Epicardial Layer Research Articles

CMR for myocardial iron overload quantification: calibration curve from the MIOT Network.

R2* cardiac magnetic resonance (CMR) allows the non-invasive measurement of myocardial iron. We calibrated cardiac R2* values against myocardial tissue-measured iron concentration by using a segmental approach and we assessed the iron distribution. Five hearts of thalassemia patients were donated after death/transplantation to the CoreLab of the Myocardial Iron Overload in Thalassemia Network. A multislice multiecho R2* approach was adopted. After CMR, used as guidance, the heart was cut in three short-axis slices and each slice was cut into different equiangular segments according to AHA segmentation and differentiated into endocardial and epicardial layers. Tissue iron concentration was measured by atomic absorption spectrometer technique. Fifty-five samples were used since only for two hearts all the 16 samples were analyzed. Mean iron concentration was 4.71 ± 4.67mg/g dw. Segmental iron levels ranged from 0.24 to 13.78mg/g dw. The coefficient of variability of iron for myocardial segments ranged from 8.08 to 24.54% (mean 13.49 ± 6.93%). Iron concentration was significantly higher in the epicardial than in the endocardial layer (5.99 ± 6.01 vs 4.84 ± 4.87mg/g dw; p = 0.042). Four different circumferential regions (anterior, septal, inferior, and lateral) were defined. A circumferential heterogeneity was noted, with more iron in the anterior region, followed by the inferior region. The direct nonlinear fitting of R2* and [Fe] data led to the calibration curve: [Fe] = 0.0022 ∙ (R2*-ROI)1.462 (R-square = 0.956). Our data further validate R2* CMR using a segmental approach as a sensitive and early technique for quantifying iron distribution in the current clinical practice. • Calibration in humans for cardiovascular magnetic resonance R2* against myocardial iron concentration was provided. • A circumferential heterogeneity in cardiac iron distribution was detected: more iron was observed in the anterior region, followed by the inferior region. This finding corroborates the use of a segmental T2* CMR approach in the clinical practice to detect a heterogeneous iron distribution. • The comparison between the cardiac T2* values obtained with the region-based and the pixel-wise approaches showed a significant correlation and no significant difference but, in presence of significant iron load, the region-based approach resulted in significantly higher T2* values.

Assessment of Strain Changes in the Triple Layers of Left Ventricle in Normotensive Versus Hypertensive Patients

The phenomenon of left ventricular remodeling caused by hypertension is a well-known affair that can be evaluated through echocardiography techniques. In recent decade, modern echocardiographic methods such as speckle tracking echocardiography have been used to evaluate left ventricular mechanical changes in hypertensive conditions. The evaluation of the strain index as an important part of the evaluation of the ventricular wall in various ventricular layers has been highly regarded in hypertensive patients. In this regard, the left global ventricular longitudinal strain (GLS) especially in the three ventricular wall layers can strongly predict mortality and morbidity of cardiovascular disease. Given that hypertensive disease is one of the most important risk factors for the development of heart failure and systolic and diastolic cardiovascular dysfunction, even in cases with preserved left ventricular ejection fraction, the exact determination of ventricular strain changes in various layers in hypertensive states would be beneficial for preventing hypertensive cardiomyopathy. In a cross-sectional study, we assessed strain changes in the triple layers of the ventricular wall in hypertensive and normotensive individuals with presence or absence of left ventricular diastolic dysfunction. In this study, both global longitudinal strain (GLS) and global circumferential strain (GCS) indices in endocardial, myocardial and epicardial layers were evaluated. We also considered the effect of diastolic ventricular dysfunction as an important confounder with the effect of hypertension on the ventricular strain. An important finding of this study was the significant effect of hypertension on reducing GLS and GCS in mid myocardial and epicardial layers in the presence of left ventricular diastolic dysfunction. At first, in case of hypertension, the presence of diastolic dysfunction in reducing the strain of the left ventricular wall seems to be necessary as a trigger factor; thus in hypertensive cases with preserved diastolic function, the strain change in left ventricular wall may not be evident. Secondly, reduction in the ventricular wall strain in the endocardial layer was not revealed but it seems that the exacerbation of uncontrolled hypertension may also lead to endocardial involvement as shown by prior studies. In total, proper control of blood pressure in patients with a history of hypertension, especially in the field of left ventricular diastolic dysfunction will improve the function of the left ventricular wall and thus improve the prognosis of these patients.Disturbance in left ventricle wall layers in the field of hypertension has been studied and confirmed in several studies, although the effective role of diastolic dysfunction has been studied less. For instance, in a study by Tadic et al., GLS was significantly lower in hypertensive than in normotensive patients (1). In Navarini et al study, although no difference was found in left ventricular volume or ejection fraction, both GLS and GCS reduced significantly in hypertensive status (2). In a study by Craciunescu et al, LV mass was higher and both the GLS and GCS parameters were significantly lower in the uncontrolled hypertension group than in patients with controlled hypertension (3). In a study by Nagata et al., the values of GLS and GCS in the endocardial layer were higher than the other layers, and this could justify the preservation of the strain in the field of hypertension in the endocardial layer (4). Finally, in a study by Sharif et al, patients with diastolic dysfunction experienced a relative decrease in GLS in all three layers of myocardial infarction, compared with those without diastolic dysfunction, which was consistent with our findings (5). What can be emphasized as the final result is that prolonged and uncontrolled hypertension with an effect on cell growth as well as cardiomyocyte fibrosis through the secretion of inflammatory and growth factors leading left ventricular hypertrophy can reduce strain in various ventricular wall layers particularly in myocardial and epicardial layers. Of course, the role of the presence of diastolic ventricular dysfunction is highly indicative in these changes.

Influences of cardiovascular risk factors on left ventricular wall motion function in patients treated with epirubicin: a clinical study by layer-specific speckle tracking imaging

Objective To investigate the influences of cardiovascular risk factors on left ventricular wall motion function in patients treated with epirubicin chemotherapy by layer-specific two-dimensional speckle tracking imaging (2D-STI). Methods Sixty-four female patients with breast cancer treated with epirubicin and 36 controls from June 2018 to March 2019 in Renmin Hospital of Wuhan University were included. According to the numbers of cardiovascular risk factors, the patients were divided into group A (without cardiovascular risk factors, 31 cases), group B (single cardiovascular risk factor, 20 cases), and group C (multiple cardiovascular risk factors, 13 cases). All patients underwent echocardiography before and after epirubicin respectively. Global longitudinal strain, circumferential strain, radial strain (GLS, GCS, GRS), endocardial and epicardial layers of GLS and GCS (endoGLS, epiGLS, endoGCS, epiGCS) were obtained by EchoPAC software analysis. The differences of GLS, EndoGLS, EpiGLS, GCS, EndoGCS, EpiGCS and GRS before and after chemotheraphy were calculated as ΔGLS, ΔEndoGLS, ΔEpiGLS, ΔGCS, ΔEndoGCS, ΔEpiGCS and ΔGRS. Results Compared with before chemotherapy, GLS, EndoGLS, EpiGLS, GCS, EndoGCS, EpiGCS and GRS were significantly reduced in group A, B and C after chemotherapy (all P<0.05). ΔEndoGLS and ΔEndoGCS showed an increasing trend in groups A, B and C, with statistical significance (all P<0.05). Correlation analysis showed that after chemotherapy with epirubicin, the numbers of cardiovascular risk factors were significantly correlated with strain parameters, and the correlation coefficient of EndoGLS was relatively higher (r=-0.582, P<0.001). Conclusions Layer-specific imaging can reliably detect the influences of cardiovascular risk factors on the left ventricular wall motion function in breast cancer patients treated with epirubicin. Parameters reflecting the endocardial longitudinal systolic function are sensitive indicators for the early detectin of myocardial damage and toxicity by epirubicin in patients with multiple cardiovascular risk factors. Key words: Two-dimensional speckle tracking imaging; Layer-specific imaging; Breast neoplasms; Epirubicin; Myocardial motion; Cardiovascular risk factors

P1752 Prognostic role of Multilayer Strain Speckle Tracking Echocardiography in patients with severe aortic stenosis treated with Transcatheter Aortic Valve Implantation

Abstract Background Myocardial Strain evaluation helps to assess the efficacy of therapeutic interventions and to predict the prognosis and clinical outcomes. The aim of the present study was to assess whether Multilayer Global longitudinal Strain (GLS) can be useful in estimation of left ventricle (LV) function in patients with severe symptomatic aortic stenosis (AS) who have undergone transcatheter aortic valve implantation (TAVI). Methods 35 patients with severe AS who successfully underwent TAVI, were enrolled in the study. GLS was measured from the endocardial layer (Endo-LS), epicardial layer (Epi-LS) and full thickness of myocardium before the procedure. Analysis included other parameters such as age, sex, LV volumes and ejection fraction (LVEF), type of prosthesis implanted, right ventricular (RV) dimension and function. Occurrence of cardiovascular (CV) events (rehospitalization for HF or CV death) were collected after 24 months follow-up.Results: CV events occurred in 7 patients (20%). Patients were divided in two groups accordingly with CV events occurrence. No differences in baseline, demographic, echocardiographic and procedural characteristics were found. Patients who developed CV events had a more impaired pre-procedural GLS (-10.2 ± 2.4% vs -12.6 ± 2.2%, p = 0.029), mostly due to his subendocardial layer (Endo-LS -10.8 ± 2 vs -13.9 ± 2, p = 0.003). Moreover, by ROC curve analysis, a cut-off value of -12.4% of endo LS was associated with CV events (sensitivity of 83% and specificity of 65 %, AUC 0.8, p = 0.024), with a log-rank p value assessed by survival analysis of 0.044. Conclusion Multilayer GLS analysis could provide additional information for prognosis stratification in patients with severe symptomatic AS before TAVI, above and beyond assessment of LVEF alone. Parameter Event-group (7/35 pz= 20%) Non-event group (28/35 pz= 80%) p Age (y.o) 86 ± 4 80 ± 7 NS LVEDV (ml) 112 ± 34 94 ± 32 NS LVESV (ml) 51.2 ± 6 56.9 ± 6 NS LVEF(%) 55.7 ± 6 56.9 ± 6 NS AVA (cm2) 0.77 ± 0.2 0.73 ± 0.2 NS GLS (%) -10.2 ± 2.4 -12.6 ± 2.2 0.029 Endo-LS (%) -10.8 ± 2 -13.9 ± 2 0.003 Epi-LS (%) -10.2 ± 2 -11.9 ± 2 NS Abstract P1752 Figure.

P1365 Different response of myocardial contractility by layer following acute pressure unloading after transcatheter aortic valve implantation

Abstract Background Transcatheter aortic valve implantation (TAVI) is an effective therapeutic option for severe symptomatic aortic stenosis (AS) with intermediate/high surgical risk. Aim of this study was to examine the acute effect of TAVI in terms of pressure unloading, on left ventricular (LV) mechanics using multilayer global longitudinal strain (GLS) by 2D speckle-tracking echocardiography (ST-E). Methods A total of 44 patients (mean age 81.8 ± 2, 34% male) with severe symptomatic AS and preserved LV ejection fraction (LVEF) underwent 2D echocardiography at baseline and 5 ± 2 days after TAVI. GLS was measured from the endocardial layer (Endo-LS), epicardial layer (Epi-LS) and full thickness of myocardium before and after the procedure. Analysis included other parameters such as age, sex, LV volumes and ejection fraction (LVEF), type of prosthesis implanted, right ventricular (RV) dimension and function. Results By dividing patients in two groups accordingly with LV geometry assessed with regional wall thickness measurement (concentric vs eccentric hypertrophy), better values of Endo-LS were recorded at baseline, in patients with concentric hypertrophy (-12.9 ± 2 vs -11 ± 3, p = 0.048). After TAVI, a significant improvement in Endo-LS was observed, but only in patients with concentric hypertrophy (-12.9 ± 2 vs -14.2 ± 2, p = 0.003). Conclusion The improvement in LS was more prominent in the endocardium, which was evident even immediately after TAVI only in patients with concentric hypertrophy. Evaluation of multilayer strain may provide new insights into the positive effects of unloading in patients with AS and may be potentially useful to predict patients with better outcome after TAVI. Parameter RWT &amp;gt; 0.42 31 pz (70%) RWT ≤ 0.42 13 pz (30%) p Male sex (n, %) 8 (25%) 7 (53%) NS Age (y.o) 81 ± 6 83 ± 7 NS CAD (n, %) 3 (9%) 8 (61%) NS LVEDV (ml) 97 ± 29 134 ± 14 0.002 LVESV (ml) 43 ± 15 72 ± 38 0.001 LVEF(%) 56.2 ± 6 50 ± 12 NS AVA (cm2) 0.8 ± 0.2 0.8 ± 0.3 NS GLS (%) -11.4 ± 3 -10.5 ± 3 NS Endo-LS (%) -12.9 ± 2 -11 ± 3 0.048 Epi-LS (%) -10.8 ± 4 -9.9 ± 3 NS Abstract P1365 Figure.

Myofiber organization in the failing systemic right ventricle

BackgroundThe right ventricle (RV) often fails when functioning as the systemic ventricle, but the cause is not understood. We tested the hypothesis that myofiber organization is abnormal in the failing systemic right ventricle.MethodsWe used diffusion-weighted cardiovascular magnetic resonance imaging to examine 3 failing hearts explanted from young patients with a systemic RV and one structurally normal heart with postnatally acquired RV hypertrophy for comparison. Diffusion compartment imaging was computed to separate the free diffusive component representing free water from an anisotropic component characterizing the orientation and diffusion characteristics of myofibers. The orientation of each anisotropic compartment was displayed in glyph format and used for qualitative description of myofibers and for construction of tractograms. The helix angle was calculated across the ventricular walls in 5 locations and displayed graphically. Scalar parameters (fractional anisotropy and mean diffusivity) were compared among specimens.ResultsThe hypertrophied systemic RV has an inner layer, comprising about 2/3 of the wall, composed of hypertrophied trabeculae and an epicardial layer of circumferential myofibers. Myofibers within smaller trabeculae are aligned and organized with parallel fibers while larger, composite bundles show marked disarray, largely between component trabeculae. We observed a narrow range of helix angles in the outer, compact part of the wall consistent with aligned, approximately circumferential fibers. However, there was marked variation of helix angle in the inner, trabecular part of the wall consistent with marked variation in fiber orientation. The apical whorl was disrupted or incomplete and we observed myocardial whorls or vortices at other locations. Fractional anisotropy was lower in abnormal hearts while mean diffusivity was more variable, being higher in 2 but lower in 1 heart, compared to the structurally normal heart.ConclusionsMyofiber organization is abnormal in the failing systemic RV and might be an important substrate for heart failure and arrhythmia. It is unclear if myofiber disorganization is due to hemodynamic factors, developmental problems, or both.

45 Severe secondary mitral regurgitation due to left ventricular non- compactation cardiomyopathy- a rare cause of heart failure

Abstract Introduction Left ventricular non-compaction is a rare form of cardiomyopathy charactherized by the presence of a two layered ventricular wall- a thinner epicardial layer and an inner, non-compacted layer with prominent trabeculations associated with deep, intratrabecular recesses that communicate with left ventricle cavity. Clinical manifestations vary in severity, including symptoms of heart failure, thromboembolic events or arrhythmias. Left ventricular (LV) dysfunction leads to tethering of the mitral apparatus and is a cause for secondary significant mitral regurgitation. Case presentation We report the case of a 57 year-old female patient, diagnosed with severe mitral regurgitation one year before presentation, with severe heart failure (HF) symptoms, referred to our clinic for the surgical replacement of the mitral valve. Clinical examination revealed no signs of pulmonary or systemic congestion and systolic apical murmur. Blood tests were normal, except for the elevated BNP (552 pg/ml). Electrocardiogram showed sinus rhythm and left ventricular hypertrophy. Coronary angiogram did not identify any coronary artery lesions. Echocardiography revealed mildly dilated left ventricle, but wih proeminent trabeculations and two distinct myocardial layers with a non-compacted/compacted ratio of 2:1 in the anterior and lateral walls, diagnostic for left ventricular non-compaction cardiomyopathy. LV ejection fraction was 40% , with severe secondary mitral regurgitation due to significant antero-posterior dilation of the mitral ring, with intact mitral leaflets; mild pulmonary hypertension was present. Magnetic resonance imaging (MRI) identified a two layer antero-lateral myocardium and confirmed the echo diagnosis; there was no evidence of scarring as there was absent late gadolinium enhacement. In the absence of fibrosis on MRI or any arrhythmic events on repeated Holter ECG monitoring, the implantation of a cardiac defibrillator was deferred. Given the secondary cause for mitral regurgitation (LV dysfunction), specific HF medication with beta blocker and renin-angiotensin-aldosterone blockade was initiated and titrated to optimal doses. With medical treatment the evolution was favourable. Currently, 3 years after the initial diagnosis, 6 minutes walk test revealed good functional capacity (510 m), a BNP value of 104 pg/l, without any worsening of LV systolic function nor progression of pulmonary hypertension. Conclusion Left ventricular non-compaction cardiomyopathy is a rare cause of heart failure, but due to advances in imaging modalities and increasing awareness, its prevalence is growing. Its pathogenesis and prognosis largely remain unknown, but early and adequate initiation of neurohormonal medication may be just as essential in order to prevent complications and improve long term prognosis, as for other forms of cardiomiopathy, even in the presence of severe secondary mitral regurgitation.

570 Myocardial deformation imaging after STEMI: can we better predict one-year mortality and heart failure development?

Abstract Prognosis after STEMI is still challenging. One-year mortality ranges between 10-12% and the incidence of heart failure (HF) is between 4% and 28%. Early and accurate identification of high-risk patients necessitates therapy intensification. Aim this study is a part of PREDICT-VT study (NCT03263949). The aim was to test whether deformation imaging based on spackle tracking echocardiography predict MACE (total mortality, HF hospitalization and NYHA class ≥3 development) better than conventional echocardiography and clinical parameters. Methods in 264 consecutive pts enrolled in PREDICT-VT study early echocardiography (5 ± 2 days after pPCI) was done including LA and multilayer LV deformation analysis with longitudinal (L), radial (R) and circumferential (C) strain (S; %) and strain rate (SR, 1/sec). LV index of post systolic shortening for longitudinal (PSS LS) and circumferential (PSS CS) strain were calculated as average of PSS over 18 LV segments. Results 198 patients completed 1-year follow-up and 22 patients (11.1%) experienced MACE. Significant echo, clinical and laboratory predictors with the ROC analysis are listed in the table according to AUC . Conclusion peak systolic longitudinal and to a lesser degree peak systolic circumferential deformation predict mortality and HF development after pPCI better than conventional echo and even clinical parameters. From diastolic parameters only radial SR during atrial contraction was better MACE predictor compared to conventional echocardiography. AUC p Cut-off Senz Spec Peak systolic LS epicardial layer 0.757 &amp;lt;0.001 -11 75 63 Radial SR during atrial contraction 0.754 &amp;lt;0.001 -0.63 65 80 Peak systolic LS mid-wall layer 0.750 &amp;lt;0.001 -12.58 80 60 PSS LS endocardial layer 0.744 &amp;lt;0.001 0.1409 70 61 Peak systolic CS endocardial layer 0.744 &amp;lt;0.001 -18.08 70 67 Wall Motion Score Index 0.740 0.001 1.53 70 70 Peak systolic CS mid-wall layer 0.730 0.001 -13.66 80 60 Peak radial LV strain 0.722 0.001 14.08 80 60 Creatine kinase peak level 0.698 0.003 2155 64 73 LV EF 0.692 0.004 47.5 67 60 TAPSE 0.685 0.015 1.95 75 60 LA strain 0.676 0.012 18.33 63 64 Killip class 0.644 0.028

Ablation of scar-related reentrant atrial tachycardias with epi-to-endo bridging is less successful

Epicardial portions of the circuit of endocardial re-entrant tachycardias are well established phenomena in the ventricles, but little is known about a similar phenomenon in post lesion atrial tachycardia (AT). Higher spatial and voltage mapping capabilities may help identify extra-endocardial bridging (EEB) during tachycardia. We retrospectively analysed our database of 119 pts with AT cases with ultra-high density mapping between March 2015 and March 2018. Epi-to-endo breakthrough sites were diagnosed when endocardial activation started at a discrete point before spreading radially in every available direction. PPI after transient entrainment at these sites confirmed local participation in AT. In 20 out of the 119 pts (mean age 70 ± 9 yrs, always with ≥ 1 prior procedures), 2 types of EEB were found. Type 1 is a “myocardial” EEB ( n = 16). Subtype 1A ( Fig. 1 ) with a visible antidromic wavefront back to a line of block ( n = 10) whereas in subtype 1B activation starts immediately adjacent to a usually large line of block. Type 2 implied an extra-atrial “venous” bridging, either as a “shunt” over a line of block (subtype 2A, n = 6) or by using an epicardial vein as a major part of a circuit (subtype 2B, n = 1). In presence of EEB, AT termination was 17/22 (77%), significantly lower than our historical cohort of nonEEB AT (97%, P = 0.03). The most successful strategy was targeting epi-endo breakthrough site. Atrial EEB using either epicardial layers of the atrial wall, or extra-atrial venous structures is confirmed. Successful ablation at epi-to-endo breakthrough site proves the validity of the concept but results of ablation are inferior to nonEEB AT.

Evaluation of left ventricular myocardial function in patients with aortic stenosis by layer-specific strain

Objective To investigate the value of layer-specific strain in evaluating the changes of left ventricular three layers and segmental myocardial function in patients with different degree of aortic stenosis (AS). Methods Ninety-eight AS patients were selected as AS group from December 2017 to June 2019 in Henan Provincial People′s Hospital, they were divided into mild AS group(30 cases), moderate AS group(33 cases), severe AS group(35 cases); 30 healthy subjects were enrolled as control group.Longitudinal strain (LS), circumferential strain (CS) of endocardium, mid-myocardium, epicardium, global full thickness and each segment of left ventricular myocardium were measured by layer-specific strain and then compared. Results Compared with the control group, Vmax, PPG, interventricular septal thickness in diastole(IVSD), left ventricular posterior wall thickness in diastole(LVPWD), left ventricular mass index(LVMI), and E/e increased in all three AS groups(all P 0.05). There were no significant difference in CS of endocardial, mid-myocardial, epicardial and global full-thickness myocardium layers in basal, middle and apical LV segments between mild AS group and control group(all P>0.05). CS of endocardial, mid-myocardial, epicardial and global full-thickness myocardium layers were decreased in moderate AS and severe AS groups compared with control group(all P<0.05). CS of endocardial, mid-myocardial myocardium layers in basal and middle LV segments were decreased in moderate AS group compared with control group(all P<0.05). CS of three myocardium layers in basal, middle and apical LV segments were decreased in severe AS group compared with control group(all P<0.05). Conclusions Layer-specific strain can quantitatively evaluate left ventricular three layers and segmental myocardial function in patients with aortic stenosis, and has certain clinical application value. Key words: Echocardiography; Layer-specific strain; Aortic stenosis; Ventricular function, left

Transcriptional heterogeneity of fibroblasts is a hallmark of the aging heart.

Aging is a major risk factor for cardiovascular disease. Although the impact of aging has been extensively studied, little is known regarding the aging processes in cells of the heart. Here we analyzed the transcriptomes of hearts of 12-week-old and 18-month-old mice by single-nucleus RNA-sequencing. Among all cell types, aged fibroblasts showed most significant differential gene expression, increased RNA dynamics, and network entropy. Aged fibroblasts exhibited significantly changed expression patterns of inflammatory, extracellular matrix organization angiogenesis, and osteogenic genes. Functional analyses indicated deterioration of paracrine signatures between fibroblasts and endothelial cells in old hearts. Aged heart-derived fibroblasts had impaired endothelial cell angiogenesis and autophagy and augmented proinflammatory response. In particular, expression of Serpine1 and Serpine2 were significantly increased and secreted by old fibroblasts to exert antiangiogenic effects on endothelial cells, an effect that could be significantly prevented by using neutralizing antibodies. Moreover, we found an enlarged subpopulation of aged fibroblasts expressing osteoblast genes in the epicardial layer associated with increased calcification. Taken together this study provides system-wide insights and identifies molecular changes of aging cardiac fibroblasts, which may contribute to declined heart function.

Cardiorespiratory fitness and right ventricular mechanics in uncomplicated diabetic patients: Is there any relationship?

This study investigated the association between cardiorespiratory fitness and right ventricular (RV) strain in uncomplicated diabetic patients. This cross-sectional study involved 70 controls and 61 uncomplicated patients with type 2 diabetes, who underwent laboratory analysis, comprehensive echocardiographic study and cardiopulmonary exercise testing. RV endocardial and mid-myocardial longitudinal strains were significantly reduced in diabetic subjects (- 27.5 ± 4.2% vs. - 25.3 ± 4.3%, p = 0.004 for endocardial strain; - 25.6 ± 3.5% vs. - 24.1 ± 3.2%, p = 0.012 for mid-myocardial strain). The same was revealed for endocardial and mid-myocardial of RV free wall. There was no difference in RV epicardial strain. VO2 was significantly lower in the diabetic group (27.8 ± 4.5ml/kg/min vs. 21.5 ± 4.2ml/kg/min, p < 0.001), whereas ventilation/carbon dioxide slope was significantly higher in diabetic subjects (25.4 ± 2.9 vs. 28.6 ± 3.3). Heart rate recovery was significantly lower in diabetic patients. HbA1c and global RV endocardial longitudinal strain were independently associated with peak VO2 and oxygen pulse in the whole study population. Diabetes impacts RV mechanics, but endocardial and mid-myocardial layers are more affected than epicardial layer. RV endocardial strain and HbA1c were independently associated with cardiorespiratory fitness in the whole study population. Our findings show that impairment in RV strain and cardiorespiratory fitness may be useful indicators in early type 2 diabetes, prior to the development of further complications.

Assessment of myocardial function in obstructive hypertrophic cardiomyopathy cats with and without response to medical treatment by carvedilol

BackgroundInconsistency of treatment response in cats with obstructive hypertrophic cardiomyopathy is well recognized. We hypothesized that the difference in response to beta-blockers may be caused by myocardial functional abnormalities. This study was designed to compare myocardial function in cats with obstructive hypertrophic cardiomyopathy with and without response to beta-blockers. Twenty-one, client-owned, hypertrophic cardiomyopathy cats treated with carvedilol were analyzed. After carvedilol treatment, cats with decreased left ventricular outflow tract velocity were categorized as responders (n = 10); those exhibiting no response (no decrease in the left ventricular outflow tract velocity) were categorized as non-responders (n = 11). The cats were examined using layer-specific assessment of the myocardial function (whole, endocardial, and epicardial layers) longitudinally and circumferentially by two-dimensional speckle-tracking echocardiography, before and after carvedilol treatment.ResultsThe non-responder cats had a significantly higher age, end-diastolic left ventricular posterior-wall thickness, peak velocity of left ventricular outflow tract, and dose of carvedilol than the responders (p = 0.04, p < 0.01, p < 0.01, and p < 0.01, respectively). The circumferential strain in the epicardial layer was lower and circumferential endocardial to epicardial strain ratio was higher in non-responders than responders (p < 0.001 and p = 0.006). According to the multivariate analysis, circumferential strain in the epicardial layer was the only independent correlate of treatment response with carvedilol.ConclusionsMyocardial function, assessed by two-dimensional speckle-tracking echocardiography, differed in cats with hypertrophic cardiomyopathy with and without response to beta-blockers. The determination of layer-specific myocardial function may facilitate detailed pathophysiologic assessment and treatment response in cats with hypertrophic cardiomyopathy.

3255Characterization of the arrhythmogenic substrate with multimodality imaging in ischemic patients undergoing VT ablation: relationship between cardiac computed tomography and magnetic resonance

Abstract Background Cardiac magnetic resonance (CMR)-aided ventricular tachycardia (VT) substrate ablation has shown to improve VT recurrence-free survival, through a better identification of the arrhythmogenic substrate. However, the access to CMR may be limited in certain centers or sometimes Its use can be contraindicated in patients with cardiac implantable electronic device. Cardiac computed tomography (CT) has shown to improve the results of substrate ablation, correlating with low-voltage areas and local abnormal ventricular activity, and identifying ridges of myocardial tissue (CT-channels) that may be appropriate target sites for ablation. Purpose To evaluate the correlation between CT and CMR imaging in identifying anatomical heterogeneous tissue channels (CMR-channels) or CT-channels in ischemic patients undergoing VT substrate ablation. Methods The study included 30 post-myocardial infarction (MI) patients (mean age 69±10; 94% male, left ventricular ejection fraction 35±10%), who underwent both CMR and cardiac CT before VT substrate ablation. Using a dedicated post-processing software, the myocardium was segmented in 10 layers from endocardium to epicardium both for the CMR and CT, characterizing the presence of CMR-channels and CT-channels, respectively, by two blinded operators, assigned either to CMR or CT analysis. CMR-channels were classified as endocardial (CMR-channels in layer &lt;50%), epicardial (CMR-channels in layers ≥50%) or transmural (in both endo and epicardial layers). Presence and location of CT and CMR-channels were compared. Results In 26/30 patients (86.7%) 91 CT-channels (mean 3.0±1.9 per patient) were identified while 30/30 (100%) showed CMR-channels (n=76; mean 2.4±1.2 per patient). We found 190 CT-channel entrances (mean 6.3±4.1 per patient), and 275 CMR-channel entrances (mean 8.9±4.9 per patient) on cardiac CT and CMR, respectively. There were 47/91 (51.6%) true positive CT-channels. On the contrary, 44/91 (48.4%) CT-channels were considered false positives [19/91 (20.9%) identified out of CMR scar], and 29/76 (38.2%) CMR-channels could not be identified on CT. Thirty-six out of 76 (47.4%) CMR-channels were considered as non-endocardial (epi- or transmural). Twenty-nine out of 36 (80.5%) non-endocardial CMR-channels were coincident with CT-channels. CT and CMR Channels Conclusion CT shows a modest sensitivity in identifying CMR-channels and fails in ascertain their complexity, underestimating the number of entrances; however, channels location at CT fit well with CMR for those classified as transmural or epicardial.

P4488Organotypic culture of the epicardium: a new tool for cardiovascular research

Abstract Background The epicardium, the most external layer of the heart, is composed of a layer of epithelial cells and underlying connective tissue. Following myocardial infarction, epicardial cells are activated and provide a source of paracrine factors and progenitor cells. In the border zone of the ischaemic tissue, the activated epicardial cells support cardiac and vascular regeneration by releasing pro-angiogenic and pro-survival factors, and by differentiating towards multiple cell lineages. During this process, activated epicardial cells migrate to the site of injury where they contribute to both post-ischemic remodelling and fibrosis. There is limited knowledge of the cellular and molecular regulation of these processes in large animals and humans, in part due to the lack of robust and representative models. Purpose In this project, we developed an ex vivo 3D organotypic model derived from porcine hearts, amenable to culture, which enables structural, molecular and cellular studies of the epicardium. Methods Thin epicardial/cardiac tissue slices (EpCardio-TS) were obtained by using a vibratome to cut the first layer of tissue from the epicardial side of porcine heart cubes. Slices were cultured for up to 72h in a bioreactor that uses a 3D printed chamber connected to a control system that allows maintenance and adjustment of culture conditions, and ensures continuous media flow. Local intracellular delivery of fluorescent quantum-dots (Qdots) was performed using nanoneedle chips to track epicardial cells, whilst cell fate is visualised in 3D by performing immunofluorescence on decolourised slices. Results Intact EpCardio-TS obtained from porcine heart included a viable epicardium, expressing typical epicardial markers (wt-1, mesothelin, uroplakin), and an electrically active myocardium. Live/dead staining showed epicardial (67.8±16.2%, N=5) and myocardial (40.8±28.6%, N=3) viability, and TUNEL assay confirmed low levels of apoptosis (6.3±5.1% of wt-1+ epicardial cells N=1). Moreover, the presence of proliferating epicardial cells (PCNA+), the increase in wt-1+ cells, and the increase in epicardial gene expression (Tbx18 and TCF21) suggested that cells maintain their progenitor phenotype and undergo activation in culture. Nanoinjection of fluorescent Qdots to EpCardio-TS localized them to the wt-1+ cells on the slice surface, presenting a strategy to mark the epicardial layer. This, combined with the successful decolourisation of the slices, provides an in vitro platform to track the role of epicardial cells in cardiac remodelling and fibrosis. Conclusions EpCardio-TS represents a robust ex vivo model merging the complexity of a 3D organotypic culture with the simplicity of the in vitro culture. EpCardio-TS are amenable to culture and cell tracking, and can therefore find application in toxicology and gene therapy screening for the modulation of epicardial interactions with myocardial and non-myocardial cells of the heart.

Pathophysiology of atrial fibrillation: Focal patterns of activation.

For decades, electrical activity recorded has been investigated to unravel pathophysiology of cardiac arrhythmias, such as atrial fibrillation (AF). Particularly high-resolution mapping studies have significantly contributed to novel insights into AF mechanisms. From these mapping studies, it appeared that persistence of AF is associated with a high incidence of focal patterns of activation. Features of these focal activation patterns indicated that they could be attributed to transmural propagation of fibrillation waves. However, "focal fibrillation waves" can only appear when there is electrical asynchrony between the endocardial and epicardial layer. By performing simultaneous high-resolution mapping of the endo- and epicardial wall of the right atrium in humans during AF, the existence of electrical asynchrony (endo-epicardial asynchrony [EEA]) between the endo- and epicardial layer was indeed confirmed. During sinus rhythm, focal patterns of activation are most frequently observed at the right atrium and a considerable degree of EEA-as large as 50ms-may occur. Furthermore, prematurely aberrant atrial extrasystoles emerging as focal waves caused the highest degree of conduction disorders, particularly in patients with left atrial dilatation and diabetes mellitus. These observations emphasize the contribution of atrial anatomy to EEA and the role of focal patterns of activation in development AF.

Novel technique for the simultaneous isolation of cardiac fibroblasts and epicardial stromal cells from the infarcted murine heart.

Myocardial infarction (MI) leads to activation of cardiac fibroblasts (aCFs) and at the same time induces the formation of epicardium-derived cells at the heart surface. To discriminate between the two cell populations, we elaborated a fast and efficient protocol for the simultaneous isolation and characterization of aCFs and epicardial stromal cells (EpiSCs) from the infarcted mouse heart. For the isolation of aCFs and EpiSCs, infarcted hearts (50 min ischaemia/reperfusion) were digested by perfusion with a collagenase-containing medium for only 8 min, while EpiSCs were enzymatically removed from the outside by applying mild shear forces via a motor driven device. Cardiac fibroblasts (CFs) isolated from unstressed hearts served as control. Viability of isolated cells was >90%. Purity of EpiSCs was confirmed by immunofluorescence staining and qPCR of various mesenchymal markers including Wilms-tumor-protein-1. Microarray analysis of CFs, aCFs, and EpiSCs on day 5 post-MI revealed a unique gene expression pattern in the EpiSC fraction, which was enriched for epithelial markers and epithelial to mesenchymal transition-related genes. Compared to aCFs, 336 significantly altered gene entities were identified in the EpiSC fraction. qPCR analysis showed high expression of Serpinb2, Cxcl13, Adora2b, and Il10 in EpiSCs relative to CFs and aCFs. Furthermore, microarray data identified Ddah1 and Cemip to be highly up-regulated in aCFs compared to CFs. Immunostaining of the infarcted heart revealed a unique distribution of Dermokine, Aquaporin-1, Cytokeratin, Lipocalin2, and Periostin within the epicardial cell layer. We describe the simultaneous isolation of viable, purified fractions of aCFs and EpiSCs from the infarcted mouse heart. In this study, several differentially expressed markers for aCFs and EpiSCs were identified, underlining the importance of cell separation to study heterogeneity of stromal cells in the healing process after MI.

Electrophysiological remodeling of the right ventricle in experimental heart failure of different etiologies

The aim of the study was to evaluate electrophysiological remodeling of the right ventricle in rats in experimental heart failure of different etiologies. Materials and methods. Isadrin-, doxorubicin- and monocrotaline-induced heart failure models were developed. Unipolar epicardial electrograms of the ventricles (256 recording sites) were recorded using a 144-channel system. The cardiac output and pressure in both ventricles of the heart were measured. Activation-recovery intervals were used as an index of duration of local repolarization, and the general and local dispersions of activation-recovery intervals were used as an index of heterogeneity of ventricular repolarization. Results. In all models of heart failure, the following were identified: 1) non-uniform prolongation of repolarization with the greatest elongation at the apex of the right ventricle; 2) an increase in apicobasal differences of repolarization with the greatest change in the right ventricle; 3) an increase in the heterogeneity of the repolarization of the epicardial layer of the ventricles with heterogeneous changes in the local heterogeneity of repolarization and a decrease in the interregional differences in the heterogeneity of the electrophysiological properties of the myocardium; 4) more pronounced changes in the repolarization of the right ventricle than in the repolarization of the left ventricle. Conclusion. Thus, irrespective of the cause of the heart failure, the following changes occur: 1) prolongation of the right ventricular repolarization occurs non-uniformly (mostly due to the apical area), which results in an increase in the right ventricular repolarization heterogeneity; 2) an increase in the heterogeneity of right ventricular repolarization is observed, which causes an increase in the overall heterogeneity of the ventricular epicardial surface.

Abstract 840: Epicardial Prestrained Confinement and Residual Stresses: A Newly Observed Heart Ventricle Confinement Interface

The heart epicardial layer, with elastin as the dominant component, has not been well investigated, specifically on how it contributes to ventricular biomechanics. In this study, we revealed and quantitatively assessed the overall status of prestraining and residual stresses exerted by the epicardial layer on the heart left ventricle (LV). During porcine heart wall dissection, we discovered that bi-layered LV surface strips, consisting of an epicardial layer and cardiac muscle, always curled towards the epicardial side due to epicardial residual stresses. We hence developed a curling angle characterization technique to intuitively and qualitatively reveal the location-dependency and direction-dependency of epicardial residual stresses. Moreover, by combining prestrain measurement and biaxial mechanical testing, we were able to quantify the epicardial prestrains and residual stresses on the unpressurized intact LV. To investigate the potential mechanical effect of epicardial prestraining, a finite-element (FE) model has been constructed, and we demonstrate that it is the prestraining of the epicardial layer, not the epicardial layer alone, providing an additional resistance mechanism during LV diastolic expansion and ventricular wall protection by reducing myocardial stress. In short, our study on healthy, native porcine hearts has revealed an important phenomenon—the epicardial layer, rich in elastin, acts like a prestrained ‘balloon’ that wraps around the heart and functions as an extra confinement and protection interface. The obtained knowledge fills a gap in ventricular biomechanics and will help design novel biomimicking materials or prosthetic devices to target the maintenance/recreation of this ventricle confinement interface.

Naringin mitigates myocardial strain and the inflammatory response in sepsis-induced myocardial dysfunction through regulation of PI3K/AKT/NF-κB pathway

Sepsis-induced myocardial dysfunction (SIMD) is a manifestation of severe sepsis and is the main cause of increased mortality in sepsis patients. Naringin (Nar) has been reported to possess various biological activities and pharmacological properties. Therefore, the present study was undertaken to evaluate whether Nar can protect rats from the effects of LPS-induced SIMD. SD Rats were pre-treated with Nar (50 and 100 mg/kg) for 7 days before administration of a single dose of LPS (10 mg/kg, i.p.) on the seventh day. We found that Nar treatment markedly improved the global strain and strain rate of longitudinal, circumference, and radial direction (GLS/GLSr, GCS/GCSr, GRS/GRSr) compared to the LPS group. The layer-specific strain decreased gradually from the endocardial layer to epicardial layer, and the most serious damage occurred in the endocardial layer. Moreover, Nar significantly decreased the levels of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) and myocardial enzymes (CK, LDH, and AST) induced by LPS and attenuated the inflammation response. Finally, Nar also inhibited NF-κB nuclear translocation and the activity of iNOS in H9c2 cardiomyocytes by activating PI3K/AKT signaling pathway. These results suggest that naringin may possess novel therapeutic potential for protection against LPS-induced myocardial dysfunction.