficiency under low-head conditions.

From video to vital signs: a new method for contactless multichannel seismocardiography

Seismocardiography (SCG) is a technique that non-invasively measures the chest wall’s local vibrations caused by the heart’s mechanical activity. Traditionally, SCG signals have been recorded using accelerometers placed at a single location on the chest wall. This study presents an innovative, cost-effective SCG method that utilizes standard smartphone videos to capture data from multiple chest locations. The analysis of vibrations from multiple points can offer a more thorough understanding of the heart’s mechanical activity compared to signals obtained solely from a single chest location. Our approach employs computer vision and deep learning techniques to extract and improve the resolution of multichannel SCG maps obtained by video capture of chest movement. We attached a grid of patterned stickers to the chest surface and recorded videos of chest movements during different respiratory phases. Using a deep learning-based object detector and a template tracking method, we tracked the stickers across video frames and extracted the corresponding SCG signals from sticker displacements. We also developed a robust algorithm to estimate heart rate (HR) from these chest videos and identify the optimal chest location for HR estimation. The method was tested on 28 chest videos captured from 14 healthy participants. The results demonstrated that our method effectively extracted multichannel SCG maps and enhanced their resolution with a mean squared error of 0.1078 and 0.0418 for right-to-left and head-to-foot SCG signals, respectively. We observed intersubject chest vibration patterns corresponding to cardiac events including opening and closure of the heart valves. Moreover, our algorithm accurately estimated HR from 1968 SCG signals extracted from the videos compared to the gold-standard HR measured from each subject’s electrocardiogram (bias ± 1.96 SD = 0.04 ± 2.14 bpm; r = 0.99, p < 0.001). The findings from this study underscore the potential of our approach in developing a cardiac monitoring tool using a smartphone that would be widely accessible to the general public and might provide more timely detection of diseases.

Robotic mitral valve surgery: evolving history, techniques, and training paths.

Over the past 25 years, robotic-assisted mitral valve surgery has gained significant recognition because of its potential to minimize patient trauma and improve clinical outcomes. This field has evolved from early efforts in minimally invasive mitral procedures to more refined and technically sophisticated approaches, driven by the need for smaller incisions and reduced recovery times. This review will delve into the historical evolution of robotic-assisted mitral valve surgery, detailing the technical advancements that have shaped current practices and outlining the essential training pathways for a career as robotic mitral valve surgeon. The development of robotic systems has marked a turning point, offering surgeons greater precision and dexterity, crucial adjuncts in complex mitral valve repairs.

Right Ventricle Function: The Role of the Forgotten Chamber in Mitral Valve Surgery.

Referred to as the "forgotten chamber," the right ventricle (RV) is now widely acknowledged as a significant factor, particularly in certain cardiovascular pathologies. Despite historically being undervalued in comparison to the left ventricle, the RV function is deemed crucial in determining patient outcomes following mitral valve (MV) surgery. In the context of MV surgery, it is important to note that the RV is highly susceptible to dysfunction before, during, and after the surgical procedure. This vulnerability is also partly compounded by a lack of precise preoperative assessment, appropriate intraoperative management, and sufficient postoperative care for the RV. Moreover, it is notable that the current preoperative risk-score evaluation does not encompass considerations for the RV. Sophisticated assessment methodologies, including echocardiography, cardiac magnetic resonance imaging, and invasive hemodynamic procedures, play a pivotal role in accurately evaluating the RV function in patients undergoing MV surgery. These methodologies offer invaluable insights into the extent of RV dysfunction both pre- and postoperatively. By furnishing precise measurements of RV performance, these techniques contribute to risk stratification, guide perioperative management, and may enhance surgical outcomes. Their integration into routine clinical practice is essential for optimizing patient care in the context of MV surgery. This review highlights the importance of evaluating the RV before surgery, ensuring proper perioperative care, and utilizing advanced imaging to monitor RV function in order to predict the outcomes. The goal is to enhance surgical outcomes by thoroughly assessing and supporting RV function during the surgical process.

Infective endocarditis caused by Gemella – a retrospective registry-based study

Purpose Infective endocarditis (IE) is diagnosed using the Duke criteria, which were updated in 2023. In the Duke-ISCVID 2023 criteria, Gemella was recognised as a typical IE pathogen. This study investigates the impact of this change and compares the clinical characteristics of Gemella IE to IE caused by other pathogens. Methods Data on IE caused by Gemella species and other pathogens was retrieved from the Swedish Registry of Infective Endocarditis (SRIE). Clinical characteristics of Gemella IE were compared to episodes of IE caused by non-beta haemolytic streptococci, by Staphylococcus aureus and by enterococci. Results In the SRIE, 29 episodes of Gemella IE were identified among a total of 7677 registered episodes, corresponding to 0.4% of all cases. The most common species were Gemella morbillorum (47%) and Gemella bergerii (27%). The proportion of episodes meeting the criteria for definite IE increased from 13 (45%) with the modified Duke criteria to 21 (72%) with the Duke-ISCVID criteria. Median age of patients with Gemella IE was 70 years, 40% were females and 90% hade native valve IE. One third of the patients underwent heart valve surgery and only one patient (3%) died. Many clinical aspects of IE caused by Gemella resembled those of IE caused by non-beta haemolytic streptococci. Conclusions Gemella IE is a rare condition and shares several characteristics with IE caused by non-beta haemolytic streptococci. The prognosis of IE caused by Gemella appears to be relatively favourable.

Pseudo-anévrisme du trigone mitro-aortique : Cas clinique et revue de littérature

We report the case of a 63-year-old patient who underwent aortic valve replacement with a biological valve for a bicuspid aortic stenosis, and LIMA-IVA single-bypass surgery. Two weeks later, he presented with Enterococcus faecillis bacteremia, attributed to left pyelonephritis and successfully treated with Amoxicillin. Two months after his surgery, he had a new bacteremia due to Enterococcus faecalis and we discovered a pseudo-aneurysm of the mitro-aortic trigone. Our patient is treated medically at first, before benefiting from the "Hemi-Commando" procedure. The mitro-aortic trigone is a fibrous area, located between the left half of the noncoronary cusp and the left coronary cusp of the aortic valve and the anterior leaflet of the mitral valve [1]. This area, important in the maintenance of mitral and aortic functions, [ii] is poorly vascularized and therefore very susceptible to infections and trauma [2]. Erosion of the aortic ring leads to the formation of a subvalvular abcess, secondarily detergated en then leads to the destruction of the trigone. Pseudoaneurysm is a rare complication of aortic valve surgery and endocarditis. Given the risk of rupture, early surgery is recommended.

Improving long-term postoperative survival in a porcine cardiac valve surgery model utilizing cardiopulmonary bypass via left thoracotomy: a single-center experience sharing insights

Improving long-term postoperative survival in a porcine cardiac valve surgery model utilizing cardiopulmonary bypass via left thoracotomy: a single-center experience sharing insights

Comparison of mitral valve repair versus replacement for mitral valve regurgitation.

Mitral regurgitation (MR) is a prevalent valvular abnormality categorized as primary or secondary based on aetiology. Surgical intervention, particularly mitral valve repair, is often preferred over replacement due to its association with better outcomes. However, the benefits of repair versus replacement, especially in secondary MR, remain debated. This study aims to evaluate the long-term survival and reoperation rates in patients undergoing mitral valve repair compared to mitral valve replacement for MR in a cardiothoracic surgery unit in North-West England and in subgroups with degenerative and secondary aetiology. We analysed 1 724 consecutive patients undergoing first-time mitral valve surgery (repair: n=1 243; replacement: n=481) between 2000-2021. Primary outcome was all-cause mortality. Genetic matching and overlap weighting were used to balance baseline characteristics. Median follow-up was 7.1 years. In the matched cohort, mitral valve replacement was associated with higher rates of blood transfusion (29%vs 22%), longer ICU stays, and more strokes (3.7%vs 0.4%). While 90-day mortality did not differ significantly between groups, long-term follow-up showed a survival advantage for repair (HR: 1.32, 95% CI: 1.08-1.63). Although repair had higher reoperation rates (4.3%vs 2.1%), the composite of death or reoperation did not differ significantly. In degenerative MR subgroup, repair showed superior long-term survival, whereas in secondary MR, no significant survival difference was observed between strategies. Among patients suitable for either surgical strategy, mitral valve repair showed better long-term survival compared to replacement, particularly in degenerative MR. However, this advantage was not observed in secondary MR.

Research on Opening Reignition Characteristics and Suppression Measures of 750 kV AC Filter Circuit Breakers

The operation of converter valves in converter stations often results in high reactive power consumption and harmonic generation, necessitating measures to maintain reactive power balance and ensure power quality. To achieve this, the filter bank circuit breaker is frequently switched on and off during daily operation. In recent years, multiple incidents of circuit breaker breakdown during the opening process have been reported. In this study, power systems computer-aided design (PSCAD)/electromagnetic transients including DC (EMTDC) V5.0 electromagnetic transient simulation software is used to simulate and calculate the overvoltage and inrush current under different configurations of circuit breaker operating mechanism dispersion, opening phase angle, and operating speed. Additionally, the suppression effects of two measures are compared: “phase selection opening” and “phase selection opening combined with controlled opening speed” to mitigate overvoltage and inrush current. The results demonstrate that for BP11/13 filters, HP24/36 filters, and HP3 filters, the combined strategy of “phase-selective opening with controlled opening speed” is more effective in suppressing inrush current and overvoltage. However, for SC filters, the suppression effect of this combined strategy is not significant. Considering economic and practical factors, it is more reasonable to adopt the phase-selective opening measure for SC filters. These findings provide guidance for ensuring the safe operation of AC filter circuit breakers.