Valve Type Research Articles

Simultaneous Aortic and Pulmonary Valve Replacement in Repaired Congenital Heart Disease.

Patients with congenital heart disease frequently require surgical or percutaneous interventional valve replacement after initial congenital heart defect (CHD) repair. In some of these patients, simultaneous replacement of both semilunar valves is necessary, resulting in increased procedural complexity, morbidity, and mortality. In this study, we analyze the outcomes of simultaneous aortic and pulmonary valve replacements following multiple surgical interventions for CHD. This was a retrospective study of 24 patients who after initial repair of CHD underwent single-stage aortic and pulmonary valve replacement at our institution between 2003 and 2021. The mean age of the patients was 28 ± 13 years; the mean time since the last surgery was 15 ± 11 years. Decellularized valved homografts (DVHs) were used in nine patients, and mechanical valves were implanted in seven others. In eight patients, DVHs, biological, and mechanical valves were implanted in various combinations. The mean cardiopulmonary bypass time was 303 ± 104 minutes, and aortic cross-clamp time was 152 ± 73 minutes. Two patients died at 12 and 16 days postoperatively. At a maximum follow-up time of 17 years (mean 7 ± 5 years), 95% of the surviving patients were categorized as New York Heart Association heart failure class I. Single-stage aortic and pulmonary valve replacement after initial repair of CHD remains challenging with substantial perioperative mortality (8.3%). Nevertheless, long-term survival and clinical status at the latest follow-up were excellent. The valve type had no relevant impact on the postoperative course. The selection of the valves for implantation should take into account operation-specific factors-in particular reoperability-as well as the patients' wishes.

Direct oral anticoagulants versus vitamin K antagonists in the first 3 months after bioprosthetic valve replacement: a systematic review and meta-analysis.

We conducted a systematic review and meta-analysis of randomized controlled trials comparing direct oral anticoagulants (DOACs) to vitamin K antagonists (VKAs) in the first 90 days after bioprosthetic valve implantation. We systematically searched Embase, Medline and CENTRAL. We screened titles, abstracts and full texts, extracted data and assessed the risk of bias in duplicate. We pooled data using the Mantel-Haenzel method and random effects modelling. We conducted subgroup analyses based on the type of valve (transcatheter versus surgical) and timing of initiation of anticoagulation (<7 vs >7 days after valve implantation). We assessed the certainty of evidence using the Grading of Recommendations, Assessments, Development and Evaluation approach. We included 4 studies of 2284 patients with a median follow-up of 12 months. Two studies examined transcatheter valves (1877/2284 = 83%) and 2 examined surgical valves (407/2284 = 17%). We found no statistically significant differences between DOACs and VKAs with regard to thrombosis, bleeding, death or subclinical valve thrombosis. However, there was a subgroup trend towards more bleeding with DOACs when initiated within 7 days of valve implantation. In the existing randomized literature on DOACs versus VKAs in the first 90 days after bioprosthetic valve implantation, there appears to be no difference with regard to thrombosis, bleeding or death. Interpretation of the data is limited by small numbers of events and wide confidence intervals. Future studies should focus on surgical valves and should include long-term follow-up to assess any potential impact of randomized therapy on valve durability.

Entropic Analysis of Processes in Control Valves

The thermodynamic analysis of irreversible processes has an important influence in energy efficiency growing of any thermodynamic processes or systems. All of thermodynamic processes are entropy generators but there are processes with such a high level of irreversibility so that couldn’t be ignored. That is why is so important to identify what causes entropy generation and also to identify those system components that contribute the most to the overall irreversibility of the thermodynamic system. One of the processes with the highest level of entropy generation is flow with friction in various ducts and flow networks such as control valves. In order to see the direct connection between frictional pressure drop and thermodynamic irreversibility the paper will firstly analyze the steady and adiabatic flow of pure substance through a short segment of pipe with variable section (control valve). Because the entropy generation value during the throttling process is proportional to control valve pressure drop, the paper will do a flow thermodynamic analysis inside the control valve and the conclusions about drop pressure in different working conditions will be taken. Pressure drops along a valve are not constant, but rather vary in relation to the port left open by the plug. They normally increase as the valve narrowest section is reduced, although the upstream drop does increase at a slower rate than the downstream one. Actual increases and decreases in pressure drop and their effects are related to valve type and flow direction. It can be deduced that, for all types, pressure drops increase at flow tending to close, mainly as a result of the increased drop generated downstream. Also, the paper will take into account the drop pressure variation during the substance flow and will be analyzed its influence on the process irreversibility. In the same time, the paper will analyze the change of state influence during the liquid throttling process on the entropy generation, in situations of low titer bipolar phase fluid or high titer bi-phase fluid and will identify this phenomenon effects and remedies.

Mathematical Geometric of Open and Closed Valve in Water Hammer

A valve is a device used to control the flow of the fluid. The control is achieved by closing, opening or partially obstructing various passageways. Valves have many applications and the valves are considered to be pipe fittings, and there are many different valve designs. Each of the many different valve designs has its own advantages and disadvantages. For example, the gate valve slides up and down like a gate, the globe valve closes a hole placed in the valve, the angle valve is a globe valve with a 90° turn, and the check valve allows the fluid to flow only in one direction. In this paper, the present investigation is to explore the effect open and close valve on water hammer and study the valve types with equations for every valve, the results give information about the pattern of valve closing and valve opening crescent water hammer.

Fabrication of Chemofluidic Integrated Circuits by Multi-Material Printing

Photolithographic patterning of components and integrated circuits based on active polymers for microfluidics is challenging and not always efficient on a laboratory scale using the traditional mask-based fabrication procedures. Here, we present an alternative manufacturing process based on multi-material 3D printing that can be used to print various active polymers in microfluidic structures that act as microvalves on large-area substrates efficiently in terms of processing time and consumption of active materials with a single machine. Based on the examples of two chemofluidic valve types, hydrogel-based closing valves and PEG-based opening valves, the respective printing procedures, essential influencing variables and special features are discussed, and the components are characterized with regard to their properties and tolerances. The functionality of the concept is demonstrated by a specific chemofluidic chip which automates an analysis procedure typical of clinical chemistry and laboratory medicine. Multi-material 3D printing allows active-material devices to be produced on chip substrates with tolerances comparable to photolithography but is faster and very flexible for small quantities of up to about 50 chips.

Long-term durability of self-expanding and balloon-expandable transcatheter aortic valve prostheses: UK TAVI registry.

With expansion of transcatheter aortic valve implantation (TAVI) into younger patients, valve durability is critically important. We aimed to evaluate long-term valve function and incidence of severe structural valve deterioration (SVD) among patients ≥ 10-years post-TAVI and with echocardiographic follow-up at least 5-years postprocedure. Data on patients who underwent TAVI from 2007 to 2011 were obtained from the UK TAVI registry. Patients with paired echocardiograms postprocedure and ≥5-years post-TAVI were included. Severe SVD was determined according to European task force guidelines. 221 patients (79.4 ± 7.3 years; 53% male) were included with median echocardiographic follow-up 7.0 years (range 5-13 years). Follow-up exceeded 10 years in 43 patients (19.5%). Valve types were the supra-annular self-expanding CoreValve (SEV; n = 143, 67%), balloon-expandable SAPIEN/XT (BEV; n = 67, 31%), Portico (n = 4, 5%) and unknown (n = 7, 3%). There was no difference between postprocedure and follow-up peak gradient in the overall cohort (19.3 vs. 18.4 mmHg; p = NS) or in those with ≥10-years follow-up (21.1 vs. 21.1 mmHg; p = NS). Severe SVD occurred in 13 patients (5.9%; median 7.8-years post-TAVI). Three cases (23.1%) were due to regurgitation and 10 (76.9%) to stenosis. Valve-related reintervention/death occurred in 5 patients (2.3%). Severe SVD was more frequent with BEV than SEV (11.9% vs. 3.5%; p = 0.02), driven by a difference in patients treated with small valves (BEV 28.6% vs. SEV 3.0%; p < 0.01). Hemodynamic function of transcatheter heart valves remains stable up to more than 10 years post-TAVI. Severe SVD occurred in 5.9%, and valve-related death/reintervention in 2.3%. Severe SVD was more common with BEV than SEV.

Sensor design for saltwater ingress detection in high reliable all-electric deep sea actuators

Subsea oil and gas production relies on Xmas Trees which are mounted on boreholes. Xmas Trees are an arrangement of different valve types and sizes actuated by hydraulic, electro-mechanic or all-electric actuators. All these actuators sharing problems with saltwater ingress and the re-sulting increased wear. This paper investigates potential effects which can be measured after saltwater ingress. Extensive testing is executed and the investigated effects are used for novel sensor designs. These designs are evaluated regarding certain requirements and a resulting sen-sor design is proposed for industrialization. The resulting sensor can then be used to collect new important data to support optimal maintenance in the subsea industry.

Three-Year Outcomes of Balloon-Expandable Transcatheter Aortic Valve Implantation According to Annular Size

Data on the association between annular size and transcatheter aortic valve implantation (TAVI) outcomes beyond 1 year are limited. The present study assessed the association between the aortic annulus size and TAVI clinical and hemodynamic outcomes at 3years of follow-up. Patients were classified according to the aortic annulus size as having small, intermediate, and large annuli (size <400, 400 to 574, and ≥575mm2, respectively). The co-primary endpoints were all-cause mortality and heart failure hospitalization. Further, the changes in hemodynamic outcomes over the follow-up period (median 37, interquartile range: 26 to 45 months) were assessed. The present analysis included 850 patients, with 182 patients (21.4%), 538 patients (63.3%), and 130 patients (15.3%) in the small, intermediate, and large-sized aortic annulus groups, respectively. The groups had comparable age and pre-TAVI pressure gradients; however, patients with small annuli had higher Society of Thoracic Surgeons risk scores. Adjusted Cox regression analysis showed that compared to patients with intermediate-sized annuli, patients with small and large annuli had similar all-cause mortality (hazard ratio [HR]=1.11, 95% confidence interval [CI] 0.72 to 1.69 and HR=0.74, 95% CI 0.48 to 1.16, respectively) and heart failure hospitalization rates (HR=0.96, 95% CI 0.55 to 1.69 and HR=1.26, 95% CI 0.73 to 2.17, respectively). However, patients with small annuli had consistently higher mean and peak pressure gradients and a higher risk of patient-prosthesis mismatch. The risks of moderate-to-severe regurgitation and structural valve deterioration were similar between the three groups. In conclusion, although patients with small annuli had higher transvalvular gradients, there was no significant association between the aortic annulus size and TAVI clinical outcomes at 3years of follow-up. Future studies should compare the performance of transcatheter valve types in patients with different aortic annulus sizes.

Effects of Pipe Fittings on the Pump Energy Requirements of a Piping System

The number of pipe fittings, as well as their type in a piping system, are very important despite generating minor energy losses that, in many cases, are not considered. However, these losses become very significant for high mass flow rates, directly affecting the energy requirements of the pump. This study presents an analysis where the energy requirements of the pump have been calculated from different numbers and types of elbows and valves, showing exactly the working conditions where the energy losses start to be significant. Three case studies have been developed to observe the behavior of the energy requirement of the pump: effect of the number of elbows and flow rates, interaction of the number of elbows–pipe diameters–flow rates, and the effect of the number of valves on the power of the pump. It has been observed that the effect of the workflow and the type of elbow on the pump power is not significant when the number of elbows is three. When the number of elbows is increased to 10, two zones arise, i.e. the zone of non-significant effect when the flow rate is lower than 9 L/s, and the zone of significant effect when the flow rate is greater than 9 L/s. For flow rates lower than 6.75 L/s, the number of ball valves has no significant effect on the increase in the energy requirement of the pump; it increases only 0.73 kW. For flows higher than 11.3 L/s, a zone of high energetic requirements, which depends on the number of valves used, has been identified.

Impact of Evolution of Self-Expandable Aortic Valve Design: Peri-Operative and Short-Term Outcomes

A few data exist on the differences of implantable aortic valve bio-prostheses. We investigate three generations of self-expandable aortic valves in terms of the outcomes. Patients undergoing transcatheter aortic valve implantation (TAVI) were allocated into three groups according to the valve type: group A (CoreValveTM), group B (EvolutTMR) and group C (EvolutTMPRO). The implantation depth, device success, electrocardiographic parameters, need for permanent pacemaker (PPM), and paravalvular leak (PVL) were assessed. In the study, 129 patients were included. The final implantation depth did not differ among the groups (p = 0.07). CoreValveTM presented greater upward jump of the valve at release (2.88 ± 2.33 mm vs. 1.48 ± 1.09 mm and 1.71 ± 1.35 mm, for groups A, B, and C, respectively, p = 0.011). The device success (at least 98% for all groups, p = 1.00) and PVL rates (67% vs. 58%, vs. 60% for groups A, B, and C, respectively, p = 0.64) did not differ. PPM implantation within 24 h (33% vs. 19% vs. 7% for groups A, B, and C, respectively, p = 0.006) and until discharge (group A: 38% vs. group B: 19% and group C: 9%, p = 0.005) was lower in the newer generation valves. Newer generation valves present better device positioning, more predictable deployment, and fewer rates of PPM implantation. No significant difference in PVL was observed.

The survival time of the ventriculo-peritoneal-shunt in children with hydrocephalus is dependent on the type of valve implanted

PurposeDespite constantly improving developments in ventriculo-peritoneal shunt systems, most patients with hydrocephalus require revision or replacement at some point of time. Therefore, this study aimed to analyse parameters that are associated with shunt dysfunction.MethodsIn this retrospective study, we included 81 patients aged 0–17 who were treated at our institution. Demographic data, etiology of the hydrocephalus, type of valve implanted, reason for any revision procedures, any complications and survival time of the ventriculo-peritoneal shunts were detected. Statistical analysis was performed using SPSS. The significance level was set at p ≤ 0.05.ResultsOver a mean study period of 18 years, we analyzed 226 valves subjected to 146 revision operations in 81 patients. The etiology of the hydrocephalus (p = 0.874) and the age of the child at the time of VP shunt implantation (p = 0.308) did not have any impact on the shunt survival time. However, the type of the valve significantly changed the survival time of the shunt (p = 0.030). Pressure differential valves presented a longer survival time than gravitational valves.ConclusionThe majority of patients in this study needed at least one replacement of the initial shunt system. Pressure differential valves may be beneficial for the survival time of the shunt system.

Influence of aortic valve morphology on vortical structures and wall shear stress.

The aim of this paper is to assess the association between valve morphology and vortical structures quantitatively and to highlight the influence of valve morphology/orientation on aorta's susceptibility to shear stress, both proximal and distal. Four-dimensional phase-contrast magnetic resonance imaging (4D PCMRI) data of 6 subjects, 3 with tricuspid aortic valve (TAV) and 3 with functionally bicuspid aortic values (BAV) with right-left coronary leaflet fusion, were processed and analyzed for vorticity and wall shear stress trends. Computational fluid dynamics (CFD) has been used with moving TAV and BAV valve designs in patient-specific aortae to compare with in vivo shear stress data. Vorticity from 4D PCMRI data about the aortic centerline demonstrated that TAVs had a higher number of vortical flow structures than BAVs at peak systole. Coalescing of flow structures was shown to be possible in the arch region of all subjects. Wall shear stress (WSS) distribution from CFD results at the aortic root is predominantly symmetric for TAVs but highly asymmetric for BAVs with the region opposite the raphe (fusion location of underdeveloped leaflets) being subjected to higher WSS. Asymmetry in the size and number of leaflets in BAVs and TAVs significantly influence vortical structures and WSS in the proximal aorta for all valve types and distal aorta for certain valve orientations of BAV. Analysis of vortical structures using 4D PCMRI data (on the left side) and wall shear stress data using CFD (on the right side).

Causes and treatment strategies of unilateral leaflet escape of bileaflet mechanical prosthetic heart valves after surgery: a case series

BackgroundDuring the eleven years from 2010 to 2021, preliminary statistics have shown that Fuwai Hospital completed 23,571 mechanical valve replacements for various types of valves, and 1139 mechanical valve replacements were performed in Guangyuan First People's Hospital. Only two patients developed valve leaflet escape, so valve leaflet escape is a rare postoperative complication.Case presentationIn 2010 and 2021, two patients were selected after they had unilateral leaflet escape after having mechanical valve replacements in Fuwai Hospital of Chinese Academy of Medical Sciences and Guangyuan First People's Hospital. Both patients underwent reoperations with the classic operation and the new bileaflet mechanical prosthetic heart valve was sutured. The treatment of detached single lobe and distal vessel was comprehensively determined, and the condition was treated according to the patient's symptoms, CT results, ultrasound results and other test results, as well as whether this detached lobe caused any abnormal hemodynamics of the distal vessel. The patient with mechanical aortic valve escape completed the 10-year follow-up, and patient with mechanical mitral valve escape completed the 3-month follow-up. there was no thrombosis or hematoma at the embolic site; the patient had no lower limb symptoms.ConclusionsThe reason for the leaflet escape may be related to the valve design and the leaflet material. If the detached leaflets are damaged and if the distal blood vessels are affected, simultaneous surgical treatment is required. Those patients whose vessels were not damaged by the valve lobe should be carefully monitored.

Subclinical Leaflet Thrombosis After Balloon versus Self-Expandable Transcatheter Aortic Valve Implantation

Hypoattenuated leaflet thickening (HALT) has been recognized as one of the complications after transcatheter aortic valve implantation and may promote structural valve degeneration and increase the risk of cerebrovascular events. The 2 main types of available transcatheter heart valves (THVs), the balloon-expandable (BE) and the self-expanding (SE), are interchangeably used in clinical practice despite substantial design differences. There is unclear evidence on whether these 2 different THV models are achieving similar or different rates of subclinical leaflet thrombosis/HALT. A systematic search of electronic databases was conducted to identify studies that reported the incidence of HALT between SE THVs and BE THVs. The Mantel-Haenszel method was used to calculate the 95% confidence interval and pooled risk ratio with a random-effects model. A total of 126 records were identified, of which 22 studies comprising 14,401 patients were included in our final analysis. Among 5,951 patients receiving SE THVs, 194 (3.2%) developed HALT, compared with 8,450 patients receiving BE THVs, of whom 484 (5.7%) developed HALT. There was a statistically significant decrease in the risk of developing HALT in patients receiving SE THVs compared with those receiving BE THVs (risk ratio 0.75, 95% confidence interval 0.59 to 0.95, I2 32%, p=0.02). In conclusion, could potentially reduce the risk of HALT/subclinical leaflet thrombosis.

Factors affecting ventriculoperitoneal shunt revision: a post hoc analysis of the British Antibiotic and Silver Impregnated Catheter Shunt multicenter randomized controlled trial.

The British Antibiotic and Silver Impregnated Catheter Shunt (BASICS) trial established level I evidence of the superiority of antibiotic-impregnated catheters in the prevention of infection of newly implanted ventriculoperitoneal shunts (VPSs). A wealth of patient, shunt, and surgery-specific data were collected from trial participants beyond that of the prespecified trial objectives. This post hoc analysis of the BASICS survival data explores the impact of patient age, hydrocephalus etiology, catheter type, valve type, and previous external ventricular drain on the risk of infection or mechanical failure. Time to failure was analyzed using Fine and Gray survival regression models for competing risk. Among 1594 participants, 75 patients underwent revision for infection and 323 for mechanical failure. Multivariable analysis demonstrated an increased risk of shunt infection associated with patient ages < 1 month (subdistribution hazard ratio [sHR] 4.48, 95% CI 2.06-9.72; p < 0.001) and 1 month to < 1 year (sHR 2.67, 95% CI 1.27-5.59; p = 0.009), as well as for adults with posthemorrhagic hydrocephalus (sHR 2.75, 95% CI 1.21-6.26; p = 0.016). Age ≥ 65 years was found to be independently associated with reduced infection risk (sHR 0.26, 95% CI 0.10-0.69; p = 0.007). Antibiotic-impregnated catheter use was also associated with reduced infection risk (sHR 0.43, 95% CI 0.22-0.84; p = 0.014). Independent risk factors predisposing to mechanical failure were age < 1 month (sHR 1.51, 95% CI 1.03-2.21; p = 0.032) and 1 month to < 1 year (sHR 1.31, 95% CI 0.95-1.81; p = 0.046). Age ≥ 65 years was demonstrated to be the only independent protective factor against mechanical failure risk (sHR 0.64, 95% CI 0.40-0.94; p = 0.024). Age is the predominant risk for VPS revision for infection and/or mechanical failure, with neonates and infants being the most vulnerable.

Differences in blood flow dynamics between balloon- and self-expandable valves in patients with aortic stenosis undergoing transcatheter aortic valve replacement

BackgroundThe differences in pre- and early post-procedural blood flow dynamics between the two major types of bioprosthetic valves, the balloon-expandable valve (BEV) and self-expandable valve (SEV), in patients with aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR), have not been investigated. We aimed to investigate the differences in blood flow dynamics between the BEV and SEV using four-dimensional flow cardiovascular magnetic resonance (4D flow CMR). MethodsWe prospectively examined 98 consecutive patients with severe AS who underwent TAVR between May 2018 and November 2021 (58 BEV and 40 SEV) after excluding those without CMR because of a contraindication, inadequate imaging from the analyses, or patients' refusal. CMR was performed in all participants before (median interval, 22 [interquartile range (IQR) 4–39] days) and after (median interval, 6 [IQR 3–6] days) TAVR. We compared the changes in blood flow patterns, wall shear stress (WSS), and energy loss (EL) in the ascending aorta (AAo) between the BEV and SEV using 4D flow CMR. ResultsThe absolute reductions in helical flow and flow eccentricity were significantly higher in the SEV group compared in the BEV group after TAVR (BEV: − 0.22 ± 0.86 vs. SEV: − 0.85 ± 0.80, P < 0.001 and BEV: − 0.11 ± 0.79 vs. SEV: − 0.50 ± 0.88, P = 0.037, respectively); there were no significant differences in vortical flow between the groups. The absolute reduction of average WSS was significantly higher in the SEV group compared to the BEV group after TAVR (BEV: − 0.6 [− 2.1 to 0.5] Pa vs. SEV: − 1.8 [− 3.5 to − 0.8] Pa, P = 0.006). The systolic EL in the AAo significantly decreased after TAVR in both the groups, while the absolute reduction was comparable between the groups. ConclusionsHelical flow, flow eccentricity, and average WSS in the AAo were significantly decreased after SEV implantation compared to BEV implantation, providing functional insights for valve selection in patients with AS undergoing TAVR. Our findings offer valuable insights into blood flow dynamics, aiding in the selection of valves for patients with AS undergoing TAVR. Further larger-scale studies are warranted to confirm the prognostic significance of hemodynamic changes in these patients.

CRT-700.3 The Association Between Gender and Complication of the Transcatheter Aortic Valve Replacement by the Difference of the Type of Valve

CRT-700.3 The Association Between Gender and Complication of the Transcatheter Aortic Valve Replacement by the Difference of the Type of Valve

Modifiable risk factors for permanent pacemaker after transcatheter aortic valve implantation: CONDUCT registry

ObjectiveThe onset of new conduction abnormalities requiring permanent pacemaker implantation (PPI) after transcatheter aortic valve implantation (TAVI) is still a relevant adverse event. The main objective of this registry was...

Intermediate Follow-Up of Balloon-Expandable Versus Self-Expanding Transcatheter Aortic Valve Implantation in Patients With Small Aortic Annuli

The clinical impact of prosthesis-patient mismatch (PPM) in patients with small aortic annuli who underwent transcatheter aortic valve (AV) implantation with either balloon-expandable (BE) or self-expanding (SE) valves remains controversial. We assessed in-hospital and intermediate clinical outcomes in 573 patients with transfemoral transcatheter AV implantation with a small AV annulus, defined as an AV annulus area ≤430mm2. A total of 337 patients treated with a 23-mm BE valve (SAPIEN 3, Ultra) were compared with 236 patients treated with a 26-mm SE valve (Evolut series). Valve-in-valve cases were excluded, and late echo follow-up (mean 674 ± 438days) was assessed in a subset of 292 patients (51.0%). Well-matched BE and SE cohorts did not differ with respect to major in-hospital outcomes, other than a borderline increase in vascular complications and composite bleeding in patients with SE. Patients with BE had a higher incidence of severe PPM on discharge echocardiography (16.9% vs 6.8%, p <0.002). The mean AV gradient at 30days was higher for patients with BE (12.2 ± 4.2 vs 6.2 ± 7.9mm Hg, p <0.001) and at late follow-up (14.0 ± 8.2 vs 7.2 ± 3.5mm Hg, p <0.001). The follow-up left ventricular ejection fraction and incidence of >mild aortic insufficiency were similar. All-cause mortality for the 2 cohorts was similar, with an overall mean (95% confidence interval) survival time of 61.2months (57.8 to 64.5; p=0.98). There were no significant survival differences between combined patients with BE and SE with no, moderate, or severe PPM, with an overall mean (95% confidence interval) survival time of 32.5 (30.5 to 34.5)months combining valve types (p=0.23). In conclusion, despite an increased incidence of PPM with higher mean AV gradients that persist on late echocardiography in the BE cohort, patients with BE and SE with small aortic annuli have similar clinical outcomes at intermediate follow-up. Moderate and severe PPM had no impact on survival at a mean follow-up of 32.5months.

Analysis of the Impact of Vibrations on a Micro-Hydraulic Valve Using a Modified Induction Algorithm

This paper addresses the impact of mechanical vibrations of different frequencies on a particular type of valve. It has been shown that a neural network can be used to compress measurement data and determine the frequency range that is most important in describing the impact of mechanical vibrations on a micro-hydraulic overflow valve. Later, induction decision trees were used for the generated areas, determining key measurement points. The most important areas of dependence are determined using inductive decision trees in induction. The entropy measure is used to determine the most significant attribute. A modified induction algorithm was used for the comprehensive analyses. The analysis carried out in the paper identified the intervals in which the flow rate plays a decisive role for the entire amplitude and frequency spectrum. An analysis was performed for the 200…900 [Hz] frequency interval of the external driving force, with a harmonic step of 10 [Hz]. The analysis was performed while considering these main valve parameters: the pressure of the overflow valve opening p = 10 [MPa]; flow rate in the valve: 0.6, 0.8 and 1 [dm3/min]; stiffness of valve spring c = 7.49 [N/mm]. Plots were presented and for each plot, the most important four intervals were determined. They are hierarchically ordered in the interval range of the whole frequency spectrum range: (coefficient IV)—the most important; (coefficient III)—important; (coefficient II)—less important; (coefficient I)—least important. A test rig and the results of a study on the effect of mechanical vibration on changes in the amplitude-frequency spectrum of pressure pulsations of a micro-hydraulic system, in which a micro-hydraulic relief valve was subjected to mechanical vibration, are presented.