Entire Valve Research Articles

Performance analysis and improvement of a novel reed valve in compressors using fluid–structure interaction method

The reed valves used as suction valves in reciprocating compressors are more susceptible to damage due to the limitation of the lift limiter which can't completely block the entire valve plate. This article proposed a novel reed valve featuring a redesigned shape aimed to solve this issue. Compared to conventional reed valves, the proposed valve could effectively mitigate the highest stress occurring at the root of the suction valve. To thoroughly investigate the characteristics of this valve type and improve its performance, a three-dimensional fluid–structure interaction (FSI) model was established and validated using experiments. The leakage through the valve gap in the FSI model was solved using a combination of user-defined function (UDF) and Scheme file in Fluent. Based on this FSI model, the dynamic characteristics and stress distribution of the valve were mainly analyzed. The effect of the lift limiter on the performance of the valve was analyzed, and a suitable lift was determined. Moreover, the influence of thickness and shape parameters, was also analyzed and an efficient improved scheme was subsequently proposed. Through this scheme, the maximum stress of the valve was reduced by 23.77% compared with that of the original valves. This article provides important information for the design and optimization of complex-shaped reed valves.

Simulation of fire combustion process in valve hall of DC converter power station

To investigate the fire danger of the valve hall, a 3D numerical model of the DC converter substation's valve hall is created by using the fire dynamics simulator (FDS) program and the fire burning process of the valve hall is simulated. In particular, the procedure of simulating the fire burning in the valve hall under various fire source positions is accomplished by varying certain parameters. The smoke spreading process, ambient temperature field, and heat release rate curve under various fire source placements are compared based on the results of the simulation calculations. The findings demonstrate that under various fire source locations, the valve hall's combustion process varies as well. This study compares the time for smoke to fill the entire valve hall, the maximum temperature within the valve hall, and the maximum fire source heat release efficiency in different fire scenes. The results indicate that in fire scenes where the fire source is closer to the middle position, the time for smoke to spread throughout the valve hall is shorter, and the fire source heat release rate is higher. Conversely, in fire scenes where the fire source is closer to the edge, the maximum temperature within the valve hall is higher. The numerical simulation of the valve hall in this DC converter station assessed the hazards under different fire scenes, aiming to maximize the safety of the valve hall. It provides reliable guidance for maximizing the safety of the valve hall and facilitating firefighting and rescue efforts, thus protecting personal safety and minimizing property damage.

Entire Mitral Valve Reconstruction Using Porcine Extracellular Matrix: Adding a Ring Annuloplasty

PurposeThis study investigated the implications of inserting a flexible annuloplasty ring after reconstructing the entire mitral valve in a porcine model using a previously investigated tube graft design made of 2-ply small intestinal submucosa extracellular matrix (CorMatrix®).MethodsAn acute model with eight 80-kg pigs, each acting as its own control, was used. The entire mitral valve was reconstructed with a 2-ply small intestinal submucosa extracellular matrix tube graft (CorMatrix®). Subsequently, a Simulus® flexible ring was inserted. The characterization was based on mitral annular geometry and valvular dynamics with sonomicrometry and echocardiography.ResultsAfter adding the ring annuloplasty, the in-plane annular dynamics were more constant throughout the cardiac cycle compared to the reconstruction alone. However, the commissure–commissure distance was statistically significantly decreased [35.0 ± 3.4 mm vs. 27.4 ± 1.9 mm, P < 0.001, diff = − 7.6 mm, 95% CI, − 9.8 to (−5.4) mm] after ring insertion, changing the physiological annular D-shape into a circular shape which created folds at the coaptation zone resulting in a central regurgitant jet on color Doppler.ConclusionWe successfully reconstructed the entire mitral valve using 2-ply small intestinal submucosal extracellular matrix (CorMatrix®) combined with a flexible annuloplasty. The annuloplasty reduced the unphysiological systolic widening previously found with this reconstructive technique. However, the Simulus flex ring changed the physiological annular D-shape into a circular shape and hindered a correct unfolding of the leaflets. Thus, we do not recommend a flexible ring in conjunction with this reconstructive technique; further investigations are needed to discover a more suitable remodelling annuloplasty.

Resection of hypertrophic papillary muscles and mitral valve replacement in a patient with midventricular hypertrophic obstructive cardiomyopathy – a new approach

Midventricular hypertrophic obstructive cardiomyopathy (HOCM) is characterized by hypertrophy of the interventricular septum (IVS) and - in rare cases - of the papillary muscles (PM), which subsequently can cause dynamic left ventricular outflow tract obstruction (LVOTO) and severe heart failure symptoms. We report on a rare case of a 44-year-old patient suffering from midventricular HOCM with hypertrophic anterolateral PM and an additional chorda between the PM and the IVS.We describe a new surgical approach via right anterolateral thoracotomy in 3-dimensional (3D) video-assisted minimal-invasive technique with resection of hypertrophic PMs as well as the entire mitral valve-apparatus and valve replacement avoiding septal myectomy and potentially associated complications. After an uneventful procedure clinical symptoms improved from NYHA III-IV at baseline to NYHA 0-I postoperatively and remained stable over a follow-up period of 24 months. Therefore, the presented technique may be considered as a new and alternative approach in patients with hypertrophic PMs and hypertrophic IVS as subtype of midventricular HOCM.

On-demand heart valve manufacturing using focused rotary jet spinning

On-demand heart valve manufacturing using focused rotary jet spinning

Revealing the static and dynamic nanomechanical properties of diatom frustules—Nature's glass lace

Diatoms are single cell microalgae enclosed in silica exoskeletons (frustules) that provide inspiration for advanced hybrid nanostructure designs mimicking multi-scale porosity to achieve outstanding mechanical and optical properties. Interrogating the structure and properties of diatoms down to nanometer scale leads to breakthrough advances reported here in the nanomechanical characterization of Coscinodiscus oculus-iridis diatom pure silica frustules, as well as of air-dried and wet cells with organic content. Static and dynamic mode Atomic Force Microscopy (AFM) and in-SEM nanoindentation revealed the peculiarities of diatom response with separate contributions from material nanoscale behavior and membrane deformation of the entire valve. Significant differences in the nanomechanical properties of the different frustule layers were observed. Furthermore, the deformation response depends strongly on silica hydration and on the support from the internal organic content. The cyclic loading revealed that the average compliance of the silica frustule is 0.019 m/N and increases with increasing number of cycles. The structure–mechanical properties relationship has a direct impact on the vibrational properties of the frustule as a complex micrometer-sized mechanical system. Lessons from Nature’s nanostructuring of diatoms open up pathways to new generations of nano- and microdevices for electronic, electromechanical, photonic, liquid, energy storage, and other applications.

Abstract 14337: Cardiac Computed Tomography for Preoperative Assessment of Valve Morphology in Aortic Valve Repair

Introduction: A pre-operative assessment of aortic valve anatomy is important in valve repair for aortic regurgitation (AR). Although echocardiogram provides precise information, clear visualization of entire aortic valve and accurate quantification of valve geometry are limited even with 3D transesophageal echocardiography. In this study, usefulness of cardiac computed tomography (CT) in the evaluation of aortic valve pathology was investigated. Methods: A total of 119 patients who underwent surgical treatment for severe AR from May 2016 to July 2021 and had preoperative CT were studied. From the CT data set, volume rendering movie image was reconstructed to visualize valve anatomy. Effective height (EH) and geometric height (GH) were measured by CT in diastole and compared to intraoperative measurements. Results: The quality of CT image was satisfactory in 100 patients (84%), acceptable in 17 patients (14%) and suboptimal in 2 patients (2%). CT could visualize such detailed anatomy as shown in the Figure. EH in 41 patients and GH in 67 were measured by both CT and surgery. The measurements showed a correlation in EH (r=0.79, p&lt;0.0001) and in GH (r=0.74, p&lt;0.0001) with minimal bias of -1.6 mm in EH and 0.4 mm in GH and narrow limits of agreement from -5.9 to2.6 mm in EH and from -3.7 to 4.6 mm in GH. Inter- observer variabilities in CT measurement of EH and GH were 3.8±2.9% and 2.6±1.8%, with interclass correlation coefficients of 0.997 and 0.980, respectively. Conclusions: Reproducibility of CT measurement was excellent, while there was a little discrepancy between CT and surgical measurement. Not all cases underwent intraoperative measurement, and cases with structurally complexity tended to have surgical measurement. Some errors may be included in also intraoperative measurements. CT feasibly visualized aortic valve en-face view with showing the etiology of AR, which gave useful information to surgeons who perform aortic valve repair.

Finite element analysis of mitral valve annuloplasty in Barlow’s disease

Barlow’s Disease affects the entire mitral valve apparatus causing mitral regurgitation. Standard annuloplasty procedures lead to an average of 55% annular area reduction of the end diastolic pre-operative annular area in Barlow’s diseased valves. Following annular reduction, mitral valvuloplasty may be needed, usually with special focus on the posterior leaflet. An in silico pipeline to perform annuloplasty by utilizing the pre- and -postoperative 3D echocardiographic recordings was developed. Our objective was to test the hypothesis that annuloplasty ring sizes based on a percentage (10%–25%) decrease of the pre-operative annular area at end diastole can result in sufficient coaptation area for the selected Barlow’s diseased patient. The patient specific mitral valve geometry and finite element model were created from echocardiography recordings. The post-operative echocardiography was used to obtain the artificial ring geometry and displacements, and the motion of the papillary muscles after surgery. These were used as boundary conditions in our annuloplasty finite element analyses. Then, the segmented annuloplasty ring was scaled up to represent a 10%, 20% and 25% reduction of the pre-operative end diastolic annular area and implanted to the end diastolic pre-operative finite element model. The pre-operative contact area decrease was shown to be dependent on the annular dilation at late systole. Constraining the mitral valve from dilating excessively can be sufficient to achieve proper coaptation throughout systole. The finite element analyses show that the selected Barlow’s diseased patient may benefit from an annuloplasty ring with moderate annular reduction alone.

Global Crystallographic Texture of Freshwater Bivalve Mollusks of the Unionidae Family from Eastern Europe Studied by Neutron Diffraction.

The crystallographic texture of the whole valves of bivalve mollusks from the family Unionidae Unio pictorum Linnaeus, 1758 and Anodonta cygnea Linnaeus, 1758 is studied using pole figures measured using neutron diffraction. The use of neutron diffraction, in contrast to X-rays, makes it possible to study the valves without destroying them. Thus, we can discuss the study of the global texture of the entire valve. It was revealed that the pole figures of aragonite in the valves repeat their shape. The pole density maxima for U. pictorum from the Danube Delta and the Gulf of Finland in the Baltic Sea, living at different salinities and temperatures, differs by 0.41 mrd. The maximum value of the crystallographic texture for A. cygnea from the Danube Delta was also measured (5.07 mrd). In terms of texture sharpness, it surpasses the shell of marine bivalve mollusks, which are partially or completely composed of aragonite. Although U. pictorum and Mya arenaria Linnaeus, 1758 have different microstructures, their pole figures are very similar in isolines pattern, but differ in pole density maxima. No relationship was found between the crystallographic texture and the microstructure in U. pictorum. In addition, we report good qualitative agreement between aragonite X-ray pole figures of Sinanodonta woodiana Lea, 1834 from the Czech river Luznice, and neutron pole figures of U. pictorum from the Danube Delta.

Visualization and Quantification of the Unrepaired Complete Atrioventricular Canal Valve Using Open-Source Software

Repair of complete atrioventricular canal (CAVC) is often complicated by residual left atrioventricular valve regurgitation. The structure of the mitral and tricuspid valves in biventricular hearts has previously been shown to be associated with valve dysfunction. However, the three-dimensional (3D) structure of the entire unrepaired CAVC valve has not been quantified. Understanding the 3D structure of the CAVC may inform optimized repair. Novel open-source work flows were created in SlicerHeart for the modeling and quantification of CAVC valves on the basis of 3D echocardiographic images. These methods were applied to model the annulus, leaflets, and papillary muscle (PM) structure of 35 patients (29 with trisomy 21) with CAVC using transthoracic 3D echocardiography. The mean leaflet and annular shapes were calculated and visualized using shape analysis. Metrics of the complete native CAVC valve structure were compared with those of normal mitral valves using the Mann-Whitney U test. Associations between CAVC structure and atrioventricular valve regurgitation were analyzed. CAVC leaflet metrics varied throughout systole. Compared with normal mitral valves, the left CAVC PMs were more acutely angled in relation to the annular plane (P<.001). In addition, the anterolateral PM was laterally and inferiorly rotated in CAVC, while the posteromedial PM was more superiorly and laterally rotated, relative to normal mitral valves (P<.001). Lower native CAVC atrioventricular valve annular height and annular height-to-valve width ratio before repair were both associated with moderate or greater left atrioventricular valve regurgitation after repair (P<.01). It is feasible to model and quantify 3D CAVC structure using 3D echocardiographic images. The results demonstrate significant variation in CAVC structure across the cohort and differences in annular, leaflet, and PM structure compared with the mitral valve. These tools may be used in future studies to catalyze future research intended to identify structural associations of valve dysfunction and to optimize repair in this vulnerable and complex population.

Encapsulated Bleb and Fibrous Ingrowth in the Ahmed Glaucoma Valve System and Bleb Revision with Mitomycin-C

Purpose: To report a case of fibrous tissue ingrowth after Ahmed valve implantation and bleb revision using mitomycin-C.Case summary: A 50-year-old man, who had received an Ahmed implantation 6 months prior, underwent bleb revision due to persistent high intraocular pressure, despite massage and multiple needling attempts. Bleb encapsulation over the entire valve plate was observed, and the bleb was gently dissected. Fibrous ingrowth over the entire valve system was confirmed. The broad stalk-like fibrous tissue was firmly adhered to the valve system. It was removed by pulling the connected bleb, taking care not to cut the stalk. Then, the long stalk-like fibrous ingrowth along the cleft between valve leaflets and main plate was removed, in the same manner. A sponge soaked with mitomycin-C (0.3 mg/mL) was instilled for 2 minutes, and the conjunctiva was sutured. Two weeks after the surgery, conjunctival suture was performed due to Ahmed valve exposure. Three weeks later, the Ahmed valve was removed due to re-exposure. Trabeculectomy surgery was performed due to uncontrolled intraocular pressure.Conclusions: There is a possibility of extensive fibrous tissue ingrowth after Ahmed valve implantation; thus, care should be taken when using mitomycin-C for bleb revision.

Dynamics Modelling and Control of a Novel Fuel Metering Valve Actuated by Two Binary-Coded Digital Valve Arrays

A fuel metering valve actuated by two binary-coded digital valve arrays (BDVAs) is proposed to improve the reliability of conventional fuel metering valves piloted by a servo valve. The design concept of this configuration is obtained from the structural characteristics of the dual nozzle-flapper and the flow regulation method of the digital hydraulic technology. The structure and working principle of the fuel metering valve are presented. Then, a mathematical model of the entire valve is developed for dynamic analysis. Subsequently, the mechanism of the transient flow uncertainty of the BDVA is revealed through simulation to determine the fluctuation in the velocity of the fuel metering valve. Furthermore, step response indicates that the delay time of the fuel metering valve is within 4.1 ms. Finally, to improve the position tracking accuracy of the fuel metering valve, a velocity feedforward proportional-integral controller with pulse code modulation is proposed. A series of comparative analyses indicate that compared with those of the velocity feedforward controller, the average and standard deviation of the position error for the proposed controller are reduced by 78 and 72.7%, respectively. The results prove the feasibility of the proposed valve and the effectiveness of the proposed control strategy.

Mid-term results of mitral valve replacement and repair: current clinical experience, technical aspects, and risk factor analysis

Aim: We evaluated the short- and mid-term results of mitral valve replacement (MVR) and mitral valve repair (MV-repair). Methods: In total, 168 patients (mean age 67 ± 11 years) underwent MVR (n = 104) and MV-repair (n = 64). To treat posterior leaflet disease, MV-repair techniques included triangular or quadrangular resection (n = 38), P1-P2 plication (n = 4), side-to side P1-P2 (n = 1), posterior-medial commissure-plasty (n = 1), and annuloplasty (n = 20). A prosthetic ring was implanted in all patients. In the presence of degenerative disease involving the anterior leaflet, extensive myxomatous and/or prolapsing pathology of the entire valve, and/or rheumatic and endocarditis degeneration, surgical orientation was to perform MVR directly. When possible, the sub-valvular apparatus with its papillary muscle was partially preserved. The mean follow-up was 38 ± 22 months. Results: Operative mortality (0.96% vs. 1.56%) and six-year survival (94% vs. 100%) were similar in MVR and MV-repair. The only independent predictor of late survival was advanced age at the operation (79.2 years vs. 66.4 years; P = 0.012). Freedom from redo-operation was 100%. Partial preservation of the sub-valvular apparatus with its papillary muscle during MVR allowed postoperatively a better left ventricular function with similar values achieved with MV-repair (P = 0.05), and it was a protective factor against the development of left ventricular dysfunction during follow-up (P = 0.01). Conclusion: MVR and MV-repair are associated with satisfactory results in the short and medium term. MV-repair to treat posterior leaflet disease is associated with a stable and long-lasting result; MVR allows equally satisfactory results in the presence of more extensive and more complex mitral valve disease. Partial preservation of the sub-valvular apparatus favors a better left ventricular systolic function.

Abstract 13940: Whole Mount Confocal Microscopy of Mouse Aortic Valve Leaflet Innervation

Introduction: Within the aortic valve leaflets (AVLs) reside a heterogeneous cell population holistically referred to as valve interstitial cells (VICs). These cells maintain the highly organized trilaminar extracellular matrix (ECM) structure in the AVL and are involved in the pathological progression of aortic valve disease (AVD). Various cell types have been reported in the AVL, including an understudied subpopulation of neurons. Since the mid-2000s, little has been done to report the possible role these neurons have in tissue homeostasis. Typically, imbedded sections of tissue chosen from specific areas of the valves are used to visualize immunoreactivity of these proteins. These sections usually come from the belly region or annular sections of the valve and seldom depict the entire leaflet anatomy. Hypothesis: Whole mount immunofluorescence microscopy allows us to map the 3D localization of these neuroendocrine markers throughout the entire aortic valve. Methods: Here, we gathered high resolution confocal microscopy images in whole mount mouse aortic valve tissues of various neuroendocrine markers such as tyrosine hydroxylase, protein gene product 9.5, and calcitonin gene related peptide. Results: We note that neuroendocrine markers mainly localize near the free edge on the ventricular surface of AVL tissue. We do not see the long dendritic neurons seen in the mitral and tricuspid valves, instead these markers are present in cells of varying morphologies throughout. Conclusions: The data gathered in this study aids our future efforts in determining mechanosensitive neural regulation of aortic valve leaflet mechanics and ECM remodeling. Future experiments will assess neuromodulation of valve rigidity under mechanical strain.

Angiotensin II receptor blockers in modulation of transforming growth factor-beta effects on mitral valve myxomatous degeneration

Abstract Growing evidence supports role transforming growth factor-β (TGF-β) as a mediator of the myxomatous changes in the mitral valve prolapse. Recently, angiotensin II receptor blockers (ARB) emerged as a potentially effective inhibitor of TGF-β signaling. Treatment of valvular interstitial cells (VICs) with ARB resulted in effective inhibition of TGF-β-induced ECM expression. Our aim was to evaluate the effect of preoperative ARB therapy in modulation of transforming growth factor-β effects on mitral valve myxomatous degeneration. Methods A total of 233 asymptomatic patients (mean age: 53.8±12.9) undergoing mitral valve surgery for severe mitral regurgitation due to mitral valve prolapse were enrolled in our retrospective, non-randomized, single-center study. Resected abnormal segments of the mitral leaflets (segment of the posterior leaflet or the entire valve) were obtained during mitral valve repair/replacement surgery and examined by experienced pathologists. Immunohistochemical characterization of mitral valve sections was performed with the primary antibodies. Quantification was performed by counting TGF-β1 and TGF-β2 positive cells within 10 random high-power fields divided by the total number of cells in specimens. Quantification of immunohistochemical staining for collagen III was performed by measurement of staining area divided by the total area of the specimens. Results Two hundred thirty-three consecutive patients (66% males, mean age 53.8±12.9 years, range 19–80) with severe MR were enrolled in the study. According to the case reports, 43 patients (18.5%) received losartan or telmisartan before surgery and were included in study group. 190 patients (81.5%) did not receive any ARB and were enrolled in the control group. Histological examination showed disorganized collagen and elastin fibers, expansion of the spongiosa layer in both groups. However, MV specimens' immunohistochemistry revealed a lower expression of type III collagen in ARB group as compared to controls (31.3% ± 10.8% vs. 43.8% ± 15.3%; p&amp;lt;0.001). MV leaflets in control group showed the increased VICs density (95.3±39.9 vs. 70.0±21.7/high-power field, p=0.0001). TGF-β1 and TGF-β2 positive cells were significantly rare in the ARB than in control MV specimens (18% vs. 33%, p=0.012 and 16% vs. 38%, p&amp;lt;0.ehab724.15541, respectively). Expression of type III collagen and TGF-β2 positive cells count showed a weak, but significant correlation (r=0.28; p=0.ehab724.155414). The multivariate Cox analysis showed a decrease in the relative risk of valvular thickening (myxomatous degeneration) with ARB therapy (0.85; 95% CI: 0.61 – 1.17; p=0.01). Conclusions We indicate a beneficial effect of ARB treatment through the inhibition of TGF-β pathway on valvular myxomatous degeneration in patients with MVP. Modulation of the progression of MVP with such therapeutic agents may have great clinical significance. Funding Acknowledgement Type of funding sources: None.

The concept of automated functional design of heart valve prostheses

Aim. To develop an algorithm for the automated functional design of the heart valve leaflet apparatus.Methods. The geometry of the aortic valve leaflet was designed in the Matlab programming environment (MathWorks, Massachusetts, USA). Numerical modeling of the opening process was performed using Abaqus/CAE (Dassault Systemes, France).Results. We developed an algorithm, with the help of which a set of models of the leaflet apparatus was designed. 8 models were subjected to numerical modeling of the stress-strain state. The locking pressure simulation has shown that the smallest von Mises stress value was recorded for a sample with a larger surface area of the leaflet belly and it equals 0.422 MPa. The results obtained show that the value of the radius of curvature significantly affects the behavior of the entire valve, which leads to the conclusion that it is necessary to carefully select the design of the valve apparatus for its correct functioning.Conclusion. The study provides the primary confirmation that the concept of the algorithm is efficient for the automated functional design of the aortic heart valve leaflet apparatus.

A Novel Two-Dimensional Echocardiography Method to Objectively Quantify Aortic Valve Calcium and Predict Aortic Stenosis Severity

Aortic valve calcium (AVC) is a strong predictor of aortic stenosis (AS) severity and is typically calculated by multidetector computed tomography (MDCT). We propose a novel method using pixel density quantification software to objectively quantify AVC by two-dimensional (2D) transthoracic echocardiography (TTE) and distinguish severe from non-severe AS. A total of 90 patients (mean age 76 ± 10 years, 75% male, mean AV gradient 32 ± 11 mmHg, peak AV velocity 3.6 ± 0.6 m/s, AV area (AVA) 1.0 ± 0.3 cm2, dimensionless index (DI) 0.27 ± 0.08) with suspected severe aortic stenosis undergoing 2D echocardiography were retrospectively evaluated. Parasternal short axis aortic valve views were used to calculate a gain-independent ratio between the average pixel density of the entire aortic valve in short axis at end diastole and the average pixel density of the aortic annulus in short axis (2D-AVC ratio). The 2D-AVC ratio was compared to echocardiographic hemodynamic parameters associated with AS, MDCT AVC quantification, and expert reader interpretation of AS severity based on echocardiographic AVC interpretation. The 2D-AVC ratio exhibited strong correlations with mean AV gradient (r=0.72, p < 0.001), peak AV velocity (r=0.74, p < 0.001), AVC quantified by MDCT (r=0.71, p <0.001) and excellent accuracy in distinguishing severe from non-severe AS (area under the curve=0.93). Conversely, expert reader interpretation of AS severity based on echocardiographic AVC was not significantly related to AV mean gradient (t=0.23, p=0.64), AVA (t=2.94, p=0.11), peak velocity (t=0.59, p=0.46), or DI (t=0.02, p=0.89). In conclusion, these data suggest that the 2D-AVC ratio may be a complementary method for AS severity adjudication that is readily quantifiable at time of TTE.

Investigation on the Characteristics of a New Structure Brake Distribution Valve

Abstract A brake distribution valve is an important part of aircraft hydraulic systems. To realize the integration and lightweight design of traditional structure valves, boost the response speed of valves, and reduce the influence of nonwork zone and damping on valve performance, this paper presents a new structure brake distribution valve which consists of pressure reducing unit, overflow unit, and embedded shuttle valve instead of the traditional valve structure. Numerical simulations and model verification experiments of the entire valve demonstrate that the new structure valve's dynamic performance has been significantly improved on the premise of ensuring linear characteristics. The simulation results show that the response time of the new structure valve is shorter than that of the traditional structure valve, with a rate of 30.77%, in case of step response simulations, and the tracking error of the valve reduces by nearly 5% in sinusoidal response simulations.

Influence of Annular Dynamics and Material Behavior in Finite Element Analysis of Barlow\u2019s Mitral Valve Disease

Barlow’s disease affects the entire mitral valve apparatus, by altering several of the fundamental mechanisms in the mitral valve which ensures unidirectional blood flow between the left atrium and the left ventricle. In this paper, a finite element model of a patient diagnosed with Barlow’s disease with patient-specific geometry and boundary conditions is presented. The geometry and boundary conditions are extracted from the echocardiographic assessment of the patient prior to surgery. Material properties representing myxomatous, healthy human and animal mitral valves are implemented and computed response are compared with each other and the echocardiographic images of the patient. This study shows that the annular dilation observed in Barlow’s patients controls several aspects of the mitral valve behavior during ventricular systole. The coaptation of the leaflets is observed to be highly dependent on annular dilation, and the coaptation area reduces rapidly at the onset of mitral regurgitation. Furthermore, the leaflet material implementation is important to predict lack of closure in the FE model correctly. It was observed that using healthy human material parameters in the Barlow’s diseased FE geometry gave severe lack of closure from the onset of mitral regurgitation, while myxomatous material properties showed a more physiological leakage.

Low-dose radiation to cardiac substructures and late-onset cardiac disease: A report from the Childhood Cancer Survivor Study (CCSS).

10027 Background: Thoracic radiotherapy (RT) is a risk factor for cardiac disease among survivors of childhood cancer based on studies considering RT doses to the entire heart. Dose to specific cardiac substructures may provide more precise dose-response associations to guide RT planning. We report associations between RT dose to cardiac substructures and risk of specific cardiac outcomes. Methods: We determined the cumulative incidences of CTCAE grade 3 – 5 coronary artery disease (CAD), heart failure (HF), and valvular disease (VD) among 25,481 5-year childhood cancer survivors diagnosed 1970 – 1999 in the CCSS. Median age at diagnosis was 6.1 years (0 – 20 years) and at last follow-up 29.8 years (5.6 – 65.9 years). For the 12,228 individuals receiving RT, fields were reconstructed on an age scaled computational phantom. Mean doses to the entire heart, cardiac chambers, valves, and left main, anterior descending (LAD), circumflex, and right coronary (RCA) arteries were estimated. Adjusted piecewise exponential models (including cumulative anthracycline dose) evaluated associations between mean RT dose to each structure and outcomes. Results: At 30 years from diagnosis, the cumulative incidences of grades 3 – 5 CAD, HF, and VD were 2.3% (95% CI 2.0 – 2.5), 2.6% (95% CI 2.4 – 2.9), and 0.6% (95% CI 0.5 – 0.8) respectively. Low dose RT (mean 5 – 9.9 Gy) to the RCA (relative rate [RR] = 2.6, 95% CI 1.6 – 4.1, p &lt; 0.001), LAD (RR = 1.9, 95% CI 1.1 – 3.3, p = 0.019), and left ventricle (RR = 2.2, 95% CI 1.3 – 3.7, p = 0.002) was associated with increased risk of CAD relative to those not exposed; mean dose of 5 – 9.9 Gy to the entire heart was not (RR = 1.1, 95% CI = 0.8 – 1.6, p = 0.59). Table shows the associated cumulative incidences of CAD for these structures. Mean RT doses of 5 – 9.9 Gy to the aortic valve (RR = 4.6, 95% CI 1.5 – 14.0, p = 0.008) and tricuspid valve (RR = 5.5, 95% CI 2.0 – 15.1, p = 0.001) were associated with risk of VD compared to those with no RT; mean heart dose 5 – 9.9 Gy was not (RR = 0.6, 95% CI = 0.2 – 1.3, p = 0.16). No cardiac structure was significantly associated with an increased risk of HF at a mean dose of 5 – 9.9 Gy. Mean RT doses below 5 Gy were not associated with increased risks of CAD, HF, or VD; doses ≥10 Gy to nearly all substructures and the entire heart were. Conclusions: Low dose RT to the coronary arteries and cardiac valves (5 – 9.9 Gy) from RT is associated with increased risk of CAD and VD, respectively. Sensitivity to low dose RT may vary across the heart and doses to specific structures may be more predictive of late cardiac disease than whole heart dose. These data can guide RT planning to prioritize substructures for avoidance.[Table: see text]