Atrioventricular Longitudinal Mechanics Using Novel Speckle-Tracking Improved Risk Stratification Beyond Baseline Thyroid Hormone in Asymptomatic Subclinical Hypothyroidism

Background: Hypothyroidism is reportedly associated with increased cardiovascular risk and heart failure. We aimed to elucidate the mechanistic influence of atrio-ventricular deformations and their prognostic utilizations in asymptomatic subclinical hypothyroidism (SCH). Methods: We assessed speckle-tracking of deformations among 4173 population-based asymptomatic individuals classified as euthyroid (0.25< thyroid-stimulating hormone [TSH] ≤4.0 μIU/mL, n=3799) or having mild (4< TSH ≤10.0 μIU/mL, n=349) or marked (TSH >10 μIU/mL, n=25) SCH. We further related deformational indices to outcomes of atrial fibrillation and heart failure. Results: Despite borderline differences in indexed left ventricular mass and left atrial volume ( P =0.054 and 0.051), those classified as mild and marked SCH presented with modest but significant reductions of global longitudinal strain, and showed elevated E/tissue Doppler imaging (TDI)-e′, markedly diminished peak atrial longitudinal strain and higher left atrial stiffness (all P <0.05) when compared with euthyroid subjects. A higher TSH level was independently associated with reduced TDI-s′/TDI-e′, worse global atrio-ventricular strains (global longitudinal strain/peak atrial longitudinal strain), elevated E/TDI-e′, and worsened left atrial strain rate components (all P <0.05). Over a median 5.6 years (interquartile range, 4.7–6.5 years) follow-up, myocardial deformations yielded independent risk prediction using Cox regression in models adjusted for baseline covariates, N-terminal pro-brain natriuretic peptide, E/e′, and treatment effect. Incorporation of global atrio-ventricular strain (global longitudinal strain/peak atrial longitudinal strain) and strain rates further showed improved risk reclassification when added to the baseline TSH strata (classified as euthyroid and mild and marked SCH; all P <0.05). Cox regression models remained significant with improved risk reclassification beyond TSH-based strata by using slightly different deformational cutoffs after excluding marked SCH group. Conclusions: Hypothyroidism, even when asymptomatic, may widely influence subclinical atrio-ventricular mechanical functions that may lead to higher heart failure and atrial fibrillation risk. We proposed the potential usefulness and prognostic utilization of myocardial strains in such population.

Numerical simulation of the dynamic distribution characteristics of the stress, strain and energy of coal mass under impact loads

To research the dynamic response characteristics of coal mass under impact loads, based on LS-DYNA software, rigid body bars are simulated to impact coal mass under different speed conditions, and the dynamic distribution characteristics of the stress, strain and energy of coal mass are analyzed. The results demonstrate that (1) the peaks of the axial and radial stresses and strain on the central axis and the radial line obey the power function distribution; at the same position, the axial and the radial stress peaks are close, and the axial strain peak is from much larger than the radial strain peak to close to. (2) The axial and radial stresses generate tensile stresses in the axial and radial propagation directions, respectively, and the coal mass is prone to damage under tensile stress. (3) When the speed is large, the axial stress–strain curve is similar to that of the dynamic load experiment. The axial stress peak, axial strain peak, critical effective stress, critical time and secant modulus have a linear relationship with the velocity. (4) When the dynamic load is large, most of the energy is in the form of kinetic energy, and the total energy loss also increases.

P340 New tools for the assesment of diastolic function in attr cardiac amyloidosis

INTRODUCCION Cardiac amyloidosis (CA) is a cardiomyopathy where the main disturbances are due to diastolic dysfunction. This requires a meticulous clinical and echocardiograpic evaluation. METHODS The aim of this study was to analyse the association between previously described parameters of diastolic dysfunction and others less known such as left atrial peak strain. RESULTS Thirty-six patients with suspicion of cardiac amyloidosis were submitted to DPD scintigraphyand transthoracic echocardiography, and were divided into two groups. Of these patients, eleven had no visual gammagraphic catchment whereas twenty-four, (68%) did. Median peak of atrial strain was 16.8 in sinus rhythm and 6.8% in atrial fibrillation (p &lt; 0.0001) with no differences in the proportion of AF. Median value of the velocity of E wave in patients with no catchment was 1.17 m/s whereas in those with ATTR-CA 0.77 m/s (p= 0.004). No differences were observed in other parameters such as A wave, E/A ratio or deceleration slope of E wave. We found that the strongest predictor of high filling pressures (E/e’&gt; 14) was systolic strain left atrial peak (p = 0,004 IC 95% 0.8-0.9) with an accurate predictive ability, AUC (76%). CONCLUSIONS Left atrial strain peak could be an interesting parameter for the assessment of diastolic dysfunction and a protective value for elevated filling pressures in CA-ATTR patients. Basal features ABSENCE OF CATCHMENT POSITIVE CATCHMENT P-value E (m/s) 0.77 1.17 0.04 A (m/s) 0.76 0.9 0.64 E/A 195 181 0.91 E/e’ 14 0.9 0.73 Atrial strain peak 8.5 11.8 0.78 35% AF 45% AF Fractional shortening (%) 34.34 31.80 0.81 Differences between both groups Abstract P340 Figure. Relationship: E/e" and atrial strain

Asphalt Pavement Mechanical Response of Accelerated Pavement Testing in Single-Axle and Dual-Axle Loading Modes

The objective of this study is to evaluate the influence of moving loads on the asphalt pavement in response to single-axle and dual-axle loading modes using the full-scale accelerated pavement testing (APT) facility from Shandong Jiaotong University. First, a test lane of pavement with four structures is constructed. Eleven strain sensors and four pressure cells are embedded at different depths and positions. Secondly, a research on the strain and stress in single-axle and dual-axle loading modes is conducted. Finally, the time accumulation of strain and stress is defined to describe the degree of pavement damage. The study reaches the following conclusions: (1) the strain reversal is induced as the wheels pass through the pavement, and the stress is always a positive value. (2) Both the strain and the stress increase as the loading increases regardless of the loading modes. (3) Comparing the two loading modes at the same velocity and loading, the horizontal tensile strain peak, the horizontal compressive strain peak, and the stress peak are all greater in the single-axle loading mode. But the degree of pavement damage is greater in the dual-axle loading mode based on the points of the time accumulations of strain and stress of each pass.

FINITELY SCOPED, HIGH RELIABILITY FATIGUE CRACK GROWTH MEASUREMENTS

ABSTRACT Classical procedures for characterizing fatigue crack growth behavior often suffer from uncertainties that make it difficult to plan for productive use of test instrument time, and that can result ultimately in too noisy measurements. An enhanced procedure has been implemented that is based on a fixed test time budget, and that establishes operating conditions that produce crack growth rates down to minimum measurable rates. The procedure features (1) a haversine pulse deformation test cycle followed by a rest period, (2) a strain peak that ramps linearly over time, (3) minimum and maximum limits on the strain peak chosen to avoid unproductive test time, and (4) a stress–strain probe cycle for purposes of observing strain energy density. A set of replicates of a carbon black filled, natural rubber bushing compound has been characterized via both procedures, and a statistical analysis is made to compare both. The new procedure significantly improves the quality of crack growth rate curve measurements.