Epicardial adipose tissue in obesity with heart failure with preserved ejection fraction: Cardiovascular magnetic resonance biomarker study

BACKGROUND Obesity has become a serious public health issue,significantly elevating the risk of various complications.It is a well-established contributor to Heart failure with preserved ejection fraction(HFpEF).Evaluating HFpEF in obesity is crucial.Epicardial adipose tissue(EAT)has emerged as a valuable tool for validating prognostic biomarkers and guiding treatment targets.Hence,assessing EAT is of paramount importance.Cardiovascular magnetic resonance(CMR)imaging is acknowledged as the gold standard for analyzing cardiac function and mor-phology.We hope to use CMR to assess EAT as a bioimaging marker to evaluate HFpEF in obese patients.AIM To assess the diagnostic utility of CMR for evaluating heart failure with preserved ejection fraction[HFpEF;left ventricular(LV)ejection fraction≥50%]by measuring the epicardial adipose tissue(EAT)volumes and EAT mass in obese patients.METHODS Sixty-two obese patients were divided into two groups for a case-control study based on whether or not they had heart failure with HFpEF.The two groups were defined as HFpEF+and HFpEF-.LV geometry,global systolic function,EAT volumes and EAT mass of all subjects were obtained using cine magnetic resonance sequences.RESULTS Forty-five patients of HFpEF-group and seventeen patients of HFpEF+group were included.LV mass index(g/m2)of HFpEF+group was higher than HFpEF-group(P<0.05).In HFpEF+group,EAT volumes,EAT volume index,EAT mass,EAT mass index and the ratio of EAT/[left atrial(LA)left-right(LR)diameter]were higher compared to HFpEF-group(P<0.05).In multivariate analysis,Higher EAT/LA LR diameter ratio was associated with higher odds ratio of HFpEF.CONCLUSION EAT/LA LR diameter ratio is highly associated with HFpEF in obese patients.It is plausible that there may be utility in CMR for assessing obese patients for HFpEF using EAT/LA LR diameter ratio as a diagnostic biomarker.Further prospective studies,are needed to validate these proof-of-concept findings.

Health-related quality of life among congestive heart failure patients with preserved and reduced ejection fraction

Objective:To determine factors that affect the health-related quality of life(HRQOL)of congestive heart failure(CHF)patients with preserved and reduced ejection fraction.Methods:A cross-sectional study design was used for this study.The stratified random sampling was applied for each subgroup.HRQOL was measured with the Minnesota Living with Hear t Failure Questionnaire.The data were analyzed using chi-square,Spearman's correlation analysis,and independent t-test.Results:A number of 67 respondents participated in the recent study.The total mean scores of HRQOL were significantly different(P=0.001)between heart failure(HF)patients with reduced and preserved ejection fractions,41.07±7.54 and 54.97±4.36,respectively.It related with the physical(mean±standard deviation[SD]=10.4±2.14;t=-10.08,95%CI=-12.46 to-8.34;P-value=0.001)and psychological(mean±SD=3.5±0.5;t=-6.68,95%CI=-4.55 to-2.45;P-value=0.001)domain.Strong correlation was found between age(r=-0.898,P<0.05),NYHA functional classes(r=-0.858,P<0.01),duration of HF(r=-0.807,P<0.01),family support(r=0.927,P<0.01),and quality of life(Qo L).Conclusions:HRQOL in HF patients with reduced ejection fraction was higher than in those with preserved ejection fraction.Family suppor t is a fur ther determinant factor that has a positive correlation to the Qo L.

Heterogeneity in cardiorenal protection by Sodium glucose cotransporter 2 inhibitors in heart failure across the ejection fraction strata:Systematic review and meta-analysis

BACKGROUND Gliflozins or Sodium glucose cotransporter 2 inhibitors(SGLT2i)are relatively novel antidiabetic medications that have recently been shown to represent favorable effects on patients’cardiorenal outcomes.However,there is shortage of data on potential disparities in this therapeutic effect across different patient subpopulations.AIM To investigate differential effects of SGLT2i on the cardiorenal outcomes of heart failure patients across left ventricular ejection fraction(LVEF)levels.METHODS Literature was searched systematically for the large randomized double-blind controlled trials with long enough follow up periods reporting cardiovascular and renal outcomes in their patients regarding heart failure status and LVEF levels.Data were then meta-analyzed after stratification of the pooled data across the LVEF strata and New York Heart Associations(NYHA)classifications for heart failure using Stata software version 17.0.RESULTS The literature search returned 13 Large clinical trials and 13 post hoc analysis reports.Meta-analysis of the effects of gliflozins on the primary composite outcome showed no significant difference in efficacy across the heart failure subtypes,but higher efficacy were detected in patient groups at lower NYHA classifications(I2=46%,P=0.02).Meta-analyses across the LVEF stratums revealed that a baseline LVEF lower than 30%was associated with enhanced improvement in the primary composite outcome compared to patients with higher LVEF levels at the borderline statistical significance(HR:0.70,95%CI:0.60 to 0.79 vs 0.81,95%CI:0.75 to 0.87;respectively,P=0.06).Composite renal outcome was improved significantly higher in patients with no heart failure than in heart failure patients with preserved ejection fraction(HFpEF)(HR:0.60,95%CI:0.49 to 0.72 vs 0.94,95%CI:0.74 to 1.13;P=0.04).Acute renal injury occurred significantly less frequently in heart failure patients with reduced ejection fraction who received gliflozins than in HFpEF(HR:0.67,95%CI:51 to 0.82 vs 0.94,95%CI:0.82 to 1.06;P=0.01).Volume depletion was consistently increased in response to SGLT2i in all the subgroups.CONCLUSION Heart failure patients with lower LVEF and lower NYHA sub-classifications were found to be generally more likely to benefit from therapy with gliflozins.Further research are required to identify patient subgroups representing the highest benefits or adverse events in response to SGLT2i.

The influence of pressure injury risk on the association between left ventricular ejection fraction and all-cause mortality in patients with acute myocardial infarction 80 years or older

BACKGROUND: We aimed to investigate whether the pressure injury risk mediates the association of left ventricular ejection fraction(LVEF) with all-cause death in patients with acute myocardial infarction(AMI) aged 80 years or older.METHODS: This retrospective cohort study included 677 patients with AMI aged 80 years or older from a tertiary-level hospital. Pressure injury risk was assessed using the Braden scale at admission, and three risk groups(low/minimal, intermediate, high) were defined according to the overall score of six different variables. LVEF was measured during the index hospitalization for AMI. All-cause death after hospital discharge was the primary outcome.RESULTS: Over a median follow-up period of 1,176 d(interquartile range [IQR], 722–1,900 d), 226(33.4%) patients died. Multivariate Cox regression analysis showed that reduced LVEF was associated with an increased risk of all-cause death only in the high-risk group of pressure injury(adjusted hazard ratios [HR]=1.81, 95% confidence interval [CI]: 1.03–3.20;P=0.040), but not in the low/minimal-(adjusted HR=1.29, 95%CI: 0.80–2.11;P=0.299) or intermediate-risk groups(adjusted HR=1.14, 95%CI: 0.65–2.02;P=0.651). Significant interactions were detected between pressure injury risk and LVEF(adjusted P=0.003). The cubic spline with hazard ratio plot revealed a distinct shaped curve relation between LVEF and all-cause death among different pressure injury risk groups.CONCLUSIONS: In older patients with AMI, the risk of pressure injury mediated the association between LVEF and all-cause death. The classification of older patients for both therapy and prognosis assessment appears to be improved by the incorporation of pressure injury risk assessment into AMI care management.

Impact of vericiguat on heart failure with reduced ejection fraction:a review

Introduction:Heart failure is a major public health issue with a prevalence of about 26 million people worldwide.Reduced nitric oxide availability,lower soluble guanylate cyclase(sGC)activity,and decreased cyclic guanosine monophosphate(cGMP)production are the causes of HF's development.Vericiguat prescribed under the brand name Verquvo was approved by U.S.Food and Drug Administration(FDA)in January 2021.It is a novel agent and the first sGC stimulator which helps to treat patients suffering from heart failure with reduced ejection fraction(HFrEF).Objective:The mechanism of action(cGMP pathway)of vericiguat,its clinical trials,its use in the treatment of heart failure,and its possible future aspects in therapeutic recommendations are all covered in this review.It will also raise awareness amongst healthcare professionals about the pharmacokinetic and pharmacodynamic parameters,dosing,administration,and drug-related problems of this new drug.Methods:Various databases for drug review were used in this review like PubMed,Medline,Google scholar,Drug bank,U.s.FDA,Medscape,and European society of cardiology guidelines.A total of 58 articles were screened out of which 39 articles were included in this review.Results:This review discusses vericiguat's mechanism of action(cGMP pathway),clinical studies,application in the treatment of heart failure,and potential future considerations in therapeutic recommendations.It will also educate healthcare professionals about the new drug's pharmacokinetics and pharmacodynamics,dose,administration,and drug-related problems.Conclusion:After hospitalization for HFrEF,the 5-year survival rate is just 25%,and disease morbidity and death are stil significant.As adjunctive therapy for individuals with heart failure and a low ejection fraction,vericiguat has a moderate level of effectiveness.Vericiguat's efficacy as an adjunct therapy to different drugs used to cure HF has to be further investigated.Vericiguat's safety and dosage in patients who have severe renal or hepatic illness need to be studied further.

Interaction between the left ventricular ejection fraction and left ventricular strain and its relationship with coronary stenosis

BACKGROUND Coronary artery stenosis(CAS)is the most common type of heart disease and the leading cause of death in both men and women globally.CAS occurs when the arteries that supply blood to the heart muscle harden and become narrower due to plaque buildup-cholesterol and other material-on their inner walls.As a result,the heart muscle cannot receive the blood or oxygen it needs.Most heart attacks happen when a blood clot suddenly cuts off the hearts'blood supply,causing permanent heart damage.AIM To analyze the relationship between the left ventricular ejection fraction(LVEF),left ventricular strain(LVS),and coronary stenosis.METHODS A total of 190 participants were enrolled in this trail.The control group comprised 93 healthy individuals,and observation group comprised 97 patients with coronary heart disease who were hospitalized between July 2020 and September 2021.Coronary lesions were assessed using the Gensini score,and the LVEF and LVS were measured using magnetic resonance imaging(MRI).The interaction between the LVEF and LVS was examined using a linear regression model.The relationship between LVEF and coronary stenosis was examined using Spearman’s correlation.RESULTS The LVEF of the observation group was lower than that of the control group.The left ventricular end-systolic volume(LVESV)and left ventricular end-diastolic volume(LVEDV)of the observation group were significantly higher than those of the control group(P<0.05).The longitudinal and circumferential strains(LS,CS)of the observation group were significantly higher than those of the control group;however,the radial strain(RS)of the observation group was significantly lower than that of the control group(P<0.05).LVS,LS,and CS were significantly negatively correlated with the LVEF,and RS was positively correlated with the LVEF.There were significant differences in the LVEF,LVESV,and LVEDV of patients with different Gensini scores;the LVEF significantly decreased and the LVESV and LVEDV increased with increasing Gensini scores(P<0.05).In the observation group,the LVEF was negatively correlated and the LVESV and LVEDV were positively correlated with coronary stenosis(P<0.05).CONCLUSION The LVEF measured using MRI is significantly linearly correlated with LVS and negatively correlated with coronary stenosis.

Targeting epicardial adipose tissue:A potential therapeutic strategy for heart failure with preserved ejection fraction with type 2 diabetes mellitus

Heart failure with preserved ejection fraction(HFpEF)is a heterogeneous syndrome with various comorbidities,multiple cardiac and extracardiac pathophysiologic abnormalities,and diverse phenotypic presentations.Since HFpEF is a heterogeneous disease with different phenotypes,individualized treatment is required.HFpEF with type 2 diabetes mellitus(T2DM)represents a specific phenotype of HFpEF,with about 45%-50% of HFpEF patients suffering from T2DM.Systemic inflammation associated with dysregulated glucose metabolism is a critical pathological mechanism of HFpEF with T2DM,which is intimately related to the expansion and dysfunction(inflammation and hypermetabolic activity)of epicardial adipose tissue(EAT).EAT is well established as a very active endocrine organ that can regulate the pathophysiological processes of HFpEF with T2DM through the paracrine and endocrine mechanisms.Therefore,suppressing abnormal EAT expansion may be a promising therapeutic strategy for HFpEF with T2DM.Although there is no treatment specifically for EAT,lifestyle management,bariatric surgery,and some pharmaceutical interventions(anti-cytokine drugs,statins,proprotein convertase subtilisin/kexin type 9 inhibitors,metformin,glucagon-like peptide-1 receptor agonists,and especially sodium-glucose cotransporter-2 inhibitors)have been shown to attenuate the inflammatory response or expansion of EAT.Importantly,these treatments may be beneficial in improving the clinical symptoms or prognosis of patients with HFpEF.Accordingly,well-designed randomized controlled trials are needed to validate the efficacy of current therapies.In addition,more novel and effective therapies targeting EAT are needed in the future.

Therapies for patients with coexisting heart failure with reduced ejection fraction and non-alcoholic fatty liver disease

Heart failure with reduced ejection fraction(HFrEF)and nonalcoholic fatty liver disease(NAFLD)are two common comorbidities that share similar pathophysiological mechanisms.There is a growing interest in the potential of targeted therapies to improve outcomes in patients with coexisting HFrEF and NAFLD.This manuscript reviews current and potential therapies for patients with coexisting HFrEF and NAFLD.Pharmacological therapies,including angiotensinconverting enzyme inhibitors/angiotensin receptor blockers,mineralocorticoids receptor antagonist,and sodium-glucose cotransporter-2 inhibitors,have been shown to reduce fibrosis and fat deposits in the liver.However,there are currently no data showing the beneficial effects of sacubitril/valsartan,ivabradine,hydralazine,isosorbide nitrates,digoxin,or beta blockers on NAFLD in patients with HFrEF.This study highlights the importance of considering HFrEF and NAFLD when developing treatment plans for patients with these comorbidities.Further research is needed in patients with coexisting HFrEF and NAFLD,with an emphasis on novel therapies and the importance of a multidisciplinary approach for managing these complex comorbidities.

Clinical efficacy of dapagliflozin in the treatment of type 2 diabetes mellitus with heart failure with mildly reduced ejection fraction

Objective:To observe the clinical efficacy of dapagliflozin in the treatment of type 2 diabetes mellitus(T2DM)complicated with heart failure with mildly reduced ejection fraction(HFmrEF,40%≤LVEF<50%).Methods:A total of 84 patients with T2DM complicated with HFmrEF hospitalized in our hospital from October 2019 to October 2021 were selected,and random number table method was used to divide into the control group and the study group each 42 cases.Both groups used basal hypoglycemic and standardized anti-heart failure therapy,and the study group was treated with dapagliflozin simultaneously.Nine months later,the following indexes were compared between the two groups before and after treatment:the cardiac function indicators:N-terminal pro brain natriuretic peptide(NT-proBNP),left ventricular ejection fraction(LVEF);exercise endurance:6-minute walk distance(6MWD),NYHA cardiac function class,the score of the Minnesota living with heart failure questionnaire(MLHFQ)and the incidence of major adverse cardiovascular events(MACE).Results:Nine months later,the two groups showed decreased NT-proBNP level,increased LVEF,prolonged 6MWD,improved NYHA cardiac function grade,decreased MLHFQ score,and statistically significant differences within both groups compared with before treatment(P<0.05),after treatment significant differences were displayed between the two groups(P<0.05).Less patients had MACE events and adverse drug reactions in the study group compared with the control group.Conclusion:Dapagliflozin in the treatment of T2DM patients with HFmrEF can improve cardiac function indicators,improve exercise endurance,improve NYHA cardiac function class,improve patient's quality of life,and reduce the incidence of MACE events,with no obvious side effects.

The Clinical Association of Left Atrial Function with Left Ventricular Ejection Fraction

The left atrium (LA) has been recognized as a morphophysiological barometer of left ventricular (LV) diastolic dysfunction. Because in the myocardial ischemia cascade where LV diastolic dysfunction often precedes LV systolic dysfunction, the LA which fashions as an early marker of diastolic anomaly, could equally reflect a declining LV function and/or be a good predictor of potential sequelae. We assessed this association of LA function with reduced LV systolic function among hospitalized patients. Among patients with reduced LV ejection fraction, LA passive ejection fraction was lower (0.172 ± 0.12 vs. 0.232 ± 0.14, p = 0.013) whereas LA kinetic energy was higher (6.48 ± 6.3 vs. 4.57 ± 3.5, p = 0.005). Echocardiographic assessment of LA function, therefore, appears correlated with LVEF and could be important when risk stratifying hospitalized patients.

Heart failure with preserved ejection fraction in the elderly: pathophysiology, diagnostic and therapeutic approach

Heart failure with preserved ejection fraction(HFpEF)is a clinical syndrome characterized by symptoms and sings of heart failure with elevated left ventricular filling pressures at rest or during exercise.It is the most common type of heart failure in the elderly and its prevalence increases with age and is higher in females at any given age.HFpEF is frequently accompanied of comorbid conditions such as diabetes mellitus,obesity,atrial fibrillation and renal dysfunction.The diagnosis relies in the integration of clinical information,laboratory data and interpretation of cardiac imaging and hemodynamic findings at rest and during exercise.Conditions that have a specific treatment such as coronary artery disease,valvular disease,cardiac amyloidosis and constrictive pericarditis should be considered and evaluated as appropriate.Aggressive management of comorbidities,optimization of blood pressure control and volume status using diuretics as needed are among the current treatment recommendations.There are no specific therapies that have shown to decrease mortality in HFpEF.In symptomatic patients with history of hospital admission for decompensated heart failure,the implantation of a wireless pulmonary artery pressure monitor should be considered.Finally,given the high mortality of this condition,goals of care discussion should be initiated early and involvement of palliative care medicine should be considered.

Diagnostic and prognostic value of circulating micro RNAs in heart failure with preserved and reduced ejection fraction

micro RNAs(mi RNAs) are powerful regulators of posttranscriptional gene expression and play an important role in pathophysiological processes. Circulating mi RNAs can be quantified in body liquids and are promising biomarkers in numerous diseases. In cardiovascular disease mi RNAs have been proven to be reliable diagnostic biomarkers for different disease entities. In cardiac fibrosis(CF) and heart failure(HF) dysregulated circulating mi RNAs have been identified,indicating their promising applicability as diagnostic biomarkers. Some mi RNAs were successfully tested in risk stratification of HF implementing their potential use as prognostic biomarkers. In this respect mi RNAs might soon be implemented in diagnostic clinical routine. In the young field of mi RNA based research advances have been made in identifying mi RNAs as potential targets for the treatment of experimental CF and HF. Promising study results suggest their potential future application as therapeutic agents in treatment of cardiovascular disease. This article summarizes the current state of the various aspects of mi RNA research in the field of CF and HF with reduced ejection fraction as well as preserved ejection fraction. The review provides an overview of the application of circulating mi RNAs as biomarkers in CF and HF and current approaches to therapeutically utilize mi RNAs in this field of cardiovascular disease.

Therapeutic interventions for heart failure with preserved ejection fraction:A summary of current evidence

Heart failure with preserved ejection fraction(HFPEF)is common and represents a major challenge in cardiovascular medicine.Most of the current treatment of HFPEF is based on morbidity benefits and symptom reduction.Various pharmacological interventions available for heart failure with reduced ejection fraction have not been supported by clinical studies for HFPEF.Addressing the specific aetiology and aggressive risk factor modification remain the mainstay in the treatment of HFPEF.We present a brief overview of the currently recommended therapeutic options with available evidence.

Role of cardiac CTA in estimating left ventricular volumes and ejection fraction

Left ventricular ejection fraction(LVEF)is an impor-tant predictor of cardiac outcome and helps in makingimportant diagnostic and therapeutic decisions suchas the treatment of different types of congestive heartfailure or implantation of devices like cardiac resynchro-nization therapy-defibrillator.LVEF can be measuredby various techniques such as transthoracic echo-cardiography,contrast ventriculography,radionuclidetechniques,cardiac magnetic resonance imaging andcardiac computed tomographic angiography(CTA).Thedevelopment of cardiac CTA using multi-detector rowCT(MDCT)has seen a very rapid improvement in thetechnology for identifying coronary artery stenosis andcoronary artery disease in the last decade.During theacquisition,processing and analysis of data to studycoronary anatomy,MDCT provides a unique opportunityto measure left ventricular volumes and LVEF simulta-neously with the same data set without the need foradditional contrast or radiation exposure.The develop-ment of semi-automated and automated software to measure LVEF has now added uniformity,efficiency and reproducibility of practical value in clinical practice rather than just being a research tool.This article will address the feasibility,the accuracy and the limitations of MDCT in measuring LVEF.

Risks of incident heart failure with preserved ejection fraction in Chinese patients hospitalized for cardiovascular diseases

Background Endogenous aldehyde damages DNA and potentiates an ageing phenotype. The aldehyde dehydrogenase 2(ALDH2) rs671 polymorphism has a prevalence of 30%–50% in Asian populations. In this study, we aimed to analyze risk factors contributing to the development of heart failure with preserved ejection fraction(HFpEF) along with the genetic exposure in Chinese patients hospitalized with cardiovascular diseases(CVD). Methods From July 2017 to October 2018, a total of 770 consecutive Chinese patients with normal left ventricular ejection fractions(LVEF) and established CVD(hypertension, coronary heart diseases, or diabetes) were enrolled in this prospective cross-sectional study. HFpEF was defined by the presence of at least one of symptom(dyspnoea and fatigue) or sign(rales and ankle swelling) related to heart failure;N-terminal pro-B-Type natriuretic peptide(NT pro-BNP ≥ 280 pg/mL);LVEF ≥ 50%;and at least one criterion related to elevated ventricular filling pressure or diastolic dysfunction(left atrial diameter > 40 mm, E/E’ ≥ 13, E’/A’ < 1 or concurrent atrial fibrillation). Logistic regression was performed to yield adjusted odds ratios(ORs) for HFp EF incidence associated with traditional and/or genetic exposures. Results Finally, among 770 patients with CVD, 92(11.9%) patients were classified into the HFpEF group according to the diagnostic criteria. The mean age of the participants was 67 ± 12 years, and 278(36.1%) patients were females. A total of 303(39.4%) patients were ALDH2*2 variant carriers. In the univariate analysis, eight exposures were found to be associated with HFpEF: atrial fibrillation, ALDH2*2 variants, hypertension, age, anaemia, smoking, alcohol consumption and sex. Multivariable logistic regression showed that 4 ‘A’ variables(atrial fibrillation, ALDH2*2 variants, age and anaemia) were significantly associated with an increased risk of HFpEF. Atrial fibrillation was associated with a 3.8-fold increased HFpEF risk(95% CI: 2.21–6.61, P < 0.001), and the other three exposures associated with increased HFpEF risk were the ALDH2*2 variant(OR = 2.41, 95% CI: 1.49–3.87, P < 0.001), age(OR = 2.14, 95% CI: 1.27–3.60, P = 0.004), and anaemia(OR = 1.79, 95% CI: 1.05–3.03, P = 0.032). These four variables predicted HFpEF incidence in Chinese CVD patients(C-statistic = 0.745, 95% CI: 0.691–0.800, P < 0.001). Conclusions 4 A traits(atrial fibrillation, ALDH2*2 variants, age and anaemia) were associated with an increased risk of HFpEF in Chinese CVD patients. Our results provide potential clues to the aetiology, pathophysiology and therapeutic targets of HFpEF.

Challenging aspects of treatment strategies in heart failure with preserved ejection fraction: “Why did recent clinical trials fail?”

Heart failure(HF) is the leading cause of hospitalization among older adults and the prevalence is growing with the aging populations in the Western countries. Epidemiologic reports suggest that approximately 50% of patients who have signs or symptoms of HF have preserved left ventricular ejection fraction. This HF type predominantly affects women and the elderly with other co-morbidities, such as diabetes, hypertension, and overt volume status. Most of the current treatment strategies are based on morbidity benefits such as quality of life and reduction of clinical HF symptoms. Treatment of patients with HF with preserved ejection fraction displayed disappointing results from several large randomized controlled trials. The heterogeneity of HF with preserved ejection fraction, understood as complex syndrome, seems to be one of the primary reasons. Here, we present an overview of the current management strategies with available evidence and new therapeutic approach from drugs currently in clinical trials, which target diastolic dysfunction, chronotropic incompetence, and risk factor management. We provide an outline and interpretation of recent clinical trials that failed to improve outcome and survival in patients with HF with preserved ejection fraction.

Analysis of melt ejection during long pulsed laser drilling

In pulsed laser drilling, melt ejection greatly influences the keyhole shape and its quality as well, but its mechanism has not been well understood. In this paper, numerical simulation and experimental investigations based on 304 stainless steel and aluminum targets are performed to study the effects of material parameters on melt ejection. The numerical method is employed to predict the temperatures, velocity fields in the solid, liquid, and vapour front, and melt pool dynamics of targets as well. The experimental methods include the shadow-graphic technique, weight method, and optical microscope imaging, which are applied to real-time observations of melt ejection phenomena, measurements of collected melt and changes of target mass, observations of surface morphology and the cross-section of the keyhole, respectively. Numerical and experimental results show that the metallic material with high thermal diffusivity like aluminum is prone to have a thick liquid zone and a large quantity of melt ejection. Additionally, to the best of our knowledge, the liquid zone is used to illustrate the relations between melt ejection and material thermal diffusivity for the first time. The research result in this paper is useful for manufacturing optimization and quality control in laser-material interaction.

Ejection Separation Characteristic Analysis of Parachute Container Cover from Return Capsule for Lunar Exploration

The parachute container cover ejection separation is the first and foremost motion for the return capsule recovery system,which is related to the success of a recovery system.Adopting the computational fluid dynamics(CFD)simulation and flight dynamics coupling method,the parachute container cover ejection separation is simulated.The rationality of the ejection separation speed and dynamic characteristics of the separation process is analyzed.Meanwhile,the influences of angle of attack,Mach number and ejection separation speed on the parachute container cover ejection are also investigated.Results show that the ejection separation speed design is reasonable.It has a certain design margin for parachute container cover to escape from the wake region,and to pull out the drag parachute completely.The results may provide a theoretical basis for recovery system engineering design of the lunar exploration project.

Biomechanical Manifestations of Diastolic and Systolic Function in Rats with Heart Failure with Preserved Ejection Fraction

Objective Heart failure(HF)is divided into two types:Heart failure with reduced ejection fraction(HFrEF)and heart failure with preserved ejection fraction(HFpEF).The latter always results in diastolic dysfunction,characterized by changes in mechanical properties.The objective of this study is to build a finite element(FE)model of HFpEF and analyze diastolic and systolic function in rats.Methods Ten Dahl salt-sensitive rats were fed either a low-salt(LS)(n=5)or highsalt(HS)(n=5)diet beginning at 7 weeks of age and scanned by ultrasonic machine at 14 weeks of age.A non-linear FE model of the left ventricle(LV)was built from cardiac echo images at end-diastole and passive material properties of the LV were prescribed using Fung’s transversely isotropic constitutive law.Fiber angles of the endocardium and epicardium were prescribed as 53°°and-52°,respectively,with respect to the circumferential direction and varied linearly through the LV wall.The method developed by Krishnamurthywas used to determine the unloaded geometry to estimate the Fung passive material parameters.LV end-diastolic pressure(EDP)was determined from the measured pressure waves and applied to the endocardium at the unloaded geometry to simulate passive filling.Active material properties of the LV were prescribed using Guccione’s time-varying elastance model and maximum isometric tension was scaled to match the measured peak systolic pressure.The finite element model was then coupled to the Windkessel model,whose parameters were adjusted to the measured hemodynamics.Results Measured LVEDPs of LS and HS rats were 4.9±3.4 mmHg and 13.2±5.4 mmHg(P-0.030 8),respectively.End-diastolic Cauchy stress along the fiber direction for LS rats was significantly lower than for HS rats(0.91±0.60 kPa vs 3.00±0.63 kPa,P=0.001 4)and there was a similar trend in end-diastolic Green Strain along the fiber direction(0.058±0.003 vs 0.072±0.010,P=0.012 8,Figure 1b),as well.There was no distinctive difference between end-systolic Cauchy stress along the fiber direction for LS rats and HS rats(17.2±4.3 kPa vs 17.2±5.5 kPa,P=0.991 9)but end-systolic Green Strain along the fiber direction for LS rats was significantly higher than for HS rats(-0. 108±0.017 vs-0.065±0.024,negative sign represents direction).Conclusions For rats with HFpEF,it is the elevated LVEDP that induces the increase in end-diastolic stress and strain,thereby leading to diastolic dysfunction.Because of the preserved ejection fraction,HFpEF has less effect on systolic function.

A novel variable topology design for a multi-flexible ejection mechanism

The airborne missile launch mechanism often subjects to significant deformations induced by the large ejection force during high-speed actuations in missile ejection process,leading to a substantial deviation of separation parameters from designed values that threats safety of the carrier.This study proposes a novel variable topology design for launch mechanism,achieved via a Prsmatic-Revolute-Revolute pair(PR-R)motion formed by the structural gap with a specific direction.It enables launch mechanism variability during missile ejection process and optimizes the ejection force given by the front and back ejection arms,and greatly optimizes the separation parameters during missile ejection.The kinetics simulation analysis is conducted under working conditions of the original ejection mechanism and the novel mechanism with variable topology design,respectively.The results show that the novel variable topology design is more befitting for the launch process in terms of system safety and controllability,effectively improving the separation posture,restraining the flexible effect of the mechanism,and fulfilling the effectiveness of the design value of multi-rigid body.