Magnitude Of Longitudinal Strain Research Articles

Molecular Dynamics Study of Collagen Fibrils: Relation between Mechanical Properties and Molecular Chirality

Collagen is a basic biopolymer usually found in animal bodies, but its mechanical property and behavior are not sufficiently understood so as to apply to effective regenerative medicine and so on. Since the collagen material is composed of many hierarchical structures from atomistic level to tissue or organ level, we need to well understand fundamental and atomistic mechanism of the collagen in mechanical response. First, we approach at exactly atomistic level by using all-atom modeling of tropocollagen (TC) molecule, which is a basic structural unit of the collagen. We perform molecular dynamics (MD) simulations concerning tensile loading of a single TC model. The main nature of elastic (often superelastic) behavior and the dependency on temperature and size are discussed. Then, to aim at coarse-graining of atomic configuration into some bundle structure of TC molecules (TC fibril), as a model of higher collagen structure, we construct a kind of mesoscopic model by adopting a simulation framework of beads-spring model which is ordinarily used in polymer simulation. Tensile or compression simulation to the fibril model reveals that the dependency of yield or buckling limit on the number of TCs in the model. Also, we compare the models with various molecular orientations in winding process of initial spiral of TC. The results are analyzed geometrically and it shows that characteristic orientational change of molecules increases or decreases depending on the direction and magnitude of longitudinal strain.

Longitudinal strain analysis allows the identification of subclinical deterioration of right ventricular function in patients with cancer therapy-related left ventricular dysfunction

Background: This study was designed to assess right ventricular systolic function in cancer patients. Methods and Results: 68 consecutive patients receiving potentially cardiotoxic agents were followed for 6 months in a single-center, observational, cohort-study. Left ventricle and free-wall right ventricular longitudinal strain were analyzed prior and after 6 months of treatment, using a vendor-independent software, together with left ventricle ejection fraction, tricuspid annulus plane systolic excursion and right ventricular fractional area change. Cancer therapy-related cardiac dysfunction was defined as a left ventricle ejection fraction drop of >10% to <53%. Both left ventricle ejection fraction (59±7% vs. 55±8%, p<0.0001) and left ventricle longitudinal strain (−19.7±2.5% vs. −17.1±2.6%, p<0.0001) were reduced at follow up, along with free-wall right ventricular longitudinal strain (−24.9±4.5% vs. −21.6±4.9%, p<0.0001). Cancer therapy-related cardiac dysfunction was detected in 20 patients (29%). In 15 out of these 20 patients (75%), a concomitant relative reduction in free-wall right ventricular longitudinal strain magnitude by 17±7% was detected. Moreover, there was a significant correlation between left ventricle and free-wall right ventricular longitudinal strain at follow-up examinations (r=0.323, p<0.0001). A relative drop of right ventricular longitudinal strain >17% had a sensitivity of 55% and a specificity of 70% (AUC=0.75, 0.7-0.8, 95% CI) to identify patients with cancer treatment related cardiac dysfunction. Neither tricuspid annulus plane systolic excursion (24±5 vs. 23±4 mm, p=0.07), nor right ventricular fractional area change (45±8% vs. 44±7%, p=0.6) showed any significant change between examinations.Conclusions: Longitudinal strain analysis allows the identification of subclinical right ventricular dysfunction appearing in the course of cancer treatment when conventional indices of right ventricular dysfunction function are unaffected.

Use of integrated imaging and serum biomarker profiles to identify subclinical dysfunction in pediatric cancer patients treated with anthracyclines

BackgroundAnthracycline induced cardiomyopathy is a major cause of mortality and morbidity among pediatric cancer survivors. It has been postulated that oxidative stress induction and inflammation may play a role in the pathogenesis of this process. Accordingly, the present study performed an assessment of biomarker profiles and functional imaging parameters focused upon potential early determinants of anthracycline induced cardiomyopathy.MethodsPatients (10–22 years) were prospectively enrolled between January 2013 and November 2014. Thirteen subjects completed the study and underwent serial cardiac magnetic resonance imaging and plasma biomarker profiling performed 24–48 h after the first anthracycline dose and at set dose intervals. In addition, we collected plasma samples from 62 healthy controls to examine normal plasma biomarker profiles.ResultsLeft ventricular ejection fraction (LVEF) decreased from 64.3 ± 6.2 at the first visit to 57.5 ± 3.3 (p = 0.004) 1 year after chemotherapy. A decline in longitudinal strain magnitude occurred at lower cumulative doses. A differential inflammatory/matrix signature emerged in anthracycline induced cardiomyopathy patients compared to normal including increased interleukin-8 and MMP levels. With longer periods of anthracycline dosing, MMP-7, a marker of macrophage proteolytic activation, increased by 165 ± 54% whereas interleukin-10 an anti-inflammatory marker decreased by 75 ± 13% (both p < 0.05). MMP7 correlated with time dependent changes in EF.ConclusionsAsymptomatic pediatric patients exposed to anthracycline therapy develop abnormal strain parameters at lower cumulative doses when compared to changes in EF. A differential biomarker signature containing both inflammatory and matrix domains occur early in anthracycline treatment. Dynamic changes in these domains occur with increased anthracycline doses and progression to anthracycline induced cardiomyopathy. These findings provide potential prognostic and mechanistic insights into the natural history of anthracycline induced cardiomyopathy.Trial registration numberNCT03211520 Date of Registration February 13, 2017, retrospectively registered.

Three‐dimensional morphology and volume of the free Achilles tendon at rest and under load in people with unilateral mid‐portion Achilles tendinopathy

What is the central question of this study? The aim was to determine the effect of mid-portion Achilles tendinopathy (MAT) on free Achilles tendon three-dimensional morphology and volume at rest and under load in people with unilateral MAT. What is the main finding and its importance? Tendinopathic tendon had a larger resting tendon cross-sectional area and anteroposterior diameter relative to healthy tendon. When loaded, tendinopathic tendon experienced a reduction in transverse morphology (i.e. cross-sectional area, anteroposterior and mediolateral diameters) and overall volume reduction. In contrast, the healthy tendon remained isovolumetric and bulged along the anteroposterior axis. These findings suggest a fundamental reorganization of tendinopathic tendon matrix components and altered tendon fluid content when under load. Mid-portion Achilles tendinopathy (MAT) adversely affects free Achilles tendon (AT) structure and composition. However, it is not known how these pathological alterations associated with MAT change the normal three-dimensional (3-D) morphology of free AT at rest and under load throughout the entire free tendon length. Here, we used 3-D ultrasound to examine the effect of unilateral MAT on free tendon 3-D morphology [length, cross-sectional area (CSA), anteroposterior (AP) diameter and mediolateral (ML) diameter] and volume at rest and during a submaximal (50%) voluntary isometric plantarflexion contraction bilaterally in individuals with unilateral MAT (n=10) compared with a matched healthy control group (n=10). The tendinopathic free AT had a greater CSA relative to the control tendons along the entire tendon length, which was mainly driven by a greater tendon AP diameter. Under load, the tendinopathic tendon experienced greater longitudinal and transverse strains than the control tendons. In contrast to the control tendons, which experienced a reduction in tendon CSA and ML diameter, bulged along the AP axis and behaved isovolumetrically under load, the tendinopathic tendon experienced a reduction in tendon CSA, AP diameter and ML diameter and an overall volume reduction. Overall, these findings suggest that the magnitude of longitudinal strain and volume change and the corresponding magnitude and direction of transverse strain under load are altered in MAT compared with normal tendon. These findings are indicative of a fundamental reorganization of the tendon matrix and alterations in tendon fluid content and distribution under load in tendinopathic tendon.

Influence of Aging on Level and Layer-Specific Left Ventricular Longitudinal Strain in Subjects Without Structural Heart Disease

Values for level- (apical, mid, and basal) and layer-based (endocardial, mid-myocardial, and epicardial) left ventricular (LV) longitudinal strain across age are scarce. The present study evaluates the effect of aging on level- and layer-specific LV longitudinal strain in subjects without structural heart disease. A total of 408 subjects (mean age 58 years [range 16 to 91]; 49% men) were evaluated retrospectively. Subjects were divided into equal groups based on age and gender. Subjects with evidence of structural heart disease or arrhythmias were excluded. Mean LV ejection fraction was 62 ± 6.2%. A gradual increase in magnitude of level LV longitudinal strain was observed from basal to mid and apical levels (-16.7 ± 2.1%, -18.8 ± 2.0%, -22.6 ± 3.8%; p <0.001, respectively). Across age groups, there was a borderline significant decrease in magnitude of basal longitudinal strain in older subjects, whereas the magnitude in the apical level significantly increased. On layer-based analysis, the magnitude of longitudinal strain increased from epicardium to endocardium across all age groups. On multivariable analysis, only diabetes mellitus was associated with more impaired longitudinal strain in the endocardium, and male gender was associated with more impaired longitudinal strain at the epicardium layer. In conclusion, with increasing age, the magnitude of LV longitudinal strain at the basal level declines while the apical LV longitudinal strain increases. In contrast, layer-specific LV longitudinal strain remains unchanged with aging. The presence of diabetes mellitus modulated the effect of age on the LV endocardial layer, and male gender was associated with more impaired longitudinal strain at the epicardial layer.

Feasibility of Echocardiographic Techniques to Detect Subclinical Cancer Therapeutics–Related Cardiac Dysfunction among High-Dose Patients When Compared with Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance imaging (CMR) is the gold standard for the quantification of global and regional myocardial function and can detect subclinical myocardial dysfunction in anthracycline-induced cardiomyopathy. The aim of this study was to ascertain reliable echocardiographic parameters that can be used for the early identification of cancer therapeutics-related cardiac dysfunction, compared with CMR. Fifty-seven pediatric cancer survivors, 10 to 42years of age, with cumulative anthracycline doses≥200mg/m(2), were studied with transthoracic echocardiography and CMR 2.4 to 26.9years after chemotherapy. Three-dimensional echocardiography had the highest sensitivity in identifying subjects with CMR-derived ejection fractions<55%. Subjects with end-systolic volume index values>29mL/m(2) were more likely to have CMR-derived ejection fractions<55%. Three-dimensional speckle-tracking echocardiographic peak global longitudinal strain magnitude<-17.5% best identified subjects with abnormal peak midwall longitudinal strain magnitude by CMR. A decrease in early atrial myocardial velocity of <10cm/sec at the interventricular septum also identified subjects with lower average peak midwall longitudinal strain and peak midwall circumferential strain magnitudes by CMR. Three-dimensional echocardiographic ejection fraction<55%, end-systolic volume index>29mL/m(2), three-dimensional speckle-tracking echocardiographic peak global longitudinal strain magnitude<-17.5%, and a decrease in early atrial myocardial velocity at the interventricular septum of <10cm/sec by Doppler tissue imaging are the most sensitive transthoracic echocardiographic parameters to identify subjects with subclinical myocardial dysfunction by CMR.

Failure load prediction of single lap adhesive joints based on a new linear elastic criterion

In this study a new failure criterion has been proposed to predict the static strength of single lap adhesive joints under tensile loading. The criterion is based on a simple 2D linear elastic finite element analysis and two material and geometry parameters. According to this method, the longitudinal strain magnitude along the adhesive layer is used as a failure parameter. The criterion suggests that fracture occurs when the failure parameter along the adhesive mid-plane reaches a critical value at a critical distance. Failure loads are also determined experimentally for a series of single lap adhesive joints of different bonding lengths. It is shown that the predictions based on the proposed criterion have good agreements with the experimental data.

Antiferroelectric to ferroelectric phase switching and dielectric properties of Ba doped lead lanthanum zirconate stannate titanate ceramics

Antiferroelectric to ferroelectric phase transition induced by electric field is accompanied by large strain and significant hysteresis. The effects of barium addition on the electrical and dielectric properties of (Pb0·94−xLa0·04Bax)(Zr,Sn,Ti)O3 antiferroelectric ceramics were investigated, with the intention of reducing phase switching field and hysteresis for actuator applications. The experimental results showed the switching field and electric hysteresis reduced with increasing Ba content, while the magnitude of longitudinal strain was almost unchanged. Further increase in Ba content destabilises the antiferroelectric state when the doping concentration reaches 8 mol.-%. The maximum value of dielectric constant ϵmax increased and the temperature Tm that corresponds to the maximal dielectric constant decreased with increasing Ba content. The barium modification causes the phase transition more diffuse.

Occult Cardiotoxicity in Childhood Cancer Survivors Exposed to Anthracycline Therapy

More than 50% of >270 000 childhood cancer survivors in the United States have been treated with anthracyclines and are therefore at risk of developing cardiotoxicity. Cardiac magnetic resonance (CMR) has demonstrated utility to detect diffuse interstitial fibrosis and changes in regional myocardial function. We hypothesized that CMR would identify occult cardiotoxicity characterized by structural and functional myocardial abnormalities in a cohort of asymptomatic pediatric cancer survivors with normal global systolic function. Forty-six long-term childhood cancer survivors with a cumulative anthracycline dose ≥200 mg/m(2) and normal systolic function were studied 2.5 to 26.9 years after anthracycline exposure. Subjects underwent transthoracic echocardiography, CMR with routine cine acquisition, tissue characterization, and left ventricular strain analysis using a modified 16-segment model. Extracellular volume was measured in 27 subjects, all of whom were late gadolinium enhancement negative. End-systolic fiber stress was elevated in 45 of 46 subjects. Low average circumferential strain magnitude (εcc) -14.9±1.4; P<0.001, longitudinal strain magnitude (εll) -13.5±1.9; P<0.001, and regional peak circumferential strain were seen in multiple myocardial segments, despite normal global systolic function by transthoracic echocardiography and CMR. The mean T1 values of the myocardium were significantly lower than that of control subjects at 20 minutes (458±69 versus 487±44 milliseconds; P=0.01). Higher mean extracellular volume was observed in female subjects (0.34 versus 0.22; P=0.01). Asymptomatic postchemotherapy pediatric patients have abnormal myocardial characteristics and strain parameters by CMR despite normal global cardiac function by standard transthoracic echocardiography and CMR measures.