Valve Configuration Research Articles

Should the annulus be fixed in aortic valve-sparing root replacement with remodeling?

If the aortic root dilates after native aortic valve-sparing root reconstruction with remodeling, aortic regurgitation may recur. However, it has not been demonstrated clearly that the aortic root dilates after remodeling. This study enrolled 15 patients who underwent an aortic valve-sparing operation with remodeling (2002-2014) but without any ventriculo-aortic junction (VAJ) fixation. Technically, special care was taken to pass the sutures through the fibrous annulus. The diameter of the aortic root (VAJ, neosinus of Valsalva, and sinotubular junction), degree of aortic regurgitation, and effective height of the aortic valve were measured in the patients. All patients had postoperative follow-up, and the median follow-up period was 7.3 (IQR: 3.1-8.3)years. The mean preoperative diameters of the VAJ, sinus of Valsalva, and sinotubular junction were 23.5 ± 2.3 (20-27)mm, 51.1 ± 7.2 (43-60)mm, and 42.4 ± 9.4 (29-58)mm, respectively. The postoperative diameters of the VAJ changed from 21.6 ± 2.6 (early) to 21.8 ± 2.9mm (late) (p = 0.75). The diameters of the sinus of Valsalva and sinotubular junction changed from 26.5 ± 3.0 (early) to 28.5 ± 4.2mm (late) (p = 0.0013), and 22.4 ± 3.0 (early) to 24.3 ± 3.3mm (late) (p = 0.0003), respectively. The effective height of the aortic valve changed from 9.7 ± 1.3 (early) to 8.9 ± 2.0mm (late) (p = 0.08). The degree of aortic regurgitation (grade: 0-4) changed from 0.3 ± 0.5 (early) to 1.2 ± 0.8 (late) (p = 01558). Significant VAJ dilation and changes in aortic valve configuration after our remodeling procedure were not observed. Therefore, fixation of the annulus with remodeling may not be needed for cases without preoperative dilation of the annulus.

Performance Evaluation of Magnetorheological Damper Valve Configurations Using Finite Element Method

The main purpose of this paper is to study various configurations of a magnetorheological (MR) damper valve and to evaluate their performance indices typically dynamic range, valve ratio, inductive time constant and pressure drop. It is known that these performance indices (PI) of the damper depend upon the magnetic circuit design of the valve. Hence, nine valve configurations are considered for which mathematical models are developed. A finite element model is built to analyze and investigate the PI of a 2-D axi-symmetric MR damper valve. All configurations of the damper valve are simulated within a given range of input current and number of turns of coil, and within this range, damping force, dynamic range, valve ratio, inductive time constant and achieved pressure drop have been evaluated. The simulation results show that the PI of the MR damper are highly dependent on the shapes of valves and hence the valve shape should be selected based on the intended application. The results obtained in this work provide an insight for designers to create application-specific MR dampers.

Repair of the Bicuspid Aortic Valve

Repair has become an alternative to replacement for bicuspid aortic valves that require surgery for regurgitation with left ventricular volume overload or aortic aneurysm. Over the past 15 years, improvements have been made regarding assessment of valve configuration and annular stabilization. Even though 20-year stability has been achieved in a relevant proportion of repaired bicuspid aortic valves, the new aspects have markedly improved short- to mid-term results and can be expected to lead to true long-term repair stability. In the presence of preserved root dimensions, isolated cusp repair techniques for correction of prolapse are sufficient. Circumferential annuloplasty has become an important part of the procedure. In the presence of root dilatation, root replacement not only eliminates the root pathology but also contributes to valve stability. Almost always cusp repair is also required.

Ischemic mitral valve prolapse.

Ischemic mitral prolapse (IMP) is a pathologic entity encountered in about one-third among the patients undergoing surgery for ischemic mitral regurgitation (IMR). IMP is generally the result of a papillary muscle injury consequent to myocardial, but the recent literature is progressively unveiling a more complex pathogenesis. The mechanisms underlying its development regards the impairment of one or more components of the mitral apparatus, which comprises the annulus, the chordae tendineae, the papillary muscle and the left ventricular wall. IMP is not only a disorder of valvular function, but also entails coexistent aspects of a geometric disturbance of the mitral valve configuration and of the left ventricular function and dimension and a correct understanding of all these aspects is crucial to guide and tailor the correct therapeutic strategy to be adopted. Localization of prolapse, anatomic features of the prolapsed leaflets and the subvalvular apparatus should be carefully evaluated as also constituting the major determinants defining patient's outcomes. This review will summarize our current understanding of the pathophysiology and clinical evidence on IMP with a particular focus on the surgical treatment.

MMP-2 Isoforms in Aortic Tissue and Serum of Patients with Ascending Aortic Aneurysms and Aortic Root Aneurysms.

ObjectiveThe need for biological markers of aortic wall stress and risk of rupture or dissection of ascending aortic aneurysms is obvious. To date, wall stress cannot be related to a certain biological marker. We analyzed aortic tissue and serum for the presence of different MMP-2 isoforms to find a connection between serum and tissue MMP-2 and to evaluate the potential of different MMP-2 isoforms as markers of high wall stress.MethodsSerum and aortic tissue from n = 24 patients and serum from n = 19 healthy controls was analyzed by ELISA and gelatin zymography. 24 patients had ascending aortic aneurysms, 10 of them also had aortic root aneurysms. Three patients had normally functioning valves, 12 had regurgitation alone, eight had regurgitation and stenosis and one had only stenosis. Patients had bicuspid and tricuspid aortic valves (9/15). Serum samples were taken preoperatively, and the aortic wall specimen collected during surgical aortic repair.ResultsPro-MMP-2 was identified in all serum and tissue samples. Pro-MMP-2 was detected in all tissue and serum samples from patients with ascending aortic/aortic root aneurysms, irrespective of valve morphology or other clinical parameters and in serum from healthy controls. We also identified active MMP-2 in all tissue samples from patients with ascending aortic/aortic root aneurysms. None of the analyzed serum samples revealed signals relatable to active MMP-2. No correlation between aortic tissue total MMP-2 or tissue pro-MMP-2 or tissue active MMP-2 and serum MMP-2 was found and tissue MMP-2/pro-MMP-2/active MMP-2 did not correlate with aortic diameter. This evidence shows that pro-MMP-2 is the predominant MMP-2 species in serum of patients and healthy individuals and in aneurysmatic aortic tissue, irrespective of aortic valve configuration. Active MMP-2 species are either not released into systemic circulation or not detectable in serum. There is no reliable connection between aortic tissue—and serum MMP-2 isoforms, nor any indication that pro-MMP-2 functions as a common marker of high aortic wall stress.

Characterization of serum matrix metalloproteinase 2/9 levels in patients with ascending aortic aneurysms.

The objectives of this study were to identify interrelations between matrix metalloproteinase-2 (MMP2)/MMP9 levels and clinical variables in patients with aortic root/ascending aortic aneurysms and to describe comorbidities as possible biasing factors in the widely discussed correlation of serum MMP levels and aortic diameter. Serum MMP9 and MMP2 levels were quantified in 32 consecutive patients with ascending aortic and/or aortic root aneurysms (>45 mm) at the Heart Center University of Freiburg from May 2013 to January 2014. The influence of comorbidities and medication on serum MMP2 and MMP9 levels was studied. We took into account ascending aortic diameter (aAD), aortic valve configuration, hypertension, age and hyperlipidaemia as factors possibly altering serum MMP levels. The relation between serum MMP levels and aAD was examined by a correlation test based on ranks. Serum MMP2 levels and aAD correlated positively. Correlation was increased in patients without hyperlipidaemia (Spearman's ρ = 0.62, P = 0.008 in patients without hyperlipidaemia; ρ = 0.409, P = 0.020 in all patients). Serum MMP9 levels did not correlate with aAD and showed greater variation. Serum MMP9 levels were significantly associated with hyperlipidaemia (P = 0.037). The distinct correlation patterns in patients with and without hyperlipidaemia have to be considered when defining the potential of MMP2 as a biomarker in future studies. The relation between MMP9 and hyperlipidaemia has to be further investigated.

Sinus Plication to Improve Valve Configuration in Bicuspid Aortic Valve Repair—Early Results

Previous experience with repair of the regurgitant bicuspid aortic valve (BAV) has shown a strong influence of commissural orientation on repair durability. We have modified commissural orientation by asymmetric plication of the fused sinuses. We analyzed the results of the modified technique. Between 2009 and 2014, 35 patients with BAV and commissural orientation of no more than 160° underwent aortic valve repair, including plication of the fused sinuses and circular annuloplasty. The control group consisted of 21 historic controls undergoing operations between 2000 and 2008 but without sinus plication; subcommissural plication was used as annuloplasty. The groups were similar in most respects; differences existed in preoperative annular diameter, prevalence of complete fusion, use of a pericardial patch, and plication of the fused cusp. At discharge the degree of aortic regurgitation (AR) was significantly lower in the study group (p= 0.004). Survival after 5 years was 100% in the study group and 95.2% in the control group after 5 and 10 years. Five-year freedom from reoperation in the study group was 93.0% and 57.1% in the control group (p= 0.0013); freedom from valve replacement was 95.8% and 79.3% (p= 0.036). Freedom from recurrent AR grade II or higher was 67.1% in the study group and 33.3% in the control group (p= 0.0024). Mean postoperative peak gradient was significantly lower in the study group (14.3 ± 6.5 mm Hg versus 28.9 ± 18.5 mm Hg, p= 0.003). Plicating the fused sinuses and thus reducing root circumference in the fused part changes commissural orientation of the BAV which leads to better short- and midterm stability in BAV repair.

Optimal sectioning of hydrocarbon transport pipeline by volume minimization, environmental and social vulnerability assessment

Sectioning is one of the key mitigation strategies in pipeline transport of liquid hydrocarbons. The valves located along pipelines reduce the maximum volume that may be spilled decreasing economic, social and environmental losses. Defining the location and number of valves in a specific pipeline section is a challenging decision due to the countless combinations of these two design components (i.e., where and how many valves). In this work, we address the valve location problem (VLP) for sectioning using an optimization approach based on a shortest path problem, which assesses the possible location of valves to minimize environmental risk and guarantee a tolerable value of individual risk. To estimate and quantify both the environmental vulnerability and individual risk a new framework is proposed, employing the spill volume and ecological and social characteristics as inputs. We present two case studies for sectioning in Latin-American pipelines; the problem is solved using a Bellman-Ford algorithm with CPU times up to 40 s. The results show reductions on the order of 50%–85% of the maximum possible spill volume compared with the current situation, in each case respectively. The resulting valve configurations cover areas with high environmental vulnerability, reducing ecological losses and guaranteeing a level of individual risks lower than the acceptable value on all populated areas.

Effect of Arched Leaflets and Stent Profile on the Hemodynamics of Tri-Leaflet Flexible Polymeric Heart Valves.

Polymeric heart valves (PHV) can be engineered to serve as alternatives for existing prosthetic valves due to higher durability and hemodynamics similar to bioprosthetic valves. The purpose of this study is to evaluate the effect of geometry on PHVs coaptation and hemodynamic performance. The two geometric factors considered are stent profile and leaflet arch length, which were varied across six valve configurations. Three models were created with height to diameter ratio of 0.6, 0.7, and 0.88. The other three models were designed by altering arch height to stent diameter ratio, to be 0, 0.081, and 0.116. Particle image velocimetry experiments were conducted on each PHV to characterize velocity, vorticity, turbulent characteristics, effective orifice area, and regurgitant fraction. This study revealed that the presence of arches as well as higher stent profile reduced regurgitant flow down to 5%, while peak systole downstream velocity reduced to 58% and Reynolds Shear Stress values reduced 40%. Further, earlier reattachment of the forward flow jet was observed in PHVs with leaflet arches. These findings indicate that although both geometric factors help diminish the commissural gap during diastole, leaflet arches induce a larger jet opening, yielding to earlier flow reattachment and lower energy dissipation.

Chaotic and Hyperchaotic Dynamics of Smart Valves System Subject to a Sudden Contraction

In this paper, we focus on determining the safe operational domain of a coupled actuator–valve configuration. The so-called “smart valves” system has increasingly been used in critical applications and missions including municipal piping networks, oil and gas fields, petrochemical plants, and more importantly, the U.S. Navy ships. A comprehensive dynamic analysis is hence needed to be carried out for capturing dangerous behaviors observed repeatedly in practice. Using some powerful tools of nonlinear dynamic analysis including Lyapunov exponents and Poincaré map, a comprehensive stability map is provided in order to determine the safe operational domain of the network in addition to characterizing the responses obtained. Coupled chaotic and hyperchaotic dynamics of two coupled solenoid-actuated butterfly valves are captured by running the network for some critical values through interconnected flow loads affected by the coupled actuators' variables. The significant effect of an unstable configuration of the valve–actuator on another set is thoroughly investigated to discuss the expected stability issues of a remote set due to others and vice versa.

Optimal Sizing of an Air Vessel in a Long-Distance Water-Supply Pumping System Using the SQP Method

AbstractBy optimizing the sizing of air vessels, not only is the damage from water hammer prevented, but also the cost of water hammer protection systems is minimized. This paper presents a numerical simulation of an air vessel in a long-distance transfer main system against water hammer resulting from sudden pump stoppage. An optimal design of air vessel parameters is obtained using sequential quadratic programming (SQP) in this case. Three types of connection configuration (between the air vessel and the main pipeline) are tested in the case study, including a vertical cylindrical vessel with a bypass line (configuration 1), a vertical cylindrical vessel with a bypass line equipped with a throttle valve (configuration 2), and a horizontal cylindrical vessel with separated inflow and outflow lines (configuration 3). The variations of optimal volume of the air vessel, VT, are plotted as a function of the allowable maximum pressure head, Hmax*, with the diameter of the bypass line, db, or the throttle valv...

A Dictionary for the Modern Trumpet Player by Elisa Koehler

Reviewed by: A Dictionary for the Modern Trumpet Player by Elisa Koehler Jim Farrington A Dictionary for the Modern Trumpet Player. By Elisa Koehler. (Dictionaries for the Modern Musician.) Lanham, MD: Rowman & Littlefield, 2015. [xi, 219 p. ISBN 9780810886575 (hard-cover), $75; ISBN 9780810886582 (e-book), $74.99.] Illustrations, appendices, bibliography. In 2014, Rowman & Littlefield began a new series of dictionaries aimed at the contemporary performer (although Susan Maclagan’s A Dictionary for the Modern Flutist [Lanham, MD: Scarecrow Press, 2009] seems to have been the model for the subsequent series). To date, volumes have appeared targeting singers, clarinetists, conductors, and now this volume for trumpeters. The dictionaries are aimed at performers both amateur and professional, teachers and students, and others needing information on specialized aspects of the instrument that would not be covered in a more general work like the Grove Dictionary of Musical Instruments. The author is a well-respected scholar of the trumpet and its history with numerous books and articles to her credit, including Fanfares and Finesse: A Performer’s Guide to Trumpet History and Literature (Bloomington: Indiana University Press, 2014), and several important articles in the International Trumpet Guild Journal, on whose editorial staff she serves. This dictionary is an excellent blend of first-rate scholarship and readability. The history of the trumpet extends back centuries, and trumpet-like instruments are found in almost every culture and made from almost any material. Many of these instruments (e.g., the shofar, the abe.n) are given some notice, often with a very useful line drawing. Indeed, the text is liberally sprinkled with more than sixty line drawings (rather than photographs, which perhaps would have increased the cost) and music examples that helpfully illustrate terms or instruments discussed in the text, all rendered especially for this book. In particular, appendix 2 (pp. 193–99) shows and describes various valve configurations that have been used in trumpet design. Appendix 3 is an equally useful classification system of different mutes in a trumpeter’s arsenal (the individual mutes are covered in the main body of the text). Also convenient in the text are translations of non-English terms of instrument names and parts (e.g., drehventil, or rotary valve), or terms (e.g., muta, which on a nineteenth-century orchestral part indicates that the player is to change the crooks, thereby changing the key of the trumpet). Equally valuable are Koehler’s extended definitions of terms related to the technical aspects of playing the trumpet. For example, in discussing “multiple tonguing,” she not only describes the basic act of rapid articulation, but also particular passages from the repertoire that require different kinds of rapid articulations, as well as very specific physical manifestations of how to do this kind of specialized tonguing in various ranges. Koehler includes terms not only from the classical tradition but from studio and jazz work as well—smear, lead trumpet, etc.—as well as certain slang and colloquial terms (e.g., spit valve, but not “octave key” which is sometimes used to denote the pinky ring on the lead pipe). Most historical and contemporary major manufacturers of instruments, mouthpieces, mutes, and related equipment, are represented with at least a paragraph. However, some notable names are not represented, including Taylor, Scodwell, Flip Oakes, York, Harrelson, and numerous European makers, so it is difficult to ascertain the criteria that were used for inclusion. Similarly curtailed is a two-page list of orchestral and [End Page 315] opera excerpts (composer and title only) frequently found on audition lists. While the list is a “greatest hits” effort, more valuable, perhaps, would have been a compiled list of known orchestral audition repertoire asked for in the past five-to-ten years of open auditions. Hundreds of short biographies are incorporated into the text. Some are given to important composers of trumpet literature, including Heinrich Biber, Leopold Mozart, and Vjacheslav Shchelokov, or to composers whose larger works have notable trumpet features (e.g., Prokofiev). The majority of the biographies, of course, are of important trumpet players and pedagogues throughout history, beginning with Gabriel and continuing through Girolamo Fantini and the Altenburgs in the seventeenth century; Ulrich Ruhe (Bach’s trumpeter in...

Shortest path algorithm for optimal sectioning of hydrocarbon transport pipeline

Pipeline transportation mode is one of most used modes in oil industries. Transportation of hazardous substances by pipelines involves environmental, social and economic risks since a failure on a pipeline generates a subsequent release of a possible hazardous material. Limiting the amount of the spill volume reduces de losses and in consequence the associated risks; this mitigation is usually achieved by the installation of sectioning valves located along the pipeline. On practice a challenging problem is how much valves and where to locate them in function of the risks presented on each section. In this work, we tackle the valve location problem (VLP) for sectioning. This problem is modeled as a shortest path problem minimizing the maximum volume that could be spilled as well as environmental and social risks. To solve the problem we use the Bellman-Ford’s algorithm, assessing the number and location of valves to minimize environmental and social consequences. The approach was tested on a case study for sectioning a pipeline in Colombia. The results show reductions around 75% of the maximum possible spilled volume and the resulting valve configurations effectively cover areas with high vulnerability, guarantying individual risks lower than the acceptable risk on all populated areas and protecting areas of environmental interest.

DIFERENCIACIÓN MORFOLÓGICA DE LAS ESPECIES DE PIANGUA ANADARA TUBERCULOSA Y ANADARA SIMILIS (ARCIDAE) EN DIFERENTES BOSQUES DE MANGLAR A LO LARGO DE LA COSTA PACÍFICA COLOMBIANA MEDIANTE MORFOMETRÍA GEOMÉTRICA

The morphological characterization of two piangua species Anadara tuberculosa (Sowerby) and Anadara similis (Adams) was performed using geometric morphometric. Shells of both species were collected in nine different areas of the Colombian Pacific coast during 2009 as part of a project on the natural populations of piangua. The left valve of the shell was used to draw seven landmarks and evaluate the geometric configuration of the shell. Pianguas were grouped based on the mangrove cover of the localities where they were collected. Intra-specific comparison showed that areas where the organisms were collected do not affect valve configuration. Contrarily, centroide size showed significant variation in organism collected in different zones. Differences due to size are not sufficient to determine the existence of different populations, mainly because these differences may happen due to differences in fishery patterns increasing the ratio of smaller sizes. Pacific Ocean current might favor the genetic flux of organisms of both species, limiting the possibility of evolution of independent populations. It is important to complement this study with other investigations in genetics and larval dispersion in order to corroborate our findings.

Measurement of reed valve kinematics

The measurement of key kinematic parameters of a reed valve movement is necessary for the further development of the reed valve system. These parameters are dependent on the geometry and material properties of the valve. As they directly affect the quantity of air flowing around the valve, a simple and easy to implement measurement of various valve configuration based on the air flow has been devised and is described in this paper, along with its technical parameters and drawbacks when evaluating reed valves used in reciprocating air compressors. Results are presented for a specimen of a compressor under examination. All kinematic parameters, and timing of the opening and closing of the valve, obtained from the measurement are presented and discussed.

Mitral valve-in-valve hemodynamic performance: An in vitro study

ObjectivesThe valve-in-valve (VinV) procedure may be used in high-risk patients with failed mitral surgical bioprostheses. The objective of this in vitro study was to assess the hemodynamic function of different VinV configurations. MethodsA double activation duplicator was used to test 11 valve configurations (surgical bioprostheses alone) and 15 VinV configurations (Sapien [Edwards Lifesciences, Irvine, Calif] implanted within the surgical bioprosthesis) under 8 different hemodynamic conditions. The internal orifice diameter (IOD) of the surgical bioprosthesis was measured with a Smartscope (OGP Multi Sensor Measuring Instruments, Singapore). ResultsThe VinV procedure was associated with significant deterioration in antegrade hemodynamic parameters compared with valve configuration (effective orifice area, 1.51 ± 0.21 cm2 vs 1.65 ± 0.37 cm2; P < .001 and regurgitant fraction, 11.5% ± 7.2% vs 4.8% ± 3.8%; P < .001). Among the 120 tested experimental VinV situations, moderate or greater mitral stenosis occurred in 52 situations and mild or greater regurgitation occurred in 28 situations. The IOD of the surgical bioprosthesis was the main independent determinant of effective orifice area and regurgitant fraction. An IOD < 22 mm was associated with higher risk of significant mitral stenosis, particularly when the oversizing was >20%, and IOD > 23 mm was associated with higher risk of paravalvular regurgitation when oversizing was <8%. ConclusionsThis in vitro study shows that VinV within mitral surgical bioprostheses provides satisfactory hemodynamic results in the majority of patients. However, significant mitral stenosis is more likely to occur when the IOD of the surgical bioprosthesis is <22 mm, and particularly when the percentage of oversizing is >20%. Significant paravalvular regurgitation is rare and occurs with larger IODs and lower percentage of oversizing (8%).

Predictive factors of long-term results following valve repair in ischemic mitral valve prolapse

BackgroundIn patients with ischemic mitral regurgitation, leaflet prolapse requires an accurate evaluation since surgical approach depends on valvular and subvalvular characteristics. This study aims to describe a cohort of patients over a long-term follow up, analyzing survival, reoperation and predictive factors of surgical outcomes. Methods and resultsFrom March 1994 to June 2011, 75 patients with ischemic mitral regurgitation and leaflet prolapse underwent surgical myocardial revascularization and mitral valve repair (90.7%) or replacement (9.3%). Our cohort was followed up until April 2015, with a mean follow up of 7±3years.Cardiac-related deaths occurred in 26 patients, with a mean survival of 114.2months, including eight patients with in-hospital mortality. Reoperation was performed in 14 patients, due to valve repair failure. Twenty-six patients experienced moderate-to-severe mitral regurgitation. A preoperative LVEDD>62mm, LVESD>52mm, previous anteroseptal myocardial infarction, diffuse coronary artery disease, papillary anatomy type 1, partial rupture of the papillary muscle, A1-A2 scallop prolapse and postoperative mitral valve configuration (tenting area, tenting height, alfa-1 angle and alfa-2 angle) were identified as independent predictors of poor outcome. An index quantifying the stress on the annulus imparted by annuloplasty was elaborated and predicted endpoints. ConclusionLeaflet prolapse is an important entity in patients with ischemic mitral regurgitation, and its pathogenic mechanism mostly relies on papillary muscle lesion or elongation. Perioperative parameters describing geometric features of left ventricle, valvular and subvalvular components should be considered to provide a tailored approach for mitral valve repair, or to opt for immediate replacement in case of unfavorable geometry.

Numerical Investigation of the Spear Valve Configuration on the Performance of Pelton and Turgo Turbine Injectors and Runners

This paper uses two modern commercial cfd software packages to compare the performance of a standard and improved impulse turbine injector developed in a previous study. The two injector designs are compared by simulating the two-dimensional (2D) axis-symmetric cases as well as full three-dimensional (3D) cases including the bend in the branch pipe and the guide vanes. The resulting jet profiles generated by these simulations are used to initialize the inlet conditions for a full Pelton and Turgo runner simulation at different operating conditions in order to assess the impact of the injector design on the performance and efficiency of a real impulse turbine. The results showed that the optimized injector design, with steeper nozzle and spear angles, not only attains higher efficiencies in the 2D and 3D injector simulations but also produces a jet which performs better than the standard design in both the Pelton and the Turgo runner simulations. The results show that the greatest improvement in the hydraulic efficiency occurs within the injector with the improved design, showing an increase in efficiency of 0.76% for the Turgo 3D injector and 0.44% for the Pelton 3D injector. The results also show that in the case of the 3D injector, the improved injector geometry produces a jet profile which induces better overall runner performance, giving a 0.5% increase in total hydraulic efficiency for the Pelton case and 0.7% for the Turgo case.

Are anticoagulant independent mechanical valves within reach-fast prototype fabrication and in vitro testing of innovative bi-leaflet valve models.

Exploration for causes of prosthetic valve thrombogenicity has frequently focused on forward or post-closure flow detail. In prior laboratory studies, we uncovered high amplitude flow velocities of short duration close to valve closure implying potential for substantial shear stress with subsequent initiation of blood coagulation pathways. This may be relevant to widely accepted clinical disparity between mechanical and tissue valves vis-à-vis thrombogenicity. With a series of prototype bi-leaflet mechanical valves, we attempt reduction of closure related velocities with the objective of identifying a prototype valve with thrombogenic potential similar to our tissue valve control. This iterative design approach may find application in preclinical assessment of valves for anticoagulation independence. Tested valves included: prototype mechanical bi-leaflet BVs (n=56), controls (n=2) and patented early prototype mechanicals (n=2) from other investigators. Pulsatile and quasi-steady flow systems were used for testing. Projected dynamic valve area (PDVA) was measured using previously described novel technology. Flow velocity over the open and closing periods was determined by volumetric flow rate/PDVA. For the closed valve interval, use was made of data obtained from quasi-steady back pressure/flow tests. Performance was ranked by a proposed thrombogenicity potential index (TPI) relative to tissue and mechanical control valves. Optimization of the prototype valve designs lead to a 3-D printed model (BV3D). For the mitral/aortic site, BV3D has lower TPI (1.10/1.47) relative to the control mechanical valve (3.44/3.93) and similar to the control tissue valve (ideal TPI ≤1.0). Using unique technology, rapid prototyping and thrombogenicity ranking, optimization of experimental valves for reduced thrombogenic potential was expedited and simplified. Innovative mechanical valve configurations were identified that merit consideration for further development which may bring the anti-coagulation independent mechanical valve within reach.

Precise De Vega Annuloplasty Using Tricuspid Valve Gauges

Simple tricuspid annuloplasty gauges are described that simulate normal tricuspid valve annular geometry and enable the surgeon to perform precise De Vega tricuspid annuloplasties, with restoration of normal tricuspid valve configuration and function.