Conventional Valve Research Articles

A Power-Split Hybrid Transmission to Drive Conventional Hydraulic Valve Controlled Architectures in Off-road Vehicles:

A Power-Split Hybrid Transmission to Drive Conventional Hydraulic Valve Controlled Architectures in Off-road Vehicles:

ULTRASONIC DECALCIFICATION OF AORTIC VALVE IN MODERN ERA: A CASE REPORT

Aortic stenosis (AS) – a constantly progressing disease characterized by thickening and calcification of leaflets of the valve, which leads to obstruction of the blood outflow from the left ventricular (LV), inadequate cardiac output, heart failure, and even sudden death. Prevalence of stenosis consistently increases with age, 0.2% incidence observes in the 50–59 year cohort of patients and almost 10% in patients from the 80–89 year cohort. We report the case of a 78-year-old man who presented with severe aortic valve stenosis. Since conventional valve replacement was problematic because of a small annular diameter we performed ultrasonic aortic valve decalcification. As a result, the systolic pressure gradient across the aortic valve decreased from 106 mm Hg to 22 mm Hg. Our case demonstrated that even in modern era ultrasonic aortic valve decalcification can be an effective option for restoration of mobility of the aortic valve cusps. We advocate the use of it for elderly patients with small aortic annulus in which surgical or transcatheter valve replacement, valve reconstruction could be extremely difficult or unavailable and consider ultrasonic valve decalcification as an additional tool in cardiac surgeon’s hands.

Picoliter liquid handling at gas/liquid interface by surface and geometry control in a micro-nanofluidic device

In micro- and nanofluidic devices, highly precise fluidic control is essential. Conventional mechanical valves in microchannels and nanochannels have size limitations, whereas hydrophobic (Laplace) valves are generally difficult to use for low-surface-tension liquids. In the present study, we developed a method for handling picoliter volumes of low-surface-tension liquids in a micro-nanofluidic device. The proposed Laplace valve is based on the pinning effect. A fused silica micro-nanofluidic device that includes a picoliter chamber whose geometry was designed to induce capillary pinning was designed and fabricated. The measured Laplace pressure of a lysis buffer (surfactant) was consistent with the calculated pressure, indicating successful fabrication and hydrophobic surface modification. The working principle of the Laplace valve was verified. The Laplace valve maintained the lysis buffer at the gas/liquid interface for 60 min, which is sufficiently long for cell lysis operations. Finally, replacement of liquids in the picoliter chamber using the valve was demonstrated. The proposed method will contribute to basic technologies for fluidic control in micro- and nanofluidic devices, and the proposed Laplace valve can be used for low-surface-tension liquids. In addition, the developed valve and picoliter chamber can be utilized for the interface in single-cell lysis, which will facilitate the development of single-cell analysis devices.

Comparative Early and Long Term Results of Mitral Valve Surgery between Right Mini Thoracotomy and Full Sternotomy Approach

Background: Conventional mitral valve surgery (MVS) requires median sternotomy. Right mini thoracotomy (RMT) MVS is an alternative non sternotomy approach aiming for less bleeding, pain reduction, rapid recovery, cosmetic satisfaction, safety and effectiveness of the procedure. Objectives: To report early and late clinical results comparing RMT versus full sternotomy (FS) MVS. Materials and Methods: 574 consecutive patients underwent MVS were prospectively non randomized reviewed during January 2002 to October 2018. There were 241 in FS group and 241 in RMT group by age and Euro II score matching. Baseline characteristics were compared. Early and late clinical outcomes of 30 days mortality, reoperation for bleeding, stroke, prolonged ventilation, renal failure, permanent pacemaker, and echocardiographic hemodynamic performance were assessed and compared between two groups. All patient follow-up to December 2020. Results: Similar results were found between RMT and FS MVS groups including age 58.8+13.6, 57.2+14.2, p=0.2, new AF 5 (2%), 4 (1.7%), p=1.0), except for more degenerative valve pathology (79%, 50%, p<0.001). There were more re operation for bleeding 2 (0.8%), 1 (0.3%), p=0.9, less aortic cross clamp time (107+37.3, 115.4+36.4, p=0.017), less cardiopulmonary bypass time (157.6+51.2, 171.3+53.4, p=0.005), less bleeding and blood transfusion requirement in the RMT group. Early clinical results of 30 days mortality, stroke, renal failure, new pacemaker, and hemodynamic performance at one month, three to six month, and one year were comparable in both groups. Mean follow-up (year) was 5.2+2.5 (RMT) and 10.2+4.0 (FS). Survival probability and freedom from MACCE at ten years in RMT and FS group were 94.05%, 95.44% and 99.5%, 90.46%, p<0.001, respectively. Conclusion: RMT approach for MVS is associated with cosmetic satisfaction, less bleeding, similar effective hemodynamic performance and non-inferiority early and late clinical results to FS approach. Keywords: Mitral valve surgery; Right mini thoracotomy

Investigation of a Digital Hydraulic Valve Operated by Servo Motors

This paper describes a new type of digital hydraulic valve run by two servo motors. Digital hydraulics is a cutting-edge technology, which saves more exhausted energy than conventional hydraulic valves. It includes conventional valves, but its working principle is different. Similar or different size valves constitute a digital hydraulic valve assembly. When the assigned valves are opened, a certain amount of flow is obtained from the output of the valve assembly. To control a digital hydraulic valve, Pulse Number Modulation (PNM) Control technique is used for equal valve flow rates, while Pulse Code Modulation (PCM) is used for different valve flow rates. Valves are exerted by independently launched electric coils. Previous studies used controller board and external power booster circuits for coils. In this study, a new type of digital hydraulic valve is designed, manufactured, and tested with the PNM method. The studied valve body has two different valve groups. Every group includes 16 equal valves and 1 camshaft rotated by 1 servo motor. The servo motors are controlled by a PLC. The calculated performance index is found to be 5.1ms which is similar to the results of previous studies. The experimental results showed that the cam and servo motor controlled digital hydraulics is applicable to variable speed control hydraulic systems.

Extreme Miller cycle with high intake boost for improved efficiency and emissions in heavy-duty diesel engines

This study experimentally investigates the impact of extreme Miller cycle strategies paired with high intake manifold pressures on the combustion process, emissions, and thermal efficiency of heavy-duty diesel engines. Well-controlled experiments isolating the effect of Miller cycle strategies on the combustion process were conducted at constant engine speed and load (1160 rpm, 1.76 MPa net IMEP) on a single cylinder research engine equipped with a fully-flexible hydraulic valve train system. Late intake valve closing (LIVC) timing strategies were compared to a conventional intake valve profile under either constant cylinder composition, constant engine-out NOx emission, or constant overall turbocharger efficiency ([Formula: see text]) to investigate the operating constraints that favor Miller cycle operation over the baseline strategy. Utilizing high boost with conventional intake valve closing timing resulted in improved fuel consumption at the expense of sharp increases in peak cylinder pressures, engine-out NOx emissions, and reduced exhaust temperatures. Miller cycle without EGR at constant [Formula: see text] demonstrated LIVC strategies effectively reduce engine-out NOx emissions by up to 35%. However, Miller cycle associated with very aggressive LIVC timings led to fuel consumption penalties due to increased pumping work and exhaust enthalpy. LIVC strategies allowed for increased charge dilution at the baseline NOx constraint of 3.2 g/kWh, resulting in significant fuel consumption benefits over the baseline case without compromising exhaust temperatures or peak cylinder pressures. As Miller cycle implementation was shown to affect the boundary conditions dictating [Formula: see text], the LIVC and conventional IVC cases were studied at an equivalent [Formula: see text] point representative of high boost operation. With high boost, LIVC yielded reduced NOx emissions, reduced peak cylinder pressures, and elevated exhaust temperatures compared to the conventional IVC case without compromising fuel consumption.

Comparative study of mechanical and transcatheter heart valves for aortic valve replacement

Heart valve diseases required prompt treatments, including medication and replacement. As for aortic valve replacement, the transcatheter heart valve (THV) was recently introduced to substitute the conventional mechanical heart valve (MHV), as the former possess lower surgical risks. However, there lies concerns on the performance of THV, upon being compared to MHV.

Surgical techniques for aortic valve xenotransplantation

BackgroundHeart valve replacement in neonates and infants is one of the remaining unsolved problems in cardiac surgery because conventional valve prostheses do not grow with the children. Similarly, heart valve replacement in children and young adults with contraindications to anticoagulation remains an unsolved problem because mechanical valves are thrombogenic and bioprosthetic valves are prone to early degeneration. Therefore, there is an urgent clinical need for growing heart valve replacements that are durable without the need for anticoagulation.MethodsA human cadaver model was used to develop surgical techniques for aortic valve xenotransplantation.ResultsAortic valve xenotransplantation is technically feasible. Subcoronary implantation of the valve avoids the need for a root replacement.ConclusionAortic valve xenotransplantation is promising because the development of GTKO.hCD46.hTBM transgenic pigs has brought xenotransplantation within clinical reach.

External or subcomissural annuloplasty in bicuspid aortic valve repair: Which is better?

Patients with a bicuspid aortic valve (BAV) are at increased risk of valvular regurgitation compared to their counterparts with a tri-leaflet aortic valve. There is now increasing emphasis to offer BAV repair to mitigate the risks of prosthesis-related complications, including thromboembolism, hemorrhage and endocarditis, as well as structural valve deterioration and future reoperation with conventional valve replacement, particularly in younger populations. Furthermore, over the preceding two decades, our greater understanding of the functional anatomy of the BAV, pathophysiological mechanisms of BAV insufficiency, and the development of a functional classification of aortic regurgitation have significantly contributed to the evolution of aortic valve reconstructive surgery. In this commentary, we discuss a recent article from the Journal of Cardiac Surgery comparing external annuloplasty and subcommissural annuloplasty as techniques for BAV repair.

Modification in gate valve using flexible membrane pipe for flow measurement

A gate valve is used to regulate discharge in pipelines. It is rotated by a wheel that is attached to a circular disc (i.e. gate) at the top of a stem. Each revolution of the wheel creates a particular linear disc movement that changes the flow zone. The paper describes the journey of gate valve from flow control device to flow measuring device and presents an experimentation on conventional gate valve and gate valve with flexible membrane pipe. The findings of experimental study are described and validated with CFD analysis of conventional and modified gate valve. The experimental study has shown that the modified gate valve can be used as flow measuring device. The results obtained represent the excellent improvement in the relationship between disc position (i.e., angle) and discharge. The results of CFD analysis for flow through gate valve with and without flexible membrane are compared. After carrying out the CFD studies without flexible membrane, it is found that, fluctuating separation zones formed on either side of gate are responsible to a great extent to the flow rate descripancies. This paper compares the experimental and CFD results and also suggests the remedy to address the problem.Article highlightsIntroduced simply a flexible membrane pipe inside PVC to convert gate valve into flow measuring device.Reduction in flow separation and fluctuation in flow rate.Smooth flow rate even though gate valve opening is small.

Permanent pacemaker implantation after On-X surgical aortic valve replacement: SWEDEHEART observational study

ObjectiveBioprosthetic aortic valves with an extended subannular component, such as transcatheter valves, exert increased compression on the cardiac conduction system and increase the risk for permanent pacemaker implantation. It is...

Utility of Collagen Matrix Insertion during Ahmed Valve Implantation with Adjunctive Mitomycin-C: Outcomes at One-year

Purpose: To compare the surgical outcomes of adjunctive mitomycin-C (MMC) Ahmed valve implantation with and without collagen matrix insertion.Methods: We retrospectively reviewed 108 eyes of 108 patients who underwent Ahmed valve implant surgery with adjunctive MMC. Collagen matrix insertion/Ahmed valve implant surgery (CM-AGV) was performed on 55 eyes, while conventional Ahmed valve implant surgery (AGV) was performed on 53 eyes. We defined surgical failure as an intraocular pressure (IOP) > 18 mmHg or <5 mmHg on two or more consecutive visits, regardless of medication status.Results: After surgery, the IOP and number of topical medications required fell significantly (compared with the preoperative period) in both groups (both p < 0.001); these findings did not significantly differ between groups. The cumulative surgical success rates at 1 year did not significantly differ between groups (78.2% vs. 79.2%, p = 0.54). The only risk factor significantly associated with surgical failure was a postoperative hypertensive phase. Anterior chamber (compared with sulcus) tube placement was significantly associated with visual acuity loss at 1 year postoperatively, but this did not significantly differ between groups.Conclusions: At the 1-year follow-up after Ahmed implant surgery with adjunctive MMC, the success rates of surgery with and without collagen matrix insertion were similar.

Transcatheter Mitral Edge-to-Edge Repair in Patients with Primary or Secondary Mitral Regurgitation


 Four systematic reviews (SRs) and 6 retrospective cohort studies provided evidence for the clinical effectiveness of transcatheter mitral valve repair (TMVR) versus open heart conventional surgical mitral valve repair or replacement (SMVR) in patients with primary or secondary mitral regurgitation (MR). No relevant evidence regarding the cost-effectiveness of TMVR versus SMVR in patients with primary or secondary MR was identified; therefore, no summary can be provided.
 There was evidence indicating a statistically significant difference in favour of TMVR over SMVR regarding the odds of post-procedure bleeding, need for permanent pacemaker implantation, 30-day readmission, and a shorter duration of hospitalization.
 There was evidence suggesting a statistically significant difference in favour of SMVR over TMVR regarding the odds of recurrent MR, the need for reoperation, and mortality rate (i.e., during hospitalization, at 1 year, and > 3 years). Also, compared with TMVR, the likelihood of residual MR grade > 2 or freedom from MR grade ≥ 2 or ≥ 3 at 4 years was statistically significantly lower or higher, respectively, with SMVR.
 Evidence regarding the comparative clinical effectiveness of TMVR versus SMVR concerning stroke, acute kidney injury (AKI), cardiogenic shock, and death during hospitalization was conflicting and inconclusive.
 There was no evidence of a significant difference between the 2 interventions regarding overall mortality or mortality at 5 years, overall survival, freedom from cardiac death at 4 years, cardiac arrest, acute myocardial infarction (MI), and respiratory or vascular complications.
 A major limitation of the evidence was that it derives from studies of low or unknown quality and risk of bias, Furthermore, all the findings are confounded by differences in patient selection, which reflect the approved indications for the interventions but prevent a direct comparison between the TMVR and SMVR groups.

Auto-Pericardial Mitral Valve Implantation: A Pilot Study

Developing nations continue to grapple with rheumatic heart disease, particularly in the young. There is a need for an alternative to prosthetic mitral valve replacement in irreparable mitral valves, which avoids the need for anticoagulation and risks of thromboembolism. Twelve (12) patients with irreparable severe mitral valve disease underwent auto-pericardial mitral valve implantation from August 2020 to February 2021. The mitral valve leaflets were excised. Autologous pericardium treated with 0.5% glutaraldehyde for 8 minutes was fashioned into anterior and posterior mitral leaflets as per the dimensions on an indigenously designed template based on the studies by Ranganathan and Lam. The pericardial leaflets were sutured onto an appropriately sized mitral annuloplasty ring. The ring with the leaflets was implanted onto the mitral annulus. The leaflets were supported with neo-chordae prepared with Gore-Tex (W L Gore and Associates, Inc. Newark, DE, USA) and polyester sutures to mimic a repaired mitral valve in its structure and dynamics. The mean cross-clamp time was 138±21.7 minutes. None of the patients required re-exploration. On the third postoperative day, a mean mitral valve orifice area of 3±0.47 cm and mean mitral valve gradient of 2±1.04 were observed. None of the patients had any more than 1+ mitral regurgitation. None of them have required a re-intervention for mitral insufficiency to date. Auto-pericardial mitral valve re-implantation is a safe and effective procedure for severe, irreparable, mitral valve pathologies. However, the mid-term and long-term results need to be compared with conventional mitral valve replacement with a prosthetic valve in a randomised controlled trial.

Design of control valve with low energy consumption based on Isight platform

The pressure drop of a control valve is directly associated with the energy consumption of the control system. The conventional design method of a control valve results in high energy consumption, while the control ability deviates from the design goal. Additionally, repeated corrections via flow experiments are inefficient. To efficiently design a low-energy-consumption control valve that satisfies control requirements, a novel design method is proposed herein. It is parametrically defined in Sculptor software based on the conventional valve spool. Various software packages are integrated using script files in the Isight platform. An approximate model is constructed using sample points generated based on the design of experiments; subsequently, it is solved using an optimization algorithm. Simulation results indicate that the output pressure of the pump and the average pressure drop of the control valve decrease by 4.38% and 5.51%, respectively, under the same flow rate. The working flow characteristics curve exhibits high linearity, implying that energy conservation is realized while the control ability is improved. Moreover, the force on the valve spool decrease by 1.36% on average, while the pressure and velocity in the flow field are reduced.

Prospective evaluation of commissural alignment of balloon-expandable transcatheter heart valves utilizing pre- and post-procedure computed-tomogrpahy

Abstract Background Previous studies suggested that bioprosthetic valve commissural alignment may improve device performance and clinical outcomes in patients undergoing transcatheter aortic valve implantation (TAVI). However, no cath-lab method for correct commissural alignment of balloon-expandable valves was described to-date. Our aim is to evaluate the impact of a predefined patient specific crimped SAPIEN 3 orientation on its final implant orientation in relation to original valve commissures and overlap with coronary arteries as demonstrated by cardiac computed tomography (CT) in tricuspid aortic valve stenosis patients. Methods and results A prospective study of patients undergoing TAVI with SAPIEN 3 (Edwards Lifesciences), including post procedure cardiac CT. Patients were divided to 2 groups, a planned group in which the SAPIEN 3 was crimped before implantation in a pre-defined position, and a control group with conventional valve deployment. All patients underwent pre and post TAVI cardiac CT, which were evaluated by cardiac imaging experts that were blinded to the method of valve deployment. Twenty-eight patients were prospectively evaluated before and after TAVI with SAPIEN 3. All patients had elevated risk for open-heart surgery (age 77.6±7.9 years, 68% male, STS PROM 4.4%±3.4%). Fifteen patients were included in the active alignment group vs. thirteen patients in the control. Patients in the active alignment group had a trend for more correct commissural alignment (73.3% vs. 38.5%, p=0.06). There was no statistically significant difference in patient characteristics, echocardiographic measures or in anatomical CT features between the active commissural alignment and control groups. Conclusion This is probably the first study that shows that patient-specific initial crimped orientation of balloon-expandable TAVI may improve our ability to have correct commissural alignment of the implanted valve. Our prospective study continues to recruit patients and updated study results will be presented. Funding Acknowledgement Type of funding sources: None.

401 Conventional Aortic Valves Versus Rapidly Deployed Valves in The Elderly Population. A Comparative Study in A Single Centre Experience

Abstract Aim Current recommendations favour TAVI over Surgical Aortic valve replacement (SAVR) for patients aged>75 years. However, in current practice a significant proportion of patients in this group are offered SAVR. Rapidly deployed valves are of increasing popularity among surgeons as they shorten the procedure time, but their benefits are yet to be investigated. Method Patients aged >75 years undergoing Aortic valve replacement with or without any concomitant procedure were included between January 2014 and January 2020 (total: 597). Patients were divided into two groups: Group A (495 patients) conventional Aortic valve and Group2 (102 patients) rapidly deployed valve. Results Preoperative variables including mean age, EuroScore II, and body mass index were of no statistical significance between the two groups. More females and Octogenarians were in the rapidly deployed valve group versus the conventional valve group, respectively. Bypass time and Cross-clamp times were shorter in rapidly deployed group. However, the length of ICU and hospital stay was not significant between the two groups. Early post-operative pacemaker implantation (Conventional 2% Vs RDV 7%) (P < 0.05) differed significantly between groups. At follow up echocardiography, pressure gradients were comparable between groups. Thirty-day mortality and valve-related complications were insignificant. Conclusions RDVs show comparable early and medium-term outcomes and valve hemodynamics. RDVs are associated with shortened operative time and cross-clamp time but may carry an increased risk of need for permanent pacing.

Minimally Invasive versus Conventional Mitral Valve Surgery: Procedures and Early Outcomes

Background: Minimal invasive mitral valve surgery gained wide acceptance. However, criticism continuous about its ability to replace the conventional full sternotomy technique.Aim of the work: The study aimed to compare between the full sternotomy and less invasive approaches for mitral valve surgery.Patients and Methods: The study recruited 100 patients. They were allocated to one of two equal groups [the traditional and minimal invasive approach]. All patients were thoroughly evaluated by history taking, physical examination, laboratory and ancillary radiological investigations. Assessment included incision length, weaning events, aortic cross clamp time, total bypass and operative times, rate of conversion from minimally invasive technique to full sternotomy. In surgical intensive care unit, ventilation hours, post-operative pain and need for analgesia, re-exploration for bleeding, blood loss and blood transfusion, and any complications were documented.Results: Preoperative New York Heart Association [NYHA] class was significantly different between groups A and B. But, no significant difference was reported for patient demographic or preoperative data. The incision length and cross clamp time was shorter in A than B group [6.56±1.88 cm, 61.78±35.91 minutes’ vs 12.54±1.78 cm, and 78.08±36.24 minutes, respectively]. Otherwise, the cannulation, bypass, operative times were significantly longer among group A. The ventilation, ICU stay, hospital stay, bleeding, serum creatinine and pain scores were significantly lower among group A. the postoperative events were comparable between both groups with slight increase of neurological events in A group [3 cases] than B group [2 cases]. At 6 months, both groups yielded non-significant difference, regardless of better outcome at direct postoperative time.Conclusion: Minimal invasive mitral valve surgery had a good short and mid-term outcome as the conventional sternotomy approach. It could replace the conventional approach as a gold-standard for mitral valve surgery.

Effects of variable valve timing on the air flow parameters in an electromechanical valve mechanism – A cfd study

In this study, volumetric efficiency, air flow rates, and cylinder pressure values were experimentally determined for a single-cylinder spark-ignition engine having conventional camshafts. Cold flow analysis was carried out using the computational fluid dynamics (CFD) method with importing combustion chamber and flow volumes of the suction and exhaust ports of the engine. After validating analyzes results with experimental data for different revolutions (RPMs), analyses were repeated using electromechanical valve mechanism (EMV) cam profiles. In the case of using EMV, advancing the intake valve opening time and advancing and retarding exhaust valve closing were simulated with CFD software. Simulations where different cam profiles were used for each revolution, volumetric efficiency, in-cylinder pressure, swirl and tumble ratio, in-cylinder total mass, and air flow rates in the cylinder were investigated numerically. As a result of the obtained data, it was seen that the use of EMV at low RPMs caused a decrease in the volumetric efficiency according to the conventional camshaft valve lifting amount and timing and it caused an increase in the volumetric efficiency at high RPMs. According to the results, it was understood that the effect of intake valve closing time is important on volumetric efficiency. Additionally, this study shows that the swirl ratio is significantly affected by EMV system.

Performance enhancement and multi-objective optimization of a double-flash binary geothermal power plant

Initiating cost-effective and technological frameworks to exploit geothermal energy is a fundamental incentive for scientists and engineers; in this regard, flash-binary geothermal power plants are plausible for high-temperature geothermal resources. Stemming from an in-depth literature review, it is conspicuous that the thermal and exergy losses of the expansion process are significant. To shed light on this matter, an ejector-expander is integrated into the conventional expansion valve of a double-flash binary geothermal power plant to enhance the plant performance. The feasibility of the contrived notion is scrutinized from energy, exergy, thermal, and cost balance standpoints and results converged in the increase in turbine output power, energy efficiency, and exergy efficiency of approximately 7.66%, 7.64%, and 7.69%, respectively. Among all components, the condenser constituted a 45.06% share of the overall exergy destruction, whilst the turbine had an exergy destruction ratio of 22.07%. An intensive parametric study is implemented that outlined that the turbine output power, energy efficiency, and exergy efficiency of the ejector-expander power system have a maximum in a specified pressure value of the first and second separator. Another merit was a marked decrease in the unit cost of power when ejector-expander is employed.