Evaporation of Ti/Cr/Ti Multilayer on Flexible Polyimide and Its Application for Strain Sensor

A flexible Ti/Cr/Ti multilayer strain gauge have been successfully developed based on polyimide substrate. The pure Ti metal strain gauge have shown the hysteresis phenomenon at the relationship between resistance and strain during tensile test. The experimental results of multilayer strain gauge show that adding Cr interlayer can improve the recovery and stability of the sensing electrode. When the interlayer Cr thickness was increased from 0 to 70 nm, the resistance decreased from 27 to 8.8 kΩ. The gauge factor (GF) value also decreased from 4.24 to 2.31 with the increase in the thickness of Cr interlayer from 30 to 70 nm, and the hysteresis phenomenon disappeared gradually. The multilayer Ti/Cr/Ti film has feasible application for strain sensor.

Direct comparison of multilayer left ventricular global longitudinal strain using CMR feature tracking and speckle tracking echocardiography

Background Cardiac magnetic resonance feature tracking (CMR-FT) and speckle tracking echocardiography (STE) are well-established strain imaging modalities. Multilayer strain measurement permits independent assessment of endocardial and epicardial strain. This novel and layer specific approach to evaluating myocardial deformation parameters may provide greater insight into cardiac contractility when compared to whole-layer strain analysis. The aim of this study is to validate CMR-FT as a tool for multilayer strain analysis by providing a direct comparison between multilayer global longitudinal strain (GLS) values between CMR-FT and STE. Methods We studied 100 patients who had an acute myocardial infarction (AMI), who underwent CMR imaging and echocardiogram at baseline and follow-up (48 ± 13 days). Dedicated tissue tracking software was used to analyse single- and multi-layer GLS values for CMR-FT and STE. Results Correlation coefficients for CMR-FT and STE were 0.685, 0.687, and 0.660 for endocardial, epicardial, and whole-layer GLS respectively (all p < 0.001). Bland Altman analysis showed good inter-modality agreement with minimal bias. The absolute limits of agreement in our study were 6.4, 5.9, and 5.5 for endocardial, whole-layer, and epicardial GLS respectively. Absolute biases were 1.79, 0.80, and 0.98 respectively. Intraclass correlation coefficient (ICC) values showed moderate agreement with values of 0.626, 0.632, and 0.671 respectively (all p < 0.001). Conclusion There is good inter-modality agreement between CMR-FT and STE for whole-layer, endocardial, and epicardial GLS, and although values should not be used interchangeably our study demonstrates that CMR-FT is a viable imaging modality for multilayer strain

Strain by speckle tracking echocardiography correlates with electroanatomic scar location and burden in ischaemic cardiomyopathy

Aims Ventricular tachycardia (VT) in ischaemic cardiomyopathy (ICM) originates from scar, identified as low-voltage areas with invasive high-density electroanatomic mapping (EAM). Abnormal myocardial deformation on speckle tracking strain echocardiography can non-invasively identify scar. We examined if regional and global longitudinal strain (GLS) can localize and quantify low-voltage scar identified with high-density EAM. Methods and results We recruited 60 patients, 40 ICM patients undergoing VT ablation and 20 patients undergoing ablation for other arrhythmias as controls. All patients underwent an echocardiogram prior to high-density left ventricular (LV) EAM. Endocardial bipolar and unipolar scar location and percentage were correlated with regional and multilayer GLS. Controls had normal GLS and normal bipolar and unipolar voltages. There was a strong correlation between endocardial and mid-myocardial longitudinal strain and endocardial bipolar scar percentage for all 17 LV segments (r = 0.76–0.87, P &lt; 0.001) in ICM patients. Additionally, indices of myocardial contraction heterogeneity, myocardial dispersion (MD), and delta contraction duration (DCD) correlated with bipolar scar percentage. Endocardial and mid-myocardial GLS correlated with total LV bipolar scar percentage (r = 0.83; 0.82, P &lt; 0.001 respectively), whereas epicardial GLS correlated with epicardial bipolar scar percentage (r = 0.78, P &lt; 0.001). Endocardial GLS −9.3% or worse had 93% sensitivity and 82% specificity for predicting endocardial bipolar scar &gt;46% of LV surface area. Conclusions Multilayer strain analysis demonstrated good linear correlations with low-voltage scar by invasive EAM. Validation studies are needed to establish the utility of strain as a non-invasive tool for quantifying scar location and burden, thereby facilitating mapping and ablation of VT.

P1782 Left ventricular deformation proprieties in aortic coarctation: insights from multilayer strain imaging

Background Patients with coarctation of the aorta (CoA) have proven impaired left ventricular (LV) myocardial deformation that will persist even after successful transcatheter intervention compared to normal controls. However, little is known about layer specific contraction in this clinical setting. Purpose To investigate multi-layer longitudinal strain in patients with repaired CoA, compared with a control group of healthy subjects. Methods In a case-control study, 13 CoA patients (F/M = 9/4, age = 15.1 ± 4.4 years) and 13 healthy age- and sex-matched controls, underwent a complete echocardiogram, including speckle tracking assessment for quantification of LV transmural global longitudinal strain (GLS), subendocardial longitudinal strain (LSsubendo), subepicardial longitudinal strain (LSsubepi), and myocardial longitudinal strain gradient (LSsubendo - LSsubpepi). Results CoA patients had similar blood pressure, heart rate, and body surface area in comparison with healthy controls. The two groups did not differ for ejection fraction and LV diastolic indices. Increased maximal gradient (&gt;20 mmHg) in descending aorta was found in 9 (69.2%) CoA patients. In CoA population, 5 (38.5%) had LV concentric remodeling (RWT &gt; 0.42) and 2 (15.4%) LV hypertrophy (Z score &gt;2.0). LV mass index (92.4 ± 31.1 vs. 60.9 ± 12.5 g/m^2.7, p = 0.002), septal wall thickness (8.7 ± 2.0 vs 6.6 ± 0.9 mm p = 0.002), posterior wall thickness (8.2 ± 1.7 vs. 6.6 ± 1.4 mm, p = 0.02) and RWT (0.38 ± 0.06 vs. 0.27 ± 0.08, p &lt; 0.001) were greater in CoA patients. By multi-layer deformation analysis, GLS (21.2 ± 1.9 vs. 22.9 ± 1.4%, p &lt; 0.01), LSsubepi (19.3 ± 1.6 vs. 21.0 ± 1.6%, p &lt; 0.01), LSsubendo (22.9 ± 1.8 vs. 25.4 ± 1.9%, p = 0.003) and longitudinal strain gradient (3.6 ± 1.1 vs. 4.7 ± 1.1, p &lt; 0.02) were lower in CoA patients than in healthy controls. Separate sub-analyses in patients without LV hypertrophy, substantially confirmed the same results: GLS 20.9 ± 1.6 vs. 22.8 ± 0.9%, p = 0.004; LSsubepi 19.0 ± 1.4 vs. 21.1 ± 1.3%, p = 0.004; and LSsubendo 22.4 ± 1.2 vs. 25.3 ± 1.4%, p &lt; 0.0001; strain gradient 3.4 ± 1.0 vs. 4.6 ± 1.1, p = 0.02. Notably, LSsubepi (18.6 ± 1.4 vs. 20.6 ± 1.0%, p = 0.03) and, with greater significance, LSsubendo (22.1 ± 1.1 vs. 24.7 ± 1.8%, p &lt; 0.0001) were lower in CoA patients with increased aortic gradient versus those without significant gradient increase. Conclusions In CoA patients, layer specific strain imaging highlights an impairment of LV longitudinal deformation, which mainly involves LSsubendo and causes reduction of longitudinal strain gradient. This preferential impairment of subendocardium is particularly evident in patients with residual aortic gradient and is independent of LV hypertrophy. Abstract P1782 Figure. Multilayer strain in CoA vs. controls

P208 Abnormal coronary flow reserve assessed with stress echocardiography induces a reduction in transmural strain gradient and an increase in heterogeneous myocardial electrical activation

OnBehalf Echo Lab INC Background The integrated quadruple stress echo (IQ-SE) is a state-of-the-art protocol that expands the risk stratification potential of SE. The coronary flow reserve (CFVR) has pronostic implication mainly in the absence of wall motion abnormalities. Longitudinal multilayer strain analysis assesses trasmural strain gradient. The prognostic value of multilayer strain analysis alongside the IQ-SE has not been established. We aim to determine the additive value of multilayer strain analysis during IQ-SE. Methods Prospective observational study. We evaluated one hundred twenty intermediate-high risk patients without obstructive coronary artery disease (mean age 61 ± 12 years, female 43%) with IQ-SE dipyridamole at our institution. Abnormal CFVR was defined as CFVR &lt;2. Multilayer strain analysis and mechanical dispersion, were performed during rest and stress, with an automatic frame-by-frame with speckle tracking. Results The IQ-SE was feasible in all patients. At rest, mean three-dimensional left ventricular ejection fraction (3D LVEF) was 59% (53-62) without wall motion abnormalities. Abnormal CFVR was seen in 38 patients (32%) and reduced left ventricular contractile reserve (LVCR) in 56 patients (46%). Patients with abnormal CFVR, showed a reduction in EndoLS and transmural strain gradient, and an increase in mechanical dispersion and in lung B-lines during stress. No differences were observed in 3D LVEF and LVCR. Conclusions Endocardial ischemia due to microvascular dysfunction leads to a reduction in transmural strain gradient. Adding multilayer strain analysis to IQ-SE might detect myocardial subclinical dysfunction, arrhythmic risk and pulmonary congestion due to microvascular dysfunction. Left ventricular mechanics analysis CVFR &lt;2 (38) CVFR &gt;2 (81) P Rest EpiLS (%) -14.9 ±4.2 -18 ± 3.7 0.001 EndoLS (%) -20.2 ± 5.9 -23.5 ± 4.5 0.001 EndoLS- EpiLS 5.1 (3.8-6.3) 5.4 (4.2-6.3) 0.27 Mechanical Dispersion (ms) 57.7 (42.2-69) 44.2 (35-54) 0.006 Stress EpiLS (%) -17.2 ± 4.8 -20 ± 4.4 0.003 EndoLS (%) -23 ± 6 -26.6 ± 5.7 0.002 EndoLS- EpiLS 5.6 (4.5-6.7) 6.3 (5.4-7.9) 0.01 Mechanical Dispersion (ms) 47 (39.5 - 59) 39 (30-54.6) 0.007 CVFR: coronary flow reserve; EpiLS: Epicardium longitudinal strain; EndoLS: endocardial longitudinal strain; EndoLS- EpiLS: trasmural strain gradient. Abstract P208 Figure. IQ-SE and Multilayer Strain

Range Variability in CMR Feature Tracking Multilayer Strain across Different Stages of Heart Failure

Heart failure (HF) is associated with progressive ventricular remodeling and impaired contraction that affects distinctly various regions of the myocardium. Our study applied cardiac magnetic resonance (CMR) feature tracking (FT) to assess comparatively myocardial strain at 3 distinct levels: subendocardial (Endo-), mid (Myo-) and subepicardial (Epi-) myocardium across an extended spectrum of patients with HF. 59 patients with HF, divided into 3 subgroups as follows: preserved ejection fraction (HFpEF, N = 18), HF with mid-range ejection fraction (HFmrEF, N = 21), HF with reduced ejection fraction (HFrEF, N = 20) and a group of age- gender- matched volunteers (N = 17) were included. Using CMR FT we assessed systolic longitudinal and circumferential strain and strain-rate at Endo-, Myo- and Epi- levels. Strain values were the highest in the Endo- layer and progressively lower in the Myo- and Epi- layers respectively, this gradient was present in all the patients groups analyzed but decreased progressively in HFmrEF and further on in HFrEF groups. GLS decreased with the severity of the disease in all 3 layers: Normal > HFpEF > HFmrEF > HFrEF (Endo-: −23.0 ± 3.5 > −20.0 ± 3.3 > −16.4 ± 2.2 > −11.0 ± 3.2, p < 0.001, Myo-: −20.7 ± 2.4 > −17.5.0 ± 2.6 > −14.5 ± 2.1 > −9.6 ± 2.7, p < 0.001; Epi-: −15.7 ± 1.9 > −12.2 ± 2.1 > −10.6 ± 2.3 > −7.7 ± 2.3, p < 0.001). In contrast, GCS was not different between the Normal and HFpEF (Endo-: −34.5 ± 6.2 vs −33.9 ± 5.7, p = 0.51; Myo-: −21.9 ± 3.8 vs −21.3 ± 2.2, p = 0.39, Epi-: −11.4 ± 2.0 vs −10.9 ± 2.3, p = 0.54) but was, as well, markedly lower in the systolic heart failure groups: Normal > HFmrEF > HFrEF (Endo-: −34.5 ± 6.2 > −20.0 ± 4.2 > 12.3 ± 4.2, p < 0.001; Myo-: −21.9 ± 3.8 > −13.0 ± 3.4 > −8.0 ± 2.7. p < 0.001; Epi-: −11.4 ± 2.0 > −7.9 ± 2.3 > −4.5 ± 1.9. p < 0.001). CMR feature tracking multilayer strain assessment identifies large range differences between distinct myocardial regions. Our data emphasizes the importance of sub-endocardial myocardium for cardiac contraction and thus, its predilect role in imaging detection of functional impairment. CMR feature tracking offers a convenient, readily available, platform to evaluate myocardial contraction with excellent spatial resolution, rendering further details about discrete areas of the myocardium. Using this technique across distinct groups of patients with heart failure (HF), we demonstrate that subendocardial regions of the myocardium exhibit much higher strain values than mid-myocardium or subepicardial and are more sensitive to detect contractile impairment. We also show comparatively higher values of circumferential strain compared with longitudinal and a higher sensitivity to detect contractile impairment. A newly characterized group of patients, HF with mid-range ejection fraction (EF), shows similar traits of decompensation but has relatively higher strain values as patients with HF with reduced EF.