Novel 2D strain-rate-dependent lamina-based and RVE/phase-based progressive fatigue damage criteria for randomly loaded multi-layer fiber-reinforced composites

Two implicit progressive fatigue damage models that rely on new equivalent-damage and equivalent-stress criteria are presented for the prediction of various failure modes of the composites. The criteria are coupled with lamina-based and representative-volume-element-based damage progression approaches. The common concepts of residual strength and residual stiffness are revisited and modified. A fatigue life assessment algorithm that incorporates the strain-rate-dependence of the fatigue strengths and stiffnesses, and random and asynchronous changes of the stress components, distinct mean values, and phase shifts of the stress components is employed. New ideas and new post-processing procedures are employed in the current research. It is the first time that the significant impacts of the strain-rate-dependence of the properties of the composites on stress and fatigue life analyses are investigated. Results of the proposed fatigue criteria are first implemented to a composite plate with a complex lamination scheme under a random transverse load and the predicted fatigue lives are verified by the experimental results. Then, these criteria are implemented to a composite chassis frame of an SUV car under realistic random road inputs and the theoretical results are verified by the experimental results. Results confirm the significant role of the strain-rate-dependence effects on the fatigue lives.

Exercise-Induced Cardiac Fatigue in Soldiers Assessed by Echocardiography

Background: Echocardiographic signs of exercise-induced cardiac fatigue (EICF) have been described after strenuous endurance exercise. Nevertheless, few data are available on the effects of repeated strenuous exercise, especially when associated with other constraints as sleep deprivation or mental stress which occur during military selection boot camps. Furthermore, we aimed to study the influence of experience and training level on potential EICF signs.Methods: Two groups of trained soldiers were included, elite soldiers from the French Navy Special Forces (elite; n = 20) and non-elite officer cadets from a French military academy (non-elite; n = 38). All underwent echocardiography before and immediately after exposure to several days of uninterrupted intense exercise during their selection boot camps. Changes in myocardial morphology and function of the 4 cardiac chambers were assessed.Results: Exercise-induced decrease in right and left atrial and ventricular functions were demonstrated with 2D-strain parameters in both groups. Indeed, both atrial reservoir strain, RV and LV longitudinal strain and LV global constructive work were altered. Increase in LV mechanical dispersion assessed by 2D-strain and alteration of conventional parameters of diastolic function (increase in E/e' and decrease in e') were solely observed in the non-elite group. Conventional parameters of LV and RV systolic function (LVEF, RVFAC, TAPSE, s mitral, and tricuspid waves) were not modified.Conclusions: Alterations of myocardial functions are observed in soldiers after uninterrupted prolonged intense exercise performed during selection boot camps. These alterations occur both in elite and non-elite soldiers. 2D-strain is more sensitive to detect EICF than conventional echocardiographic parameters.

704 Stress echocardiography: myocardial work ‘works’

Stress echocardiography is a widely employed diagnostic technique relying on subjective assessment of left ventricular wall motion and particular expertise. We report a case of a male patient with chronic coronary syndrome, who underwent dipyridamole echocardiography before planned non cardiac surgery. Despite the absence of symptoms and relevant electrocardiographic and wall motion changes, only 2D strain and, especially, Myocardial Work analysis was able to detect abnormalities suggestive of myocardial ischaemia. Thus, coronary angiography was performed, showing critical stenosis of the proximal Circumflex artery, that was treated with angioplasty and drug-eluting stent implantation. Interestingly, the location of strain and myocardial work abnormalities was consistent with the culprit vessel territory. This case highlights the particular usefulness of advanced echocardiographic techniques, especially for the detection of one-vessel coronary artery disease, during stress echocardiography.

RV free wall longitudinal strain as an independent predictor of survival in wtATTR-CA patients

Background Wild type transthyretin cardiac amyloidosis (wtATTR-CA) is increasingly recognized as a cause of heart failure with preserved ejection fraction (HFpEF) but prognosis is often limited due to late or misdiagnosis.Longitudinal left ventricular strain and biomarkers are established as markers of disease severity, but the role of RV free wall strain, reflecting RV contractility, is less well understood. Purpose We sought to determine whether RV free wall strain might add incremental prognostic value in wtATTR-CA. Methods Consecutive patients diagnosed with wtATTR-CA with tissue confirmation at Mayo clinic between 2013 and 2015 were included. Patients with TTR gene mutations were excluded. Baseline characteristics and transthoracic echocardiography measurements were obtained from the medical records. Speckle tracking RV free wall longitudinal 2D strain and peak LA longitudinal 2D strain were measured using Tom Tec Imaging System. Survival was determined using Kaplan Meier estimates and using the cox proportional hazard ratio, univariate and multivariable analysis were performed to identify predictors of mortality in patients with wtATTR. Results The study group comprised 139 patients (mean age 74.9±8.6, 92.8% male), of which 102 had adequate image quality for RV strain, and 99 for LA strain. Amongst these, 102 (73.3%) had AF and 118 patients (84.8%) had HF. During 3.23±2.0 years of follow up, 66 patients died. Both mean RV and LA strain were impaired at baseline: RV free wall strain was −14.7±4.9, and peak atrial longitudinal strain (PALS) was 13.2±8.8%. Using ROC analysis, RV strain of −16.8% was an independent predictor of all-cause mortality. In univariate modeling, higher levels of NT-proBNP (HR: 1.1 per 1000 pg.ml; 95%, CI 1.05–1.15, p<0.001) and Troponin T (HR: 2.0 per 0.1ng/ml; 95% CI 1.49–2.61, p<0.001) were associated with increased all-cause mortality. In addition, LV GLS (HR: 1.13 per 1%; 95% CI1.04–1.24, p=0.003), RV free wall LS (HR: 2.16 per 5%; 95%, CI 1.57–3.03, p<0.0001), and PALS (HR: 0.91 per1%; 95% CI 0.85–0.96, p<0.0001) were univariate predictors of all-cause mortality. In multivariate analysis using a stepwise regression model, RV free wall longitudinal strain (HR: 1.81; 95% CI 1.29–2.62, p<0.001) and Troponin T (HR: 1.7; 95% CI 1.25–2.26, p=0.001) remained independent predictors. Kaplan-Meier survival analysis demonstrated a higher mortality rate above −16.8 RV strain cut-off (Wilcoxon <0.0001). All stages were divided into two groups by −16.8% RV strain, and survival in individual stages analyzed. Stage 1 and 2 with <−16.8 RV free wall strain value had higher mortality than ≤-16.8% RV strain (Stage 1: Wilcoxon = 0.0041 and Stage 2: Wilcoxon = 0.023). However, there was not a survival difference between two RV strain groups in stage3 (Wilcoxon = 0.34) Conclusion RV free wall strain is an independent predictor of survival in wtATTR patients and may add incremental prognostic value to NT-proBNP and Troponin. FUNDunding Acknowledgement Type of funding sources: None. Kaplan-Meier curve of all patients Kaplan-Meier curve of stages

Πρώιμη καρδιοτοξικότητα και ακτινοδερματίτιδα σε υποκλασματοποιημένη ακτινοθεραπεία μαστού

Η ακτινοθεραπεία του καρκίνου του μαστού έχει ξεκάθαρο όφελος τόσο για την μακρόχρονη επιβίωση όσο και για το ποσοστό τοπικής υποτροπής. Ωστόσο, τα υγιή γειτονικά όργανα, συμπεριλαμβανομένης της καρδιάς, μπορούν να προσβληθούν, επηρεάζοντας κατ’ επέκταση την ποιότητα ζωής των ασθενών. Εκτός της έντονης ανησυχίας σχετικά με την πρώιμη μετακτινική καρδιακή τοξικότητα, η μετακτινική δερματίτιδα αποτελεί μία από τις πιο συχνές ανεπιθύμητες ενέργειες διατηρώντας το επιστημονικό ενδιαφέρον σχετικά με το ιδανικό σχήμα κλασματοποίησης. Σκοπός της μελέτης μας είναι να αποσαφηνιστεί η συμβολή ορισμένων βιοδεικτών του πλάσματος αλλά και της απεικόνισης της ιστικής παραμόρφωσης του μυοκαρδίου στην αποκάλυψη πρώιμης καρδιοτοξικότητας. Επιπλέον, θεωρούμε χρήσιμο να αξιολογήσουμε την μετακτινική δερματίτιδα μετά από χορήγηση υποκλασματοποιημένης ακτινοθεραπείας. Το δείγμα της μελέτης αποτελείται από 25 γυναίκες με πρώιμο καρκίνο του αριστερού μαστού . Αξιολογήθηκαν αναδρομικά οι δόσεις ακτινοθεραπείας στο σύνολο της καρδιάς, την αριστερή πρόσθια κατιούσα αρτηρία και την αριστερή κοιλία. Επιπλέον, 2D strain υπερηχοκαρδιογράφημα και μέτρηση βιοδεικτών του πλάσματος ( Ferr, Alb, CRP, TroponinI) διενεργήθηκαν σε όλες τις ασθενείς πριν και ένα έτος μετά την ολοκλήρωση της ακτινοθεραπείας. Τέλος, αξιολογήθηκε η μετακτινική δερματίτιδα αμέσως μετά το τέλος της ακτινοθεραπείας, 6 μήνες και 1 έτος μετά την ολοκλήρωση της σύμφωνα με τα RTOG / EORTC criteria.Τα πρώιμα αποτελέσματα της μελέτης έδειξαν χαμηλή έκθεση του συνόλου της καρδιάς και της αριστερής κοιλίας ενώ η αριστερή πρόσθια κατιούσα αρτηρία ήταν η πιο εκτεθειμένη δομή . Ο μη παραμετρικός έλεγχος του Wilcoxon υπέδειξε μη στατιστικώς σημαντική διαφορά τόσο του ρυθμού ποσοστιαίας παραμόρφωσης του μυοκαρδίου (GLS) όσο και του κλάσματος εξώθησης της αριστερής κοιλίας (LVEF) , πριν και μετά την ακτινοθεραπεία .Παρομοίως, όσον αφορά τις μεταβλητές του αίματος , δεν βρέθηκε στατιστικώς σημαντική διαφορά μεταξύ των δύο μετρήσεων για όλες τις μεταβλητές της μελέτης μας .Τέλος, παρατηρήθηκε μη στατιστικά σημαντική διαφορά στη μέση τιμή του Δείκτη Μάζας Σώματος και του βαθμού δερματικής τοξικότητας ενώ επίσης δεν φάνηκε σαφής γραμμική σχέση είτε ανάμεσα στο χρώμα του δέρματος είτε στο μέγεθος του μαστού και στον βαθμό δερματικής τοξικότητας τόσο αμέσως μετά την ακτινοθεραπεία όσο και έξι μήνες και δώδεκα μήνες μετά την ολοκλήρωση της. Η πρόληψη και η πρώιμη διάγνωση της μετακτινικής καρδιοτοξικότητας πρέπει να αποτελεί προτεραιότητα όλης της θεραπευτικής διαδικασίας στοχεύοντας να βρεθούν τα χρήσιμα εργαλεία για την πρώιμη ανίχνευση της. Τέλος, η αποτελεσματική αντιμετώπιση της ακτινοδερματίτιδας προϋποθέτει την ορθή παρακολούθηση της βαρύτητας των συμπτωμάτων βάση των κατευθυντήριων οδηγιών.

Predicting postoperative hypertension among patients with ventricular septal defect in infants.

Background: Patients with strong pulmonary vascular occlusive lesions are at risk of developing postoperative pulmonary hypertension (PH). We aimed to evaluate preoperative right ventricular (RV) function in patients with ventricular septal defect (VSD) who required cardiac surgery during infancy and consequently developed postoperative PH and to determine whether we could preliminarily evaluate postoperative PH in these patients. Methods: We retrospectively analyzed 55 infants with VSD who underwent cardiac surgery between March 2014 and April 2020. We evaluated the measurements of preoperative general function and 2D strain between these two groups: a group with postoperative PH (post-PH, n=10) and a group without postoperative PH (post-NPH, n=45). Results: Post-PH patients had a significantly lower tricuspid annular plane systolic excursion (TAPSE) (11.1 mm), TAPSERA (the proportion of TAPSE due to right atrial (RA) contraction alone) (7.0 mm), RA ejection fraction (36.1 %) and RA expansion index (56.4 %) than the post-NPH patients. Furthermore, the post-PH group had a significantly lower peak RA longitudinal strain (PRALS) (32.0 %) than the post-NPH group (43.0%). Multivariate logistic regression model demonstrated that PRALS was independent echocardiographic parameters for the presence of post-PH (OR 1.18, 95% CI: 1.02 - 1.36, p = 0.03) . The sensitivity and specificity of predicting post-PH for ≤ 35 % of the PRALS were 88.9 % and 70.0 %, respectively, with an area under the curve of 0.85 (p < 0.01). Conclusion: RA parameters demonstrated preoperative RV diastolic dysfunction in the post-PH group. PRALS could be useful factors for predicting postoperative PH.

Left ventricular dyssynchrony and post-systolic shortening in young bodybuilders using anabolic-androgenic steroids

Background: Left ventricular (LV) remodeling, characterized by increased LV hypertrophy and depressed function, is observed in strength-trained athletes who use anabolic-androgenic steroids (AAS). Previous studies reported an increase in cardiac fibrosis in these athletes, which could promote intraventricular dyssynchrony. In this context, this study evaluated LV dyssynchrony in strength-trained athletes using AA; hypothesizing that the use of AAS leads to an increase in LV dyssynchrony with an increase in post-systolic shortening. Methods: Forty-four participants (aged 20-40 years) were divided into three age-matched groups: strength-trained athletes using AAS (users, n=14) and those who were not (non-users, n=15), and healthy sedentary men (controls, n=15),. After completing a survey, each participant was assessed with 2D-strain echocardiography. Left ventricular dyssynchrony was quantified using the standard deviation of the time to peak for longitudinal strains (SD), the longitudinal strain delay index (LSDI) and the segmental post-systolic index (PSI). Results: Users exhibited a greater LV mass index and higher systolic and diastolic functions than both controls and non-users. The decrease in LV strains in users was predominantly observed at the interventricular segments. The SD, LSDI and PSI, calculated on the basal inferoseptal, basal anteroseptal and basal inferolateral segments, were higher in users. Conclusion: The results strongly support that the specific LV remodeling observed in young AAS users was associated with an increase in LV dyssynchrony. The correlations with ejection fraction suggested that wasted energy, due to post-systolic shortenings, contributed in part to the decrease in LV function in strength-trained athletes using AAS.

Left ventricle longitudinal strain of the endocardial and epicardial layers and left ventricle remodelling in children born with low and extremely low body weight aged from one to five years old

Background. In last decades, the number of babies born preterm has increased significantly. Premature newborns are more susceptible to cardiovascular disease in the long-term. To identify subclinical myocardial impairment in premature infants, an assessment of of the left ventricle (LV) deformation could be used.Objective. The aim of the study was to study the left ventricle (LV) Longitudinal Strain of the endocardial, middle and epicBardial layers in children born with very low and extremely low body weight, at the age from one to five years.Design and methods. The study included 88 children aged from one to 5 years old, born very premature with very low and extremely low body weight. The comparison group consisted of 43 healthy children of the same age, born full-term. The LV Longitudinal Strain of the endocardial, middle and epicardial layers was studied using the Speckle Tracking Imaging-2D Strain.Results. In children aged 1 to 5 years, born with very low and extremely low body weight, changes in the gradient of transmural wall Strain and a decrease in LV segments longitudinal strain were detected in 15.90 % and 14.77 % of cases, respectively. Mothers of children born prematurely and who subsequently registered disturbance of the transmural gradient of left ventricular strain in 10 cases (71.43 %) had a history of threatened termination of pregnancy. The threat of termination of pregnancy was noted in all women whose children had a decrease in LV segmental strain. In children who have normal of LV segmental strain, the threat of termination of pregnancy in mothers was registered in 16 cases (26.23 %). LV remodeling is observed in children with a change in the gradient of transmural wall strain or and with a decrease in LV longitudinal segment strain. Conclusion. Changes in the transmural gradient of wall deformation or reduction of segmental LV deformation in the longitudinal direction in premature infants require correction of the conventional algorithm of dispensary observation in an outpatient setting.