Strain Rate Measurements Research Articles

Automated tissue Doppler imaging for identification of occluded coronary artery in patients with suspected non-ST-elevation myocardial infarction

PurposeIdentification of regional dysfunction is important for early risk stratification in patients with suspected non-ST-elevation myocardial infarction (NSTEMI). Strain echocardiography enables quantification of segmental myocardial deformation. However, the clinical use is hampered by time-consuming manual measurements. We aimed to evaluate whether an in-house developed software for automated analysis of segmental myocardial deformation based on tissue Doppler imaging (TDI) could predict coronary occlusion in patients with suspected NSTEMI.MethodsEighty-four patients with suspected NSTEMI were included in the analysis. Echocardiography was performed at admission. Strain, strain rate and post-systolic shortening index (PSI) were analyzed by the automated TDI-based tool and the ability to predict coronary occlusion was assessed. For comparison, strain measurements were performed both by manual TDI-based analyses and by semi-automatic speckle tracking echocardiography (STE). All patients underwent coronary angiography.ResultsSeventeen patients had an acute coronary occlusion. Global strain and PSI by STE were able to differentiate occluded from non-occluded culprit lesions (respectively − 15.0% vs. -17.1%, and 8.1% vs. 5.1%, both p-values < 0.05) and identify patients with an acute coronary occlusion (AUC 0.66 for both strain and PSI). Measurements of strain, strain rate and PSI based on TDI were not significantly different between occluded and non-occluded territories.ConclusionAutomated measurements of myocardial deformation based on TDI were not able to identify acute coronary occlusion in patients with suspected NSTEMI. However, this study confirms the potential of strain by STE for early risk stratification in patients with chest pain.

Cardiovascular magnetic resonance myocardial feature tracking for the determination of left atrial strain in hypertensive left ventricular hypertrophy and hypertrophic cardiomyopathy

To measure the left atrial (LA) function in patients with hypertrophic cardiomyopathy (HCM; with [OHCM] and without obstruction [NOHCM]) and hypertension-related left ventricular hypertrophy (H-LVH) using cardiovascular magnetic resonance imaging feature tracking (CMR-FT). Patients who met the criteria for HCM (n=68), H-LVH (n=46), and 30 healthy controls participated. Left atrial strain was analysed using CMR-FT in cine images with two and four chambers. The strain rate and LA strain measurements showed that patients with HCM, and H-LVH had impaired conduit and reservoir functions (versus controls). These capacities were more severely impaired in OHCM than those seen in NOHCM and H-LVH. The LA volume parameters (LAVIpac, LAVImin and LAVImax) from the OHCM group were higher than both the NOHCM and H-LVH groups (all p<0.05). There were differences between the OHCM and H-LVH groups in terms of the parameters for LA reservoir function (εs), booster pump function (SRa), and conduit function (SRe, LA passive EF, εe; p<0.05). The strongest correlations included the associations between LA total EF and εs, εe and LA passive EF, and SRe and LA passive EF. CMR-FT can reliably identify LA dysfunction and deformation in the early stages of HCM and H-LVH.

Assessment of Myocardial Mechanics in Acute Rheumatic Fever Using Speckle-Tracking Echocardiography.

This study aims to evaluate the role of speckle-tracking echocardiography to identify myocardial deformation in acute rheumatic fever. Twenty-seven patients and 27 healthy children were prospectively evaluated. The patient group was divided into 2 subgroups based on echocardiographic findings, with or without carditis. The left ventricular global longitudinal strain and strain rate, left ventricular global circumferential strain and strain rate, and right ventricular global lon-gitudinal strain and strain rate were assessed by speckle-tracking echocardiography. In the acute phase of the disease, all values except the right ventricular global longitudinal strain were found to be significantly below the control group in the patient cohort. No significant difference was found between the patients grouped as carditis and non-carditis in the acute period. Comparison of the acute period with the post-treatment period revealed a significant increase in all strain values of the patients with carditis and significant increases observed in all values except left ventricular global longitudinal strain rate, left ventricular global circumferential strain rate, and right ventricular global longitudinal strain rate values in patients without carditis. Apart from the right ventricular global longitudinal strain rate, which was significantly lower in the non-carditis group compared to the control group, there was no significant difference in strain values between the patient and control groups following treatment. In the present study, we found that all patients, including patients in whom no valvular involvement was detected by echocardiography in the acute phase of acute rheumatic fever, had a lower right and left ventricular strain and strain rate measurements and that these findings improved after treatment, suggesting that strain echocardiography may be a helpful diagnostic method, especially in patients without valvular involvement.

Extinction and NO formation of ammonia-hydrogen and air non-premixed counterflow flames

Green ammonia, produced using renewable energy, is a promising carbon-free energy vector and fuel. This work studies combustion of ammonia-hydrogen fuel mixtures with air in counterflow diffusion flame experiments and provides an improved kinetic mechanism for modeling ammonia combustion. The extinction strain rate is measured for a range of 0 to 15% hydrogen in the fuel blend. The flame structure is also investigated with quantitative laser-induced fluorescence (LIF) measurements of nitric oxide (NO) for the same hydrogen concentrations and strain rate range from 26 to 134 s−1. For these conditions, NO concentration increases with both strain rate and fuel hydrogen content. The previously published kinetic model developed by the authors is used to perform one-dimensional flame simulations of the experimental setup and conditions, and results are compared to three other recently published ammonia mechanisms. None of the selected models satisfactorily predict both the measured extinction strain rate and flame NO concentration. The models mainly fail to predict extinction strain rate at higher H2 fraction and NO formation at the highest experimental strain rates and H2 fraction. The reaction rate parameters for some of the key reactions in the published model developed by authors were updated to improve agreement with experimental results. The updated model results are closely aligned with extinction strain rate measurements, and have improved prediction of flame NO concentration. The model reveals that the reactions from the NH2 and NH sub-mechanism are sensitive in predicting the extinction strain rate as well as NO. In particular, the reaction NH+NO=N2O+H had significant impact on NO predictions.

Refining Rates of Active Crustal Deformation in the Upper Plate of Subduction Zones, Implied by Geological and Geodetic Data: The E-Dipping West Crati Fault, Southern Italy

We investigate crustal deformation within the upper plate of the Ionian Subduction Zone (ISZ) at different time scales by (i) refining geodetic rates of crustal extension from continuous Global Navigation Satellite System (GNSS) measurements and (ii) mapping sequence of Late Quaternary raised marine terraces tectonically deformed by the West Crati normal fault, in northern Calabria. This region experienced damaging earthquakes in 1184 (M 6.75) and 1854 (M 6.3), possibly on the E-dipping West Crati fault (WCF) which, however, is not unanimously considered to be a seismogenic source. We report geodetic measurements of extension and strain rates across the strike of the E-dipping WCF and throughout the northern Calabria obtained by using velocities from 18 permanent GNSS stations with a series length longer than 4.5 years. These results suggest that crustal extension may be seismically accommodated in this region by a few normal faults. Furthermore, by applying a synchronous correlation approach, we refine the chronology of understudied tectonically deformed palaeoshorelines mapped on the footwall and along the strike of the WCF, facilitating calculation of the associated fault-controlled uplift rates. Raised Late Quaternary palaeoshorelines are preserved on the footwall of the WCF indicating that “regional” uplift, likely related to the deformation associated either with the subduction or mantle upwelling processes, is affected by local footwall uplift. We show that GIS-based elevations of Late Quaternary palaeoshorelines, as well as temporally constant uplift rates, vary along the strike of the WCF, implying normal faulting activity through time. This suggests that (i) the fault slip rate governing seismic hazard has also been constant over the Late Quaternary, over multiple earthquake cycles, and (ii) our geodetically derived fault throw rate for the WCF is likely a more than reasonable value to be used over longer time scales for an improved seismic hazard assessment. Overall, we emphasize the importance of mapping crustal deformation within the upper plate above subduction zones to avoid unreliable interpretations relating to the mechanism controlling regional uplift.

Extinction strain rates of premixed ammonia/hydrogen/nitrogen-air counterflow flames

Chemical energy vectors will play a crucial role in the transition of the global energy system, due to their essential advantages in storing energy in form of gaseous, liquid, or solid fuels. Ammonia (NH3) has been identified as a highly promising candidate, as it is carbon-free, can be stored at moderate pressures, and already has a developed distribution infrastructure. As a fuel NH3 has poor combustion properties that can be improved by the addition of hydrogen, which can be obtained energy-efficiently by partially cracking ammonia into hydrogen (H2) and nitrogen (N2) prior to the combustion process. The resulting NH3/H2/N2 blend leads to significantly improved flame stability and resilience to strain-induced blow-out, despite similar laminar flame properties compared to equivalent methane/air flames. This study reports the first measurements of extinction strain rates, measured using the premixed twin-flame configuration in a laminar opposed jet burner, for two NH3/H2/N2 blends over a range of equivalence ratios. Local strain rates are measured using particle tracking velocimetry (PTV) and are related to the inflow conditions, such that the local strain rate at the extinction point can be approximated. The results are compared with 1D-simulations using three recent kinetic mechanisms for ammonia oxidation. By relating the extinction strain rates to laminar flame properties of the unstretched flame, a comparison of the extinction behaviour of CH4 and NH3/H2/N2 blends can be made. For lean mixtures, NH3/H2/N2-air flames show a significant higher extinction resistance in comparison to CH4/air. In addition, a strong non-linear dependence between the resistance to extinction and equivalence ratio for NH3/H2/N2 blends is observed.

On the measurement of hardness at high strain rates by nanoindentation impact testing

Recent advances in electronics have enabled nanomechanical measurements with very low noise, fast time constants and high data acquisition rates. These capabilities open the door for a wide range of ultra-fast nanomechanical testing. Given the inherent dynamic nature of high-speed testing, a thorough understanding of the testing system's dynamics and electronics is extremely important for accurate measurements. In this work, an analytical framework that includes the mechanical and electronic contributions of the instrument and the material constitutive response is presented to provide guidelines for performing high strain rate measurements of hardness by nanoindentation testing. Simple closed-form solutions that provide insights on the choice of test methodology, test parameters and instrument design are presented along with the strain rate range over which accurate measurements can be performed with commercially available nanoindenters.

Inter-field strength agreement of cardiovascular magnetic resonance cine-derived strain and strain rate measures: a randomised study

Abstract Background Left ventricular (LV) strain and strain rate measurements can be derived from routinely acquired cardiovascular magnetic resonance (CMR) cine images by feature tracking techniques. However, the inter-field strength agreement of strain measurements derived from these techniques is not known. We hypothesised that there would be excellent inter-field strength agreement (between 1.5 and 3 Tesla [T]) for the measurement of global strain and strain rate derived from cine imaging. Methods Prospective, randomised cross-over observational study. Healthy volunteers each underwent CMR scans at 1.5T and 3T within 30 minutes on the same day in a randomised order. Retrospectively ECG gated, short and long-axis balanced steady state free precession cine images were obtained using standardised acquisition parameters at both field strengths. Two software packages were used to derive LV global longitudinal, circumferential and long and short axis radial systolic strain, peak systolic, early diastolic and late diastolic strain rates. All strain values are expressed as positive numbers. Results Twenty-two subjects (mean age 36±12 years; 45% male) were studied. No differences in heart rate and blood pressure measurements during scanning were observed between field strengths. The abstract figure shows an example of strain analysis and Bland-Altman plots for global longitudinal and circumferential strain. Minimal bias was seen in all strain and strain rate measurements between field strengths using the first software package. Strain and strain rate values derived from long axis images (longitudinal and long axis radial) showed poor to fair agreement (intraclass correlation co-efficient (ICC) range 0.39–0.71), whereas measures derived from short axis images (circumferential and short axis radial) showed good to excellent agreement between field strengths (ICC range 0.78–0.91). Similar results were observed with the second software package, though the differences in agreement between long and short axis derived measures were less pronounced. Conclusion Longitudinal strain and strain rate measures derived from CMR feature tracking have poor inter-field strength agreement between 1.5T and 3T. By contrast, agreement of circumferential and short axis radial strain and strain rate measurements at 1.5T and 3T is good. These results need to be considered when assessing strain at different field strengths. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): United Kingdom National Institute for Health Research

Shear Rate Imaging Using A Polarization Camera And A Birefringent Aqueous Cellulose Nanocrystal Suspension

Two aqueous cellulose nanocrystal suspensions are used to experimentally measure the shear and strain rates in a two-dimensional fluid flow. Cellulose nanocrystals are rod-like particles that align when subjected to shear, whereas at rest, they are randomly orientated by Brownian motion. The alignment causes birefringence, a phenomenon also known as flow-induced birefringence. The amount of birefringence is measured using a rotatable linear polarizer and a polarization camera. The linear polarizer is rotated to nine different positions. At each position, light from a light source becomes linear polarized before entering the birefringent fluid. Because of the birefringence the state of polarization is changed. This change is measured by the polarization camera. From the nine measurements the two-dimensional birefringence distribution is determined and from the amount of birefringence the strain rate is derived with the help of the data published by Lane et al. (2022a). We define Λ_0 as the angle between the (maximum) strain rate and the direction of flow. A shearing flow leads to Λ_0=45°, whereas Λ_0=0° and Λ_0=90° describe a flow down the centerline of a symmetrically converging and diverging channel, respectively. The measured strain rates are compared to simulations. The reference data in (Lane et al., 2022a) was taken at Λ_0=45°. For Λ_0≈45°, measurements and simulations correspond well to each other. If Λ_0≈0° is assumed, measured strain rates appear too high whereas they are too low for Λ_0≈90°. These results may be of interest for two reasons. First, shear rate imaging gave satisfying results in areas where Λ_0≈45°. Therefore, we propose the study of shear rates in a two-dimensional shearing flow by means of the presented method. Second, the results indicate that the flow state affects the degree of particle alignment and thus birefringence. This finding is in line with the statements made by Wayland (1960, 1964). The study of particle alignment and its influencing factors is of interest, and the experimental approach presented here is thought to be practicable for such studies.

Appropriate Window Function and Window Length in Multifrequency Velocity Estimator for Rapid Motion and Locality of Layered Myocardium.

The heart wall has a multilayered structure and moves rapidly during ejection and rapid filling periods. Local strain rate (SR) measurements of each myocardial layer can contribute to accurate and sensitive evaluations of myocardial function. However, ultrasound-based velocity estimators using a single-frequency phase difference cannot realize these measurements owing to insufficient maximum detectable velocity, which is limited by a quadrature frequency. We previously proposed a velocity estimator using multifrequency phase differences to improve the maximum detectable velocity. However, the improvement is affected by a spatial discrete Fourier transform (DFT) window length that represents the locality of the velocity estimation. In this article, we theoretically describe that shortening the window increases the interference between different frequency components and decreases the maximum detectable velocity. The tradeoff between the maximum detectable velocity and the window length was confirmed through simulations and a water-tank experiment. Under the tradeoff, the Hanning window, which was used in previous studies, is not always appropriate for the local measurement of the velocity, which sometimes exceeds 100 mm [Formula: see text] depending on the subject, direction of the ultrasound beam to the heart wall, and cardiac periods. In the in vivo measurement with the short window, the Tukey window with a large flat part that has a high-frequency resolution and ameliorates the discontinuity at both edges of the windowed signal was appropriate to measure the maximum velocity. This study offers the potential for local measurements of each myocardial layer using the multifrequency velocity estimator with the appropriate window function and window length.

2Pa5-1 Improvement of Precision in Strain Rate Measurement Using Spatial Distribution of Envelope of RF Echoes

2Pa5-1 Improvement of Precision in Strain Rate Measurement Using Spatial Distribution of Envelope of RF Echoes

Application of High-Resolution X-ray Diffractometry in Measurements of Residual Stress and Strain Rate on Deformed Quartz from Malanjkhand Copper Deposit, India

Application of High-Resolution X-ray Diffractometry in Measurements of Residual Stress and Strain Rate on Deformed Quartz from Malanjkhand Copper Deposit, India

Role of Grain Size and Shape in Superplasticity of Metals

Superplasticity is characterized by an elongation to failure of &amp;gt;300% and a measured strain rate sensitivity (SRS), close to 0.5. The superplastic flow is controlled by diffusion processes; it requires the testing temperature of 0.5Tm or greater where Tm is the absolute melting temperature of metals. It is well established that a reduction in grain size improves the optimum superplastic response by lowering the deformation temperature and/or raising the strain rate. The low-temperature superplasticity (LTSP) is attractive for commercial superplastic forming, in view of lowering energy requirement, increasing life for conventional or cheaper forming dies, improving the surface quality of structural components, inhibiting quick grain growth and solute-loss from the surface layers, thus resulting in better post-forming mechanical properties. This paper will summarize the dependence of superplasticity on grain size and shape in various metallic materials, including ferrous and non-ferrous alloys, which has been considered as an effective strategy to enable the LTSP.

Thermal Effects on Far-Field Distributed Acoustic Strain-Rate Sensors

Summary Fiber-optic cables cemented outside of the casing of an unconventional well measure crosswell strain changes during fracturing of neighboring wells with low-frequency distributed acoustic sensing (LF-DAS). As a hydraulic fracture intersects an observation well instrumented with fiber-optic cables, the fracture fluid injected at ambient temperatures can cool a section of the sensing fiber. Often, LF-DAS and distributed temperature sensing (DTS) cables are run in tandem, enabling the detection of such cooling events. The increasing use of LF-DAS for characterizing unconventional hydraulic fracture completions demands an investigation of the effects of temperature on the measured strain response by LF-DAS. Researchers have demonstrated that LF-DAS can be used to extract the temporal derivative of temperature for use as a differential-temperature-gradient sensor. However, differential-temperature-gradient sensing is predicated on the ability to filter strain components out of the optical signal. In this work, beginning with an equation for optical phase shift of LF-DAS signals, a model relating strain, temperature, and optical phase shift is explicitly developed. The formula provides insights into the relative strength of strain and temperature effects on the phase shift. The uncertainty in the strain-rate measurements due to thermal effects is estimated. The relationship can also be used to quantify uncertainties in differential-temperature-gradient sensors due to strain perturbations. Additionally, a workflow is presented to simulate the LF-DAS response accounting for both strain and temperature effects. Hydraulic fracture geometries are generated with a 3D fracture simulator for a multistage unconventional completion. The fracture width distributions are imported by a displacement discontinuity method (DDM) program to compute the strain rates along an observation well. An analytic model is used to approximate the temperature in the fracture. Using the derived formulae for optical phase shift, the model outputs are then used to compute the LF-DAS response at a fiber-optic cable, enabling the generation of waterfall plots including both strain and thermal effects. The model results suggest that before, during, and immediately following a fracture intersecting a well instrumented with fiber, the strain on the fiber drives the LF-DAS signal. However, at later times, as completion fluid cools the observation well, the temperature component of the LF-DAS signal can be equal to or exceed the strain component. The modeled results are compared to a published field case in an attempt to enhance the interpretation of LF-DAS waterfall plots. Finally, we propose a sensing configuration to identify the events when “wet fractures” (fractures with fluids) intersect the observation well.

Abstract 11241: Longitudinal Myocardial Mechanics in Covid-19 Survivors with Normal Left Ventricular Ejection Fraction, a Single Center Study

Introduction: Subclinical cardiovascular involvement in COVID-19 patients has not been well described. 2D-Speckle Tracking Echocardiography derived global longitudinal strain (GLS) and systolic and early diastolic strain rate (SRs, SRe) measurements are more sensitive than standard echocardiographic parameters to diagnose subclinical mechanical dysfunction in patients with normal Left Ventricle Ejection Fraction (LVEF). Hypothesis: Evaluate subclinical myocardial mechanical function and reserve in active COVID-19 systemic disease patients with normal LVEF vs controls and between survivors and non survivors of COVID-19 in the longitudinal domain of contractility. Methods &amp; Results: 166 adult patients with active COVID 19 having normal LVEF were included and compared to 89 healthy volunteers. Baseline parameters were recorded. Peak GLS, SRs and SRe, were measured offline. Mean age was 62.53 ± 18.96 years and 87 (52%) were males and Mean LVEF was 62±5%. COVID-19 patients had higher GLS compared to controls (-20.93%±0.30 vs. -18.48%±0.40; p value &lt;0.0001), SRs was similar (-0.97 s -1 ±0.10 vs. -0.98 s -1 ±0.02, p value 0.2528) and SRe was lower (0.85 s -1 ±0.0 vs. 1.05 s -1 ±0.02; p value &lt;0.0001) respectively. After adjusting for age and sex, GLS, SRs and SRe was significant (p&lt;0.001). GLS, SRs and SRe were similar in survivors vs. non survivors (p NS), both groups had elevated biomarkers (cardiac troponin, NT-pro BNP, CRP), but non survivors had higher levels (3.22±0.18 vs 3.62±0.28, p = 0.2371, 5.86±0.19 vs 7.15±0.27, p = 0.0004, 3.75±0.14 vs 4.31±0.21, p = 0.0422, 7.64±0.17 vs 8.26±0.25, p=0.0487 respectively) (Table 1). Conclusions: In our cohort, COVID-19 patients had better systolic reserve and abnormal relaxation compared to controls. There was no significant difference in strain (GLS) and strain rate (SRs &amp; SRe) amongst survivors and non survivors in the longitudinal domain of contractility despite of higher inflammatory biomarkers in non-survivors.

The Use of Two Dimensional Speckle Tracking Echocardiography in Veterinary Cardiology

The aim of this study is to present short-axis radial and circumferential strain and strain rate measurements by speckle tracking echocardiography technique in healthy cats and dogs. The study was performed at Small Animal Training and Research Hospital, Ankara University. Retrospective data from cats (n=5) and dogs (n=5), which are applied to the animal hospital for cardiological examination, were analyzed. Two-dimensional speckle tracking echocardiography was performed without sedation, and patients were manually restrained in the right and left lateral positions. Peak systolic radial strain, radial strain rate, circumferential strain, circumferential strain rate means were 24.47 ± 1.22%, 0.29 ± 0.20 s-1, -15.33 ± 2.56%, 0.05 ± 0.27 s-1 respectively for cats and were 39.33 ± 14.02%,-0.47s -1 ± 0.55 s-1, -23.13 ± 1.53%, -0.63 s-1± 0.18 s-1 respectively for dogs. It is thought that speckle tracking echocardiography can be included in routine echocardiographic examinations because this technique provides detailed information for determining the systolic potential of the left ventricle and the examination time is not much different compared to conventional echocardiographic examinations.

Normal Left Ventricular Systolic and Diastolic Strain Rate Values in Children Derived from Two-Dimensional Speckle-Tracking Echocardiography

Strain rate (SR) parameters derived from two-dimensional speckle-tracking echocardiography have prognostic value in children with heart disease. Routine use is hindered by a lack of normative data. The aim of this study was to determine reference values and Z scores for left ventricular systolic and diastolic SR in a large cohort of healthy children. Echocardiograms from 577 subjects ≤18years of age (mean age, 9.6±5.6years; range, 1day to 18.0years; 46% female) with structurally and functionally normal hearts were retrospectively included. Left ventricular longitudinal and circumferential systolic and early and late diastolic SR were measured using two-dimensional speckle-tracking echocardiography from the apical four-chamber and short-axis mid-papillary views. Associations with age and body surface area were assessed using Spearman correlation and generalized additive modeling. The relationship between systolic SR and wall stress (afterload) was examined. Analyses were conducted with and without correction for heart rate. Multivariable linear regression modeling was used to identify independent factors associated with the SR parameters. Z score equations were derived from a selected best-fit parametric model. All SR parameters differed significantly by age group. The magnitude of all SR values decreased with increasing age and body surface area. Systolic SR magnitude was inversely related to wall stress in children ≤7years of age but not did not vary significantly in the older age groups. All relationships were maintained after heart rate correction. SR measurements had very good or excellent agreement. Longitudinal and circumferential systolic and diastolic SR parameters are presented from a large cohort of healthy children using two-dimensional speckle-tracking echocardiography from the Philips platform. SR values differ significantly by age and body surface area. These results suggest that the myocardium becomes less sensitive to afterload with maturity. Z score equations based on age are presented, which should promote further clinical and research use.

Strain Rate Distribution in Layered Myocardium Measured Using Local Velocity Estimator with Multifrequency Phase Differences

Measurement of the myocardial strain rate (SR), with high spatial resolution, is useful in evaluation of the transmurality of myocardial infarction. As the SR distribution is calculated using velocities observed at multiple positions in the heart wall, it is necessary to estimate the local velocity to measure SR distribution. In the present study, our previously proposed local velocity estimator, with multifrequency phase differences, was used to measure SR distribution in the heart wall. The SR distribution measured with the proposed local velocity estimator revealed alternate layers of contraction and relaxation, which were not measured with the conventional velocity estimator with spatial averaging. The reproducibility of the SR distributions was confirmed in three consecutive heartbeats with three subjects. High-spatial-resolution SR measurement with the proposed local velocity estimator will allow myocardial layer-specific analysis in the transmural direction.

The Prevalence of Advanced Interatrial Block and Its Relationship to Left Atrial Function in Patients with Transthyretin Cardiac Amyloidosis.

Background: Advanced interatrial block (aIAB), which is associated with incident atrial fibrillation and stroke, occurs in the setting of blocked interatrial conduction. Atrial amyloid deposition could be a possible substrate for reduced interatrial conduction, but the prevalence of aIAB in patients with transthyretin cardiac amyloidosis (ATTR-CA) is unknown. We aimed to describe the prevalence of aIAB and its relationship to left atrial function in patients with ATTR-CA in comparison to patients with HF and left ventricular hypertrophy but no CA. Methods: The presence of aIAB was investigated among 75 patients (49 patients with ATTR-CA and 26 with HF but no CA). A comprehensive echocardiographic investigation was performed in all patients, including left atrial strain and strain rate measurements. Results: Among patients with ATTR-CA, 27% had aIAB and in patients with HF but no CA, this figure was 21%, (p = 0.78). The presence of aIAB was associated with a low strain rate during atrial contraction (<0.91 s−1) (OR: 5.2 (1.4–19.9)), even after adjusting for age and LAVi (OR: 4.5 (1.0–19.19)). Conclusions: Advanced interatrial block is common among patients with ATTR-CA, as well as in patients with heart failure and left ventricular hypertrophy but no CA. aIAB is associated with reduced left atrial contractile function.

Impairment of left atrial function in pediatric patients with repaired tetralogy of Fallot: a cardiovascular magnetic resonance imaging study.

We aimed to assess left atrial (LA) strain before LA dilatation in patients with repaired tetralogy of Fallot (rTOF) compared with healthy controls. We also determined the effects of right atrial (RA) dilatation on LA performance using cardiovascular magnetic resonance-feature tracking (CMR-FT). Forty-nine pediatric patients with rTOF and 36 age- and sex-matched healthy controls were prospectively recruited between June 2017 and August 2019. Balanced steady-state free precession (2D b-SSFP) cine, 2D late gadolinium enhancement (LGE) and phase-contrast (PC) sequences were acquired on 1.5 and 3.0 Tesla scanners. Both ventricular and atrial volumes and ejection fraction were measured. Left ventricular (LV) strain and diastolic strain rates were evaluated between the rTOF patient and control groups. LA reservoir (Ɛs), conduit (Ɛe), and booster strain (Ɛa) were determined at LV end-systole, LV diastasis, and pre-LA systole, respectively. The first derivatives of the respective strains yielded corresponding peak strain rates. Statistical analysis was performed using the t-test and Mann-Whitney test for parametric and non-parametric variables, respectively. Correlations were assessed using Pearson's correlation coefficient for normally distributed variables and Spearman's correlation coefficient for non-parametric data. Intra-observer and inter-observer variabilities of LA strain and strain rate measurements were determined from ten randomly selected rTOF patients and ten control subjects. LA strain was significantly lower in patients with rTOF compared with controls (Ɛs, P < 0.001; Ɛe, P = 0.002; Ɛa, P < 0.001). The correlations between LA strain and RA stroke volume indices (SVi) and RA ejection fraction (EF) were moderate (Ɛs and SVi, r = 0.538, P < 0.001; Ɛs and RA EF, r = 0.493, P < 0.001; Ɛe and SVi, r = 0.532, P < 0.001; Ɛe and RA EF, r = 0.466, P < 0.001). LA strain and strain rates had good reproducibility in intra-observer and inter-observer analyses. LA strain and strain rates decreased in pediatric patients with rTOF compared with controls before LA enlargement. A dysfunction in LA performance might precede LV dysfunction in patients with rTOF, even in the early stages after repair.