Trileaflet Valve Research Articles

Comparative analyses of blood flow through mechanical trileaflet and bileaflet aortic valves

Purpose: The primary aim of the present study was to compare the bileaflet and trileaflet aortic valves’ performance during uniform blood flow model and boundary conditions. The secondary aim of the study was to determine the effect of Newtonian/non-Newtonian fluid flow assumption on blood flow directly behind the trileaflet valve. Methods: The geometrical model of the whole system consist of the left ventricle, fragment of the aorta and mechanical valves. A representation of pulsatile flow was obtained by measuring blood flow velocity (Doppler ultrasound examination). We have assumed turbulent blood flow. We considered two blood models, Newtonian and non-Newtonian (Carreau model). The valves’ performance was assessed using the reduced stress in the valves, the shear stress in the aortic wall, flow velocity field and the effective orifice area. Results: The maximum von Mises stress for the bileaflet valve leaflets was 0.3 MPa and for the trileaflet valve – 0.06 MPa. The maximum flow velocity for the bileaflet valve was 4.52 m/s for 40° and for the trileaflet valve – 5.74 m/s. Higher shear stress was present in the bileaflet (151.5 Pa) than for the trileaflet valve (49.64 Pa). Conclusions: The results indicate that central blood jet for the trileaflet valve contributes to more physiological blood flow and decreases the risk of haemolysis. The central flow minimises the risk of leaflet dislocation. In addition, lower stresses extend the durability of the valve. However, the trileaflet valve geometry has also disadvantages, for instance, small peripheral streams or relatively low effective orifice area.

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.

NOTCH Signaling in Aortic Valve Development and Calcific Aortic Valve Disease.

NOTCH intercellular signaling mediates the communications between adjacent cells involved in multiple biological processes essential for tissue morphogenesis and homeostasis. The NOTCH1 mutations are the first identified human genetic variants that cause congenital bicuspid aortic valve (BAV) and calcific aortic valve disease (CAVD). Genetic variants affecting other genes in the NOTCH signaling pathway may also contribute to the development of BAV and the pathogenesis of CAVD. While CAVD occurs commonly in the elderly population with tri-leaflet aortic valve, patients with BAV have a high risk of developing CAVD at a young age. This observation indicates an important role of NOTCH signaling in the postnatal homeostasis of the aortic valve, in addition to its prenatal functions during aortic valve development. Over the last decade, animal studies, especially with the mouse models, have revealed detailed information in the developmental etiology of congenital aortic valve defects. In this review, we will discuss the molecular and cellular aspects of aortic valve development and examine the embryonic pathogenesis of BAV. We will focus our discussions on the NOTCH signaling during the endocardial-to-mesenchymal transformation (EMT) and the post-EMT remodeling of the aortic valve. We will further examine the involvement of the NOTCH mutations in the postnatal development of CAVD. We will emphasize the deleterious impact of the embryonic valve defects on the homeostatic mechanisms of the adult aortic valve for the purpose of identifying the potential therapeutic targets for disease intervention.

Aortic valve replacement in sheep with a novel trileaflet mechanical heart valve prosthesis without anticoagulation

BackgroundEven after decades of intensive research, an ideal heart valve prosthesis remains elusive. Shortcomings of conventional devices include reduced durability of bioprostheses and the thrombogenicity of mechanical substitutes, necessitating anticoagulation and resulting in imperfect hemodynamics. Here we present in vivo results of a novel mechanical heart valve prosthesis aiming for freedom from anticoagulation. MethodsFour female sheep had their aortic valves replaced using the novel mechanical heart valve (size 21 mm), with no postoperative anticoagulation treatment. This trileaflet heart valve was designed with the pivots in the systolic central flow. Hemodynamics, biochemistry, hematology, and macroscopy and microscopy were studied at 90 days in 2 sheep and at 1 year in the other 2 sheep. ResultsMean (<6 mm Hg) and peak (<10 mm Hg) aortic transvalvular gradients remained low during the study period. Aortic regurgitation was trivial, and central traces were only rarely observed. The rate of thrombotic events was very low, with none macroscopically and microscopically visible thrombotic material on the device. Biochemistry and hemotology were unchanged without hemolysis. In 3 sheep, the fibrous pannus and mitral leaflet were partially folded over the edge of the annular body. Apart from organic/inorganic deposits on the leaflets after 1 year, the ultrastructurally evaluated leaflets were similar to those of nonimplanted controls. ConclusionsThe preliminary in vivo results of this novel anticoagulation-free aortic mechanical heart valve are promising with excellent hemodynamics and a very low risk of thrombotic events.

Aortic Root Replacement With Autologous Pericardium Valved Conduit

Available aortic prosthesis replacement options present a challenge to achieving low perioperative morbidity, low pressure gradients, and prolonged durability. Trileaflet aortic valve reconstruction using autologous pericardium offers an alternative treatment option with excellent postoperative gradients, large effective orifice areas, and the avoidance of long-term anticoagulation. The modified Bentall procedure with either tissue xenograft valved conduit or mechanical valved conduit is considered the gold standard for patients with aortic root pathology requiring surgical replacement. We report a novel adaptation of the modified Bentall procedure with a self-fabricated valved conduit with trileaflet aortic valve neocuspidization using autologous pericardium.

Trileaflet Aortic Valve Reconstruction Using Bovine Pericardium

For several years now, trileaflet aortic valve reconstruction has been performed in patients with various aortic valve diseases. This study aimed to explore the feasibility and durability of trileaflet aortic valve reconstruction with bovine pericardium. Trileaflet aortic valve reconstruction with bovine pericardium was performed in 519 patients with various aortic valve diseases from April 2008 to December 2019. The results for all 519 patients were reviewed retrospectively. Mean age was 48.04±19.08 years (range, 13-80 years), and 40 patients were younger than 18 years of age. Thirty-four (34) patients had aortic stenosis, 344 patients had aortic regurgitation, and 141 patients had both aortic stenosis and regurgitation. One hundred and fifty-four (154) patients had bicuspid aortic valves, and three patients had quadricuspid aortic valves. The size of the pericardial leaflets was designed to be individually proportional to the size of the aortic root. Mean length of follow-up was 41.97±22.68 years (range, 1-127 months). In total, 448 patients were reviewed, and the follow-up rate was 86.4%. All procedures were successful without conversion to prosthetic valve replacement during the procedure. Six (6) patients died after the procedure (in-hospital mortality, 1.2%). All-cause mortality occurred in 11 patients during the follow-up period. The 10-year cumulative survival rate was 94.7%±2.9%. Redo aortic valve surgery was performed in 11 patients after the procedure. The actuarial freedom from redo aortic valve surgery after the procedure was 88.2%±5.2%. At the end of the follow-up, the mean peak was 29.1±9.6 mmHg and mean gradient was 15.6±6.2 mmHg. The mid- and long-term outcomes in patients with various aortic valve diseases undergoing trileaflet aortic valve reconstruction with bovine pericardium are encouraging. The engineered pericardial leaflets should be individually proportional to the size of the aortic root.

In-vivo Evaluation of a Novel Surgical Heart Valve Prosthesis Designed to Be Durable, Anticoagulant-free and Silent

Objective: Heart valves prostheses still face limitations: reoperations with tissue valves or lifelong anticoagulation with mechanical valves. The Triflo valve, a tri-leaflet valve made of high-resistant bio-inert materials, aimed at overcoming these limitations. We studied safety and performance in a chronic sheep model. Methods: The Triflo valve (size 21mm) was implanted in two models: 90 days in aortic position (n=7) and 70 days in pulmonary position (n=4). In the pulmonary model, On-X valves (n=2) were used as control. After 7 days of low-molecular-weight heparin, no further anticoagulant was administered. Serial blood testing, echocardiography, acoustic measurements, fluoroscopy and autopsy were done. Results: The Triflo valve demonstrated excellent surgical handling. There were one aborted procedure and one early death in the aortic study, both unrelated to the prosthesis. All other sheep (n=9) recovered fast and remained in excellent clinical condition until the scheduled sacrifice. In aortic position, we observed low peak and mean gradients (8.1+/-2.7 and 4.8+/-1.9 mmHg), high effective orifice area (2.3+/-0.2 cm2), no valvular regurgitation, and perfect left ventricular function. At explantation, the surface of all Triflo valves was clean, without any valve thrombosis. All major organs were free from thrombo-embolic (TE) damage. In pulmonary position, leaflet mobility of all valves remained also normal and no TE-damage was found in the lungs. Hematological parameters were stable without any sign of hemolysis. On-X valves in pulmonary position functioned well, but generated significantly louder acoustic signals (p < 0.05). Conclusions: The Triflo valve showed safety and effectiveness in both aortic and pulmonary position. These favorable in-vivo results, with excellent hemodynamic behavior and stable long-term function even in the absence of anticoagulants, demonstrate that this valve can proceed to first-in-human studies.

Accuracy of stroke volume measurement with phase-contrast cardiovascular magnetic resonance in patients with aortic stenosis

BackgroundPhase contrast (PC) cardiovascular magnetic resonance (CMR) in the ascending aorta (AAo) is widely used to calculate left ventricular (LV) stroke volume (SV). The accuracy of PC CMR may be altered by turbulent flow. Measurement of SV at another site is suggested in the presence of aortic stenosis, but very few data validates the accuracy or inaccuracy of PC in that setting. Our objective is to compare flow measurements obtained in the AAo and LV outflow tract (LVOT) in patients with aortic stenosis.MethodsRetrospective analysis of patients with aortic stenosis who had CMR and echocardiography. Patients with mitral regurgitation were excluded. PC in the AAo and LVOT were acquired to derive SV. LV SV from end-systolic and end-diastolic tracings was used as the reference measure. A difference ≥ 10% between the volumetric method and PC derived SVs was considered discordant. Metrics of turbulence and jet eccentricity were assessed to explore the predictors of discordant measurements.ResultsWe included 88 patients, 41% with bicuspid aortic valve. LVOT SV was concordant with the volumetric method in 79 (90%) patients vs 52 (59%) patients for AAo SV (p = 0.015). In multivariate analysis, aortic stenosis flow jet angle was a strong predictor of discordant measurement in the AAo (p = 0.003). Mathematical correction for the jet angle improved the concordance from 59 to 91%. Concordance was comparable in patients with bicuspid and trileaflet valves (57% and 62% concordance respectively; p = 0.11). Accuracy of SV measured in the LVOT was not influenced by jet eccentricity. For aortic regurgitation quantification, PC in the AAo had better correlation to volumetric assessments than LVOT PC.ConclusionLVOT PC SV in patients with aortic stenosis and eccentric jet might be more accurate compared to the AAo SV. Mathematical correction for the jet angle in the AAo might be another alternative to improve accuracy.

Isogeometric finite element-based simulation of the aortic heart valve: Integration of neural network structural material model and structural tensor fiber architecture representations.

The functional complexity of native and replacement aortic heart valves (AVs) is well known, incorporating such physical phenomenons as time-varying non-linear anisotropic soft tissue mechanical behavior, geometric non-linearity, complex multi-surface time varying contact, and fluid-structure interactions to name a few. It is thus clear that computational simulations are critical in understanding AV function and for the rational basis for design of their replacements. However, such approaches continued to be limited by ad-hoc approaches for incorporating tissue fibrous structure, high-fidelity material models, and valve geometry. To this end, we developed an integrated tri-leaflet valve pipeline built upon an isogeometric analysis framework. A high-order structural tensor (HOST)-based method was developed for efficient storage and mapping the two-dimensional fiber structural data onto the valvular 3D geometry. We then developed a neural network (NN) material model that learned the responses of a detailed meso-structural model for exogenously cross-linked planar soft tissues. The NN material model not only reproduced the full anisotropic mechanical responses but also demonstrated a considerable efficiency improvement, as it was trained over a range of realizable fibrous structures. Results of parametric simulations were then performed, as well as population-based bicuspid AV fiber structure, that demonstrated the efficiency and robustness of the present approach. In summary, the present approach that integrates HOST and NN material model provides an efficient computational analysis framework with increased physical and functional realism for the simulation of native and replacement tri-leaflet heart valves.

The art of aortic valve repair

The art of aortic valve repair

Numerical simulations of flow patterns in the human left ventricle model with a novel dynamic mesh morphing approach based on radial basis function

We present a new numerical simulation framework for prediction of flow patterns in the human left ventricle model. In this study, a radial basis function (RBF) mesh morphing method is developed and applied within the finite-volume computational fluid dynamics (CFD) approach. The numerical simulations are designed to closely mimic details of recent tomographic particle image velocimetry (TomoPIV) experiments. The numerically simulated dynamic motions of the left ventricle and tri-leaflet biological mitral valve are emulated through the RBF morphing method. The arbitrary Lagrangian-Eulerian (ALE) based CFD is performed with the RBF-defined deforming wall boundaries. The results obtained show a good agreement with experiments, confirming the reliability and accuracy of the developed simulation framework.

Fabrication and in-vitro characterization of a polymeric aortic valve for minimally invasive valve replacement

The valve replacement therapy is the standard treatment for severe heart valve diseases. Nowadays, two types of commercial prosthesis are available: mechanical and biological, but both of them have severe limitations. Moreover, alternative therapeutic approach for valve replacement, based on minimally invasive techniques (MIAVR), motivates the search for new valve materials. In this study a polyurethane-based self-expandable tri-leaflets heart valve compatible with MIAVR procedure is proposed. The device is based on the development, fabrication and characterization of three different elements: the leaflets, the polymeric stent for supporting the leaflets, and the external metallic stent for anchoring the valve to the native aortic root. The polymeric stent and the valve leaflets were fabricated using a thermoplastic silicone-polycarbonate-urethane using 3D printing and spray technology while the external metallic stent was made in nickel titanium (Nitinol) to obtain a self-expandable valve after the crimping process. The three elements were assembled in the completed device and tested by crimping, fatigue and fluid-dynamic test. The novel polymeric valve proposed showed promising results about valve crimping capabilities, durability and fluid dynamic performances. This approach could offer advantages such as low cost and to produce a tailor-made device basing on patient's imaging data. Moreover, the selected biomaterial offers the potential to have a device that could need of permanent anticoagulation and lack of calcification.

Possible Early Generation of Physiological Helical Flow Could Benefit the Triflo Trileaflet Heart Valve Prosthesis Compared to Bileaflet Valves.

Background—Physiological helical flow in the ascending aorta has been well documented in the last two decades, accompanied by discussions on possible physiological benefits of such axial swirl. Recent 4D-MRI studies on healthy volunteers have found indications of early generation of helical flow, early in the systole and close to the valve plane. Objectives—Firstly, the aim of the study is to investigate the hypothesis of premature swirl existence in the ventricular outflow tract leading to helical flow in the valve plane, and second to investigate the possible impact of two different mechanical valve designs on the preservation of this early helical flow and its subsequent hemodynamic consequences. Methods—We use a pulse duplicator with an aortic arch and High-Speed Particle Image Velocimetry to document the flow evolution in the systolic cycle. The pulse-duplicator is modified with a swirl-generating insert to generate early helical flow in the valve plane. Special focus is paid to the interaction of such helical flow with different designs of mechanical prosthetic heart valves, comparing a classical bileaflet mechanical heart valve, the St. Jude Medical Regent valve (SJM Regent BMHV), with the Triflo trileaflet mechanical heart valve T2B version (Triflo TMHV). Results—When the swirl-generator is inserted, a vortex is generated in the core flow, demonstrating early helical flow in the valve plane, similar to the observations reported in the recent 4D-MRI study taken for comparison. For the Triflo trileaflet valve, the early helical flow is not obstructed in the central orifice, similar as in the case of the natural valve. Conservation of angular momentum leads to radial expansion of the core flow and flattening of the axial flow profile downstream in the arch. Furthermore, the early helical flow helps to overcome separation at the outer and inner curvature. In contrast, the two parallel leaflets for the bileaflet valve impose a flow straightener effect, annihilating the angular momentum, which has a negative impact on kinetic energy of the flow. Conclusion—The results imply better hemodynamics for the Triflo trileaflet valve based on hydrodynamic arguments under the discussed hypothesis. In addition, it makes the Triflo valve a better candidate for valve replacements in patients with a pathological generation of nonaxial velocity in the ventricle outflow tract.

Abstract 14086: Early Results of a Novel EPTFE-based Pulmonary Valved Conduit in a Pediatric Patient Population

Introduction: This prospective, multicenter, single-arm, early feasibility study evaluates the safety and performance of an investigational ePTFE-based valve for replacement of the pulmonary valve and reconstruction of the Right Ventricular Outflow Tract. A novel polymeric pulmonary valved conduit, resistant to calcification and structural valve deterioration, may provide a more durable therapy option for the pediatric population by preventing loss of right ventricular function and increased freedom from valve-related reintervention and mortality. Methods: The primary endpoints at 6 months adjudicated by an independent Clinical Events Committee are valve-related mortality and device-related reintervention. The investigational device is a valved conduit comprised of ePTFE with stretch technology and a flexible tri-leaflet polymeric valve made of an advanced proprietary composite material, which can be tailored to length requirements of the anatomy. All enrolled patients met study inclusion/exclusion criteria and had a signed informed consent form. All patients had pre- and postoperative evaluation via transthoracic echocardiography (TTE). Aspirin was administered for a minimum of three months post procedure and, per institutional protocols, four patients were on temporary Coumadin. Results: Of the 17 patients enrolled from three sites, 52.9% were male. Ages ranged from 6 to 17 years (mean 11.5 ± 3.7). BSA ranged from 0.82 to 1.57 m 2 . At six months follow up, 100% of subjects successfully met the primary endpoint of freedom from valve-related mortality and device-related reintervention. No patient exhibited an RVOT gradient &gt; 20 mmHg. No patients had pulmonary regurgitation above baseline (≤ mild) observed through six months. Throughout postoperative serial TTE evaluation at discharge, 1, 3, and 6 months, no evidence of worsening valvular insufficiency was observed. No patient developed endocarditis and TTE detected no clinically significant thrombus formation. Conclusions: These preliminary data of a novel Pulmonary Valve Conduit suggest improved pulmonic and right ventricular function based on TTE measurements, no unexpected findings, no valve-related adverse events and encouraging hemodynamic performance through 6 months.

Right ventricular outflow reconstruction with handmade valve conduit - A short experience from a developing country. Case series

ObjectivesRight ventricular outflow tract continuity abnormalities are one of the most commonly encountered entities in the field of congenital cardiac surgery. Various strategies including homograft, valve conduit, Contegra are used to restore continuity between right ventricle and pulmonary artery. In countries like Pakistan these may not be easily available and affordable. We report the experience of our short observational study of using a handmade trileaflet valve conduit to reconstruct the right ventricular outflow tract. MethodologyFrom September 2015 to December 2016, a total of 15 patients with different congenital heart diseases underwent open-heart surgery at our institute. Restoration of right ventricular to pulmonary artery continuity was achieved using handmade valve conduit utilizing bovine pericardium and thin sheet PTFE sheets (0.1 mm) as conduit and valve respectively. ResultsPatients ranged from 1 to 16 years. Seven patients had previous palliation including 4 blalock taussig (BT) Shunts and 3 pulmonary artery (PA) banding. Postoperative complications were observed in 4 patient including 2 in hospital deaths and 2 required interventions. One patient developed aneurysm at RV- conduit junction requiring surgical repair and the other underwent conduit dilatation for moderate to severe stenosis (gradient 60 mmHg). No significant regurgitation was observed in this series. Overall postoperative gradients were stable with mean gradient 25.3 mmHg (8 mmhg - 60 mmHg). ConclusionThe use of handmade valve conduits has acceptable morbidity and mortality. These are cost effective alternatives in this part of the world, where well-established conduits have cost implications and uncertain availability.

Excellent Hemodynamic Performance After Aortic Valve Neocuspidization Using Autologous Pericardium

Aortic valve neocuspidization (AVNeo) for trileaflet aortic valve reconstruction using autologous pericardium (Ozaki procedure) offers an alternative treatment modality to overcome drawbacks of conventional prosthetic aortic valve replacement. Between October 2016 and April 2019, 103 patients underwent surgery. Mean follow-up was 426 ± 270 days. Aortic stenosis was the leading diagnosis in 80 patients (77.7%) and aortic regurgitation in 23 (22.3%), respectively. Mean age was 54.0 ± 16.4 years (range, 13.8-78.5). A bicuspid valve was found in 81 patients (78.6%). Transthoracic echocardiography was performed at discharge and at 6 to 12 months after surgery. During AVNeo surgery valve sizing for an Abbott/St Jude Trifecta bioprosthesis (virtually implanted Trifecta bioprosthesis; St Jude Medical, St Paul, MN) was performed to compare pressure gradients and effective orifice area with published data. Trileaflet aortic valve reconstruction was achieved in all patients. In 38 patients neocommissures were created (36.9%). Mean cross-clamp time was 135 ± 20 minutes. Four patients underwent reoperation; the overall freedom from reoperation was 96.1%. Echocardiographic 6- to 12-months follow-up after surgery was available in 93.8% of patients and did not show any change in hemodynamic parameters compared with discharge. Comparison between AVNeo and virtually implanted Trifecta Bioprosthesis revealed a significantly lower mean pressure gradient (8.5 ± 3.7 mm Hg vs 10.2±2.0 mm Hg, P < .001) and higher mean effective orifice area (2.2 ± 0.7 cm2 vs 2.1 ± 0.4 cm2, P= .037) for AVNeo. AVNeo shows low reoperation rates after surgery within the first 2 years. The hemodynamic performance is excellent, and the effective orifice area and mean pressure gradient remain stable within the first year.

Hemodynamics and tissue biomechanics of the thoracic aorta with a trileaflet aortic valve at different phases of valve opening.

In a normal cardiac cycle, the trileaflet aortic valve opening is progressive, which correlates with the phasic blood flow. Therefore, we aimed to determine the impact of including an anatomically accurate reconstructed trileaflet aortic valve within a fluid-structure interaction (FSI) simulation model and determine the cyclical hemodynamic forces imposed on the thoracic aortic walls from aortic valve opening to closure. A pediatric patient with a normal trileaflet valve was recruited. Using the Cardiac Magnetic Resonance Data (CMR), a 3D model of the aortic valve and thoracic aorta was reconstructed. FSI simulations were employed to assess the tissue stress during a cardiac cycle as the result of changes in the valve opening. The blood flow was simulated as a mixture of blood plasma and red blood cells to account for non-Newtonian effects. The computation was validated with phase-contrast CMR. Windkessel boundary conditions were employed to ensure physiological pressures during the cardiac cycle. The leaflets' dynamic motion during the cardiac cycle was defined with an analytic grid velocity function. At the beginning of the valve opening a thin jet is developing. From mid-open towards full opening the stress level increases where the jet impinges the convex wall. At peak systole two counter-rotating Dean-like vortex cores manifest in the ascending aorta, which correlates with increased integrated mean stress levels. An accurate trileaflet aortic valve is needed for capturing of both primary and secondary flow features that impact the forces on the thoracic aorta wall. Omitting the aortic valve underestimates the biomechanical response.

The Leaflex™ Catheter – A Novel Device for Treating Calcific Aortic Stenosis – First-in-Human Intra-Operative Assessment of Safety and Efficacy

ABSTRACT Background The Leaflex™ is a novel percutaneous device for restoring calcified aortic valve leaflet mobility by mechanical scoring. To demonstrate the safety and efficacy of the Leaflex™ during surgical aortic valve replacement and examination of excised valve tissue. In a growing elderly population with multiple comorbidities, increasing frailty, and often limited mobility a simple mechanical intervention for severe aortic stenosis (AS) may be appropriate in selected patients as a standalone first intervention. Methods Five patients with severe AS (including one with fused leaflets) were treated with the Leaflex™ during cardiopulmonary bypass prior to valve excision. Estimated pressure gradient (PG) was assessed by the force required to pull a cone through the valve before and after Leaflex therapy. The change in the estimated aortic valve area (AVA) was then calculated based on the Gorlin equation. The excised aortic leaflets were examined histologically, radiographically and by micro-CT, for leaflet integrity. Results The Estimated PG based on the pullback force decreased by 75% (±2.7%) and estimated AVA increased by 99% (±11%) across 4 tri-leaflet aortic valves and by 53% and 46%, respectively, in one valve with fused commissures. Micro-CT and histology confirmed ventricular surface integrity at the site of scoring in all five cases. Conclusions In the intraoperative setting, the Leaflex™ was effective in decreasing estimated PG and increasing estimated AVA with the maintenance of valve tissue integrity. Although the results of the pressure gradient are estimates, these encouraging results support further assessment of the Leaflex™ approach in patients with calcific AS.

Fetal Transcatheter Trileaflet Heart Valve Hemodynamics: Implications of Scaling on Valve Mechanics and Turbulence.

The scarcity of data available on the best approach for pulmonary fetal valve replacement or implantation necessitate an investigation on whether practices using adult transcatheter valves could be translated to fetal applications. The objective of this study is to evaluate the hemodynamic characteristics and the turbulent properties of a fetal sized trileaflet transcatheter pulmonary valve in comparison with an adult balloon-expandable valve in order to assess the possibility of designing valves for fetal applications using dynamic similarity. A 6mm fetal trileaflet valve and a 26mm SAPIEN 3valve were assessed in a pulse duplicator. Particle image velocimetry was performed. Pressure gradient (ΔP), effective orifice area (EOA), regurgitant fractions (RF), pinwheeling indices (PI) and turbulent stresses were evaluated. ΔP was 8.56 ± 0.139 and 7.76 ± 0.083mmHg with fetal valve and SAPIEN respectively (p < 0.0001); EOA was 0.10 ± 0.0007 and 2.1 ± 0.025cm2 with fetal valve and SAPIEN respectively (p < 0.0001); RF with the fetal valve was 2.35 ± 1.99% and with SAPIEN 10.92 ± 0.11% (p < 0.0001); PI with fetal valve was 0.404 ± 0.01 and with SAPIEN 0.37 ± 0.07; The flow regime with the fetal valve was turbulent and Reynolds numbers reached about 7000 while those with the SAPIEN reached about 20,000 at peak velocity. Turbulent stresses were significantly higher with fetal valve compared with SAPIEN. Instantaneous viscous shear stresses with fetal valve were 5.8 times higher than those obtained with SAPIEN and Reynolds shear stresses were 2.5 times higher during peak systole. The fetal valve implantation leads to a turbulent flow (specific to this particular type and design of valve) regime unlike what is expected of a small valve with different flow properties compared to adult valves.

In vitro Assessment of the Impacts of Leaflet Design on the Hemodynamic Characteristics of ePTFE Pulmonary Prosthetic Valves.

Prosthetic pulmonary valves are widely used in the management procedures of various congenital heart diseases, including the surgical pulmonary valve replacement (PVR) and right ventricular outflow tract reconstruction (RVOT). The discouraging long-term outcomes of standard prostheses, including homografts and bioprosthetic, constrained their indications. Recent developments in the expanded-polytetrafluoroethylene (ePTFE) pulmonary prosthetic valves provide promising alternatives. In this study, the hemodynamic characteristics of bileaflet and trileaflet ePTFE valve designs were experimentally evaluated. The in vitro tests were performed under the right ventricle (RV) flow conditions by using an in vitro RV circulatory system and particle image velocimetry (PIV). The leaflet kinetics, trans-valvular pressure gradients, effective orifice areas, regurgitant fractions, energy losses, velocity fields, and Reynolds shear stress (RSS) in both prostheses were evaluated. The opening of the bileaflet and trileaflet valve takes 0.060 and 0.088 s, respectively. The closing of the former takes 0.140 s, in contrast to 0.176 s of the latter. The trans-valvular pressure is 6.8 mmHg in the bileaflet valve vs. 7.9 mmHg in the trileaflet valve. The effective orifice area is 1.83 cm2 in the bileaflet valve and 1.72 cm2 in the trileaflet valve. The regurgitant fraction and energy loss of bileaflet are 7.13% and 82 mJ, which are 7.84% and 101.64 mJ in its bileaflet counterpart. The maximum RSS of 48.0 and 49.2 Pa occur at the systole peak in the bileaflet and trileaflet valve, respectively. A higher average RSS level is found in the bileaflet valve. The results from this preliminary study indicate that the current bileaflet prosthetic valve design is capable of providing a better overall hemodynamic performance than the trileaflet design.