Valve Surgery Research Articles

Fluid-structure interaction simulation of the three-leaflet aortic valve using COMSOL

The simulation of the aortic valve (AV) remains challenging due to its geometric complexity and the multi-physics nature of the problem. In this study, we utilized COMSOL to establish a three-dimensional, three-leaflet AV fluid-structure interaction model and investigated the influence of material properties on the valve's mechanical behavior in a healthy state. The results indicated that variations in the aortic wall material model had a minor impact on AV hemodynamics. Additionally, while the linear elastic properties of the leaflets limit valve opening and closing, this material model allows for rapid assessment of AV performance within the range of material deformation.

Analysis of Echocardiography Indicators Depending on the Type of Surgical Correction of the Mitral Valve in Patients with Ischemic Heart Disease

The aim. To study the influence of echocardiography indicators on the choice of surgical intervention on the mitral valve in patients with mitral insufficiency and coronary heart disease. Materials and methods. The study included patients with mitral insufficiency who underwent myocardial revascularization and mitral valve reconstruction (plasty or replacement). The mean age of the study participants was 65.9 ± 4.0 years. The material for analysis was data from the primary medical records: medical history, clinical and instrumental examination data and protocols of operations. The division into study groups was performed retrospectively, according to the mitral valve operation performed: plasty (experimental group) or replacement (control group). Results. We identified the features of the main echocardiographic data that guide the cardiologist when choosing the tactics of surgical correction of the mitral valve. It was established that in patients of the research group, the following was reliably significant: moderate degree of mitral insufficiency (p = 0.02; χ2 = 9.38), decrease in the systolic function of the left ventricle (p = 0.001; χ2 = 10.75); it was found that calcium deposits on the fibrous ring of the mitral valve were insignificant. When analyzing the morphological changes in patients of the experimental group, we found a significantly lower frequency of anterior leaflet prolapse (p = 0.04; χ2 = 4.21) and in general the frequency of all prolapses of any type, while in the control group the frequency of all prolapses was significantly higher (p = 0.04; χ2 = 4.0). In patients of the control group, a significantly higher frequency of akinesis (p = 0.04; χ2 = 4.21) and hypokinesis zones of the posterior-inferior-lateral wall (p = 0.001; χ2 = 19.76) was established, which is an additional sign of involvement of the chordal-muscular apparatus of the mitral valve in pathological process. Conclusions. As a result of the study, echocardiographic differences in the structure of the mitral valve were established, which influenced the selection of the intervention volume. It was found that in patients of the experimental group, the early postoperative mortality and the duration of inpatient treatment were significantly higher than in patients of the control group, which indicates the imperfection of the criteria used by cardiac surgeons when choosing the tactics of surgical correction of the mitral valve in an attempt to perform organ-preserving surgery.

Experimental investigation of online solving for critical valve opening for eliminating severe slugging in pipeline-riser systems

In an offshore pipeline-riser system, the critical opening of choke valve, i.e., the maximum permanent opening to eradicate severe slugging, plays an important role in both pipeline design and offshore oil and gas production processes. However, solving critical opening online in an offshore oil field is very difficult because only topside measurements are available and system information such as inlet gas–liquid flow rates and transfer functions are unavailable or far from precise. In order to cope with this problem, manually traversal experiments were first conducted in a large-scale experimental system consists of a 114-m horizontal pipeline, an 18.7-m downward-inclined pipeline with an inclination angle of −5˚ and a 16.3-m riser. Based on the results, a new process variable characterizing cut-off ratio of outflow and a new valve parameter describing the influence of valve on flow were derived. An approximate linear relation between these two parameters was found, with which critical openings can be calculated by processing real-time data. Finally, a control scheme was designed to overcome the calculation errors and solve for critical openings on line. The performance was validated by automatic control experiments.

Relationship between Preoperative Red Cell Distribution Width and Prolonged Postoperative Use of Catecholamines in Minimally Invasive Mitral Valve Surgery Patients: A Retrospective Cohort Study.

Background/Objectives: Elevated RDW has emerged in cardiac surgery as a potential means of preoperative risk stratification with the capacity to predict short- and long-term postoperative mortality, acute kidney injury, and postoperative atrial fibrillation. The question as to whether perioperative hemodynamic instability may be predicted by such a marker remains a topic of ongoing debate. The aim of this study was to explore the relationship between preoperative RDW and prolonged postoperative catecholamine use in minimally invasive mitral valve surgery. Methods: We performed a retrospective monocentric cohort study in an academic hospital; we enrolled patients who had undergone minimally invasive mitral valve surgery (including both robot-assisted and non-robot-assisted procedures) between January 2019 and December 2022. We considered the use of inotropes and/or vasopressors for at least twelve hours after post-surgery ICU admission to qualify as the prolonged postoperative use of catecholamines (PPUC). The RDW was obtained from the routine full blood count analysis performed upon admission or a maximum of 72 h before surgery. We also performed a multivariable logistic regression analysis with PPUC as the dependent variable. Results: We finally enrolled 343 patients. Upon multivariate analysis, RDW >14.4% was independently associated with prolonged postoperative catecholamine use when compared to the reference group (OR 2.62 [1.06-4.84]; p = 0.03). Moreover, the EuroSCORE II score (OR 1.38 [1.03-1.85]; p = 0.03), the cross-clamp time (OR 1.01 [1.01-1.02]; p < 0.01), and robot-assisted mitral valve surgery (OR 0.53 [0.30-0.93]; p < 0.03) were independently associated with the prolonged postoperative use of catecholamines. Conclusions: This study identified that an elevated preoperative RDW (>14.4%), the EuroSCORE II score, and the cross-clamp time independently predict prolonged postoperative catecholamine use in minimally invasive mitral valve surgery patients. Conversely, the robot-assisted approach was associated with a smaller hemodynamic impairment.

A comparative analysis of the accuracy of cardiac surgery risk scores in tricuspid valve procedures undertaken in the republic of Georgia

Background: Tricuspid valve (TV) surgeries present significant challenges marked by elevated risk and mortality rates. Despite the application of established risk scores like ACEF-II, EuroSCORE-II, and Hannan EL et al's risk stratification (HRS), their accuracy in predicting mortality rates for these procedures in a third-world setting remains under-researched. This study sought to assess the predictive performance and overall accuracy of these risk scores in the context of TV surgeries performed in the Republic of Georgia. Methods: A cohort of 63 patients who underwent TV procedures was retrospectively analyzed. ACEF-II, EuroSCORE-II, and HRS were applied and run through statistical analysis to assess their predictive capabilities. Results: ACEF-II demonstrated an accuracy rate of 58.7%, an area under the curve (AUC) of 0.819, and an expected-to-observed mortality ratio of 0.16. EuroSCORE-II exhibited an accuracy rate of 61.9%, an AUC of 0.866, and an expected-to-observed mortality ratio of 0.17. The HRS demonstrated an accuracy rate of 65.1%, an AUC of 0.882, and an expected-to-observed mortality ratio of 0.35. Conclusion: While the risk scores show promise, our study highlights their limitations in accurately predicting mortality rates of TV surgeries by underestimating them and emphasizes the need for refinement or the development of risk scores tailored specifically to TV procedures in third-world countries.

Preoperative fibrinogen level predicts the risk and prognosis of patients with native valve infective endocarditis undergoing valve surgery.

The aim of this study was to assess the clinical significance and prognostic value of the preoperative fibrinogen (FBG) level in patients with native valve infective endocarditis (NVIE) who underwent valve surgery. This retrospective study included a total of 163 consecutive patients who were diagnosed with NVIE and underwent valve surgery from January 2019 to January 2022 in our hospital. The primary endpoint was all-cause mortality. All-cause mortality was observed in 9.2% of the patients (n = 15). Body mass index (BMI) was lower in the survival group (p = 0.025), whereas FBG (p = 0.008) and platelet count (p = 0.044) were significantly greater in the survival group than in the death group. Multivariate Cox proportional hazards analysis revealed that FBG (HR, 0.55; 95% CI, [0.32-0.94]; p = 0.029) was an independent prognostic factor for all-cause mortality. Furthermore, Kaplan‒Meier survival curve analysis revealed that patients with low FBG levels (<3.28 g/L) had a significantly greater mortality rate (p = 0.034) than did those with high FBG levels (>3.99 g/L). In the trend analysis, the FBG tertiles were significantly related to all-cause mortality in all three adjusted models, and the p values for trend were 0.017, 0.016, and 0.028, respectively. Preoperative FBG may serve as a prognostic factor for all-cause mortality, and an FBG concentration less than 3.28 g/L was associated with a greater risk of all-cause mortality in NVIE patients undergoing valve surgery.

Novel Retractor–Camera System Facilitates Less Traumatic Minimally Invasive Procedures and Declutters the Operation Field

Objective: To develop a novel endoscopic system that reduces trauma to the patient and declutters the surgical field for the surgeon in minimally invasive heart valve surgery. Methods: We designed and developed a retractor–camera combination for minimally invasive heart surgery; the cable and camera were connected to the underbelly of the left atrial retractor blade to provide an illuminated, wide-angle view of the mitral valve. We conducted ex vivo, in vivo, and, ultimately, a first-in-man randomized, nonanonymized clinical trial on 20 patients who required minimally invasive mitral valve surgery. Data from the preoperative period and the immediate postoperative period were gathered, and patients were followed for 3 months. Results: Our camera–retractor combo demonstrated safe and efficient exposure and vision in all detailed studies. The total operation time for the intervention group (316.5 ± 65.1 min) was slightly shorter than for the control group (317.5 ± 50.8 min). There was no significant difference in the ability to provide exposure of the mitral valve and surrounding left atrial tissue for both control and test articles. The novel camera–retractor reduced clutter in the operation field substantially and eliminated chest penetration for the camera. We also observed that the camera did not fog, did not stain with blood, and did not require frequent corrections to its position. Conclusions: We launch a novel atrial retraction–imaging platform that is less invasive for the patient and eliminates clutter and redundant movements for the surgeon.

Optimization and analysis of the inflow distribution influence on the middle discharge blow tank pneumatic conveying characteristics

The influence of different inflow gas distribution modes on the pneumatic conveying characteristics of the middle discharge blow tank was studied using an in-house pneumatic conveying experimental setup. The flow rates of pressurized gas, supplementary gas, and fluidized gas were varied in this study. The gas distribution mode was then optimized to improve the energy efficiency of the blow tank of a pneumatic conveying system. The results show that the particle mass flow rate, the solid-to-gas ratio, and the pressure drop increase first and then decrease with the pressurized gas and fluidized gas valves opening. In the case of supplementary gas, the particle mass flow rate and solid-to-gas ratio increase first and then decrease. However, an opposite trend is observed for the pressure drop, which decreases first and then increases. The results highlighted that the optimized gas distribution mode increases the mass flow rate of particles and the solid-to-gas ratio by 28.48% and 15.15%, respectively. The pressure drop of the blow tank has also increased slightly, by 0.88%. Therefore, the delivery capacity and efficiency of the middle discharge blow tank are greatly improved at the cost of a slight increase in energy consumption.

Adults who Smoke Should Have Pulmonary Function Testing Before and After Coronary Artery Bypass Grafting (CABG)

Background: Recent research has shown that coronary artery bypass grafting (CABG) has a mortality rate of 0.6–3.0%, making it a popular and generally safe cardiac operation. The purpose of this study is to examine the relationship between sex, age, and diabetes in the early changes in lung volumes measured by pulmonary function tests before and after coronary artery bypass grafting (CABG) in individuals who smoke. Subjects and procedures: Elective coronary artery bypass surgery was the procedure of choice for 200 consecutive patients in this prospective controlled trial. Participants who were not part of the trial were those who were in an emergency or who had a valve operation done alongside a CABG procedure. Based on the data from the operation, the cardiopulmonary bypass time was 98.89 minutes with a standard deviation of 25.14 minutes. The average time for cardiac ischemia was 67.8 minutes with a standard deviation of 26.6 minutes and a range of 25 to 227 minutes. The total time spent in the intensive care unit was 53.54 hours with a standard deviation of 27.98 hours and a range of 4 to 102 hours. Thirteen patients, or 6.5%, were cold, while the remaining patients were warm. Thirteen patients, or 6.5%, used ice slush as a topical cooling method. The results of the pulmonary function tests taken before and after surgery were significantly different. Conclusion: Postoperative obstructive and restrictive breathing problems are associated with cigarette smoking's detrimental effects on pulmonary functioning. Patients with a smoking history who are scheduled for elective revascularization surgery should have their pulmonary status evaluated before surgery, and they should be strongly encouraged to quit smoking as soon as possible before surgery to minimize the risk of respiratory complications after surgery.

Impact of multidisciplinary Endocarditis Team on management of infective endocarditis

Infective Endocarditis (IE) is a complex, life-threatening disease. The aim of the present study was to evaluate the impact of the Endocarditis-Team on management of IE. This observational study conducted at a university hospital (2015‒22), included adult patients with IE. The study period was divided in two periods: before (pre-Endocarditis-Team; pre-ET) and after the establishment of the Endocarditis-Team (post-Endocarditis-Team; post-ET) on January 2018. Among 505 IE episodes (187 in pre-Endocarditis-Team, 318 in post-ET period), 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography was more commonly used in post-ET period (14 % vs. 28 %; p < 0.001). Overall, thirty-day and one-year mortality were 14 % and 27 %, respectively; no difference was observed between the two periods. In post-ET period, the administration of 4-weeks, rather than 6-weeks, of intravenous antimicrobial treatment was higher than in the post-ET period (15 % vs. 45 %; p < 0.001). Indication for surgery was present in 115 (61 %) patients in pre-ET and in 153 (48 %) in the post-ET period. In post-ET period, among patients with indication, valve surgery was more frequently performed (66 % vs. 78 %; p = 0.038). Such difference was due to a higher acceptance of operative indication by the cardiac surgeon (69 % vs. 94 %; p = 0.013). The observed increase in number of patients benefiting from cardiac surgery in the post-ET period led to a decrease of subsequent embolic events, since among patients with operative indication (n = 268), new embolic events after the establishment of the indication were more common in the pre-ET period compared to post-ET (23 % vs. 12 %; p = 0.033). After the implementation of the multidisciplinary Endocarditis-Team we observed several improvements in the general management of IE patients.

Simultaneous beating-heart mitral valve replacement and aortic repair following Bentall procedure via double right mini-thoracotomies: a case report

BackgroundRedo mitral valve surgery by re-sternotomy approach has challenges such as bleeding and organ injury due to adhesion dissection, sternal bone infection, and poor field of view of mitral valve. On the other hand, redo mitral valve surgery via a right mini-thoracotomy approach appears to address these challenges. We successfully performed a double right mini-thoracotomies approach for mitral valve replacement and pseudoaneurysm repair under the beating-heart condition. Herein, we report the effectiveness and the safety of this technique and detailed procedure.Case presentation.The patient is a 71-year-old man with a history of Bentall procedure using a mechanical valve at another hospital 30 years ago. He developed acute heart failure due to severe mitral valve regurgitation. After medication, he was referred to our department for the purpose of surgery for mitral valve regurgitation. Preoperative transesophageal echocardiography showed extensive degenerative change of the both leaflets and chordae tendineae rupture at the P3 segment. Both left atrium and ventricle dilated, and left ventricle contractility reduced. Aortic mechanical valve had no problem. In addition, preoperative contrast enhanced computed tomography revealed a pseudoaneurysm at the distal anastomotic site of Bentall procedure. We performed mitral valve replacement by mechanical valve and repair of distal anastomotic cite under beating heart condition, utilizing a double right mini-thoracotomies approach for mitral valve and ascending aortic pseudoaneurysm respectively. The postoperative course was uneventful, the patient was discharged without complications.ConclusionThe right mini-thoracotomies approach efficiently accessed mitral valve and ascending aorta in reoperations, reducing the adhesion dissection risks and ensuring clear exposure. Moreover, concomitant use of beating-heart technique minimized adhesion dissection for aortic cross-clamp, preserved cardiac function.

Sutureless Aortic Prosthesis Valves versus Transcatheter Aortic Valve Implantation in Intermediate Risk Patients with Severe Aortic Stenosis: A Literature Review.

Aortic stenosis remains the most frequently occurring valvular pathology in the elderly population of Western countries. According to the latest guidelines, the therapeutic choice of aortic stenosis depends on the age of the patient (<75 years or >75 years) and the risk class (STS-Prom/Euroscore II < o >4%). Therefore, if the surgical indication is clear in young and low-risk patients and percutaneous treatment is the gold standard in older and high-risk patients, the therapeutic choice is still debated in intermediate-risk patients. In this group of patients, aortic valve stenosis treatment depends on the patient's global evaluation, the experience of the center, and, no less importantly, the patient's will. Two main therapeutic options are debated: surgical aortic valve replacement with sutureless prosthesis versus transcatheter aortic valve implantation. In addition, the progressive development of mininvasive techniques for aortic valve surgery (right-anterior minithoracotomy) has also reduced the peri- and post-operative risk in this group of patients. The purpose of this review is to compare sutureless aortic valve replacement (SuAVR) versus TAVI in intermediate-risk patients with severe aortic stenosis.

Analysis of predictive factors for late recurrence of atrial fibrillation after surgical ablation in patients undergoing rheumatic valve surgery

ObjectivesTo identify independent predictors of late recurrence of atrial fibrillation (AF) after surgical ablation in patients undergoing rheumatic valve surgery.MethodsA total of 258 patients who underwent surgical ablation for AF with rheumatic heart disease at our hospital between January 2019 and June 2022 were retrospectively included. The patients were followed up for 12 months. Late recurrence was defined as any AF recurrence longer than 30 s between 3 and 12 months. Patients with or without late recurrence were divided into non-recurrence and recurrence groups. Univariate and multivariate analyses were performed to identify the predictors of late recurrence.ResultsThe in-hospital mortality rate was 0.8% (2/258), and the late recurrence rate of AF was 38.4%, including 152 and 95 cases in the non-recurrent and recurrent groups respectively, with a follow-up completion rate of 96.5% (247/256). There were no deaths during follow-up, two patients (0.8%) experienced a stroke, and one patient (0.4%) experienced gastrointestinal hemorrhage. The results of the univariate and multivariate analyses of the preoperative risk factors for late recurrence showed a left atrial (LA) anteroposterior diameter ≥ 52.9 mm (odds ratio [OR] = 2.366, 95% confidence interval [CI] = 1.089–5.138, P = 0.030], ratio of the superoinferior to the anteroposterior diameters of LA (S-AR) < 1.19 (OR = 4.639, 95% CI = 2.181–9.865, P < 0.001), and AF duration ≥ 39 months (OR = 6.152, 95% CI = 2.897–13.061, P < 0.001), and cardiothoracic ratio ≥ 0.63 (OR = 2.716, 95% CI = 1.314–5.612, P = 0.007) were the most significant independent risk factors.ConclusionsLA anteroposterior diameter ≥ 52.9 mm, S-AR < 1.19, and AF duration ≥ 36 months and cardiothoracic ratio ≥ 0.63 are independent predictors for late recurrence of AF after surgical ablation in patients undergoing rheumatic valve surgery.

Variation of Seismocardiogram-Derived Cardiac Time Intervals and Heart Rate Variability Metrics Across the Sternum

Abstract Cardiac time intervals (CTIs) are vital indicators of cardiac health and can be noninvasively assessed using a combination of electrocardiography (ECG) and seismocardiography (SCG), a method of capturing cardiac-induced chest vibrations via accelerometers. SCG signals can be measured from different chest locations. However, more investigations are needed to evaluate the impact of sensor placement on SCG-derived cardiac parameters. This study investigates the effect of accelerometer placement along the sternum on SCG-derived CTI estimations and heart rate variability (HRV) parameters. A semi-automated algorithm was developed to detect SCG fiducial points and seven CTIs from thirteen healthy individuals. Comparative analysis with manually selected peaks and gold-standard ECG was conducted to assess fiducial point detection accuracy. Results indicate the highest recall and precision in aortic valve opening (0.84–1.00 and 0.96–1.00, respectively) and mitral valve closure (0.77–1.00 and 0.93–1.00, respectively) detection. Aortic valve closure (0.43–1.00 and 0.61–1.00, respectively) and mitral valve opening (0.64–1.00 and 0.91–1.00, respectively) detection, although slightly less accurate due to signal intensity variations, demonstrated overall effectiveness compared to manually selected peaks. Furthermore, SCG-derived heart rates showed a high correlation coefficient (r &amp;gt; 0.9) with the gold-standard ECG heart rates. Single-factor ANOVA revealed significant differences (p &amp;lt; 0.05) in SCG-derived CTI estimations based on sensor locations on the sternum, highlighting the importance of sensor placement for accurate assessments.

Unsteady aerodynamic interaction in regulated two-stage radial turbine at pulsating conditions

Regulated multi-stage turbocharging is an indispensable technology to achieve high boosting pressure and hence power recovery for High-Altitude Long-Endurance Unmanned Aerial Vehicle (HALE UAV). Inevitably, unsteady interstage coupling has become a key factor restricting the pursuit of higher aerodynamic performance in multi-stage turbochargers. This study is to investigate the unsteady gasdynamic behavior of two-stage radial turbines and aimed to obtained the knowledge of unsteady aerodynamic interaction at pulsating conditions. Results reveal an obvious difference in the performance discrepancy mechanisms of high-pressure turbine (HPT) and low-pressure turbine (LPT). HPT shows more unsteady than that of LPT according to the discussion on mass accumulation and local temporal gradient. Furthermore, this unsteadiness is drastically enhanced when the valve is open. For HPT with open valve, a sharp reduction of up to 10.7% in the cycle-averaged efficiency is observed. Both the volute and the rotor are the main components causing the deterioration of efficiency. Swirling flow precession leads to a dramatically loss generation in the volute. Leading-edge separation and tip leakage flow are the dominated factors in rotor. The former is primarily attributed to inlet swirling flow and the latter is predominantly attributed to the pulsating effect. For LPT, the performance is not sensitive to the valve state, with no more than 3% discrepancy on efficiency. At specific velocity ratio, the negative swirling flow tends to exert a positive effect to the rotor efficiency, whereas the positive swirling flow leads to a higher entropy generation in rotor passage.

Water hammer protection of one-way surge tanks considering the effect of check valve

ABSTRACT One-way surge tanks are commonly employed as water hammer protection devices. However, the action process of the check valve is often disregarded in the design of protective measure. In this study, a one-way surge tank model incorporating a check valve was developed based on the method of characteristics. The check valve action process and different installation positions for one-way surge tanks were investigated based on an actual water supply project. The results show that, compared with the existing one-way surge tank mathematical model, the pipeline pressure calculated by the new model is smaller and the water replenishment is slower, which means that there is a safety risk based on the calculation results of the existing model. As the opening process of the check valve slows down, the pipeline minimum pressure is reduced. When the valve opening rate reaches 0.5 s, negative pressure appears in the pipeline. In addition, for undulated terrain with two obvious high points, when the first one-way surge tank is installed at the node behind the pump, the second one should be installed at the highest point to ensure that the pipeline pressure is greater than 0 m.

Influence of variable enhanced LIVC miller cycle coupled with high compression ratio on the performance and combustion of a supercharged spark ignition engine

A novel variable enhanced late intake valve closing (LIVC) Miller cycle with asynchronous valve opening was proposed. Relevant tests were carried out in a supercharged spark ignition (SI) engine with high compression ratio, which mainly included the effects of variable valve timing on performance and combustion characteristics, as well as the comparison with the baseline engine. The purpose of this study was to explore the effect of different intake and exhaust opening timing on the performance and combustion characteristics of the enhanced LIVC Miller cycle with asynchronous valve opening, and further explore the energy saving potential of this Miller cycle. The results showed that the application of variable enhanced Miller cycle effectively improved the anti-knock ability and pumping loss of the engine with high compression ratio. On the one hand, the optimization of pumping loss substantially improved the fuel economy under small load conditions. On the other hand, better combustion performance and air-fuel ratio could be achieved at medium and high loads. Meanwhile, the exhaust valve should be opened as earlier as possible to achieve the best fuel economy. Correspondingly, under optimal valve timing, compared with the baseline engine, the asynchronous intake valve opening variable enhanced Miller cycle engine with high compression ratio had a fuel economy optimization of more than 3.5 % under all loads, and the maximum fuel economy optimization was 12.74 % under the condition of 11 bar.

Results of surgical treatment of aortic stenosis in patients with a narrow aortic root after Ozaki surgery and bioprosthetics: A retrospective single-center study

BACKGROUND: Aortic stenosis (AS) itself is a common disease in patients of older populations, and its combination with a narrow aortic root puts the surgeon in front of choosing the most optimal option. The advantages of Ozaki's operation include hemodynamics close to the native aortic valve (AV) and the absence of the need for lifelong anticoagulant therapy. AIM: To evaluate the hospital and long-term results of surgical treatment of patients with AS and a narrow fibrous ring who underwent Ozaki surgery or AV prosthetics with a biological prosthesis. MATERIALS AND METHODS: In total, 836 isolated Ozaki operations or combined interventions of this kind were performed at the Federal Center for Cardiovascular Surgery (Penza). This retrospective single-center study included 150 patients with critical AC (effective opening area ≤1 cm2) in whose surgical treatment tactics Ozaki surgery or prosthetics with a biological prosthesis were used. RESULTS: In the early postoperative period, group 1 patients had significantly lower values of the average and maximum gradients on the aortic valve and a larger area of the effective opening of the aortic valve. Also, in group 1 patients, the postoperative period of stay in intensive care is significantly higher, which is a consequence of the longer duration of the operation, the time of artificial circulation and myocardial ischemia. Long-term mortality is higher in the group with prosthetics of AV (Log Rank=0.006). Freedom from re-operation according to the analysis, there was no significant difference between the groups (Log Rank=0.226). CONCLUSION: Ozaki surgery demonstrates the best hemodynamic characteristics on AV in comparison with a biological prosthesis in patients with a narrow fibrous ring of AV in the early and long-term follow-up periods.

Physiological control for left ventricular assist devices based on deep reinforcement learning.

The improvement of controllers of left ventricular assist device (LVAD) technology supporting heart failure (HF) patients has enormous impact, given the high prevalence and mortality of HF in the population. The use of reinforcement learning for control applications in LVAD remains minimally explored. This work introduces a preload-based deep reinforcement learning control for LVAD based on the proximal policy optimization algorithm. The deep reinforcement learning control is built upon data derived from a deterministic high-fidelity cardiorespiratory simulator exposed to variations of total blood volume, heart rate, systemic vascular resistance, pulmonary vascular resistance, right ventricular end-systolic elastance, and left ventricular end-systolic elastance, to replicate realistic inter- and intra-patient variability of patients with a severe HF supported by LVAD. The deep reinforcement learning control obtained in this work is trained to avoid ventricular suction and allow aortic valve opening by using left ventricular pressure signals: end-diastolic pressure, maximum pressure in the left ventricle (LV), and maximum pressure in the aorta. The results show controller obtained in this work, compared to the constant speed LVAD alternative, assures a more stable end-diastolic volume (EDV), with a standard deviation of 5 mL and 9 mL, respectively, and a higher degree of aortic flow, with an average flow of 1.1 L/min and 0.9 L/min, respectively. This work implements a deep reinforcement learning controller in a high-fidelity cardiorespiratory simulator, resulting in increases of flow through the aortic valve and increases of EDV stability, when compared to a constant speed LVAD strategy.

Enhancing efficiency of large cold store refrigeration systems through automated fault identification and intelligent energy optimization

Refrigeration systems in large cold stores frequently operate suboptimally due to component faults, leading to significant energy wastage and high carbon emissions. This study introduces a novel procedure that leverages data mining to automatically analyze and identify faults, thereby enhancing the intelligence of refrigeration equipment. The research focused on abnormal suction temperatures of compressors during the defrosting of air coolers in a large cold store. Through theoretical analysis and key data acquisition, the root cause of defrosting issues was traced to the abnormal operation of gas-powered suction stop valves, causing leakage of high-pressure hot gas. Clustering methods, Self-Organizing Maps (SOM), were utilized to classify system states and achieved high accuracy rates of 88.6 % to 93.8 % for the three fault modes during the defrosting process, respectively. The resolution of defrosting faults resulted in an energy consumption reduction of up to 18.3 %, aligning with global sustainability initiatives. The study also evaluated the carbon emission reduction, providing a comprehensive approach to improving the efficiency and environmental impact of cold store operations.