Cardiac Dilatation Research Articles

Electrocardiographic markers of myocardial conduction and repolarization in Boxer dogs

ABSTRACT: Electrocardiographic markers have been used in people to classify arrhythmogenic risk. The aims of this study were to investigate electrocardiographic markers of conduction and repolarization in Boxers and non-Boxer dogs, and compare such findings between groups. Ten-lead standard electrocardiograms of Boxer dogs and non-Boxers recorded from 2015 to 2018 were retrospectively reviewed. Dogs ≥4 years of age and weighing >20kg were included. Animals with valvular insufficiencies, congenital cardiopathies, cardiac dilation, suspected systolic dysfunction, biphasic T-wave, bundle branch blocks, and those receiving antiarrhythmics were excluded. Electrocardiographic markers of conduction, QRS duration (QRSd) and dispersion (QRSD), and repolarization (corrected QT interval, Tpeak-Tend, JT and JTpeak), as well as derived indices, were measured. Two hundred dogs met the inclusion/exclusion requirements, including 97 Boxers (8.1±2.5 years old; 30±7kg) and 103 non-Boxer (8.8±2.5 years old, 30±8kg). QRSd and QRSD, and repolarization markers in lead II and left precordial lead V4 were considered similar between groups. Dispersion of late repolarization on lead rV2, Tpeak-Tend interval, was considered longer in Boxers (45±8ms vs 38±10ms, P=0.01). The Tpeak-Tend/JTpeak and the JTpeak/JT also differed between groups. Our results indicate that the dispersion of myocardial late repolarization in lead rV2 is slower in Boxers than other dog breeds.

Abstract 547: Hur Dependent Regulation of Inflammatory Remodeling Following Myocardial Ischemia/reperfusion Injury

Myocardial infarction (MI), resulting from ischemia/reperfusion (I/R) injury due to the obstruction of coronary blood flow, affects an estimated 800,000 Americans annually resulting in a cost of nearly 12 billion dollars to the health care system. Recent medical advances have led to improved survival following acute MI, but unfortunately, the post-MI inflammatory and fibrotic remodeling of the heart is driving an increase in the prevalence of heart failure. Preliminary data from our lab shows that the RNA binding protein Human antigen R (HuR) undergoes nuclear-to-cytoplasmic translocation within 30 minutes and is increased in expression at both 2 hours and 7 days post-I/R. The objective of this work is to determine the mechanistic role of HuR on the regulation of cardiac cytokine/chemokine expression and the functional effect of HuR on macrophage infiltration and polarization post-I/R. Wild-type mice were subjected to 30 minutes of LAD (left anterior descending) coronary artery ligation (ischemia) followed by reperfusion with HuR inhibitor or vehicle control administered at the start of reperfusion. Our results show that inhibition of HuR reduces cardiac mRNA expression of IL-6, TNF-alpha, and ICAM-1 at 2 hours post-reperfusion, but does not affect initial (24 hour) infarct size. In addition, HuR inhibition reduces macrophage infiltration at 7 days post-I/R, as well as cardiac fibrosis and ventricular dilation while preserving cardiac function at 14 days post-I/R. Furthermore, H9c2s treated with HuR inhibitor blunts the mRNA expression of CCL2 after acute stimulation of lipopolysaccharide. In conclusion, we show that HuR inhibition at the time of reperfusion is protective against post-MI inflammatory and fibrotic remodeling through a reduction in inflammatory gene expression and macrophage infiltration. Previous work by the lab has demonstrated a direct role for HuR in cardiac myocytes, but these results also suggest that HuR-mediated gene expression in macrophages may play a role in post-MI inflammatory and fibrotic remodeling.

Abstract 339: Runx1 Knock-down by Adeno Associated Viral Mediated-delivery of Short Hairpin RNA Preserves Cardiac Contractility Following Myocardial Infarction

Myocardial infarction (MI) is a leading cause of heart failure (HF) and mortality worldwide. Preservation of contractile function and prevention of adverse cardiac remodelling following MI are essential to limit progression to HF. Expression of the Runx1 transcription factor in border zone cardiomyocytes is increased within 24 hours after MI. Genetically modified mice with Runx1 deficiency demonstrate an absence of cardiac dilation and preservation of left ventricular (LV) contractility following MI without a change of infarct size. Here, we investigate if adeno-associated viral (AAV)-mediated gene transfer to knock-down Runx1 expression post-MI attenuates adverse cardiac remodelling in mice. Male C57BL/6J mice underwent LAD ligation followed by intravenous injection of AAV-Runx1-shRNA or control AAV-scramble-shRNA (1x10 11 viral genomes). LV contractility (% fractional shortening, FS) was assessed by M-mode echocardiography. RNAscope assessed Runx1 expression in border zone cardiomyocytes and infarct size was histologically quantified using Picro sirius red stain. Runx1 expression within border zone cardiomyocytes was reduced by 30% in AAV-Runx1-shRNA treated mice (37.8±4.5 vs. 53.9±6.4% of cardiomyocytes; AAV-Runx1-shRNA vs. control). LV contractile function was significantly preserved as early as 1 day post-MI (%FS, day 1; 37.7±1.4 vs . 27.6±1.4, day 7; 37.2 ±1.2 vs .28.2±1.4; LV internal dimension during systole day 1; 2.9±0.2 vs . 2.4±0.1, day 7; 3.1±0.2 vs . 2.5±0.1mm; AAV-Runx1-shRNA vs. control, P <0.05). Interestingly, infarct size was reduced with AAV-Runx1-shRNA (31.7±2.0 vs . 40.4±1.4% of LV; AAV-Runx1-shRNA vs . control, P <0.05). In conclusion, a therapeutic approach utilising AAV-mediated knock-down of Runx1 preserved LV contractility and reduced infarct size following MI. These data further highlight Runx1 as a key driver of adverse cardiac remodelling and a therapeutic target with translational potential to prevent adverse cardiac remodelling following MI.

Over-expression of microRNA-145 drives alterations in β-adrenergic signaling and attenuates cardiac remodeling in heart failure post myocardial infarction.

Background: Numerous studies have highlighted the crucial role of microRNA-145 (miR-145) in coronary atherosclerosis and myocardial ischemia reperfusion injury. However, effects of miR-145 on β-adrenergic signaling and cardiac remodeling in heart failure (HF) remains unclarified.Methods and Results: We established HF model in rats with left anterior descending coronary artery (LAD) occlusion. Four weeks after LAD ligation, rats showed substantial aggravation of cardiac dilation and electrophysiological instability. Up-regulation of miR-145 ameliorated HF-induced myocardial fibrosis and prolonged action potential duration. Echocardiography revealed increased basal contractility and decreased left ventricular inner-diameter in miR-145 over-expressed heart, while cardiac response to β-adrenergic receptor (βAR) stimulation was reduced. Furthermore, miR-145 increased L-type calcium current (ICa) density while decreased ICa response to β-adrenergic stimulation with isoproterenol. The alterations in βAR signaling might be predominant due to miR-145-mediated activation of Akt/CREB cascades. At high frequency pacing, Ca2+ transient, cell shortening and frequency of Ca2+ waves were significantly improved in AD-miR-145 group. Western blotting revealed that increased expression of Cav1.2, Ca2+-ATPase, β2AR, GNAI3 and decreased level of CaMKII might be attributed to the cardioprotective effects of miR-145.Conclusion: miR-145 effectively alleviates HF-related cardiac remodeling by improving cardiac dilation, fibrosis, intracellular Ca2+ mishandling and electrophysiological instability.

The phospholamban p.(Arg14del) pathogenic variant leads to cardiomyopathy with heart failure and is unresponsive to standard heart failure therapy

Phospholamban (PLN) plays a role in cardiomyocyte calcium handling as primary inhibitor of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA). The p.(Arg14del) pathogenic variant in the PLN gene results in a high risk of developing dilated or arrhythmogenic cardiomyopathy with heart failure. There is no established treatment other than standard heart failure therapy or heart transplantation. In this study, we generated a novel mouse model with the PLN-R14del pathogenic variant, performed detailed phenotyping, and tested the efficacy of established heart failure therapies eplerenone or metoprolol. Heterozygous PLN-R14del mice demonstrated increased susceptibility to ex vivo induced arrhythmias, and cardiomyopathy at 18 months of age, which was not accelerated by isoproterenol infusion. Homozygous PLN-R14del mice exhibited an accelerated phenotype including cardiac dilatation, contractile dysfunction, decreased ECG potentials, high susceptibility to ex vivo induced arrhythmias, myocardial fibrosis, PLN protein aggregation, and early mortality. Neither eplerenone nor metoprolol administration improved cardiac function or survival. In conclusion, our novel PLN-R14del mouse model exhibits most features of human disease. Administration of standard heart failure therapy did not rescue the phenotype, underscoring the need for better understanding of the pathophysiology of PLN-R14del-associated cardiomyopathy. This model provides a great opportunity to study the pathophysiology, and to screen for potential therapeutic treatments.

The Effects of L-Carnitine on Echocardiographic Changes in Patients With β-Thalassemia Major and Intermedia.

Heart failure, fatal arrhythmias, and cardiac dilatation because of anemia are common causes of β-thalassemia major-related deaths. The aim of this study was to determine the effect of L-carnitine on echocardiographic changes in β-thalassemia major and intermedia patients in Besat Hospital in Sanandaj, Iran. In a randomized clinical trial, 60 β-thalassemia patients who were eligible for L-carnitine administration were randomly divided into 2 placebo and study drug groups. The duration of the study was 6 months. Using echocardiography and blood tests, cardiac parameters including left ventricular dilatation, left ventricular hypertrophy, and a number of cardiac blood indices were examined before and after the intervention. The data were analyzed using SPSS V.23 software, χ, and covariance statistical tests. There was no significant difference between the 2 groups in terms of age and sex. Patients treated with L-carnitine have a reduced rate of left ventricular dilatation, left ventricular hypertrophy, and systolic blood pressure compared with controls (P<0.05). Cardiac output increased from 43.5 to 56.5 (P=0.002). The results of this study showed that the drug has a positive effect on the improvement of cardiac indices in β-thalassemia patients. Therefore, we suggest that further studies with more samples and other diagnostic modalities of the drug's effect be investigated.

Bi-allelic missense disease-causing variants in RPL3L associate neonatal dilated cardiomyopathy with muscle-specific ribosome biogenesis

Dilated cardiomyopathy (DCM) belongs to the most frequent forms of cardiomyopathy mainly characterized by cardiac dilatation and reduced systolic function. Although most cases of DCM are classified as sporadic, 20–30% of cases show a heritable pattern. Familial forms of DCM are genetically heterogeneous, and mutations in several genes have been identified that most commonly play a role in cytoskeleton and sarcomere-associated processes. Still, a large number of familial cases remain unsolved. Here, we report five individuals from three independent families who presented with severe dilated cardiomyopathy during the neonatal period. Using whole-exome sequencing (WES), we identified causative, compound heterozygous missense variants in RPL3L (ribosomal protein L3-like) in all the affected individuals. The identified variants co-segregated with the disease in each of the three families and were absent or very rare in the human population, in line with an autosomal recessive inheritance pattern. They are located within the conserved RPL3 domain of the protein and were classified as deleterious by several in silico prediction software applications. RPL3L is one of the four non-canonical riboprotein genes and it encodes the 60S ribosomal protein L3-like protein that is highly expressed only in cardiac and skeletal muscle. Three-dimensional homology modeling and in silico analysis of the affected residues in RPL3L indicate that the identified changes specifically alter the interaction of RPL3L with the RNA components of the 60S ribosomal subunit and thus destabilize its binding to the 60S subunit. In conclusion, we report that bi-allelic pathogenic variants in RPL3L are causative of an early-onset, severe neonatal form of dilated cardiomyopathy, and we show for the first time that cytoplasmic ribosomal proteins are involved in the pathogenesis of non-syndromic cardiomyopathies.

ERBB2 Targeting Increases Cardiomyocyte β1-Adrenergic Receptor Density

Objective: To determine the underlying pathways that promote cardiotoxicity following anti-ERBB2 cancer therapeutics. Background: Epidermal growth factor receptor 2 (EGFR2/ERBB2) is a member of EGFR (ERBB) family represented by ERBB 1 through 4 that either homo- or hetero-dimerize to signal. ERBB2 has constitutively active confirmation but explicitly needs to hetero-dimerize with either ERBB1 or ERBB4 to mediate signaling and cardiac hypertrophy. Less is known about the mechanisms through which ERBB2 mediates the adaptive cardiac hypertrophy given that anti-ERBB2 therapeutics results in cardiac dilation of the otherwise healthy heart. Methods: We generated transgenic (Tg) mice with cardiomyocyte-specific overexpression of microRNA-7 (miRNA-7) that targets ERBB2. Echocardiography, immunohistochemistry and β-adrenergic receptor (βAR) density were assessed upon aging and transverse aortic constriction (TAC). To determine whether inhibition of ERBB2 has similar outcomes, C57Bl/6 mice were administered ERBB2-specific inhibitor AG825. Also, βAR density was assessed in end-stage human heart failure patient samples with Adriamycin cardiotoxicity. Results: Loss in ERBB2 expression due to miRNA-7 targeting or ERRB2 inhibition by AG 825 results in cardiac dilation. Loss of ERBB2 in miRNA-7 Tg mice leads to increased fibrosis post-TAC. Selective significant increase in β1AR density is observed in miRNA-7 Tg mice or in mice following ERBB2 inhibition by AG825 and in the human heart failure patient samples due to Adriamycin cardiotoxicity. Conclusions: Cardiomyocyte ERBB2 expression and function is required for maintaining the normal cardiac function. Targeting ERBB2 leads to selective and significant increase in β1ARs that may promote cardiac dilation and heart failure.

Short interposition with a small-diameter prosthetic graft for flow reduction of a high-flow arteriovenous fistula

ObjectiveThe objective of this study was to evaluate the outcome of a short interposition using a small-diameter prosthetic graft as a flow-limiting procedure to manage symptomatic high-flow arteriovenous fistula (AVF). MethodsA retrospective review of medical records on a case series was conducted. From June 2004 to April 2017, there were 25 patients with clinical symptoms of high output cardiac failure and progressive dilation of aneurysmal fistula vein due to high-flow AVF (≥1.5 L/min) who underwent short interposition with a 5-mm prosthetic graft at Saitama Medical Center. The primary outcome was the relief of clinical symptoms; other outcome measures included technical success, surgical complications, patency of vascular access, and postoperative changes in local and systemic hemodynamics as assessed by Doppler ultrasound. ResultsTwenty-five patients underwent short interposition for cardiac indications (n = 16) and aneurysmal dilation (n = 9). The technical success rate was 100%. The clinical symptoms were relieved in 24 patients (96.0%). Mean reduction in access blood flow was 52.4%. Cumulative primary unassisted patency rates (± standard error) at 1 year, 2 years, and 3 years were 76.2% ± 9.3%, 70.4% ± 10.3%, and 58.1% ± 11.6%, respectively. Secondary patency rates (± standard error) at 1 year, 2 years, and 3 years were 81.8% ± 8.2%, 71.5% ± 9.9%, and 71.5% ± 9.9%, respectively. Complications included access occlusion due to late thrombosis (n = 5 [21.7%]) and graft infection (n = 1 [4.3%]) in the median follow-up period of 3.9 years. ConclusionsShort interposition with a prosthetic graft is a simple, effective, and durable treatment option for end-stage renal disease patients with cardiac symptoms and progressive dilation of the fistula vein due to high-flow AVF, offering clinical symptom resolution while preserving the autologous behavior of the initial access.

S100A9 Links Inflammation and Repair in Myocardial Infarction.

The alarmin S100A9 has been identified as a potential therapeutic target in myocardial infarction. Short-term S100A9 blockade during the inflammatory phase post-myocardial infarction inhibits systemic and cardiac inflammation and improves cardiac function long term. To evaluate the impact of S100A9 blockade on postischemic cardiac repair. We assessed cardiac function, hematopoietic response, and myeloid phagocyte dynamics in WT (wild type) C57BL/6 mice with permanent coronary artery ligation, treated with the specific S100A9 blocker ABR-238901 for 7 or 21 days. In contrast to the beneficial effects of short-term therapy, extended S100A9 blockade led to progressive deterioration of cardiac function and left ventricle dilation. The treatment reduced the proliferation of Lin-Sca-1+c-Kit+ hematopoietic stem and progenitor cells in the bone marrow and the production of proreparatory CD150+CD48-CCR2+ hematopoietic stem cells. Monocyte trafficking from the spleen to the myocardium and subsequent phenotype switching to reparatory Ly6CloMerTKhi macrophages was also impaired, leading to inefficient efferocytosis, accumulation of apoptotic cardiomyocytes, and a larger myocardial scar. The transcription factor Nur77 (Nr4a1 [nuclear receptor subfamily 4 group A member 1]) mediates the transition from inflammatory Ly6Chi monocytes to reparatory Ly6Clo macrophages. S100A9 upregulated the levels and activity of Nur77 in monocytes and macrophages in vitro and in Ly6Chi/int monocytes in vivo, and S100A9 blockade antagonized these effects. Finally, the presence of reparatory macrophages in the myocardium was also impaired in S100A9-/- mice with permanent myocardial ischemia, leading to depressed cardiac function long term. We show that S100A9 plays an important role in both the inflammatory and the reparatory immune responses to myocardial infarction. Long-term S100A9 blockade negatively impacts cardiac recovery and counterbalances the beneficial effects of short-term therapy. These results define a therapeutic window targeting the inflammatory phase for optimal effects of S100A9 blockade as potential immunomodulatory treatment in acute myocardial infarction.

CITED4 Protects Against Adverse Remodeling in Response to Physiological and Pathological Stress.

Cardiac CITED4 (CBP/p300-interacting transactivators with E [glutamic acid]/D [aspartic acid]-rich-carboxylterminal domain4) is induced by exercise and is sufficient to cause physiological hypertrophy and mitigate adverse ventricular remodeling after ischemic injury. However, the role of endogenous CITED4 in response to physiological or pathological stress is unknown. To investigate the role of CITED4 in murine models of exercise and pressure overload. We generated cardiomyocyte-specific CITED4 knockout mice (C4KO) and subjected them to an intensive swim exercise protocol as well as transverse aortic constriction (TAC). Echocardiography, Western blotting, qPCR, immunohistochemistry, immunofluorescence, and transcriptional profiling for mRNA and miRNA (microRNA) expression were performed. Cellular crosstalk was investigated in vitro. CITED4 deletion in cardiomyocytes did not affect baseline cardiac size or function in young adult mice. C4KO mice developed modest cardiac dysfunction and dilation in response to exercise. After TAC, C4KOs developed severe heart failure with left ventricular dilation, impaired cardiomyocyte growth accompanied by reduced mTOR (mammalian target of rapamycin) activity and maladaptive cardiac remodeling with increased apoptosis, autophagy, and impaired mitochondrial signaling. Interstitial fibrosis was markedly increased in C4KO hearts after TAC. RNAseq revealed induction of a profibrotic miRNA network. miR30d was decreased in C4KO hearts after TAC and mediated crosstalk between cardiomyocytes and fibroblasts to modulate fibrosis. miR30d inhibition was sufficient to increase cardiac dysfunction and fibrosis after TAC. CITED4 protects against pathological cardiac remodeling by regulating mTOR activity and a network of miRNAs mediating cardiomyocyte to fibroblast crosstalk. Our findings highlight the importance of CITED4 in response to both physiological and pathological stimuli.

Retrospective Study of Intercalated Disk Defects Associated with Dilated Cardiomyopathy, Atrial Thrombosis, and Heart Failure in BALB/c Mice Deficient in IL4 Receptor α.

An increased incidence of dilated cardiomyopathy and atrial thrombosis was noted in a breeding colony of BALB/c mice deficient in IL4 receptor α. The condition affected mice of both sexes and of various ages, and extensive testing (microbiology, serology, histopathology) failed to ascertain the cause. Transmission electron microscopy of heart samples showed structural defects in the myocardial intercalated disks, characterized by unorganized and heavily convoluted arrangement with lower density and less prominent desmosomes and adherens junctions, widening of the intercellular space, myofibrillar lysis adjacent to intercalated disks, occasional sarcomere lysis with marked myofiber degeneration, vacuolation, accumulation of cell debris, and myelin figures. The intercalated disk contains cell adhesion molecules that form cell junctions, allowing contraction coupling of cardiomyocytes and the electrical and mechanical connection between cardiac fibers. Thus, defects at this level result in poor myocardial contraction, intracardiac blood stagnation, and consequently cardiac dilation with clinical signs of heart failure. The background strain or, potentially, the Cre-loxP-mediated recombination system used to create these mice may have contributed to the elevated incidence of cardiomyopathy and atrial thrombosis in this colony. Due to the backcrossing breeding scheme used, we cannot discount the emergence and colonywide dissemination of a spontaneous mutation that affects the intercalated disk. This report underscores the importance of carefully monitoring genetically modified mice colonies for unexpected phenotypes that may result from spontaneous or unintended mutations or enhanced strain background pathology.

Analysis of Cardiac Amyloidosis Progression Using Model-Based Markers.

Deposition of amyloid in the heart can lead to cardiac dilation and impair its pumping ability. This ultimately leads to heart failure with worsening symptoms of breathlessness and fatigue due to the progressive loss of elasticity of the myocardium. Biomarkers linked to the clinical deterioration can be crucial in developing effective treatments. However, to date the progression of cardiac amyloidosis is poorly characterized. There is an urgent need to identify key predictors for disease progression and cardiac tissue function. In this proof of concept study, we estimate a group of new markers based on mathematical models of the left ventricle derived from routine clinical magnetic resonance imaging and follow-up scans from the National Amyloidosis Center at the Royal Free in London. Using mechanical modeling and statistical classification, we show that it is possible to predict disease progression. Our predictions agree with clinical assessments in a double-blind test in six out of the seven sample cases studied. Importantly, we find that multiple factors need to be used in the classification, which includes mechanical, geometrical and shape features. No single marker can yield reliable prediction given the complexity of the growth and remodeling process of diseased hearts undergoing high-dimensional shape changes. Our approach is promising in terms of clinical translation but the results presented should be interpreted with caution due to the small sample size.

Genetic basis and molecular biology of cardiac arrhythmias in cardiomyopathies.

Cardiac arrhythmias are common, often the first, and sometimes the life-threatening manifestations of hereditary cardiomyopathies. Pathogenic variants in several genes known to cause hereditary cardiac arrhythmias have also been identified in the sporadic cases and small families with cardiomyopathies. These findings suggest a shared genetic aetiology of a subset of hereditary cardiomyopathies and cardiac arrhythmias. The concept of a shared genetic aetiology is in accord with the complex and exquisite interplays that exist between the ion currents and cardiac mechanical function. However, neither the causal role of cardiac arrhythmias genes in cardiomyopathies is well established nor the causal role of cardiomyopathy genes in arrhythmias. On the contrary, secondary changes in ion currents, such as post-translational modifications, are common and contributors to the pathogenesis of arrhythmias in cardiomyopathies through altering biophysical and functional properties of the ion channels. Moreover, structural changes, such as cardiac hypertrophy, dilatation, and fibrosis provide a pro-arrhythmic substrate in hereditary cardiomyopathies. Genetic basis and molecular biology of cardiac arrhythmias in hereditary cardiomyopathies are discussed.

Plasma levels of soluble TNF receptors are associated with cardiac function in patients with Chagas heart disease

BackgroundThe soluble receptors tumor necrosis factor-alpha (sTNFRs) can lead to an increase in the expression of tumor necrosis factor, increasing its detrimental to systemic inflammatory activation in Chagas cardiomyopathy (ChC). However, the correlation between sTNFRs levels, echocardiographic, and functional levels in patients with ChC remains unknown. This study aimed to verify the correlation between the plasma sTNFRs levels, echocardiographic, and NYHA functional levels in patients with ChC. MethodsSixty-four patients with ChD (54 ± 2 years, 44% males, NYHA I-II) were evaluated by anamnesis protocol, echocardiography, and plasma sTNFR1 and sTNFR2 measurement. Linear regression analysis and Student's t-test were used as appropriate. ResultsHigher plasma sTNFR1 and sTNFR2 levels were associate with worse systolic function (R2 = 0.10; p = 0.008 and R2 = 0.44; p < 0.001) and cardiac dilation (R2 = 0.13; p = 0.002 and R2 = 0.43; p < 0.001). Patients with systolic dysfunction and cardiac dilatation had higher sTNFRs levels (p < 0.001). There were no significant differences among NYHA functional classes for both sTNFRs. ConclusionPlasma sTNFR1 and sTNFR2 levels are associated with greater cardiac dilation and poor systolic function in ChC patients.

Cardiac remodeling secondary to chronic volume overload is attenuated by a novel MMP9/2 blocking antibody.

ObjectiveMonoclonal antibody derivatives are promising drugs for the treatment of various diseases due to their high matrix metalloproteinases (MMP) active site specificity. We studied the effects of a novel antibody, SDS3, which specifically recognizes the mature active site of MMP9/2 during ventricular remodeling progression in a mouse model of chronic volume overload (VO).MethodsVO was induced by creating an aortocaval fistula (ACF) in 10- to 12-week-old C57BL male mice. The VO-induced mice were treated with either vehicle control (PBS) or with SDS3 twice weekly by intraperitoneal (ip) injection. The relative changes in cardiac parameters between baseline (day 1) and end-point (day 30), were evaluated by echocardiography. The effects of SDS3 treatment on cardiac fibrosis, cardiomyocyte volume, and cardiac inflammation were tested by cardiac staining with Masson's trichrome, wheat Germ Agglutinin (WGA), and CD45, respectively. Serum levels of TNFα and IL-6 with and without SDS3 treatment were tested by ELISA.ResultsSDS3 significantly reduced cardiac dilatation, left ventricular (LV) mass, and cardiomyocyte hypertrophy compared to the vehicle treated animals. The antibody also reduced the heart-to-body weight ratio of the ACF animals to values comparable to those of the controls. Interestingly, the SDS3 group underwent significant reduction of cardiac inflammation and pro-inflammatory cytokine production, indicating a regulatory role for MMP9/2 in tissue remodeling, possibly by tumor necrosis factor alpha (TNFα) activation. In addition, significant changes in the expression of proteins related to mitochondrial function were observed in ACF animals, these changes were reversed following treatment with SDS3.ConclusionThe data suggest that MMP9/2 blockage with SDS3 attenuates myocardial remodeling associated with chronic VO by three potential pathways: downregulating the extracellular matrix proteolytic cleavage, reducing the cardiac inflammatory responses, and preserving the cardiac mitochondrial structure and function.

Acute, subacute and chronic sequelae of horses accidentally exposed to monensin-contaminated feed.

Monensin is highly toxic to horses and inadvertent ingestion can result in cardiac injury and death. To describe sequelae of monensin ingestion and to determine clinical predictors of outcome. Observational clinical study. Physical examination, electrocardiogram and echocardiography were performed on 76 horses accidentally exposed to monensin-contaminated feed. Four horses were examined within 14days of exposure (acute period), 29 horses were examined between 15 and 45dayspost-exposure (subacute period) and 70 horses were examined 4-10months after exposure (chronic period). Follow-up information was obtained for 56 horses by telephone interviews approximately 16months after exposure. Cardiac abnormalities were detected in 4/4, 19/29 and 31/70 horses during the acute, subacute and chronic periods, respectively. Sixteen months post-exposure, 34 of the 64 horses (53%) for which the outcome was known had returned to their previous use, 13 (20%) were reported to be exercise intolerant, three (5%) were retired and 14 (22%) were dead (two deaths, 12 euthanasia). Thinning of the myocardium observed at any point in time was associated with a negative outcome. Heterogeneity of the myocardium observed in the acute/subacute period was associated with a negative outcome while subjective contractile intraventricular dyssynchrony, cardiac chamber dilation, decreased fractional shortening and multiple premature ventricular complexes observed in the chronic period were associated with a negative outcome. Some horses with significant changes associated with a negative outcome in the chronic phase still returned to their previous work. No control group and only 27 horses were examined more than once. Clinical outcome of horses exposed to sublethal doses of monensin is highly variable. The presence of heterogeneity and thinning of the myocardium shortly after intoxication were associated with a negative outcome.

A murine model of increased coronary sinus pressure induces myocardial edema with cardiac lymphatic dilation and fibrosis.

Myocardial edema is a consequence of many cardiovascular stressors, including myocardial infarction, cardiac bypass surgery, and hypertension. The aim of this study was to establish a murine model of myocardial edema and elucidate the response of cardiac lymphatics and the myocardium. Myocardial edema without infarction was induced in mice by cauterizing the coronary sinus, increasing pressure in the coronary venous system, and inducing myocardial edema. In male mice, there was rapid development of edema 3 h following coronary sinus cauterization (CSC), with associated dilation of cardiac lymphatics. By 24 h, males displayed significant cardiovascular contractile dysfunction. In contrast, female mice exhibited a temporal delay in the formation of myocardial edema, with onset of cardiovascular dysfunction by 24 h. Furthermore, myocardial edema induced a ring of fibrosis around the epicardial surface of the left ventricle in both sexes that included fibroblasts, immune cells, and increased lymphatics. Interestingly, the pattern of fibrosis and the cells that make up the fibrotic epicardial ring differ between sexes. We conclude that a novel surgical model of myocardial edema without infarct was established in mice. Cardiac lymphatics compensated by exhibiting both an acute dilatory and chronic growth response. Transient myocardial edema was sufficient to induce a robust epicardial fibrotic and inflammatory response, with distinct sex differences, which underscores the sex-dependent differences that exist in cardiac vascular physiology.NEW & NOTEWORTHY Myocardial edema is a consequence of many cardiovascular stressors, including myocardial infarction, cardiac bypass surgery, and high blood pressure. Cardiac lymphatics regulate interstitial fluid balance and, in a myocardial infarction model, have been shown to be therapeutically targetable by increasing heart function. Cardiac lymphatics have only rarely been studied in a noninfarct setting in the heart, and so we characterized the first murine model of increased coronary sinus pressure to induce myocardial edema, demonstrating distinct sex differences in the response to myocardial edema. The temporal pattern of myocardial edema induction and resolution is different between males and females, underscoring sex-dependent differences in the response to myocardial edema. This model provides an important platform for future research in cardiovascular and lymphatic fields with the potential to develop therapeutic interventions for many common cardiovascular diseases.

Canine Dilated Cardiomyopathy: Diffuse Remodeling, Focal Lesions, and the Involvement of Macrophages and New Vessel Formation.

Dilated cardiomyopathy (DCM) is among the most common cardiac diseases in dogs. Its pathogenesis is not fully understood, but myocardial remodeling and inflammation are suspected to be involved. The present study aimed to characterize the pathological processes in canine DCM, investigating morphological changes in association with the expression of relevant cytokines and remodeling markers. The myocardium of 17 dogs with DCM and 6 dogs without cardiac diseases was histologically evaluated, and selected cases were further examined by immunohistochemistry, morphometry, and reverse transcription quantitative PCR. In DCM, the myocardium exhibited subtle but statistically significant diffuse quantitative changes. These comprised increased interstitial collagen deposition and macrophage numbers, as well as an overall reduced proportion of contractile tissue. This was accompanied by a significant increase in myocardial transcription of intracellular adhesion molecule (ICAM) 1, inflammatory cytokines, and remodeling enzymes. Laser microdissection showed that cardiomyocytes transcribed most relevant markers including ICAM-1, tumor necrosis factor α, transforming growth factor β (TGF-β), matrix metalloproteinase 2 (MMP-2), tissue inhibitor of MMP (TIMP) 1 and TIMP-2. In addition, there were multifocal cell-rich lesions characterized by fibrosis, neovascularization, macrophage infiltration, and cardiomyocyte degeneration. In these, macrophages were often found to express ICAM-1, TGF-β, and vascular endothelial growth factor; the former two were also expressed by cardiomyocytes. These results characterize the diffuse myocardial remodeling processes that occur in DCM. The observed multifocal cell-rich lesions might result from reduced tissue perfusion. Macrophages and cardiomyocytes seem to actively contribute to the remodeling processes, which ultimately lead to cardiac dilation and dysfunction. The precise role of the involved cells and the factors initiating the remodeling process still needs to be identified.

Ebstein's anomaly: contemporary management strategies.

Ebstein’s anomaly (EA) is a rare congenital cardiac anomaly. It is a disease at a minimum of the tricuspid valve (TV) and the right ventricular myocardium. Presentation varies from a severe symptomatic form during the neonatal period to an incidental detection later in life due to the wide morphological variation of the condition. The neonatal presentation can be severe and every attempt should be made at medical management ideally into infancy and early childhood. Neonates not eligible or failing medical management should be surgically managed either with a single ventricle palliative approach or a more desirable biventricular repair with a neonatal TV valvuloplasty. Some neonates initially committed to a single ventricle pathway may be converted to a biventricular repair by a delayed TV valvuloplasty. The da Silva Cone repair has become the valvuloplasty of choice especially beyond the neonatal period and can be applied to a wide morphological variation of the condition with good long-term durability. If the chance of a successful TV valvuloplasty is high, it should be offered early in childhood to prevent further cardiac dilation. Adding a Bidirectional Glenn to a valvuloplasty may help salvage marginal risk patients or marginally repairable valves. If valve replacement is the only option, a bioprosthetic valve should be used as it is less thrombogenic especially with marginal right ventricular function. Heart transplantation should be considered in patients with associated left ventricular dysfunction.