Average Circumferential Strain Research Articles

Relationships between biventricular myocardial function and oxygen uptake during exercise in healthy adolescent male athletes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): UK Research and Innovation Medical Research Council Doctoral Training Programme Grant Work supported as part of a research partnership between the University of Bristol and Canon Medical Systems UK that determines the independence of the research from either parties. Background Biventricular cardiac function improves with increasing work-rate during exercise in healthy elite athletes, but how it relates to concomitantly measured oxygen uptake (VO2) is not well known. Assessing cardiac determinants of cardiorespiratory fitness through multimodal evaluations may lead to improvements in clinical stress testing protocols and better understanding of exercise physiology. Purpose The aim of this study was to investigate whether left and right ventricular (LV and RV) systolic function measured by speckle tracking echocardiography (STE) at submaximal exercise (moderate and high intensity domains) is associated with concomitantly measured VO2 in healthy adolescent male athletes. Methods Elite male football players <16 years-old underwent cardiopulmonary exercise testing with concomitant STE at 50 W steps. Exercise intensity domains were defined based on the gas exchange threshold (GET). LV and RV free wall (FW) peak systolic longitudinal strain (Sl), strain rate (SRl) and LV average (12 mid and basal segments) circumferential strain (Sc) and strain rate (SRc) were measured. Cardiac function relation to peak VO2 was evaluated using linear regression, and its relationships to VO2 within each exercise intensity domain using repeated measures mixed linear models, before and after adjusting for heart rate (HR). Results A total of n=94 athletes were included (mean age 14.7 ± 1 years). Mean peak VO2 and work-rate were 43 ± 7 mL·min-1·kg-1 and 215 ± 40 W, respectively. Relationships between cardiac function and VO2, by exercise intensity domain are shown in Figure 1 with all regression coefficients shown in Table 1. Only LV Sl at high intensity was correlated to peak VO2 (p = 0.04). Within exercise intensity domains higher LV Sl (Figure 1A) and SRl (Figure 1B) were associated with higher concomitantly measured VO2 at both moderate and high intensity. Higher SRc (Figure 1C) and RV FW SRl (Figure 1F) were associated with higher VO2 only at moderate intensity. LV Sc (Figure 1C) and RV FW Sl (Figure 1E) were not associated with concomitant VO2 during exercise at moderate or high intensity. Only LV Sl and SRl at moderate and high intensity remained significantly associated to concomitantly measured VO2 after further adjusting by HR (Table 1). Conclusions In healthy adolescent athletes, only LV longitudinal strain and strain rate measured at moderate and high intensity were associated with VO2 independent of HR response. There were differences in myocardial response to exercise both between the two ventricles, and between the longitudinal and circumferential components of LV function. These require further research, both in healthy and disease groups, especially in RV pathology, where components of myocardial function could play different roles in limiting exercise capacity.

Assessment of left ventricular mechanics in right ventricular overload using in silico rat models

Abstract Background To preserve cardiac function in overload conditions, the RV adapts by developing muscular hypertrophy through progressive tissue remodelling. This process may lead to a vicious cycle with detrimental effects on RV diastolic and systolic function, as seen in pulmonary arterial hypertension (PAH) patients [1]. However, how RV overload affects LV function and remodelling remains an open question [2]. Computational models of cardiac physiology offer an opportunity for investigating mechanisms difficult or impossible to analyse otherwise due to the existence of overlapping factors and technical limitations. Aim This study aims to assess the acute effects of RV overload and increased myocardial passive stiffness on the LV mechanical properties in an anatomically-based computational model of healthy rat heart. Methods A computational simulation pipeline of cardiac mechanics based on the Holzapfel-Ogden model has been implemented using MR images from a healthy rat. Whereas LV function was modelled realistically using catheter measurements conducted on the same subject than the MR imaging, RV function was based on representative literature values for healthy and PAH rats with RV overload. The following cases were defined (Fig. 1): CTRL, with normal RV function; PAH1, with 30% increase in RV ESV (end-systolic volume) and 15% increase in RV ESP (end-systolic pressure) in comparison to CTRL; and PAH2, with 60% increase in RV ESV and 30% increase in RV ESP compared to CTRL. The cardiac cycle was simulated for all cases whilst fitting the experimentally measured LV pressure and volume values from a healthy rat, which allowed quantifying the effects of RV overload on LV function. Results The increase of average circumferential strain in the LV correlated with the degree of RV overload simulated (CTRL: −8.7%, PAH1: −8.9%, PAH2: −9.2%), whilst average radial (CTRL: 35.2%, PAH1: 34.8%, PAH2: 30.3%) and longitudinal strains decreased (CTRL: −7.7%, PAH1: −7.4%, PAH2: −6.6%), as seen in Fig.2. However, regional differences in strain were significant: under RV overload conditions, circumferential strain increased in the septum (−3.5% difference in PAH2 vs. CTRL) but lower values were observed in the lateral wall (+1.7% difference in PAH2 vs. CTRL). Cardiac function of case PAH2 was simulated also with increased myocardial passive stiffness (2.67 kPa instead of 1.34 kPa) which presented a mild strain increase in the mid LV ventricle in comparison to PAH2 with normal stiffness (circumferential strain: −0.8%, radial strain: +0.5%, longitudinal strain: −0.2%). Conclusion Our study provides mechanistic evidence on how RV overload and increased passive myocardial stiffness causes a redistribution of strain and fibre stress in the LV, which may play a significant role in LV remodelling and function. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): K.G. Jebsen Center for Cardiac Research Figure 1. Pressure – volume loopsFigure 2. Mean mid-LV strains

Residual strains estimation in the annulus fibrosus through digital image correlation

Up-to-date, back pain is among the most prevalent health issues and generally takes its origins from lesions of the annulus fibrosus (AF). While the AF ex vivo mechanical properties are increasingly well understood, in vivo data are still missing. In particular, very few studies have precisely measured the residual strains within the AF and thus the in vivo deformation state of the AF is still miss-interpreted and miss-evaluated. In this work, we propose an original and robust method for the AF residual strains quantification via digital image correlation technics. Ten pig annulus fibrosus were extracted from adjacent vertebrae followed by a radial incision to release the residual strains. The operations were filmed and then analyzed by a custom digital image correlation software in order to quantify the circumferential, radial and shear residual deformations. Our results show that residual strains are of the same order of magnitude than the in vivo one. The average circumferential strains are in tension on the outer periphery ([3.32; 5.94]%) and in compression on the inner periphery ([−6.4; −1.69]%). The mean radial residual strains are essentially in compression ([−10.4; 2.29]%). Locally, radial and circumferential residual strains can reach really large values up to 40% of compression. The mean shear strains remain very small (−0.04% ± 2.88%). This study also shows that circumferential and radial residual strains evolve linearly along the radius and non-linearly along the angle. We propose a simple model to predict their spatial variations. Our results and methods will allow the quantification of more realistic in vivo strains and stresses within the human intervertebral disc.

Assessment of left ventricular mechanics in right ventricular overload using in silico rat models

Abstract Background To preserve cardiac function in overload conditions, the RV adapts by developing muscular hypertrophy through progressive tissue remodelling. This process may lead to a vicious cycle with detrimental effects on RV diastolic and systolic function, as seen in pulmonary arterial hypertension (PAH) patients [1]. However, how RV overload affects LV function and remodelling remains an open question [2]. Computational models of cardiac physiology offer an opportunity for investigating mechanisms difficult or impossible to analyse otherwise due to the existence of overlapping factors and technical limitations. Aim This study aims to assess the acute effects of RV overload and increased myocardial passive stiffness on the LV mechanical properties in an anatomically-based computational model of healthy rat heart. Methods A computational simulation pipeline of cardiac mechanics based on the Holzapfel-Ogden model has been implemented using MR images from a healthy rat. Whereas LV function was modelled realistically using catheter measurements conducted on the same subject than the MR imaging, RV function was based on representative literature values for healthy and PAH rats with RV overload. The following cases were defined (Fig. 1): CTRL, with normal RV function; PAH1, with 30% increase in RV ESV (end-systolic volume) and 15% increase in RV ESP (end-systolic pressure) in comparison to CTRL; and PAH2, with 60% increase in RV ESV and 30% increase in RV ESP compared to CTRL. The cardiac cycle was simulated for all cases whilst fitting the experimentally measured LV pressure and volume values from a healthy rat, which allowed quantifying the effects of RV overload on LV function. Results The increase of average circumferential strain in the LV correlated with the degree of RV overload simulated (CTRL: −8.7%, PAH1: −8.9%, PAH2: −9.2%), whilst average radial (CTRL: 35.2%, PAH1: 34.8%, PAH2: 30.3%) and longitudinal strains decreased (CTRL: −7.7%, PAH1: −7.4%, PAH2: −6.6%), as seen in Fig.2. However, regional differences in strain were significant: under RV overload conditions, circumferential strain increased in the septum (−3.5% difference in PAH2 vs. CTRL) but lower values were observed in the lateral wall (+1.7% difference in PAH2 vs. CTRL). Cardiac function of case PAH2 was simulated also with increased myocardial passive stiffness (2.67 kPa instead of 1.34 kPa) which presented a mild strain increase in the mid LV ventricle in comparison to PAH2 with normal stiffness (circumferential strain: −0.8%, radial strain: +0.5%, longitudinal strain: −0.2%). Conclusion Our study provides mechanistic evidence on how RV overload and increased passive myocardial stiffness causes a redistribution of strain and fibre stress in the LV, which may play a significant role in LV remodelling and function. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): K.G. Jebsen Center for Cardiac Research Figure 1. Pressure – volume loopsFigure 2. Mean mid-LV strains

Inter-observer and Inter-vendor Variability in Strain Measurements in Patients with Single Right Ventricular Anatomy.

Myocardial strain offers new insights into ventricular performance, There are software packages from several different companies used to ascertain this, and little data is available in patients with single right ventricle (sRV) physiology. We aimed to compare the analysis of two strain software applications using a cohort of patients with sRV for both inter-vendor and inter-observer variability. Echocardiograms from 85 patients with sRV (122 separate studies) were prospectively evaluated. All had Glenn and/or Fontan palliation. Longitudinal 4-chamber (4LS), inflow/outflow (IO), circumferential, and radial strain were assessed using Velocity Vector Imaging (VVI, Seimens, Munich) and Automated Functional Imaging (AFI, General Electric, Boston) software. In a subset of 45 patients (61 separate studies), strain measurements were obtained by two sonographers so a paired "inter-observer" analysis could be performed. A moderate correlation between measurements made by the two systems was observed. Circumferential strain assessment had the highest R value (0.77) with all others having R values < 0.6. Both software packages showed modest inter-observer reproducibility for longitudinal and circumferential strain. VVI intraclass correlation coefficients (ICC) for 4LS and average circumferential strain (ACS) were 0.6 and 0.58, compared to 0.68 and 0.59 for AFI. Other than radial strain and VVI IO inferior strain, mean strain differences between AFI and VVI were ≤ 1%. Inter-observer variability is modest, however, mean differences are minimal suggesting reasonable clinical reliability. Inter-vendor variability is greater and not as clinically reliable. In patients with sRV, serial assessments with strain should be performed using the same software.

The role of circumferential strain in the differential diagnosis of cardiomyopathies with left ventricular hypertrabeculation

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Supported by the ÚNKP-19-3-II New National Excellence Program of the Ministry for Innovation and Technology Dilated (DCM), hypertrophic (HCM) and noncompaction cardiomyopathy (NCMP) are genetically and morphologically overlapping diseases, however they differ in clinical manifestation, treatment and prognosis. Cardiac MRI feature-tracking might help to differentiate between these cardiomyopathies with left ventricular (LV) hypertrabeculation. We aimed to describe the differences in the functional and strain parameters of NCMP patients with good LV ejection fraction (EF, NCMP-G) compared with patients with HCM, and NCMP patients with reduced EF (NCMP-R) compared with patients with DCM . We included 62 NCMP patients from which 31 had good LV function and 31 had decreased LV-EF. The NCMP-G group was compared with an HCM population (n = 31) and the NCMP-R group was compared with a DCM group (n = 31) matching in age and sex (age, EF; NCMP-G 46.0 ± 13.0 years, 65.5 ± 5.3% vs. HCM 47.2 ± 14.4 years, 74.8 ± 6.3%; NCMP-R 54.5 ± 12.1 years, 32.8 ± 10.1% vs. DCM 50.8 ± 16.7 years, 34.0 ± 8.2%). 1.5 T Philips Achieva and Siemens Aera MRI machines were used for the scans, Medis Suite program was used for analysis and MedCalc software for statistics, p &amp;lt; 0.05 was considered statistically significant. Significant differences were found between the functional parameters of HCM and NCMP-G patients, while the DCM and NCMP-R groups differed only in the trabecular mass values (LV-trab, NCMP-G vs. HCM: 26.2 ± 7.5 vs. 30.7 ± 7.0 g/m2, NCMP-R vs. DCM: 48.2 ± 13.2 vs. 42.1 ± 10.1 g/m2, p &amp;lt; 0.05). The global longitudinal strain values of the studied populations were not significantly different, however the global circumferential strain (GCS) values were significantly better in patients with HCM and DCM compared with the NCMP groups (GCS, NCMP-G vs. HCM: -31.2 ± 4.9 vs. -43.0 ± 8.4%, NCMP-R vs. DCM: -11.7 ± 7.3 vs. -16.9 ± 6.1%). The average circumferential strain values of the LV basal, mid and apical parts were significantly better in the HCM and DCM groups compared with the NCMP groups (NCMP-G vs. HCM: -35.7 ± 9.5 vs. -50.5 ± 14.1%, NCMP-R vs. DCM: -29.5 ± 13.2 vs. -15.6 ± 6,7%). We assessed the cut-off point of the average LV apical circumferential strain to differentiate the studied populations (HCM vs. NCMP-G cut-off: -47.3% sens.: 83.9%, spec.: 67.7%, AUC: 0.81; DCM vs. NCMP-R cut-off: -19.3% sens.: 83.9%, spec.: 83.9%, AUC: 0.86). The diverse circumferential strain values of the hypertrabeculated LV apical third could help the differential diagnosis of NCMP, DCM and HCM.

The inflation response of the human lamina cribrosa and sclera: Analysis of deformation and interaction

This study investigated the inflation response of the lamina cribrosa (LC) and adjacent peripapillary sclera (PPS) in post-mortem human eyes with no history of glaucoma. The posterior sclera of 13 human eyes from 7 donors was subjected to controlled pressurization between 5–45 mmHg. A laser-scanning microscope (LSM) was used to image the second harmonic generation (SHG) response of collagen and the two-photon fluorescent (TPF) response of elastin within the volume of the LC and PPS at each pressure. Image volumes were analyzed using digital volume correlation (DVC) to calculate the three-dimensional (3D) deformation field between pressures. The LC exhibited larger radial strain, Err, and maximum principal strain, Emax, (p < 0.0001) and greater posterior displacement (p=0.0007) compared to the PPS between 5–45 mmHg, but had similar average circumferential strain, Eθθ, and maximum shear strain, Γmax. The Emax and Γmax were highest near the LC-PPS interface and lowest in the nasal quadrant of both tissues. Larger LC area was associated with smaller Emax in the peripheral LC and larger Emax in the central LC (p ≤ 0.01). The Emax, Γmax, and Eθθ in the inner PPS increased with increasing strain in adjacent LC regions (p ≤ 0.001). Smaller strains in the PPS were associated with a larger difference in the posterior displacement between the PPS and central LC (p < 0.0001 for Emax and Err), indicating that a stiffer pressure-strain response of the PPS is associated with greater posterior bowing of the LC. Statement of SignificanceGlaucoma causes vision loss through progressive damage of the retinal ganglion axons at the lamina cribrosa (LC), a connective tissue structure that supports the axons as they pass through the eye wall. It is hypothesized that strains caused by intraocular pressure may initiate this damage and that these strains are modulated by the combined deformation of the LC and adjacent peripapillary sclera (PPS). In this study we present a method to measure the pressure-induced 3D displacement and strain field in the LC and PPS simultaneously. Regional strain variation in the LC and PPS was investigated and compared and strains were analyzed for associations with age, LC area, LC strain magnitude, and LC posterior motion relative to the PPS.

Prediction of subtle left ventricular systolic dysfunction in homozygous and heterozygous familial hypercholesterolemia: Genetic analyses and speckle tracking echocardiography study.

Few studies have shown the direct effect of familial hypercholesterolemia (FH) on myocardial systolic function. Studies focused on heterozygote FH patients but not homozygote ones, and they did not perform genetic analyses. We aimed to evaluate all types of patients with FH using the potentially more sensitive speckle tracking echocardiography (STE) technique to identify early left ventricular (LV) dysfunction. Genetic analyses of patients with FH were conducted for LDL-receptor, PCSK9, and ApoB100. Nine homozygote, two compound heterozygote, and 82 heterozygote FH patients and 85 healthy subjects were prospectively studied. Longitudinal and circumferential strain measurements and conventional echocardiography findings were obtained. LV ejection fractions were similar for all (homozygote, heterozygote, and control) groups. The LV average longitudinal strain (aLS) and average circumferential strain (aCS) levels were significantly reduced in the homozygote and heterozygote groups when compared with the controls (for aLS, P=.008 (<.001); for aCS, P=<.001). A significant inverse correlation was found between LDL-C levels and LS (P<.001, r=.728) and CS (P<.001, r=.642) for all FH patients. This study demonstrates the potential of using systolic strain values obtained using 2D STE for determining lipotoxicity in the myocardium owing to hypercholesterolemia. Our study found that cardiac functions of homozygote patients who had the highest cholesterol levels were disrupted at very early ages. Therefore, starting lipid reduction treatment and early reverse LV remodelling therapy at early ages may be beneficial for high-risk patients.

Left ventricular remodelling and vascular adaptive changes in adolescents with obesity.

The aim of this study was to determine the effects of obesity on myocardial mechanics and ventriculo-arterial coupling (V-A) in children. Strain parameters, stroke volume, arterial elastance, left ventricular (LV) elastance and V-A were compared after adjusting for age and hypertension and after multivariate sub-group analysis between patients with and without obesity. Among 123 retrospectively enrolled subjects, 6-21years age, 79.7% males, 52% were obese. Median (range) Body Mass Index Z score was +2.35 (1.67-4.43) for obese and +0.68 (-2.48-1.63) for non-obese. Subjects with obesity had higher LV mass indexed2.7 (LVMI2.7 ) compared with non-obese (P<0.001). Lower global longitudinal strain (GLS) (P=0.012), global circumferential strain (GCS) (P=0.004), average longitudinal strain rate (P=0.002) and average circumferential strain rate (P<0.001) were seen in subjects with obesity; no difference was noted in arterial elastance, LV end systolic elastance and V-A. Increased LVMI2.7 , decreased GLS, GCS, average longitudinal strain rate, average circumferential strain rate and maintained V-A were noted in the multivariate analysis between subgroups. Obesity causes alterations in myocardial mechanics with preserved V-A in children. These findings may aid intervention in preventing the long-term cadiovascular effects of obesity.

The Effects of Surgical Myectomy on Left Ventricular Mechanics in Patients with Hypertrophic Obstructive Cardiomyopathy

Background: Hypertrophic obstructive cardiomyopathy (HOCM) is an inherited disorder, characterized by left ventricle outflow tract obstruction. We performed this study to investigate the changes in left ventricular mechanics after surgical myectomy in patients with HOCM. Materials and methods: We enrolled 15 patients with HOCM referred to surgical myectomy according to the recommendation of American Heart Association. All patients underwent transthoracic 2D speckle-tracking echocardiography to measure cardiac dimensions and mechanics before and after surgery. statistical analyses were performed using GraphPad Instat and MedCalc software. Results: Following myectomy, all patients reported improved symptoms and increased functional capacity. Conventional echocardiographic measurements showed that surgical myectomy significantly decreased left atrial volume index (r=0.83, p˂0.0001), interventricular septum thickness (p˂0.0001, r=0.79), left-ventricular mass index (p˂0.0001, r=0.49) and resting left-ventricular outflow tract pressure gradient (p˂0.0001, r=-0.03). In terms of leftventricular function, we observed significant decreases in fractional shortening (r=0.16, p˂0.0001) and ejection fraction (p=0.01, r=-0.04) after the procedure in comparison to baseline functional data. We further significant postoperative reductions in terms of average circumferential strain (p˂0.0001, r=0.49), basal rotation (p=0.03, r=0.97), apical rotation (p˂0.0001, r=0.94) and LV twist (p˂0.0001, r=0.96). However, no significant changes were observed after myectomy in terms of most longitudinal strain and left ventricular synchrony measures. Conclusion: Surgical myectomy improves symptoms, relieves left ventricular outflow tract obstruction and decreases left atrial volume index in patients with HOCM, but shows no significant changes in LV longitudinal strain and LV synchrony measures. Future studies should employ a larger sample size and more sensitive methods of synchrony detection.

Myocardial Strain Using Cardiac MR Feature Tracking and Speckle Tracking Echocardiography in Duchenne Muscular Dystrophy Patients.

Duchenne muscular dystrophy (DMD) is an inherited X-linked disorder with an incidence of 1 in 3500 male births, and cardiomyopathy is becoming the leading cause of death. While Cardiac MRI (CMR) and late gadolinium enhancement (LGE) are important tools in recognizing myocardial involvement, myocardial strain imaging may demonstrate early changes and allow patients to avoid gadolinium contrast. We performed CMR feature tracking (FT) and echo-based speckle tracking (STE) strain measures on DMD patients and age/sex matched controls who had received a CMR with contrast and transthoracic echocardiogram. Data were collected for longitudinal strain in the apical four-chamber view and circumferential strain in the mid-papillary parasternal short axis. Segmental wall analysis was performed and compared with the presence of LGE. Data were analyzed using student's t tests or one-way ANOVA adjusting for multiple comparisons. We measured 24 subjects with DMD and 8 controls. Thirteen of 24 DMD subjects were LGE positive only in the lateral segments in short-axis views. Average circumferential strain (CS) measured by FT was significantly decreased in DMD compared to controls (- 18.8 ± 6.1 vs. - 25.5 ± 3.2; p < 0.001) and showed significant differences in the anterolateral, inferolateral, and inferior segments. Average CS by STE trended towards significance (p = 0.06) but showed significance in only the inferior segment. FT showed significant differences in the inferolateral segment between LGE positive (- 15.5 ± 9.0) and LGE negative (- 18.2 ± 8.3) in DMD subjects compared to controls (- 28.6 ± 7.3; p ≤ 0.04). FT also showed significant differences between anteroseptal and inferolateral segments within LGE-positive (p < 0.003) and LGE-negative (p < 0.03) DMD subjects while STE did not. There were no significant differences in longitudinal strain measures. CMR-FT-derived myocardial strain was able to demonstrate differences between subjects with DMD and controls not detected by STE. FT was also able to demonstrate differences in LGE-positive and LGE-negative segments within patients with DMD. FT may be able to predict LGE-positive segments in DMD without the use of gadolinium contrast.

Fetal myocardial deformation in maternal diabetes mellitus and obesity

Experimental evidence suggests that changes in the fetal myocardium result from intrauterine effects of maternal diabetes mellitus and obesity. The aim of this study was to assess fetal cardiac function using two-dimensional speckle-tracking echocardiography to determine the effects of maternal diabetes and obesity on the fetal myocardium. Comparative cross-sectional evaluation of myocardial function in fetuses of mothers with diabetes mellitus (FDM) or obesity (FO) and normal gestational age-matched control fetuses (FC) was performed using two-dimensional speckle-tracking echocardiography at two centers. In total, 178 fetuses (82 FDM, 26 FO and 70 FC) met the enrolment criteria. Mean gestational age at assessment was similar among groups: 25.3 ± 5.1 weeks for FDM, 25.0 ± 4.6 weeks for FO and 25.1 ± 4.9 weeks for FC. Mean maternal body mass index was significantly higher in FDM and FO groups compared with the FC group. Statistically significant differences in fetal cardiac function were detected between FDM and FC for global longitudinal strain (mean ± SD, -21.4 ± 6.5% vs -27.0 ± 5.2%; P < 0.001), global circumferential strain (mean ± SD, -22.6 ± 6.5% vs -26.2 ± 6.8%; P = 0.002), average longitudinal systolic strain rate (median, -1.4 (interquartile range (IQR), -1.7 to -1.1)/s vs -1.6 (IQR, -2.0 to -1.4)/s; P = 0.001) and average circumferential systolic strain rate (median, -1.4 (IQR, -1.9 to -1.1)/s vs -1.6 (IQR, -2.1 to -1.3)/s; P = 0.006). Cases of non-obese FDM also had abnormal strain parameters compared with FC. Global longitudinal strain (mean ± SD, -21.1 ± 7.5%) and average circumferential systolic strain rate (median, -1.3 (IQR, -1.8 to -1.1)/s) were significantly lower in FO compared with FC. Unfavorable changes occur in the fetal myocardium in response to both maternal diabetes mellitus and obesity. The long-term prognostic implications of these changes require further study. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Bi-ventricular finite element model of right ventricle overload in the healthy rat heart.

The recognition of RV overpressure is critical to human life, as this may signify morbidity and mortality. Right ventricle (RV) dysfunction is understood to have an impact on the performance of the left ventricle (LV), but the mechanisms remain poorly understood. It is understood that ventricular compliance has the ability to affect cardiac performance. In this study, a bi-ventricular model of the rat heart was used in preference to other, single-ventricle models. Finite element analysis (FEA) of the bi-ventricular model provides important information on the function of the healthy heart. The passive myocardium was modelled as a nearly incompressible, hyperelastic, transversely isotropic material using finite element (FE) methods. Bi-ventricular geometries of healthy rat hearts reconstructed from magnetic resonance images were imported in Abaqus©. In simulating the normal passive filling of the rat heart, pressures of 4.8kPa and 0.0098kPa were applied to the inner walls of the LV and RV respectively. In addition, to simulate the overpressure of the RV, pressures of 2.4kPa and 4.8kPa were applied to the endocardial walls of the LV and RV respectively. As boundary conditions, the circumferential and longitudinal displacements at the base were set to zero. The radial displacements at the base were left free. The results show that the average circumferential stress at the mid-wall in the overloaded model increased from 2.8kPa to 18.2kPa. The average longitudinal stress increased from 1.5kPa to 9.7kPa. Additionally, in the radial direction, the average stress increased from 0.1kPa to 0.6kPa in the mid-wall. The average circumferential strain was found to be 0.138 and 0.100 on the endocardium of the over pressured and healthy model respectively. The average circumferential stress at the epicardium, mid-wall and endocardium in the case of a normal heart is 10 times lower than in the overloaded heart model. The finite analysis method is able to provide insights into the behaviour of the over pressured model (myocardium). In the overloaded model the high stresses and strains were observed on the septal wall. The bi-ventricular model was shown to provide useful information relating to the over pressured ventricle. The possible heart dysfunction may be attributable to high stress and strain in the over pressured heart.

Obstructive Sleep Apnea Is Related to Increased Arterial Stiffness in Ultrasound Speckle-Tracking Analysis.

Obstructive sleep apnea (OSA) is an independent risk factor for atherosclerosis. The aim of our study was to determine arterial stiffness in OSA patients by means of the ultrasound speckle-tracking-based method. Twenty six OSA patients and 17 control subjects were enrolled in the study. The speckle-tracking-based analysis of carotid artery included circumferential strains, circumferential strain rates, radial displacement, and radial strain rates. We found that the global average circumferential strains, circumferential strain rates, and radial displacement were significantly lower in OSA patients compared to controls (2.19 ± 0.30% vs. 4.17 ± 0.33%, 0.22 ± 0.03l/s vs. 0.31 ± 0.02l/s, 0.10 ± 0.01mm vs. 0.16 ± 0.02mm, respectively, p < 0.05 for all). There were no significant differences in radial strain rates between the groups (0.32 ± 0.04% vs. 0.33 ± 0.01%). We conclude that OSA is associated with an increased arterial stiffness.

Abstract 15755: Adverse Cardiac Remodeling in Obese Children

Background: Obesity (OB) and hypertension (HTN) are risk factors for early cardiovascular disease (CVD). The aim of this study was to determine the effect of OB and HTN on myocardial mechanics in children using speckle-tracking echocardiography (STE). Methods: Echocardiograms (echo) and ambulatory blood pressure monitors were performed in children referred for HTN from 2009 to 2014. Traditional echo Doppler indices, mass and volume parameters, 24-hr systolic blood pressures (24SBP) and 24-hr diastolic BP indices were obtained. Post-processing was performed on the 2D gray scale images of LV in apical 4-chamber and parasternal short axis mid-papillary views to obtain strain indices (Image Arena, Tomtec). Associations of obesity and BP to the myocardial indices were explored independently using Spearman correlation coefficient. Results: Among 107 patients, 6 - 21 yrs age, 79.4% were males; 42% OB and 53% were hypertensive. Mean Z scores for BMI were 1.5 ± 1.1 and SBP were 1.5 ± 1.2. Mean LV mass (LVM, 2D area-length) was 131 + 42.8 gms, LVMI 2.7 was 40.7 + 9.6 gms, LVM/volume ratio was 0.94 + 0.17. Mean mitral septal E/e’ was 8.3 + 2.1, lateral E/e’ was 5.9 + 1.5 and mitral E/A ratio was 1.8 + 0.4. The mean global longitudinal strain (GLS) was – 17.7 + 3.6, global circumferential strain (GCS) was -20.4 + 3.8, average radial strain (ARS) was 22 + 11.9, average longitudinal strain rate (ALSR) was -1.0 + 0.35 and average circumferential strain rate (ACSR) was -1.5 + 0.5 for all patients. BMI Z scores positively correlated with LVM (r=0.38, p&lt;0.01), LVM/vol (r=0.32, p&lt;0.01), mitral E/e’ (r=0.28, p&lt;0.01), LVMI 2.7 (r=0.5, &lt;0.01). Increased BMI negatively correlated to GLS, GCS and ACSR (r=0.3, p&lt;0.01). Higher SBP, diastolic and mean BP were associated with higher mitral medial E/e’ (r=0.3, p&lt;0.01), however did not have statistically significant correlations to strain indices. Conclusions: Obesity causes adverse cardiac remodeling in obese children. This may provide insights into mechanisms of long-term CV effects of obesity. Myocardial effects of HTN were not apparent, possibly due to heterogeneity of the study group and low power.

A Novel Method for Quantifying Smooth Regional Variations in Myocardial Contractility Within an Infarcted Human Left Ventricle Based on Delay-Enhanced Magnetic Resonance Imaging

Heart failure is increasing at an alarming rate, making it a worldwide epidemic. As the population ages and life expectancy increases, this trend is not likely to change. Myocardial infarction (MI)-induced adverse left ventricular (LV) remodeling is responsible for nearly 70% of heart failure cases. The adverse remodeling process involves an extension of the border zone (BZ) adjacent to an MI, which is normally perfused but shows myofiber contractile dysfunction. To improve patient-specific modeling of cardiac mechanics, we sought to create a finite element model of the human LV with BZ and MI morphologies integrated directly from delayed-enhancement magnetic resonance (DE-MR) images. Instead of separating the LV into discrete regions (e.g., the MI, BZ, and remote regions) with each having a homogeneous myocardial material property, we assumed a functional relation between the DE-MR image pixel intensity and myocardial stiffness and contractility--we considered a linear variation of material properties as a function of DE-MR image pixel intensity, which is known to improve the accuracy of the model's response. The finite element model was then calibrated using measurements obtained from the same patient--namely, 3D strain measurements-using complementary spatial modulation of magnetization magnetic resonance (CSPAMM-MR) images. This led to an average circumferential strain error of 8.9% across all American Heart Association (AHA) segments. We demonstrate the utility of our method for quantifying smooth regional variations in myocardial contractility using cardiac DE-MR and CSPAMM-MR images acquired from a 78-yr-old woman who experienced an MI approximately 1 yr prior. We found a remote myocardial diastolic stiffness of C(0) = 0.102 kPa, and a remote myocardial contractility of T(max) = 146.9 kPa, which are both in the range of previously published normal human values. Moreover, we found a normalized pixel intensity range of 30% for the BZ, which is consistent with the literature. Based on these regional myocardial material properties, we used our finite element model to compute patient-specific diastolic and systolic LV myofiber stress distributions, which cannot be measured directly. One of the main driving forces for adverse LV remodeling is assumed to be an abnormally high level of ventricular wall stress, and many existing and new treatments for heart failure fundamentally attempt to normalize LV wall stress. Thus, our noninvasive method for estimating smooth regional variations in myocardial contractility should be valuable for optimizing new surgical or medical strategies to limit the chronic evolution from infarction to heart failure.

Feasibility and Reproducibility of Echocardiographic Measures in Children with Muscular Dystrophies.

Cardiac disease is a major cause of death in patients with muscular dystrophies. The use of feasible and reproducible echocardiographic measures of cardiac function is critical to advance the field of therapeutics for dystrophic cardiomyopathy. Participants aged 8 to 18 years with genetically confirmed Duchenne muscular dystrophy (DMD), Becker muscular dystrophy, or limb-girdle muscular dystrophy were enrolled at five centers, and standardized echocardiographic examinations were performed. Measures of systolic and diastolic function and speckle-tracking echocardiography-derived cardiac strain were reviewed independently by two central readers. Furthermore, echocardiographic measures from participants with DMD were compared with those from retrospective age-matched control subjects from a single site to assess measures of myocardial function. Forty-eight participants (mean age, 13.3 ± 2.7 years) were enrolled. Shortening fraction had a greater interobserver correlation (intraclass correlation coefficient [ICC] = 0.63) compared with ejection fraction (ICC = 0.49). One reader could measure ejection fraction in only 53% of participants. Myocardial performance index measured by pulse-wave Doppler and Doppler tissue imaging showed similar ICCs (0.55 and 0.54). Speckle-tracking echocardiography showed a high ICC (0.96). Focusing on participants with DMD (n = 33), significantly increased mitral A-wave velocities, lower E/A ratios, and lower Doppler tissue imaging mitral lateral E' velocities were observed compared with age-matched control subjects. Speckle-tracking echocardiography demonstrated subclinical myocardial dysfunction with decreased average circumferential and longitudinal strain in three distinct subgroups: participants with DMD with normal shortening fractions, participants with DMD aged < 13 years, and participants with DMD with myocardial performance index scores < 0.40 compared with control subjects. In a muscular dystrophy cohort, assessment of cardiac function is feasible and reproducible using shortening fraction, diastolic measures, and myocardial performance index. Cardiac strain measures identified early myocardial disease in patients with DMD.

Occult Cardiotoxicity in Childhood Cancer Survivors Exposed to Anthracycline Therapy

More than 50% of >270 000 childhood cancer survivors in the United States have been treated with anthracyclines and are therefore at risk of developing cardiotoxicity. Cardiac magnetic resonance (CMR) has demonstrated utility to detect diffuse interstitial fibrosis and changes in regional myocardial function. We hypothesized that CMR would identify occult cardiotoxicity characterized by structural and functional myocardial abnormalities in a cohort of asymptomatic pediatric cancer survivors with normal global systolic function. Forty-six long-term childhood cancer survivors with a cumulative anthracycline dose ≥200 mg/m(2) and normal systolic function were studied 2.5 to 26.9 years after anthracycline exposure. Subjects underwent transthoracic echocardiography, CMR with routine cine acquisition, tissue characterization, and left ventricular strain analysis using a modified 16-segment model. Extracellular volume was measured in 27 subjects, all of whom were late gadolinium enhancement negative. End-systolic fiber stress was elevated in 45 of 46 subjects. Low average circumferential strain magnitude (εcc) -14.9±1.4; P<0.001, longitudinal strain magnitude (εll) -13.5±1.9; P<0.001, and regional peak circumferential strain were seen in multiple myocardial segments, despite normal global systolic function by transthoracic echocardiography and CMR. The mean T1 values of the myocardium were significantly lower than that of control subjects at 20 minutes (458±69 versus 487±44 milliseconds; P=0.01). Higher mean extracellular volume was observed in female subjects (0.34 versus 0.22; P=0.01). Asymptomatic postchemotherapy pediatric patients have abnormal myocardial characteristics and strain parameters by CMR despite normal global cardiac function by standard transthoracic echocardiography and CMR measures.

151 MYOCARDIAL PERFUSION, STRAIN AND PRE-CONTRAST T1 VALUES IN MODERATE ASYMPTOMATIC AORTIC STENOSIS

<h3>Introduction</h3> In severe aortic stenosis (AS) myocardial perfusion and myocardial strain (in particular longitudinal strain-LS) are reduced. Reduced myocardial perfusion in severe AS is thought to occur in the subendocardium due to increased LV pressure, leading to reduced LS and increased fibrosis. Our group previously showed a good correlation between pre-contrast T1 values using SHMOLLI (Shortened Modified Look-Locker Inversion recovery) sequence and histological quantification of diffuse fibrosis in severe AS. We hypothesised that impaired myocardial perfusion in patients with moderate AS would relate to impaired LS and increased pre-contrast T1 values (reflecting more diffuse fibrosis). <h3>Methods</h3> 31 patients (8 female) with asymptomatic moderate AS (by echo criteria) and normal ejection fraction were recruited. All subjects underwent CMR scanning at 1.5T for pre-contrast T1-mapping using the ShMOLLI sequence, stress and rest perfusion imaging, tagging and valve assessment. Average T1 values were analysed on a per-case basis. Perfusion scans were analysed to determine the myocardial perfusion reserve index (MPRI) and tagging to determine strain. <h3>Results</h3> All patients (average age 67±12 years) underwent CMR scanning at 1.5 T. The average MPRI was 1.3±0.4. Average T1 values were 956±32 ms. There was a significant correlation between MPRI and LS (&lt;0.05, r=−0.4, figure&nbsp;1) but not circumferential strain (CS). Average LS was −11.1%±2%, average CS was −17%±3%. There was also a significant correlation of MPRI with aortic valve area (as measured by CMR planimetry mean (1.7±0.4 cm², p&lt;0.05 r=0.4). There was no significant correlation between MPRI and pre-contrast T1 values. Pre-contrast T1 values correlated strongly with LV mass (mean 147±40 g) (r=0.4 p&lt;0.01) and peak aortic velocity (mean 3.1±0.4 m/s) (p&lt;0.0001 r=0.5). <h3>Conclusions</h3> In moderate AS, there is a significant correlation between reduced MPRI and impaired longitudinal but not circumferential strain. This supports the hypothesis that impairment of myocardial perfusion predominantly affects the subendocardial longitudinal myocardial fibres (rather than the mid-wall circumferential fibres) in moderate AS. The exact relationship of perfusion and diffuse fibrosis in moderate AS is yet to be fully established. In this study pre-contrast T1 values (as a surrogate marker for diffuse fibrosis) were not affected by changes in myocardial perfusion.

Defining late onset occult asymptomatic cardiotoxicity in childhood cancer survivors exposed to anthracycline therapy: a cardiac magnetic resonance imaging study

Background There are over 270,000 childhood cancer survivors in the US. Of these survivors, more than 50% have been treated with anthracyclines and are at risk of developing progressive cardiotoxicity. Novel cardiac magnetic resonance imaging (CMRI) techniques are now able to reliably detect diffuse myocardial fibrosis and changes in regional myocardial function. We hypothesized that these novel CMRI techniques will identify occult asymptomatic cardiotoxicity in a cohort of childhood cancer survivors with normal global systolic function. Methods Twenty seven long-term childhood cancer survivors between 11.8-28.8 years with a cumulative dose >240mg/ m2 (mean 363±89) and normal systolic function (SF>29%) were studied 2.4-24 years after exposure to anthracycline therapy. Patients underwent CMRI techniques to characterize changes in T1 relaxation time, left ventricular myocardial peak circumferential and longitudinal strain parameters and were analyzed using the 17-segment model. Extracellular volume (ECV) was measured in 13 subjects all of whom were late gadolinium enhancement (LGE) negative. We performed standard CMRI assessment and quantification of myocardial mass, end-systolic and end-diastolic volumes, ejection fraction, and end systolic fiber stress. Results Twenty seven of 60 planned subjects have been imaged. End systolic fiber stress was significantly increased with higher cumulative anthracycline dose (R2=0.18, p<0.03) and younger age at diagnosis (R2=0.20, p<0.02). Lower average circumferential strain magnitude (ecc) and regional changes in peak circumferential strain were seen in multiple segments despite n ormal values of global systolic function by echocardiography and CMRI (Figure1). T1 maps are depicted in Figure 1. The mean T1 values of the myocardium were not significantly different between patients and controls at 4 min (375±67ms vs.389±36, p<0.07) and 10 min (433±52 ms vs.435±36, p<0.39), but were significantly lower at 20 minutes (455±50ms vs. 487 ±44, p<0.003) (Figure 2). Low myocardial T1 at 20 minutes was significantly associated with increases in end systolic fiber stress (R2=0.7, p<0.002). Higher mean ECV was observed in patients with cumulative dose ≥400mg/m2 (0.27 vs. 0.21, p<0.05). Conclusions