Small Valve Research Articles

Real Structural Valve Deterioration of the Mitroflow Aortic Prosthesis: Competing Risk Analysis

Introduction and objectivesThe Mitroflow aortic prosthesis is a bovine pericardial bioprosthesis specially designed to increase the valve area in relation to its size. There is controversy regarding the pattern of structural valve deterioration (SVD). Our aim was to determine the cumulative incidence of SVD, risk factors influencing its occurrence, and its impact on mortality. MethodsA total of 1028 patients were clinically and echocardiographically followed up. Because the study population was elderly and had heart disease, we used a competing risk analysis. ResultsThe percentage of patients with SVD at 5 years was 4.22% (95%CI, 2.96-5.81) and was 15.77% at 8 years (95%CI, 12.46-19.43). The incidence was higher for small valves (19mm and 21mm) reaching 6.43% at 5 years (95%CI, 4.48-8.84) and 20.06% at 8 years (95%CI, 15.53-25.01). Severe patient-prosthesis mismatch (PPM) influenced the incidence of SVD (sHR, 3.53; 95%CI, 2.20-5.66; P < .001) but moderate PPM had no impact. The most powerful predictor of mortality was the presence of SVD (HR, 4.59; 95%CI, 2.91-7.22; P < .001). ConclusionsThis study used a definition based on the increase in the transprosthetic gradient and found a higher incidence of SVD of the Mitroflow prosthesis than that reported by other series, especially for sizes 19mm and 21mm and in patients with severe PPM. The incidence of SVD increased exponentially from the fifth year after implantation and its occurrence led to a 4.5-fold increase in the risk of death.

Hybrid Palliation for Interrupted Aortic Arch With Small Aortic Valve.

Open heart surgery for interrupted aortic arch in the neonatal period is still a high-risk procedure related in part to patient factors such as low birth weight, other morphologic anomalies, and, especially, small aortic valve size. Recently, we performed hybrid palliation with bilateral pulmonary artery banding and ductal stenting as the first-stage palliation for such cases. In this study, the outcomes of this procedure were examined. Six cases of interrupted aortic arch with a small aortic valve underwent the hybrid procedure in the neonatal period in our institute from 2010 to 2015 (mean age: 6.8 days, mean body weight: 3.2 kg, mean z score of the aortic valve annulus: -8.3). Their postoperative clinical courses and results of the second-stage surgery were evaluated. No mortality or severe morbidity was seen in association with initial hybrid palliation. Five of six patients were discharged from the hospital; the one exception had a significant urinary tract anomaly. None needed an additional catheter intervention or surgical procedure postoperatively. All surviving patients underwent second-stage surgery; three had biventricular repair by the conventional method or Damus-Kaye-Stansel anastomosis with the Rastelli procedure and the other three proceeded toward staged Fontan reconstruction. Growth of the aortic valve was seen in four patients, and increased indexed left ventricle volume was recognized in one after the palliation. Hybrid palliation could be useful not only to avoid high-risk neonatal surgery but also to allow for eventual selection of the second-stage surgery based on the observations of potential interval development of left ventricular structures.

Investigation of the unsteady-flow characteristics in the control valve of a diesel engine unit pump fuel system

The control valve determines the fuel offloading process of the high-pressure fuel system in diesel engines. During the fuel offloading process, when the control valve instantaneously opens, the inlet pressures and the outlet pressures of the valve change quickly, and the inner flow of the control valve is transient and unsteady. This study presents an investigation into the flow characteristics in the control valve region during the fuel-offloaded process of a diesel unit pump fuel system, studies the reasons for unsteady-flow conditions and further analyses the effects on the flow capacity of the valve based on the computational fluid dynamics method. The results reveal that the key reason for unsteady flow in the control valve is the dynamic movement of the valve needle, which induces changes in the inlet pressure and the outlet pressure so that the fluid in the conical region accelerates. In comparison with steady flow, unsteady flow in the control valve has different pressures in the conical region and at the conical outlet, different cavitation intensities and different locations of the bubbles. Moreover, the differences between unsteady flow and steady flow become greater, particularly for small valve needle openings. Unsteady flow in the control valve greatly influences the fuel offloading process of the unit pump fuel system.

La degeneración real de la prótesis aórtica Mitroflow: análisis con riesgos competitivos

Introduction and objectivesThe Mitroflow aortic prosthesis is a bovine pericardial bioprosthesis specially designed to increase the valve area in relation to its size. There is controversy regarding the pattern of structural valve deterioration (SVD). Our aim was to determine the cumulative incidence of SVD, risk factors influencing its occurrence, and its impact on mortality. MethodsA total of 1028 patients were clinically and echocardiographically followed up. Because the study population was elderly and had heart disease, we used a competing risk analysis. ResultsThe percentage of patients with SVD at 5 years was 4.22% (95%CI, 2.96-5.81) and was 15.77% at 8 years (95%CI, 12.46-19.43). The incidence was higher for small valves (19mm and 21mm) reaching 6.43% at 5 years (95%CI, 4.48-8.84) and 20.06% at 8 years (95%CI, 15.53-25.01). Severe patient-prosthesis mismatch (PPM) influenced the incidence of SVD (sHR, 3.53; 95%CI, 2.20-5.66; P < .001) but moderate PPM had no impact. The most powerful predictor of mortality was the presence of SVD (HR, 4.59; 95%CI, 2.91-7.22; P < .001). ConclusionsThis study used a definition based on the increase in the transprosthetic gradient and found a higher incidence of SVD of the Mitroflow prosthesis than that reported by other series, especially for sizes 19mm and 21mm and in patients with severe PPM. The incidence of SVD increased exponentially from the fifth year after implantation and its occurrence led to a 4.5-fold increase in the risk of death.Full English text available from:www.revespcardiol.org/en

Growth of left ventricular outflow tract and predictors of future re-intervention after repair for ventricular septal defect and aortic arch obstruction.

We carried out a retrospective review of patients who underwent repair for ventricular septal defect and aortic arch obstruction - coarctation or interrupted aortic arch - between July, 2002 and June, 2013. Echocardiographic data were reviewed, and the need for re-intervention was evaluated. A total of 89 patients were included in this study. A significant left ventricular outflow tract growth was noticed after surgical repair. Preoperatively, the mean left ventricular outflow tract Z-score was -1.46±1 (range -5.5 to 1.1) and increased to a mean value of -0.7±1.3 (range -2.7 to 3.2) at last follow-up (p=0.0001), demonstrating relevant growth of the left ventricular outflow tract after repair for ventricular septal defect and aortic arch obstruction. After primary repair, 11 patients (12.3%) required re-intervention with surgical repair for left ventricular outflow tract obstruction after a mean period of 36±21 months. There were no significant differences in age, weight, and indexed aortic valve and left ventricular outflow tract measurements between those who developed obstruction and those who did not. Significant left ventricular outflow tract growth is expected after repair of ventricular septal defect and aortic arch obstruction. Small aortic valve and left ventricular outflow tract at diagnosis are not risk factors to predict the need for surgical re-intervention for left ventricular outflow tract obstruction in future.

Small intestinal submucosa tricuspid valve tube graft shows growth potential, remodelling and physiological valve function in a porcine model†.

Tricuspid valve reconstruction using small intestinal submucosal extracellular matrix (ECM) designed as a tube graft is possible in severe valve pathology. Using cardiac magnetic resonance imaging (MRI) and digital photograph imaging, valves were evaluated after 6 months in a porcine model. Ten 60 kg pigs received a tricuspid valve tube graft. A baseline MRI was performed after 2 weeks ( n = 8). A follow-up MRI was performed in three of five 6 months' survivors to assess function and haemodynamics of the tricuspid tube graft. Valves were explanted in five animals for gross examination. No statistical comparisons were made due to low numbers. : Compared to the original tube graft, leaflet area and leaflet height decreased after 6 months (32 ± 0 vs 14.7 ± 4 cm 2 and 3.2 ± 0 vs 1.7 ± 0.3 cm, respectively). Both imaging modalities showed septal dehiscence in all tube grafts after 6 months causing haemodynamically severe paravalvular regurgitation. Cardiac MRI showed a significant remodelling of the right ventricular and annular dimensions. The cardiac output decreased (67 ± 16 vs 34 ± 5 ml/min/kg), while right ventricular stroke volume increased from 64.4 ± 14.6 to 107 ± 63.9 ml. This corresponded to a paravalvular regurgitant volume increasing from 7.2 ± 7.3 to 71.7 ± 69.6 ml. The ECM tube grafts seemed to remodel over time with loss of redundant ECM material. However, tube graft dehiscence caused severe tricuspid paravalvular regurgitation and heart failure. These data suggest that surgical reinforcement, e.g. adjunct annuloplasty, should be considered to improve durability.

Preclinical determination of the best functional position for transcatheter heart valves implanted in rapid deployment bioprostheses.

The aim of this study was to determine the best functional position of a transcatheter heart valve (THV) implanted as a valve-in-valve (ViV) procedure in small rapid deployment valves (RDV) in an in vitro model. A 21 mm Perceval, Enable or INTUITY RDV was mounted into a pulse duplicator and a 23 mm balloon-expandable or a self-expanding THV was deployed (valve-in-valve) in two different positions. Under physiological hydrodynamic conditions, the performance of the THV was characterised by mean transvalvular pressure gradient (MPG), effective orifice area (EOA) and regurgitation volume (RV). Leaflet kinematics were assessed with high-speed video recordings, and X-ray images were acquired. All THV/RDV combinations met ISO requirements regarding hydrodynamic performance. In most cases, the higher position of the THV performed better than the lower one in terms of a lower MPG and increased EOA. Leaflet motion of the implanted THV was impaired in the lower position. In contrast, regurgitation volumes were relatively small and similar, regardless of the THV position. ViV implantation of a THV in a small RDV yielded satisfactory hydrodynamic results. In most cases, a high implantation position achieved lower MPG, higher EOA and a reduced risk of impaired THV leaflet function. Fluoroscopy images of the best functional ViV positions are presented as a blueprint for patient procedures.

流体アクチュエータの駆動を目的とした微粒子励振による小型三方弁の開発

Hydraulic actuators are expected to be applied to robots because they have a small volume, large power, and low damage. However, the hydraulic control systems for multiple degrees of freedom mechanisms have a large volume because such system has many control components. The purpose of this research is to develop a small hydraulic flow control valve. In our previous research, we have applied a small flow control valve using particle excitation by a piezoelectric vibrator to a hydraulic system. In this paper, we have developed a three-way valve using two piezoelectric vibrators. This three-way valve can switch inlet and outlet vibrators by applying different driving frequencies because two vibrators have different natural frequencies. In addition, we have applied this three-way valve to drive a fluidic actuator, and evaluated driving characteristics of the actuator.

Hydraulic Control by Flow Control Valve Using Particle Excitation

In this paper, we report on the hydraulic characteristics of a particle-excitation control valve, which was originally developed for flow rate control in pneumatic actuators. The orifices are opened and closed with particles excited by the vibration of the orifice plate and the fluid force. This results in a more simple and compact structure, and higher flow rate-to-weight ratio than in conventional pneumatic valves. Because the traditional hydraulic valves are bulky and heavy, the purpose of this study is the development of a small and lightweight hydraulic valve by applying the working principle of the particle-excitation valve to hydraulics. We have focused on two characteristics affected by changing the working fluid from air to oil. One is the vibration of the orifice plate and the other is the movement of the particles. As a result, it is found that the inertia of the working fluid reduces the vibrational velocity of the orifice plate by 24%, whereas the viscosity of the working fluid raises the required operating voltage of the valve by 167% because of its influence on the movement of particles. In addition, when silicone oils are used as the working fluid, with kinematic viscosity values of 1 mm2/s, 2 mm2/s, and 3 mm2/s, the maximum volumetric flow rates of the prototype valve are 891 ml/min, 887 ml/min, and 838 ml/min, respectively. These experimental results demonstrate the potential of the proposed valve for hydraulics.

微粒子励振型流量制御弁による人工筋の制御

In general, a hydraulic proportional valve has a large body because of their complicated structures using solenoids or motors. Therefore, it is difficult to realize lightweight hydraulic systems. The purpose of this research is to develop a small hydraulic flow control valve to control hydraulic actuators for a small hydraulic actuator system. In this paper, a McKibben artificial muscle has been controlled by small flow control valves. These valves can control the flow rate using particles excited by piezoelectric vibrators. Thus, the speed of the artificial muscle has been successfully controlled by the fabricated flow control valves.

TCT-669 Valve-in-Valve in Small Surgical Valves: Predictors for Survival and Elevated Post Procedural Gradients. Insights from the Valve-in-Valve International Data (VIVID) Registry

Small surgical valves are associated with higher mortality after valve in valve (ViV) implantation. We aimed to identify key predictors of elevated post- procedural gradients and mortality in this challenging patient population. A total of 1,565 patients that underwent aortic ViV from the Valve in

Experiments on transient performance of a low specific speed centrifugal pump with open impeller

In order to meet the needs in engineering, an existing low specific speed centrifugal pump may have to be run at a high rotating speed. Unfortunately, experiments on transient performance of such a kind of centrifugal pump in starting and stopping periods at a high speed have been unavoidable so far. In this paper, the transient hydraulic performance of a low specific speed centrifugal pump with an open impeller during starting and stopping periods is measured with an updated test rig. The correlations of rotating speed, flow rate, head, static pressures at the pump inlet and outlet, and shaft power with time are obtained at different discharge valve openings. The results show that the flow rate rises slowly at the beginning of starting period, and suddenly drops at the end of stopping process. There is an obvious impact phenomenon in local static pressure curves at the pump inlet and outlet during starting period. With the augment of discharge valve opening, the required time for flow rate to reach a steady value is gradually prolonged, and the impact phenomenon in local static pressures at the pump inlet is postponed and the impact difference is also decreased step by step. The impact phenomenon in shaft powers is also very prominent, especially at small discharge valve openings. At the beginning of stopping process, the flow rate declining delay phenomenon becomes weak with increasing discharge valve opening, and the time for flow to stop fully is also extended gradually.

IMPACT OF VASCULAR BURDEN IN AORTIC STENOSIS SEVERITY ASSESSMENT OF NORMAL FLOW-LOW GRADIENT PATIENTS

Fifty percent of Normal-Flow (NF), Low-Gradient (LG) patients (i.e. low mean gradient [MG] and small aortic valve area [AVA]) have severe aortic valve calcification (AVC) as measured by computed tomography. However, NF/LG patients are considered as moderate aortic stenosis (AS) in current ACC/AHA guidelines. The objective of this study was to evaluate the effect of hypertension (HTN) and systemic arterial compliance (SAC) on MG measurements and its relationship with AVC in patients with NF.

Mitral valve-in-valve and valve-in-ring: technical aspects and procedural outcomes.

There is a growing practice of transcatheter treatment of failed mitral valves after cardiac surgery, including valve-in-valve and valve-in-ring. Although commonly successful, these procedures can be associated with device malposition (including delayed malposition) and elevated post-procedural gradients (especially when performed inside small surgical valves). Valve-in-ring procedures have elevated risks of left ventricular outflow tract obstruction and post-procedural regurgitation. Careful patient selection and meticulous evaluation of patient anatomy and surgical implant characteristics are essential to achieve optimal clinical results with mitral valve-in-valve and valve-in-ring implantation.

Effects of orifice on pressure difference in pilot-control globe valve by experimental and numerical methods

Pilot-Control Globe Valve (PCGV) can utilize pressure difference caused by fluid flow through the orifice on valve core as its power, for open and close the main valve with a small pilot valve. It has obvious advantages of energy conservation and quick response. Orifice structure on the valve core is the main component to determine the pressure difference, which is used to push the valve core. In this paper, the numerical model with User Defined Functions (UDFs) method is carried out, and the experimental device is arranged. The numerical and experimental results of valve core displacements achieve agreements. Then, analysis of pressure difference under different static pressures, inlet velocities and different orifice diameters are carried out. It shows that pressure difference has no relationship with static pressure, thus PCGV can be adopted in hydrogen pipelines. Meanwhile, higher inlet velocity can turn out larger pressure difference with quicker response of PCGV. In addition, there exits an unbalanced moment, and 15 mm is the extreme diameter of the orifice for DN150 PCGV. Finally, the design method of the orifice structure in PCGV is proposed with design formulas. This work can help the precise design work of PCGV, and it can be referred by other researchers who are also deal with orifice structures in similar valves design work.

Hemodynamic Performance of Endovascular Valves as Valve-in-Valve in Small Stented Bioprosthesis.

Background Endovascular valve in stented biological valve implantation (valve-in-valve transcatheter aortic valve implantation [TAVI ViV]) is increasingly becoming a valid option for bioprosthesis degeneration. TAVI implantation in small stented biological valves below 23 mm is controversially discussed. Reduced opening area and high gradients are typical objections against this procedure in cases of small bioprosthesis. Systematic studies about the hemodynamic performance of endovascular valves in small stented bioprosthesis, however, do not exist. Methods Stented biological valves of 21 mm size were analyzed in a pulse duplicator (cardiac output 4.9 L/min). Edwards Perimount Magna (EP; Edwards Lifesciences, Irvine, California, United States), Medtronic Mosaic (MM; Medtronic Inc., Minneapolis, Minnesota, United States), and Sorin Mitroflow (SM; Milan, Italy) were investigated (three valves, each type). Mean transvalvular gradients were measured before and after implantation of Edwards Sapien 23 mm (SAP) as ViV. Results There were no marked differences of mean transvalvular gradients before and after ViV (EP21: 12.3 mm Hg; EP21 + SAP: 11.1 mm Hg; SM21: 13.5 mm Hg; SM21 + SAP: 14.9 mm Hg; MM21: 21.4 mm Hg; MM21 + SAP: 15.1 mm Hg). MM valves fabricated from porcine cusps showed higher initial gradients in contrast to valves constructed with pericardium (EP and SM). After ViV, however, this difference was reduced. Conclusion This in vitro study shows that hemodynamic performance of endovascular valves as ViV in small bioprosthesis does not differ significantly from the performance of the initial implanted prosthesis. Hemodynamic performance of porcine cusp valves could even be optimized. It can thus be speculated that TAVI ViV also offers a reasonable option for patients with typical stented bioprosthetic degeneration to substantially prolong adequate function with one initial surgical and one consecutive interventional procedure even in small valves.

Alginate Sulfate-Nanocellulose Bioinks for Cartilage Bioprinting Applications.

One of the challenges of bioprinting is to identify bioinks which support cell growth, tissue maturation, and ultimately the formation of functional grafts for use in regenerative medicine. The influence of this new biofabrication technology on biology of living cells, however, is still being evaluated. Recently we have identified a mitogenic hydrogel system based on alginate sulfate which potently supports chondrocyte phenotype, but is not printable due to its rheological properties (no yield point). To convert alginate sulfate to a printable bioink, it was combined with nanocellulose, which has been shown to possess very good printability. The alginate sulfate/nanocellulose ink showed good printing properties and the non-printed bioink material promoted cell spreading, proliferation, and collagen II synthesis by the encapsulated cells. When the bioink was printed, the biological performance of the cells was highly dependent on the nozzle geometry. Cell spreading properties were maintained with the lowest extrusion pressure and shear stress. However, extruding the alginate sulfate/nanocellulose bioink and chondrocytes significantly compromised cell proliferation, particularly when using small diameter nozzles and valves.

Growing potential of small aortic valve with aortic coarctation or interrupted aortic arch after bilateral pulmonary artery banding.

Bilateral pulmonary artery banding (bPAB) is utilized for some patients with a ventricular septal defect (VSD) and aortic coarctation (CoA) or interrupted aortic arch (IAA). We evaluated aortic valve (AoV) diameter and patient outcomes following bPAB. Between August 2010 and September 2015, 10 consecutive patients with VSD and patent ductus arteriosus-dependent CoA or IAA underwent bPAB because of an AoV diameter of approximately <50% of the normal value (n = 6), severe subaortic stenosis and poor patient condition (n = 1, respectively), or low birthweight (n = 2). Second-stage operations were conventional total repair in five and Damus-Kaye-Stansel anastomosis, aortic arch reconstruction and right ventricle-pulmonary artery shunt (modified Norwood) type repair in five. After modified Norwood-type repair, four patients were Yasui-type repair candidates and one was a Fontan candidate. For all patients, the mean AoV diameter increased from 3.7 ± 0.7 mm before bPAB to 4.6 ± 0.8 mm before the second-stage operation. In five patients with CoA or IAA type A, the AoV diameter significantly increased from 3.5 ± 0.3 mm to 4.5 ± 0.5 mm during the term between bPAB and the second-stage operation, with an AoV Z-score increase from -5.82 ± 0.92 to -4.28 ± 0.86. IAA type B showed a slight increase in the AoV diameter. Initial palliation with bPAB enables AoV diameter growth in some patients, improving the likelihood of conventional total repair adaptation rate, particularly for CoA or IAA type A.

Experimental and Numerical Study of Supercritical Carbon Dioxide Flow Through Valves

The supercritical carbon dioxide (sCO2) Brayton cycle shows advantages such as high efficiency, compactness, and low capital cost. These benefits make it a competitive candidate for future-generation power-conversion cycles. In order to study this cycle, valve characteristics under sCO2 flow conditions must be studied. However, the traditional models for valves may not be accurate due to the real gas property of sCO2. In this study, this problem was studied both experimentally and numerically. A small valve was tested in the authors’ experiment facility first to provide validation data. For this valve, numerical predictions of mass flow rate agree with experimental data. Then, simulations were scaled up to valves in a real power-cycle design. The traditional gas-service valve model fails to predict mass flow rate at low-pressure ratios. A modification was proposed to improve the current gas-service valve model by changing the choked-flow check.

Comparison of Edwards SAPIEN 3 versus SAPIEN XT in transfemoral transcatheter aortic valve implantation: Difference of valve selection in the real world

BackgroundThe SAPIEN 3 (S3; Edwards Lifescience, Irvine, CA, USA) is a new-generation percutaneous aortic valve with better profile, more precise handling and positioning, designed to reduce the risk of post-procedural paravalvular aortic leak (PVL). The aim of this study was to compare the S3 valve and SAPIEN XT valve (SXT). MethodsThe last 89 transfemoral transcatheter aortic valve implantation (TAVI) cases using SXT were compared to the first 111 cases using the S3. ResultsPatient age and logistic EuroSCORE were similar (83.1 years vs 83.0 years and 18.2% vs 16.6%) in the S3 and SXT groups, respectively as were other baseline characteristics. The ratio of valve diameter/calculated annulus average diameter (CAAD) by multi-detector row computed tomography was significantly lower in the S3 group (1.06 vs 1.09, p<0.001) as was the annular area oversizing percentage (11.3% vs 20.5%, p<0.001). Furthermore, a smaller valve was selected in S3 cases with borderline CAAD compared to SXT cases. Nevertheless, the frequency of paravalvular aortic leakage (PVL) ≥2 tended to be reduced in the S3 group (5% vs 9%, p=0.339). The rate of major vascular complications was significantly lower with S3 (3% vs 12%, p=0.013). In addition, 30-day mortality was significantly lower in the S3 group (0% vs 5%, p=0.044). ConclusionsAlthough TAVI using S3 tended to be carried out with a less oversized valve compared to TAVI using SXT, the frequency of post-procedural PVL ≥2 tended to be lower in the S3 group. The outcomes including vascular complications and 30-day mortality showed a trend in favor of the S3 group.