Influence of Heart Rate on Left and Right Ventricular Longitudinal Strain in Patients with Chronic Heart Failure

Over the past years, a number of studies have demonstrated the relevance of strain assessed by two-dimensional speckle tracking echocardiography (STE) in evaluating ventricular function. The aim of this study was to analyze changes in left (LV) and right ventricular (RV) longitudinal strain associated with variations of heart rate (HR) in participants with and without chronic heart failure (CHF). We enrolled 45 patients, 38 of these diagnosed with CHF and carrying an implantable cardioverter defibrillator, and seven patients with pacemakers and without CHF. The frequency of atrial stimulation was increased to 90 beats/min and an echocardiogram was performed at each increase of 10 beats/min. Global LV and RV longitudinal strain (LVGLS and RVGLS, respectively) and RV free wall longitudinal strain (RVfwLS) were calculated at each HR. When analyzed as continuous variables, significant reductions in LVGLS were detected at higher HRs, whereas improvements in both RVGLS and RVfwLS were observed. Patients with a worsening of LVGLS (76% overall) were more likely to present lower baseline LV function. Only a few patients (18% for RVGLS and 16% for RVfwLS) exhibited HR-related deteriorations of RV strain measures, which was associated with lower levels of baseline RV function and higher pulmonary systolic pressures. Finally, 21 (47%) and 25 (56%) participants responded with improvements in RVGLS and RVfwLS, respectively. Our findings revealed heterogeneous RV and LV responses to increases in HR. These findings might ultimately be used to optimize cardiac functionality in patients diagnosed with CHF.

Comparative assessments of strain measures for nonlinear analysis of truss structures at large deformations

PurposeIn this paper the use of classical strain measures in analysis of trusses at finite deformations will be discussed. The results will be compared to the ones acquired using a novel strain measure based on the Hyperbolic Sine function. Through the evaluation of results, algebraic development and graph analysis, the properties of the Hyperbolic Sine strain measure will be examined.Design/methodology/approachThrough graph plotting, comparisons between the novel strain measure and the classic ones will be made. The formulae for the implementation of the Hyperbolic Sine strain measure into a positional finite element method are developed. Four engineering applications are presented and comparisons between results obtained using all strain measures studied are made.FindingsThe proposed strain measure, Hyperbolic Sine, has objectivity and symmetry. The linear constitutive model formed by the Hyperbolic Sine strain and its conjugated stress presents an increasing stiffness, both in compression and tension, a behavior that can be useful in the modeling of several materials.Research limitations/implicationsThe structural analysis performed on the four examples of trusses in this article did not consider the variation of the cross-sectional area of the elements or the buckling phenomenon, moreover, only elastic behavior is considered.Originality/valueThe present article proposes the use of a novel strain measure family, based on the Hyperbolic Sine function and suitable for structural applications. Mathematical expressions for the use of the Hyperbolic Sine strain measure are established following the energetic concepts of the positional formulation of the finite element method.

Speckle tracking strain and ECG heterogeneity correlate in transcatheter aortic valve replacement-induced left bundle branch blocks and right ventricular paced rhythms

ObjectiveTranscatheter aortic valve replacement (TAVR) complications include left bundle branch block (LBBB) and right ventricular paced rhythm (RVP). We hypothesised that changes in electrocardiographic heterogeneity would correlate better with speckle tracking strain measures than with left ventricular ejection fraction (LVEF) on transthoracic echocardiogram (TTE) among patients with TAVR-induced conduction abnormalities.MethodsWe reviewed medical records of 446 consecutive patients who underwent TAVR at our institution. Of the 238 patients with 12-lead electrocardiograms (ECGs) that met our inclusion criteria, 58 had pre-TAVR and post-TAVR TTEs adequate for strain assessment. We compared patients who did not have an LBBB or RVP pre-TAVR and post-TAVR (controls, n=11) with patients who developed LBBBs (n=11) and who required RVPs (n=10) post-TAVR. In our study population (n=32, 41% female, mean age 85.8 years), we evaluated QRS complex duration, R-wave heterogeneity (RWH), T-wave heterogeneity (TWH), LVEF, global longitudinal strain (GLS) and mechanical dispersion (MD).ResultsTAVR-induced changes on ECG did not correlate with LVEF. TAVR-induced changes in MD and QRS complex duration correlated among all patients (r=0.4, p=0.04). GLS and RWH correlated among RVP patients (r=0.7, p=0.00003). MD and TWH correlated among LBBB patients (r=0.7, p=0.00004).ConclusionsIn this convenience sample of patients with TAVR-induced conduction abnormalities, RWH and TWH correlated with strain measures but not with LVEF. Strain measures, RWH and TWH may offer additional insights for pre-TAVR evaluation and post-TAVR clinical management.

On the comparison of strain measurements from fibre optics with dense seismometer array at Etna volcano (Italy)

We demonstrate the capability of Distributed Acoustic Sensing (DAS) in recording volcano related dynamic strain at Etna (Italy). In summer 2019, we gathered DAS measurements from a 1.5 km long fibre in a shallow trench and seismic records from a conventional dense array comprising 26 broadband sensors deployed in Piano delle Concazze close to the summit area. The multifaceted style of Etna activity during the acquisition period gives the extraordinary opportunity to record and detect tiny strain changes (few 10−8 strain) in correspondence with volcanic events. To validate the DAS strain measures, we explored array-derived methods to estimate strain changes from the seismic signals and to compare with strain DAS signals. A general good agreement was found between array-derived strain and DAS measures along the fibre optic cable. Short wavelength discrepancies correspond with fault zones, showing the potential of DAS in mapping local perturbations of the strain field, and thus site effect, due to small-scale heterogeneities in volcanic settings.

The hierarchical finite cell method for nonlinear problems: Moment fitting quadratures, basis function removel, and remeshing

In this thesis, several approaches are discussed in order to further enhance the performance of the finite cell method (FCM). Thereby, novel moment fitting quadrature schemes are introduced that allow to reduce the effort of the numerical integration process significantly. Further, a basis function removal scheme is proposed to improve the conditioning behavior of the resulting equation system. Finally, an innovative remeshing strategy is presented that overcomes the problem of severely distorted elements for simulations with large deformations. Contents 1 Introduction 1 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Goal and scope of this thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Outline of this thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 Basic elements of continuum mechanics 6 2.1 Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.1 Motion and deformation . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.2 Strain measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 Equilibrium and stress measures . . . . . . . . ....

A new approach to curvature measures in linear shell theories

The paper presents a coordinate-free analysis of deformation measures for shells modeled as 2D surfaces. These measures are represented by second-order tensors. As is well-known, two types are needed in general: the surface strain measure (deformations in tangential directions), and the bending strain measure (warping). Our approach first determines the 3D strain tensor E of a shear deformation of a 3D shell-like body and then linearizes E in two smallness parameters: the displacement and the distance of a point from the middle surface. The linearized expression is an affine function of the signed distance from the middle surface: the absolute term is the surface strain measure and the coefficient of the linear term is the bending strain measure. The main result of the paper determines these two tensors explicitly for general shear deformations and for the subcase of Kirchhoff-Love deformations. The derived surface strain measures are the classical ones: Naghdi’s surface strain measure generally and its well-known particular case for the Kirchhoff-Love deformations. With the bending strain measures comes a surprise: they are different from the traditional ones. For shear deformations our analysis provides a new tensor [Formula: see text], which is different from the widely used Naghdi’s bending strain tensor [Formula: see text]. In the particular case of Kirchhoff–Love deformations, the tensor [Formula: see text] reduces to a tensor [Formula: see text] introduced earlier by Anicic and Léger (Formulation bidimensionnelle exacte du modéle de coque 3D de Kirchhoff–Love. C R Acad Sci Paris I 1999; 329: 741–746). Again, [Formula: see text] is different from Koiter’s bending strain tensor [Formula: see text] (frequently used in this context). AMS 2010 classification: 74B99

Left ventricular segmental strain and the prediction of cancer therapy-related cardiac dysfunction

Aims We aimed to determine the early changes and predictive value of left ventricular (LV) segmental strain measures in women with breast cancer receiving doxorubicin. Methods and results In a cohort of 237 women with breast cancer receiving doxorubicin with or without trastuzumab, 1151 echocardiograms were prospectively acquired over a median (Q1–Q3) of 7 (2–24) months. LV ejection fraction (LVEF) and 36 segmental strain measures were core lab quantified. A supervised machine learning (ML) model was then developed using random forest regression to identify segmental strain measures predictive of nadir LVEF post-doxorubicin completion. Cancer therapy-related cardiac dysfunction (CTRCD) was defined as a ≥10% absolute LVEF decline pre-treatment to a value <50%. Median (Q1–Q3) baseline age was 48 (41–57) years. Thirty-five women developed CTRCD, and eight of these developed symptomatic heart failure. From pre-treatment to doxorubicin completion, longitudinal strain worsened across the basal and mid-LV segments but not in the apical segments; circumferential strain worsened primarily in the septum; radial strain worsened uniformly and transverse strain remained unchanged across all LV segments. In the ML model, anterolateral and inferoseptal circumferential strain were the most predictive features; longitudinal and transverse strain in the basal inferoseptal, anterior, basal anterolateral, and apical lateral segments were also top predictive features. The addition of predictive segmental strain measures to a model including age, cancer therapy regimen, hypertension, and LVEF increased the area under the curve (AUC) from 0.70 (95% confidence interval (CI) 0.60–0.80) to 0.87 (95% CI 0.81–0.92), ΔAUC = 0.18 (95% CI 0.08–0.27) for the prediction of CTRCD. Conclusion Our findings suggest that segmental strain measures can enhance cardiotoxicity risk prediction in women with breast cancer receiving doxorubicin.