Left Ventricular Chamber Dimensions Research Articles

Deep learning for fully automated echocardiographic measurements of left ventricular wall thickness and chamber dimensions in the parasternal long-axis view

Abstract Background Accurate quantification of left ventricular (LV) wall thickness and chamber dimensions in the echocardiographic parasternal long-axis view (PLAX) is crucial for clinical decisions in patients with heart disease. However, there is a need for more reproducible and time-efficient methods. Fully automated deep learning (DL)-based methods could address this need. Purpose To develop a DL-based method for fully automated measurements of LV wall thickness and chamber dimensions in PLAX, validate its performance in a large population cohort, and evaluate its capacity to differentiate between hypertensive and normotensive groups. Methods DL networks were trained on PLAX recordings from 207 subjects. The DL method performed cardiac segmentation, timing of end-systole and end-diastole, and measured LV wall thickness and chamber dimensions in PLAX. The model was validated in a large populational echocardiography dataset including a subset with test-retest evaluation. Agreement with expert reference measurements, test-retest reproducibility, and comparison of normotensive and hypertensive (defined as those on hypertensive medication or with systolic blood pressure >160 mmHg) groups were evaluated. Results In the populational study of 2047 subjects, the novel DL method demonstrated a feasibility of 97.6%. Strong agreement was observed between the automated DL method and expert readers in measuring end-diastolic septal thickness, posterior wall thickness, and LV diameter (bias 0.1 mm, 0.2 mm, and 2.2 mm, respectively, Figure 1). In a test-retest dataset (n=40, with 2 recordings per patient and 4 readers), the novel DL method displayed improved reproducibility compared to inter-reader measurements, with minimal detectable change for interventricular septal diameter 2.2 mm versus 2.6 mm, posterior wall diameter 1.2 mm versus 2.5 mm, and LV diameter 5.0 mm versus 6.3 mm (Figure 2). The DL method measured significantly wider septal diameter in the hypertensive group compared to normotensive group (p<0.001). Mean analysis time for wall thickness and chamber dimensions using the DL method was 1.2 seconds. Conclusion The novel DL method accurately measured LV wall thickness and chamber dimensions in the PLAX view, and demonstrated improved test-retest reproducibility compared to experienced echocardiographers. Additionally, it was able to detect significantly wider septal diameters in the hypertensive population. By providing fast and reliable measurements in retrospective data, and with potential for real-time measurements during image acquisition, this DL method has the potential to improve the yield, efficiency, and workflow in echocardiography.Bland-Altman posterior wall diameterTest-retest posterior wall diameter

Cardiac Structural and Functional Remodeling After Transcatheter Mitral Valve in Valve Implantation: Early Changes and Prognostic Significance

BackgroundTranscatheter mitral valve-in-valve (MViV) replacement has emerged as an alternative to redo mitral valve (MV) surgery for the management of failed bioprosthetic MVs. The degree of cardiac remodeling assessed by echocardiography has been shown to have prognostic implications in degenerative mitral regurgitation patients undergoing MV surgery. The impact of transcatheter MViV in patients with degenerative bioprosthetic MV failure on cardiac remodeling and its associated prognosis remains undescribed. ObjectivesThe aim of this study is to describe the early anatomic and functional changes of the left-sided chambers and right ventricle by echocardiography posttranscatheter MViV intervention and their impact on mortality outcomes. Additionally, we sought to analyze the outcome of heart failure in bioprosthetic MV failure patients undergoing transcatheter MViV replacement. MethodsWe analyzed consecutive patients undergoing MViV intervention for symptomatic bioprosthetic MV failure. Echocardiograms before intervention and within 100 days postintervention were analyzed. A chart review was performed to obtain baseline characteristics, follow-up visits, 30-day heart failure and 1-year all-cause mortality outcomes. ResultsA total of 62 patients (mean age 69 ± 13 years, 61% male) were included in the study. Most patients were undergoing MViV intervention for prosthetic mitral stenosis n = 48 (77.4%) and the rest for mitral regurgitation or mixed disease. Compared with baseline, significant reductions were observed in median left atrial volume (LAV; 103 [81–129] ml vs. 95.2 [74.5–117.5] ml, p < 0.01) and mean (SD) left atrial conduit strain (9.1% ± 5.2% vs. 10.8% ± 4.8%, p = 0.039) within 100 days postintervention. Early reduction in right ventricular free wall global longitudinal strain and fractional area change also occurred postintervention. No significant change in left ventricular chamber dimensions or ejection fraction was observed. During the 1-year follow up period, 5 (8%) patients died. While baseline LAV was not associated with 1-year all-cause mortality (OR 0.98 CI 0.95–1.01; p = 0.27), a change in LAV in the follow up period was associated with all-cause mortality at 1 year (OR 1.06 CI 1.01–1.12; p = 0.023). At 30 days postintervention, 65% of patients had an improvement in their New York Heart Association functional class. ConclusionIn this retrospective study of patients undergoing transcatheter MViV intervention for failed bioprosthetic MVs, early reverse remodeling of the left atrium occurs within 100 days postintervention and reduction in LAV is associated with reduced all-cause mortality at 1 year. In addition, there is significant improvement in heart failure symptoms at 30 days following intervention but further investigation into the longitudinal remodeling changes and long-term outcomes is needed.

Abstract 15371: Mice Lacking S-Nitrosoglutathione Reductase (GSNOR -/- ), a Mouse Model of Preeclampsia, Exhibited Nitroso-Redox Imbalance and Deterioration of Cardiovascular Structure and Function in Postpartum Mothers

Introduction: Preeclampsia (PE), a leading cause of maternal mortality, is linked to persistent pathological changes in the heart, predisposing the mother to increased risk of chronic cardiovascular (CV) disease later in life. PE is characterized by increased S-nitrosylated (SNO) proteins and nitroso-redox imbalance. We recently showed that mice lacking S-nitrosoglutathione reductase (GSNOR -/- mice), a denitrosylase that regulates protein S-nitrosylation, exhibit the clinical features of PE including maternal hypertension, blunted increase in cardiac output, abnormal remodeling of left ventricular (LV) cardiac structure, dysregulation in nitrosylation and nitroso-redox imbalance. Hypothesis: The nitroso-redox imbalance seen during pregnancy in GSNOR -/- mice persists in postpartum (PP), leading to increased maternal susceptibility to CV injury. Methods: Pregnant control (WT [C57Bl/6J]) and GSNOR -/- mice (N=5) were examined at baseline, late-stage pregnancy (17.5 dpc) and 6 weeks PP. LV structure, cardiac output and stroke volume were determined using echocardiography (Vevo 2100). Cardiomyocytes (CM) were isolated at 6 weeks PP and ROS and peroxynitrite levels determined using fluorescent dyes. Results: In WT mice, all normal maternal CV adaptions to pregnancy, reverted to pre-pregnant levels 6 weeks PP. In contrast, GSNOR -/- mice exhibited increased cardiac output (+21% vs. -19% in WT), stroke volume (+21% vs. -41% in WT), and LV chamber dimension (+13% vs. -4% in WT) at 6 weeks PP, indicating high cardiac output LV cardiomyopathy. CM isolated from GSNOR -/- hearts showed ~5-fold more ROS generation (9.9x10 -4 ±9x10 -5 vs. 2.1x10 -4 ±1.5 x10 -4 ΔF/F max .min -1 ) and elevated peroxynitrite levels (0.318±0.011 vs. 0.243±0.012 ΔF/F 0 ) compared to WT at 6 weeks PP, suggesting the presence of nitroso-redox imbalance. All changes P&lt;0.05. Conclusion: Postpartum GSNOR -/- (preeclamptic) mothers exhibited cardiac dysfunction which was accompanied by the presence of of nitroso-redox imbalance. These changes may predispose the mother to higher risk for future CV injury.

Natural history of cardiac findings in mucopolysaccharidosis type I: report from an international registry.

Mucopolysaccharidosis type I is an inborn error of glycosaminoglycan catabolism with phenotypes ranging from severe (Hurler syndrome) to attenuated (Hurler-Scheie and Scheie syndromes). Cardiovascular involvement is common and contributes significantly to morbidity and mortality. We conducted a retrospective analysis of the prevalence and natural history of cardiac abnormalities in treatment-naïve individuals enrolled in the international Mucopolysaccharidosis Type I Registry. Interrogation of echocardiography data (presence of cardiac valve regurgitation and/or stenosis; measurements of left ventricular chamber dimensions in diastole and systole, diastolic left ventricular posterior wall and interventricular septal thicknesses and ventricular systolic function (shortening fraction)) showed that mitral regurgitation was the most common and earliest finding for individuals with both severe (58.3%, median age 1.2 years) and attenuated (74.2%, median age 8.0 years) disease. Left-sided valve stenosis was also common in individuals with attenuated disease (mitral 30.3%; aortic 25%). Abnormal ventricular wall and septal thickness (Z-scores ≥2) were observed early in both phenotypes. Z-scores for diastolic left ventricular posterior wall and interventricular septal thicknesses increased with age in the severe phenotype (annualised slopes of 0.2777 [p = 0.037] and 0.3831 [p = 0.001], respectively); a similar correlation was not observed in the attenuated phenotype (annualised slopes of -0.0401 [p = 0.069] and -0.0029 [p = 0.875], respectively). Decreased cardiac ventricular systolic function (defined as shortening fraction <28%) was uncommon but, when noted, was more frequent in infants with the severe phenotype. While cardiac abnormalities occur early in both severe and attenuated mucopolysaccharidosis type I, the pattern of valve dysfunction and progression of ventricular abnormalities vary by phenotype.

Abstract P3100: Mice Lacking S-nitrosoglutathione Reductase (gsnor -/- ), A Mouse Model Of Preeclampsia, Exhibit Increases In Oxidative And Nitrosative Stress And Deterioration Of Cardiovascular Structure And Function In The Mother Postpartum.

Introduction: Preeclampsia (PE), a leading cause of maternal mortality, is linked to persistent pathological changes in the heart, predisposing the mother to increased risk of chronic cardiovascular (CV) disease later in life. PE is characterized by increased S-nitrosylated (SNO) proteins and nitrosative stress. We recently showed that mice lacking S-nitrosoglutathione reductase (GSNOR -/ - mice), a denitrosylase that regulates protein S-nitrosylation, exhibit the clinical features of PE including maternal hypertension, blunted increase in cardiac output, abnormal remodeling of left ventricular (LV) cardiac structure, dysregulation in nitrosylation and increased nitrosative stress. We hypothesize that the aberrant nitrosylation and nitrosative stress seen during pregnancy persist postpartum (PP), leading to increased maternal susceptibility to CV injury. Methods: Pregnant control (WT [C57Bl/6J]) and GSNOR -/- mice (N=5) were examined at baseline, late-stage pregnancy (17.5 dpc) and 6 weeks PP. LV structure, cardiac output and stroke volume were determined using echocardiography (Vevo 2100). Cardiomyocytes (CM) were isolated at 6 weeks PP and ROS and peroxynitrite levels determined using fluorescent dyes. Results: In WT mice, all normal maternal CV adaptions to pregnancy, reverted to pre-pregnant levels 6 weeks PP. In contrast, GSNOR -/- mice exhibited increased cardiac output (+21% vs. -19% in WT), stroke volume (+21% vs. -41% in WT), and LV chamber dimension (+13% vs. -4% in WT) at 6 weeks PP, indicating high cardiac output LV cardiomyopathy. CM isolated from GSNOR -/- hearts showed ~5-fold more ROS generation (9.9x10 -4 ±9x10 -5 vs. 2.1x10 -4 ±1.5 x10 -4 ΔF/F max .min -1 ) and elevated peroxynitrite levels (0.318±0.011 vs. 0.243±0.012 ΔF/F 0 ) compared to WT at 6 weeks PP, suggesting the presence of oxidative and nitrosative stress. All changes P&lt;0.05. Conclusion: Postpartum GSNOR -/- (preeclamptic) mothers exhibited cardiac dysfunction characterized by high cardiac output LV cardiomyopathy, which was accompanied by elevated levels of oxidative and nitrosative stress. These changes may predispose the mother to higher risk for future CV injury.

Chronic troponin elevation assessed by myocardial T1 mapping in patients with stable coronary artery disease.

Cardiac troponin detected with sensitive assays can be chronically elevated, in the absence of unstable coronary syndromes. In patients with chronic coronary artery disease, clinically silent ischemic episodes may cause chronic troponin release. T1 mapping is a cardiovascular magnetic resonance technique useful in quantitative cardiac tissue characterization. We selected patients with anatomically and functionally normal hearts to investigate associations between chronic troponin release and myocardial tissue characteristics assessed by T1 mapping. We investigated the relationship between cardiac troponin I concentrations and cardiovascular magnetic resonance T1 mapping parameters in patients with stable coronary artery disease enrolled in MASS V study before elective revascularization. Participants had no previous myocardial infarction, negative late gadolinium enhancement, normal left ventricular function, chamber dimensions and wall thickness. A total of 56 patients were analyzed in troponin tertiles: nativeT1 and extracellular volume (ECV) values (expressed as means ± standard deviations) increased across tertiles: nativeT1 (1006 ± 27 ms vs 1016 ± 27 ms vs 1034 ± 37 ms, ptrend = 0.006) and ECV (22 ± 3% vs 23 ± 1.9% vs 25 ± 3%, ptrend = 0.007). Cardiac troponin I concentrations correlated with native T1(R = 0.33, P = .012) and ECV (R = 0.3, P = .025), and were independently associated with nativeT1 (P = .049) and ventricular mass index (P = .041) in multivariable analysis. In patients with chronic coronary artery disease and structurally normal hearts, troponin I concentrations correlated with T1 mapping parameters, suggesting that diffuse edema or fibrosis scattered in normal myocardium might be associated with chronic troponin release.

Long-term consumption of artificial sweeteners does not affect cardiovascular health and survival in rats.

BackgroundRecent epidemiological cohort studies have suggested that consumption of artificial sweeteners (AS) is associated with adverse cardiovascular events and mortality. However, these population association studies cannot establish a causal relationship. In this study we investigated the effect of long-term (1-year) consumption of AS (Equal and Splenda, two commonly used AS) on cardiovascular health and survival in rats.MethodsAdult Sprague-Dawley rats (both sexes, 4–5 months old) were randomized into the following 3 groups: control (n = 21), AS Equal (n = 21) and Splenda (n = 18). In the AS groups, Equal or Splenda was added to the drinking water (2-packets/250 ml), while drinking water alone was used in the control rats. The treatment was administered for 12 months. Cardiovascular function and survival were monitored in all animals.ResultsIt was found that rats in the AS groups consistently consumed more sweetened water than those in the control group. AS did not affect body weight, non-fasting blood cholesterol, triglycerides, blood pressure or pulse wave velocity. There were no significant differences in left ventricular wall thicknesses, chamber dimension, cardiac function or survival. AS did not affect heart rate or atrial effective refractory period. However, rats in both Equal and Splenda groups had prolonged PR intervals (63 ± 5ms in Equal, 68 ± 6 ms in Splenda, vs 56 ± 8 ms in control, p < 0.05) and a tendency of increased atrial fibrillation inducibility.ConclusionLong-term consumption of AS does not affect cardiovascular structure, function or survival but may cause some electrophysiological abnormalities with prolonged PR intervals and a tendency of increased atrial fibrillation inducibility in rats.

ВЛИЯНИЕ АРТЕРИАЛЬНОЙ ГИПЕРТЕНЗИИ И ХРОНИЧЕСКОЙ СЕРДЕЧНОЙ НЕДОСТАТОЧНОСТИ НА ЭФФЕКТИВНОСТЬ ВОССТАНОВЛЕНИЯ СИНУСОВОГО РИТМА У БОЛЬНЫХ С ТРЕПЕТАНИЕМ ПРЕДСЕРДИЙ

The use of overdrive transesophageal cardiac pacing (OTECP) in atrial flutter (AF) can reduce the number of external electrical cardioversion (EEC) in arrhythmia refractory to drug-induced cardioversion. The conversion of AF to atrial fibrillation (AFib) with subsequent spontaneous sinus rhythm (SR) restoration with the help of OTECP and accompanying antiarrhythmic therapy (AAT) was carried out in 59 patients with diseases of the cardiovascular system aged 40 to 77 years. The duration of AF before pacing was 35.93 ± 5.25 days. The efficiency of OTECP was 71.19%, and the time for spontaneous SR restoration was on average 16.92 ± 2.67 h. During pacing, the combined AAT has no advantages over monotherapy, despite its higher efficiency before OTECP. The obtained results indicate that the duration of AF prior to the OTECP procedure did not affect either the effectiveness of the procedure or the timing of spontaneous SR restoration. Inadequate control of blood pressure during treatment was a risk factor for reducing the effectiveness of OTECP, and contributed to the persistence or recurrence of arrhythmia. In patients with AF without AH, a decrease in left ventricular contractility and severe grade of CHF with an increase in left ventricular chamber dimension at end systole, a decrease in ejection fraction (EF) and fractional shortening (FS), reduces the likelihood of spontaneous SR restoration after OTECP, while additional administration of digoxin to increase myocardial contractility did not influence the effectiveness the therapy being carried out. The enlarged dimensions of the left atrium, which did not go beyond the critical dimensions, also had no influence on the effectiveness of the therapy. The efficiency of SR restoration against the background of AAT was 71.19%. Taking into account the EEC accompanied by the treatment performed corresponds to 83.05%. The effectiveness of OTECP when performed on the background of mono- or combined AAT did not differ significantly and amounted to 70.83 and 71.43%, as well as the terms of spontaneous SR restoration — 16.94 ± 2.86 and 16.89 ± 2, 48 hours respectively. The effectiveness of OTECP during mono- or combined AAT was 70.83% and 71.43%, respectively, and the time for spontaneous SR restoration was 16.94 ± 2.86 and 16.89 ± 2.48 hours. Medicamentous cardioversion of AF prior to the OTECP procedure is effective in 54.29% of cases and only with the combined AAT.

Cardiomyocyte-GSK-3β deficiency induces cardiac progenitor cell proliferation in the ischemic heart through paracrine mechanisms.

Cardiomyopathy is an irreparable loss and novel strategies are needed to induce resident cardiac progenitor cell (CPC) proliferation in situ to enhance the possibility of cardiac regeneration. Here, we sought to identify the potential roles of glycogen synthase kinase-3β (GSK-3β), a critical regulator of cell proliferation and differentiation, in CPC proliferation post-myocardial infarction (MI). Cardiomyocyte-specific conditional GSK-3β knockout (cKO) and littermate control mice were employed and challenged with MI. Though cardiac left ventricular chamber dimension and contractile functions were comparable at 2 weeks post-MI, cKO mice displayed significantly preserved LV chamber and contractile function versus control mice at 4 weeks post-MI. Consistent with protective phenotypes, an increased percentage of c-kit-positive cells (KPCs) were observed in the cKO hearts at 4 and 6 weeks post-MI which was accompanied by increased levels of cardiomyocyte proliferation. Further analysis revealed that the observed increased number of KPCs in the ischemic cKO hearts was mainly from a cardiac lineage, as the majority of identified KPCs were negative for the hematopoietic lineage marker, CD45. Mechanistically, cardiomyocyte-GSK-3β profoundly suppresses the expression and secretion of growth factors, including basic-fibroblast growth factor, angiopoietin-2, erythropoietin, stem cell factor, platelet-derived growth factor-BB, granulocyte colony-stimulating factor, and vascular endothelial growth factor, post-hypoxia. In conclusion, our findings strongly suggest that loss of cardiomyocyte-GSK-3β promotes cardiomyocyte and resident CPC proliferation post-MI. The induction of cardiomyocyte and CPC proliferation in the ischemic cKO hearts is potentially regulated by autocrine and paracrine signaling governed by dysregulated growth factors post-MI. A strategy to inhibit cardiomyocyte-GSK-3β could be helpful for the promotion of in situ cardiac regeneration post-ischemic injury.

Trimetazidine Attenuates Heart Failure by Improving Myocardial Metabolism via AMPK.

Energic deficiency of cardiomyocytes is a dominant cause of heart failure. An antianginal agent, trimetazidine improves the myocardial energetic supply. We presumed that trimetazidine protects the cardiomyocytes from the pressure overload-induced heart failure through improving the myocardial metabolism. C57BL/6 mice were subjected to transverse aortic constriction (TAC). After 4 weeks of TAC, heart failure was observed in mice manifested by an increased left ventricular (LV) chamber dimension, an impaired LV ejection fraction evaluated by echocardiography analysis, which were significantly restrained by the treatment of trimetazidine. Trimetazidine restored the mitochondrial morphology and function tested by cardiac transmission electron microscope and mitochondrial dynamic proteins analysis. Positron emission tomography showed that trimetazidine significantly elevated the glucose uptake in TAC mouse heart. Trimetazidine restrained the impairments of the insulin signaling in TAC mice and promoted the translocation of glucose transporter type IV (GLUT4) from the storage vesicle to membrane. However, these cardioprotective effects of trimetazidine in TAC mice were notably abolished by compound C (C.C), a specific AMPK inhibitor. The enlargement of neonatal rat cardiomyocyte induced by mechanical stretch, together with the increased expression of hypertrophy-associated proteins, mitochondria deformation and dysfunction were significantly ameliorated by trimetazidine. Trimetazidine enhanced the isolated cardiomyocyte glucose uptake in vitro. These benefits brought by trimetazidine were also removed with the presence of C.C. In conclusion, trimetazidine attenuated pressure overload-induced heart failure through improving myocardial mitochondrial function and glucose uptake via AMPK.

Abstract P409: GSK-3β Deficiency In Cardiomyocyte Induces Cardiac Progenitor Cell Proliferation In The Ischemic Heart

The cardiomyocytes are terminally differentiated cells and ischemia-induced cardiomyopathy is an irreparable loss. Novel strategies are needed to induce resident cardiac progenitor cells (CPCs) proliferation in situ to enhance the possibility of cardiac regeneration. Here we sought to identify a potential role for glycogen synthase kinase-3β (GSK-3β), a critical regulator of cell proliferation and differentiation, in CPCs proliferation in the ischemic heart. Cardiomyocyte-specific conditional GSK-3β knockout (cKO) and littermate control mice were recruited and challenged with myocardial infarction (MI). The cardiac function was assessed using trans-thoracic M-mode echocardiography. The level of CPC proliferation in the ischemic cKO hearts was determined at 2, 4 and 8 weeks post-MI through immunofluorescence labeling of stem cell marker c-Kit. To confirm the lineage of identified c-Kit -positive cells (KPCs) in the heart, a hematopoietic lineage marker was stained along with c-Kit. The cardiac left ventricular chamber dimension (LVID) and contractile functions were comparable until 2 weeks post-MI. The cKO mice displayed significantly preserved LV chamber [LVIDd(mm); 5.01±0.67 vs.6.09±0.65, p =0.01] and contractile function [LVEF(%); 31.98±8.52 vs. 18.06±7.11., p =0.01] in comparison to control mice at 4 week post-MI. Consistent with protective phenotypes, an increased percentage of KPC was observed in the cKO hearts at 4 and 6-weeks post-MI which was accompanied by an increased level of cardiomyocyte proliferation. Further analysis revealed that the observed increased number of KPCs in the ischemic cKO hearts were mostly from a cardiac lineage as the majority of identified KPCs were negative for the hematopoietic marker, CD45. In conclusion, our findings strongly suggest that GSK-3β inhibits CPCc proliferation post-ischemia, and loss of GSK-3β in cardiomyocytes promotes resident CPCc proliferation potentially through paracrine mechanisms.

Long‐term Consumption of Artificial Sweeteners Does not Affect Cardiovascular Function but May Cause Cardiac Electrophysiological Abnormalities in Rats

Introduction Artificial sweeteners are commonly used as sugar substitutes. Because they have virtually no calories, they are believed to be useful in combatting obesity, metabolic syndrome, and diabetes. However, there is still uncertainty about their potential health problems. Recent population studies have suggested that consumption of artificial sweeteners was associated with adverse cardiovascular events - in particular, increasing coronary artery disease, stroke and all-cause mortality. Nevertheless, those population association studies cannot establish a causal relationship. We hypothesized that long-term consumption of artificial sweeteners could cause cardiovascular dysfunction. Thus, in this study we investigated the effect of long-term (1 year) consumption of artificial sweeteners (Equal and Splenda, 2 commonly used artificial sweeteners) in drinking water on cardiovascular health in rats. Methods Adult Sprague-Dawley rats (both sexes, 4-5 months old) were randomized into the following 3 groups: control group (n=21), artificial sweetener Equal group (n=21) and Splenda group (n=18). In the artificial sweetener groups, Equal or Splenda (at concentration of 2 packs per cup of water) was added to the drinking water, while drinking water alone was used in the control rats. The treatment was administered for 12 months. At the end of the treatment, blood pressure, pulse wave velocity (an index of arterial stiffness), left ventricular pressure and cardiac function were measured using catheter approach and echocardiography. ECG and cardiac electrophysiology was determined using intracardiac catheter approach. Blood glucose and lipids levels were also measured. Results Rats consistently consumed more sweetened water in both Equal and Splenda groups than that in the control group (e.g., 45±6ml in control, 72±5ml in Equal and 74±14ml in Splenda groups at 2 week treatment, P<0.01). The body weight was comparable among the 3 groups. The blood pressure and pulse wave velocity were not altered after 1-year treatment. There were no significant differences in left ventricular wall thicknesses, chamber dimension and cardiac function evaluated with cardiac echocardiography and left ventricular hemodynamic at the end of the experiment. There were no differences in blood lipids and glucose levels. Artificial sweeteners did not affect heart rate and atrial effective refractory period. However, rats in both Equal and Splenda groups had longer PR intervals (63±5ms in Equal, 68±6 ms in Splenda, vs 56±8ms in control, p<0.01) and a tendency of increased atrial fibrillation inducibility (60% in Equal, 70% in Splenda vs 31% in control). The survival (15/21 in Equal, 10/18 in Splenda, and 16/21 in control) was not significantly affected by the 1-year treatment. Conclusions Long-term consumption of artificial sweeteners in drinking water did not affect blood glucose and lipids levels. The artificial sweeteners did not affect blood pressure and cardiovascular function but caused some electrophysiological abnormalities with prolonged PR interval and a tendency of increased atrial fibrillation inducibility in rats. The 1-year survival was not significantly affected in these animals.

Epigenetic Mechanisms Underlying Anthracycline-Induced Cardiotoxicity

We sought to develop a mouse model of pediatric anthracycline cardiotoxicity to test our hypothesis for an epigenetic mechanism (including epigenetic memory), which may be operating to explain delayed-onset anthracycline-induced cardiotoxicity. Three week-old male and female C57Bl/6J mice were administered 5 weekly injections with low-dose doxorubicin (1mg/kg) (n=24) or saline (n=8). Half of the doxorubicin-treated (DOX) mice (n=12) and all controls (n=8) were sacrificed 1 week after the last injection; the rest of DOX mice (n=12) were given 4 weeks of drug-free holiday before sacrifice. Echocardiographic measurements were obtained before the first injection, 1 week after the final injection, and before sacrifice. Gene expression profiles were assessed by RNA-sequencing, genome-wide DNA methylation by reduced representation bisulphite sequencing (RRBS), and chromatin accessibility by ATAC-seq. These analyses were performed on purified pools of isolated cardiac myocytes, procured using a published Langendorff-free method. With the selected dosing regimen, there was no death in either the DOX or control mice. Left ventricular chamber dimension and wall thickness as well as fractional shortening did not differ between DOX and controls, implying the lack of obvious functional insufficiency from this dose of DOX. Similarly, DOX mice did not differ in body weight, heart weights (HW), and HW-to-tibia length ratios compared with controls. Cardiomyocyte dimensions and myocardial interstitial fibrosis (using picrosirius red) were the same between groups. Despite the lack of echocardiographic and histological changes in DOX mice, RNA-sequencing analysis revealed profound and significant differentially expressed genes between the DOX mice and controls. Importantly, a significant proportion of downregulated and upregulated genes persisted, despite the period of drug-free holiday (Figure 1). Moreover, despite being taken off DOX, cardiomyocytes appeared to display new gene expression changes taking place even 4 weeks after stopping DOX. Detailed results of RNA-sequencing, RRBS and ATAC-Seq will be presented during the meeting. These results suggest that cardiomyocytes display DOX-related epigenetic alterations, which may implicate the basis for delayed-onset anthracycline-induced cardiotoxicity.

N-Acetylcysteine prevents the decreases in cardiac collagen I/III ratio and systolic function in neonatal mice with prenatal alcohol exposure

Prenatal alcohol exposure (PAE) is often associated with congenital heart defects, most commonly septal, valvular, and great vessel defects. However, there have been no known studies on whether PAE affects the resulting fibroblast population after development, and whether this has any consequences in the postnatal period. Our previous study focused on the effects of PAE on the postnatal fibroblast population, which translated into changes in cardiac extracellular matrix (ECM) composition and cardiac function in the neonatal heart. Moreover, our lab has previously demonstrated that alcohol-induced fibrosis is mediated by oxidative stress mechanisms in adult rat hearts following chronic alcohol exposure. Thus, we hypothesize that PAE alters cardiac ECM composition that persists into the postnatal period, leading to cardiac dysfunction, and these effects are prevented by antioxidant treatment. To investigate these effects, pregnant mice were intraperitoneally injected with 2.9 g EtOH/kg body weight on gestation days 6.75 and 7.25. Controls were injected with vehicle saline. Randomly selected dams in both groups were then treated with 100 mg/kg body weight of the antioxidant N-acetylcysteine (NAC) immediately after EtOH or vehicle administration. Left ventricular (LV) chamber dimension and function were assessed in sedated animals on neonatal day 5 using echocardiography. Ejection fraction decreased in the PAE group. NAC treatment prevented this depression of systolic function in PAE neonates. Hearts were analyzed for expression of fibroblast activation markers. Alpha smooth muscle actin (α-SMA) increased in PAE neonatal hearts, and this increase was prevented by NAC treatment. In PAE pups, collagen I decreased, but collagen III expression increased compared to saline animals; the overall collagen I/III ratio significantly decreased. When PAE mice were treated with NAC, collagen I/III ratio did not change. Overall, our data demonstrate that prenatal alcohol exposure produces changes in collagen subtype in neonatal cardiac ECM and a decline in systolic function, and these adverse effects were prevented by NAC treatment.

Prenatal Alcohol Exposure Causes Adverse Cardiac Extracellular Matrix Changes and Dysfunction in Neonatal Mice.

Fetal alcohol syndrome (FAS) is the most severe condition of fetal alcohol spectrum disorders (FASD) and is associated with congenital heart defects. However, more subtle defects such as ventricular wall thinning and cardiac compliance may be overlooked in FASD. Our studies focus on the role of cardiac fibroblasts in the neonatal heart, and how they are affected by prenatal alcohol exposure (PAE). We hypothesize that PAE affects fibroblast function contributing to dysregulated collagen synthesis, which leads to cardiac dysfunction. To investigate these effects, pregnant C57/BL6 mice were intraperitoneally injected with 2.9g EtOH/kg dose to achieve a blood alcohol content of approximately 0.35 on gestation days 6.75 and 7.25. Pups were sacrificed on neonatal day 5 following echocardiography measurements of left ventricular (LV) chamber dimension and function. Hearts were used for primary cardiac fibroblast isolation or protein expression analysis. PAE animals had thinner ventricular walls than saline exposed animals, which was associated with increased LV wall stress and decreased ejection fraction. In isolated fibroblasts, PAE decreased collagen I/III ratio and increased gene expression of profibrotic markers, including α-smooth muscle actin and lysyl oxidase. Notch1 signaling was assessed as a possible mechanism for fibroblast activation, and indicated that gene expression of Notch1 receptor and downstream Hey1 transcription factor were increased. Cardiac tissue analysis revealed decreased collagen I/III ratio and increased protein expression of α-smooth muscle actin and lysyl oxidase. However, Notch1 signaling components decreased in whole heart tissue. Our study demonstrates that PAE caused adverse changes in the cardiac collagen profile and a decline in cardiac function in the neonatal heart.

Role of type 2A phosphatase regulatory subunit B56α in regulating cardiac responses to β-adrenergic stimulation in vivo.

AimsB56α is a protein phosphatase 2A (PP2A) regulatory subunit that is highly expressed in the heart. We previously reported that cardiomyocyte B56α localizes to myofilaments under resting conditions and translocates to the cytosol in response to acute β-adrenergic receptor (β-AR) stimulation. Given the importance of reversible protein phosphorylation in modulating cardiac function during sympathetic stimulation, we hypothesized that loss of B56α in mice with targeted disruption of the gene encoding B56α (Ppp2r5a) would impact on cardiac responses to β-AR stimulation in vivo.Methods and resultsCardiac phenotype of mice heterozygous (HET) or homozygous (HOM) for the disrupted Ppp2r5a allele and wild type (WT) littermates was characterized under basal conditions and following acute β-AR stimulation with dobutamine (DOB; 0.75 mg/kg i.p.) or sustained β-AR stimulation by 2-week infusion of isoproterenol (ISO; 30 mg/kg/day s.c.). Left ventricular (LV) wall thicknesses, chamber dimensions and function were assessed by echocardiography, and heart tissue collected for gravimetric, histological, and biochemical analyses. Western blot analysis revealed partial and complete loss of B56α protein in hearts from HET and HOM mice, respectively, and no changes in the expression of other PP2A regulatory, catalytic or scaffolding subunits. PP2A catalytic activity was reduced in hearts of both HET and HOM mice. There were no differences in the basal cardiac phenotype between genotypes. Acute DOB stimulation induced the expected inotropic response in WT and HET mice, which was attenuated in HOM mice. In contrast, DOB-induced increases in heart rate were unaffected by B56α deficiency. In WT mice, ISO infusion increased LV wall thicknesses, cardiomyocyte area and ventricular mass, without LV dilation, systolic dysfunction, collagen deposition or foetal gene expression. The hypertrophic response to ISO was blunted in mice deficient for B56α.ConclusionThese findings identify B56α as a potential regulator of cardiac structure and function during β-AR stimulation.

Abstract 405: Antioxidant Treatment Prevents Profibrotic Changes And Cardiac Dysfunction In Prenatal Alcohol Exposure

Prenatal ethanol exposure is often associated with cardiac defects. Our studies focus on the role of cardiac fibroblasts in the developing heart, and how they are affected by prenatal ethanol exposure. There have been numerous studies demonstrating the protective effects of antioxidant treatment against alcohol-induced injury during cardiac development. Thus, we hypothesize that in utero ethanol (EtOH) exposure creates oxidative stress and activates neonatal cardiac fibroblasts, leading to a profibrotic phenotype and cardiac dysfunction. Further, we hypothesize that these effects are prevented by antioxidant treatment. We performed in utero EtOH administration to C57/BL6 mice on gestation days 6.75 and 7.5. Dams were intraperitoneally injected with 2.9 g EtOH/kg body weight to produce a blood EtOH content of ~0.26 g/dL each time. Controls were injected with vehicle saline. Randomly selected dams in both groups were treated with 100 gram/kg body weight of the antioxidant N-acetylcysteine (NAC) immediately after EtOH or vehicle administration. Left ventricular (LV) chamber dimension and function were assessed in sedated animals on neonatal day 5 using echocardiography. Eccentric index was calculated as a ratio of LV interior diameter and LV posterior wall thickness*2 at diastole. Eccentric index increased in EtOH-exposed animals (2.2±0.1 EtOH vs 1.8±0.1 saline, p&lt;0.05). There were no changes in EtOH animals treated with NAC (1.9±0.1, NS). Additionally, ejection fraction decreased in the EtOH group (60±2% EtOH vs 68±2% saline). NAC treatment prevented this depression of systolic function in EtOH-exposed neonates (72±2%). Hearts were analyzed for expression of profibrotic proteins. In EtOH-exposed pups, collagen I decreased (0.02±.01 vs 0.04±.01 au), but collagen III expression increased (0.21±.02 vs 0.13±.01 au) compared to saline animals; the overall collagen I/III ratio significantly decreased (0.47±0.07 vs 1.0±0.17). When EtOH-exposed mice were treated with NAC, collagen I/III ratio did not change (0.83±0.11). Overall, our data demonstrate that in utero EtOH exposure produces a profibrotic phenotype in neonatal hearts and a decline in both diastolic and systolic function. These adverse effects were prevented by antioxidant treatment.

Morphological changes and myocardial function assessed by traditional and novel echocardiographic methods in preadolescent athlete's heart.

Background Athlete's heart is a term used to describe the morphological and functional changes in the hearts of athletes. Recent studies suggest that these changes may occur even in preadolescent athletes. This study aims to improve our understanding of the changes occurring in the preadolescent athlete's heart. Design and methods Cardiac morphology and function in 76 preadolescent cross-country skiers (aged 12.1 ± 0.2 years) were compared with 25 age-matched non-competing preadolescents. Echocardiography was performed in all subjects, including 2D speckle-tracking strain echocardiography and 3D echocardiography. All participants underwent cardiopulmonary exercise testing to assess oxygen uptake and exercise capacity. Results Athletes had greater indexed VO2 max (62 ± 7 vs. 44 ± 5 mL/kg per min, p < 0.001), indexed left ventricular end-diastolic volume (79 ± 7 vs. 68 ± 7 mL/m2, p < 0.001), left ventricular mass (69 ± 12 vs. 57 ± 13 g/m2, p < 0.001), indexed right ventricular basal diameter (28.3 ± 3.0 vs. 25.4 ± 3.5 mm/m2, p < 0.001) and right atrial area (10.6 ± 1.4 vs. 9.7 ± 1.2 cm2/m2, p < 0.01). There was no difference in left ventricular ejection fraction, global longitudinal strain, and global circumferential strain and right ventricular fractional area change between the groups. Controls had higher right ventricular global longitudinal strain (-28.1 ± 3.5 vs. -31.1 ± 3.3%, p < 0.01). VO2 max was highly correlated to left ventricular end-diastolic volume ( r = 0.76, p < 0.001). Conclusion Athletes had greater left ventricular mass and greater left and right ventricular chamber dimensions compared with controls, while left ventricular function did not differ. Interestingly, right ventricular deformation was significantly lower compared with controls. This supports the notion that there is physiological, adaptive remodelling in preadolescent athlete's heart.

In utero alcohol exposure alters the collagen profile in neonatal hearts and leads to cardiac dysfunction

Fetal alcohol syndrome is often associated with congenital heart defects. Our studies focus on the role of cardiac fibroblasts in the developing heart, and how they are affected by prenatal ethanol exposure. Fibroblasts are the most numerous cardiac cell type and play an essential role in development of the heart. They are responsible for synthesis of the extracellular matrix, which provides the scaffold for heart muscle. Our lab has previously shown that ethanol exposure in adult hearts promote fibroblast activation and transition into myofibroblasts. Based on this, we believe that in utero ethanol exposure causes alterations in fibroblast function that could contribute to dysregulation in collagen synthesis and impaired scaffolding of the neonatal heart. Therefore, we hypothesize that in utero ethanol activates neonatal cardiac fibroblasts, which leads to a profibrotic phenotype and cardiac dysfunction.To investigate these effects, we performed in utero EtOH administration in wildtype dams. Pregnant mice were intraperitoneally injected with 2.9 g EtOH/kg body weight to achieve a blood ethanol content of approximately 0.26 on gestation day 6.75. On neonatal day 5, pups were weighed prior to sacrifice. Body weight was decreased in the WT+EtOH pups, which is a hallmark of fetal alcohol syndrome. Hearts were homogenized, and Western Blot analysis was performed to determine protein expression. Collagen I decreased in ethanol exposed neonates, but collagen III expression was significantly increased, so the collagen I/III ratio was decreased. Collagen I gives hearts a more tensile and stiff phenotype, whereas collagen III gives a more compliant phenotype; therefore, a decrease in collagen I/III ratio would correlate with a dilated heart. Subsequently, this can significantly impair diastolic function. Overall, our data shows a correlation between prenatal ethanol exposure and a profibrotic phenotype in neonatal hearts.We were further interested in assessing whether these changes in collagen translated into changes in cardiac function. Left ventricular (LV) chamber dimension and function were assessed in sedated animals on neonatal day 5 using echocardiography. Eccentric index was calculated as a ratio of LV interior diameter and LV posterior wall thickness*2 at diastole and at systole. There was a significant increase in the eccentric index at both systole and diastole in ethanol exposed animals, indicative of LV dilation. This is in agreement with our previous collagen findings, which further supports the possibility of a dilated cardiac phenotype. In analyzing systolic function, LV end systolic volume increased, and both ejection fraction and fractional shortening decreased in the ethanol treated animals. Our functional measurements demonstrate that in utero ethanol exposure decreases collagen I/III protein ratio in neonatal hearts, which ultimately causes a decline in both diastolic and systolic function.Support or Funding InformationSaving Tiny Hearts SocietyThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Novel Histone Deacetylase (HDAC) Inhibitor Attenuates Cardiac Dysfunction in the Setting of Pressure Overload Heart Failure

Background: Histone deacetylases (HDACs) are a family of epigenetic regulator enzymes responsible for chromatin conformation and reversible protein acetylation. HDAC inhibitors have previously been shown to be cardioprotective in acute myocardial infarction and heart failure. HDAC inhibition is thought to attenuate cardiac remodeling and improve cardiac function by enhancing acetylation of sarcomeric proteins, suppressing autophagy and apoptosis, bolstering protective genes and inhibiting pro-inflammatory genes. Objective: We investigated the efficacy of a novel, orally active HDAC class I inhibitor, MRL-003, in a murine model of pressure overload induced heart failure. Methods and Results: All studies were performed in a fully blinded manner, data analysis was performed off site by independent statisticians, and data was only unblinded following completion of statistical analysis of all parameters. Mice (C57 BL6J) at age 8-10 weeks were subjected to transverse aortic constriction (TAC) to induce pressure overload heart failure. Cardiac function was monitored sequentially using echocardiography and terminal hemodynamic measurements were taken. At 3 weeks post-TAC 3 doses (10, 30, and 100 mg/kg/day) of MRL-003 were provided to the mice in a blinded manner in chow ad libitum for 13 weeks. MRL-003 (100 mg/kg/d) significantly improved left ventricular (LV) ejection fraction and LV chamber dimensions compared to TAC-vehicle. LV end-diastolic pressure (LVEDP) was significantly increased in the vehicle treated group compared to sham and there was no significant difference in LVEDP in mice treated with MRL-003 (100 mg/kg/d) compared to sham. Conclusion: HDAC inhibition with MRL-003 significantly improves cardiac function and remodeling in the setting of pressure overload heart failure. Further studies are warranted to assess the molecular changes associated with these functional improvements.