Decline In Myocardial Function Research Articles

A Cardioprotective perfusion protocol limits myocardial functional decline during ex situ heart perfusion

A Cardioprotective perfusion protocol limits myocardial functional decline during ex situ heart perfusion

Identification of molecular signatures in acute myocardial infarction based on integrative analysis of proteomics and transcriptomics

BackgroundMyocardial infarction (MI) is one of the most serious cardiovascular diseases, characterized by a rapid and irreversible decline in myocardial function. Early detection of patients with MI and prolonging the optimal therapeutic window of acute myocardial infarction (AMI) are particularly important. This study aimed to identify the diagnostic biomarkers and novel therapeutic targets for acute myocardial infarction. MethodWe generated the AMI mouse models by ligating the proximal left anterior descending coronary artery. Six time points—Sham, AMI 10-min, 1-h, 6-h, 24-h, and 72-h—were chosen to examine the molecular changes that occur during the AMI process. RNA-seq and DIA-MS were performed on the infarcted left ventricular tissues of AMI mice at each time point. Co-expression pattern genes were screened from myocardial infarction samples at different time points by time-series analysis. Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were used to examine these genes. Using the Interactive Gene/Protein Retrieval Tool (STRING) database, the protein-protein interaction network (PPI) was constructed and the hub genes were identified. In order to evaluate the diagnostic value of hub genes, a receiver operating characteristic (ROC) curve was constructed. An independent data set, GSE163772, confirmed the diagnostic value of hub genes further. ResultWe obtained the expression profiles at different time points after the occurrence of heart failure through high-throughput sequencing, and found 167 genes with similar expression patterns through time series analysis. The immune response and immune-related pathways had the greatest enrichment of these genes. Among them, Itgb2 Syk, Tlr4, Tlr2, Itgax, and Lcp2 may play key roles as hub genes. Combined with the results of proteomic analysis, it was found that the expression of Coro1a in both omics increased with time. The results of external validation showed that TLR2, ITGAX, and LCP2 had good predictive ability for AMI diagnosis. ConclusionItgb2, Syk, Tlr4, Tlr2, Itgax, Lcp2 and Coro1a are considered to be the seven key genes significantly associated with AMI. Our results may provide potential targets for the prevention of adverse ventricular remodeling and the treatment of AMI.

Heart Failure Impairs Bone Marrow Hematopoietic Stem Cell Function and Responses to Injury.

Background Heart failure (HF) is a clinical syndrome associated with a progressive decline in myocardial function and low-grade systemic inflammation. Chronic inflammation can have lasting effects on the bone marrow (BM) stem cell pool by impacting cell renewal and lineage differentiation. However, how HF affects BM stem/progenitor cells remains largely unexplored. Methods and Results EGFP+ (Enchanced green fluorescent protein) mice were subjected to coronary artery ligation, and BM was collected 8 weeks after myocardial infarction. Transplantation of EGFP+ BM into wild-type mice revealed reduced reconstitution potential of BM from mice subjected to myocardial infarction versus BM from sham mice. To study the effects HF has on human BM function, 71 patients, HF (n=20) and controls (n=51), who were scheduled for elective cardiac surgery were consented and enrolled in this study. Patients with HF exhibited more circulating blood myeloid cells, and analysis of patient BM revealed significant differences in cell composition and colony formation potential. Human CD34+ cell reconstitution potential was also assessed using the NOD-SCID-IL2rγnull mouse xenotransplant model. NOD-SCID-IL2rγnull mice reconstituted with BM from patients with HF had significantly fewer engrafted human CD34+ cells as well as reduced lymphoid cell production. Analysis of tissue repair responses using permanent left anteriordescending coronary arteryligation demonstrated reduced survival of HF-BM reconstituted mice as well as significant differences in human (donor) and mouse (host) cellular responses after MI. Conclusions HF alters the BM composition, adversely affects cell reconstitution potential, and alters cellular responses to injury. Further studies are needed to determine whether restoring BM function can impact disease progression or improve cellular responses to injury.

Vascular dysfunction in HFpEF: Potential role in the development, maintenance, and progression of the disease.

Heart failure with preserved ejection fraction (HFpEF) is a complex, heterogeneous disease characterized by autonomic imbalance, cardiac remodeling, and diastolic dysfunction. One feature that has recently been linked to the pathology is the presence of macrovascular and microvascular dysfunction. Indeed, vascular dysfunction directly affects the functionality of cardiomyocytes, leading to decreased dilatation capacity and increased cell rigidity, which are the outcomes of the progressive decline in myocardial function. The presence of an inflammatory condition in HFpEF produced by an increase in proinflammatory molecules and activation of immune cells (i.e., chronic low-grade inflammation) has been proposed to play a pivotal role in vascular remodeling and endothelial cell death, which may ultimately lead to increased arterial elastance, decreased myocardium perfusion, and decreased oxygen supply to the tissue. Despite this, the precise mechanism linking low-grade inflammation to vascular alterations in the setting of HFpEF is not completely known. However, the enhanced sympathetic vasomotor tone in HFpEF, which may result from inflammatory activation of the sympathetic nervous system, could contribute to orchestrate vascular dysfunction in the setting of HFpEF due to the exquisite sympathetic innervation of both the macro and microvasculature. Accordingly, the present brief review aims to discuss the main mechanisms that may be involved in the macro- and microvascular function impairment in HFpEF and the potential role of the sympathetic nervous system in vascular dysfunction.

Dynamic Metabolic Changes During Prolonged Ex Situ Heart Perfusion Are Associated With Myocardial Functional Decline.

Ex situ heart perfusion (ESHP) was developed to preserve and evaluate donated hearts in a perfused beating state. However, myocardial function declines during ESHP, which limits the duration of perfusion and the potential to expand the donor pool. In this research, we combine a novel, minimally-invasive sampling approach with comparative global metabolite profiling to evaluate changes in the metabolomic patterns associated with declines in myocardial function during ESHP. Biocompatible solid-phase microextraction (SPME) microprobes serving as chemical biopsy were used to sample heart tissue and perfusate in a translational porcine ESHP model and a small cohort of clinical cases. In addition, six core-needle biopsies of the left ventricular wall were collected to compare the performance of our SPME sampling method against that of traditional tissue-collection. Our state-of-the-art metabolomics platform allowed us to identify a large number of significantly altered metabolites and lipid species that presented comparable profile of alterations to conventional biopsies. However, significant discrepancies in the pool of identified analytes using two sampling methods (SPME vs. biopsy) were also identified concerning mainly compounds susceptible to dynamic biotransformation and most likely being a result of low-invasive nature of SPME. Overall, our results revealed striking metabolic alterations during prolonged 8h-ESHP associated with uncontrolled inflammation not counterbalanced by resolution, endothelial injury, accelerated mitochondrial oxidative stress, the disruption of mitochondrial bioenergetics, and the accumulation of harmful lipid species. In conclusion, the combination of perfusion parameters and metabolomics can uncover various mechanisms of organ injury and recovery, which can help differentiate between donor hearts that are transplantable from those that should be discarded.

Abstract 9052: Upregulation of Cardiac SERCA 2a is a Key Molecular Mechanism of the Protective Effect on Myocardial Aging in Beta3-Adrenergic Receptor Deficiency Mice

Background: We have shown previously that aging-induced cardiomyocyte dysfunction and impaired β-adrenergic regulation were prevented in β 3 -adrenergic receptor (AR) knockout (β 3 KO) aged mice. However, the molecular mechanism is unclear. We hypothesize that reversal of aging-induced down-regulation of SR Ca 2+ -ATPase (SERCA 2a) and β 1 -ARs by β 3 -AR deficiency may play a key role for the protective effect. Methods: We compared cardiac SERCA 2a, phospholamban (PLB), β 1 - and β 3 -AR protein expression and myocyte contractile and [Ca 2+ ] i transient ([Ca 2+ ] iT ) responses to isoproterenol (ISO, 10 -8 M) in left ventriclar (LV) myocytes obtained from 2 young (Y)(~4-6 mo) and 2 aged (A) (~18-24 mo) groups (7/group) of wild-type (WT) and β 3 KO mice, respectively. Results: Compared with YWT, AWT myocytes had significantly decreased SERCA 2a (66%, AWT: 0.21 vs YWT: 0.61), SERCA 2a/PLB ratio (0.76 vs 1.77) and β 1 -AR (33%, 0.39 vs 0.58), but increased β 3 -AR (93%, 0.27 vs 0.14). These changes were associated with reduced basal cell contraction (dL/dt max ) (AWT: 84.3 vs YWT: 124.8 μm/s), relaxation (dR/dt max ) (60.1 vs 89.8 μm/s) and [Ca 2+ ] iT (0.17 vs 0.22). This was accompanied by diminished ISO-stimulated positive inotropic effect; in AWT myocytes, ISO (10 -8 M) caused significantly less increases in dL/dt max (AWT: 33% vs YWT: 81%), dR/dt max (24% vs 58%), and [Ca 2+ ] iT (14% vs 34%). Compared with YWT, Yβ 3 KO did not alter basal contraction and ISO response of myocytes, but SERCA 2a (Yβ 3 KO: 1.2 vs YWT: 0.61) and SERCA 2a/PLB ratio were doubled with relatively unchanged β 1 -AR (0.62 vs 0.58); Aβ 3 KO mice had similar alterations. Importantly, in contrast to AWT, in Aβ 3 KO myocytes, the increased SERCA 2a (1.1) and β 1 -AR (0.61) correlated with normal basal cell contraction and relaxation with preserved ISO-stimulated positive inotropic response. ISO caused similar increases in dL/dt max (84% vs 82%) and [Ca 2+ ] iT (32% vs 34%) compared to Yβ 3 KO mice. Conclusions: Chronic β 3 -AR deficiency upregulates cardiac SERCA 2a, prevents aging-induced downregulation of β 1 -ARs, and leads to the preservation of myocyte function, [Ca 2+ ] iT , and β-adrenergic responsiveness in aged hearts. Thus, antagonizing β 3 -AR could be a new therapeutic strategy for age-related decline in myocardial function.

Cardiac MicroRNA Expression Profile After Experimental Brain Death Is Associated With Myocardial Dysfunction and Can Be Modulated by Hypertonic Saline.

Brain death (BD) is associated with systemic inflammatory compromise, which might affect the quality of the transplanted organs. This study investigated the expression profile of cardiac microRNAs (miRNAs) after BD, and their relationship with the observed decline in myocardial function and with the changes induced by hypertonic saline solution (HSS) treatment. Wistar rats were assigned to sham-operation (SHAM) or submitted to BD with and without the administration of HSS. Cardiac function was assessed for 6 h with left ventricular (LV) pressure-volume analysis. We screened 641 rodent miRNAs to identify differentially expressed miRNAs in the heart, and computational and functional analyses were performed to compare the differentially expressed miRNAs and find their putative targets and their related enriched canonical pathways. An enhanced expression in canonical pathways related to inflammation and myocardial apoptosis was observed in BD induced group, with 2 miRNAs, miR-30a-3p, and miR-467f, correlating with the level of LV dysfunction observed after BD. Conversely, HSS treated after BD and SHAM groups showed similar enriched pathways related to the maintenance of heart homeostasis regulation, in agreement with the observation that both groups did not have significant changes in LV function. These findings highlight the potential of miRNAs as biomarkers for assessing damage in BD donor hearts and to monitor the changes induced by therapeutic measures like HSS, opening a perspective to improve graft quality and to better understand the pathophysiology of BD. The possible relation of BD-induced miRNA's on early and late cardiac allograft function must be investigated.

Abstract 12808: Mechanism of Chronic Ranolazine Caused Regression of Cardiac Dysfunction in a Murine of Diabetic Cardiomyopathy: Beneficial Effects on Cardiomyocyte Contractile Function, [Ca 2+ ] i Regulation and Beta-Adrenergic Modulation

Background: Diabetic cardiomyopathy (DCM) increases the risk of heart failure. As yet, no effective therapeutic strategies exist. Recent evidence indicates that intracellular Na + concentration ([Na + ] i ) is augmented in the myocytes from diabetic hearts, where it causes oxidative stress, augments the sarcoplasmic reticulum Ca 2+ leak and contributes to electrical, structural and functional remodeling. Ranolazine (RAN), inhibiting persistent or late inward Na + current has been proposed to be a therapeutic choice for DCM. However, the role and mechanism of chronic RAN in DCM are unclear. We assessed the hypothesis that RAN improves myocyte function, [Ca 2+ ] i regulation, and β-adrenergic receptor (AR) signaling effectiveness, thus limiting DCM. Methods: We compared LV myocyte function, [Ca 2+ ] i transient ([Ca 2+ ] iT ) and responses to the stimulation of β-AR in 3 groups wild-type (WT) female mice over 10 weeks (W):1) DM (n=8), 10 W after receiving streptozotocin (STZ, 200 mg/kg, ip); 2) DM/RAN (n=6), 6 W after STZ, RAN (10 -5 M/kg/day, mini-pump) was initiated and was given for 4 W; and 3) Sham controls (C) (n=8). Results: Versus control, STZ-treated WT mice had DM with significantly elevated blood glucose levels (410 vs 128mg/dl) followed by LV myocyte dysfunction with decreases in myocyte contractility (dL/dt max ) (75.0 vs 140.1 μm/s), relengthening (dR/dt max ) (62.5 vs 116.6 μm/s) and [Ca 2+ ] iT (0.15 vs 0.22). In DM myocytes, the ability of β-AR agonist, isoproterenol (ISO, 10 -8 M) to increase cell contractility was blunted. Versus control, in DM myocytes, ISO-induced increases in dL/dt max (31% vs 60%), dR/dt max (23% vs 50%) and [Ca 2+ ] iT (15% vs 30%) were significantly reduced. By contrary, versus DM alone, DM/RAN myocytes showed normal basal cell contraction (137.8 μm/s), relaxation (117.2 μm/s) and [Ca 2+ ] iT (0.22) with preserved ISO-stimulated positive inotropic effect. Compared control, in DM/RAN, ISO caused similar increases in dL/dt max (62% vs 60%), dR/dt max (52% vs 50%) and [Ca 2+ ] iT (32% vs 30%). Conclusion: Chronic ranolazine leads to the preservation of myocyte function, [Ca 2+ ] iT and β-AR responsiveness in DCM. Thus, antagonizing myocyte [Na + ] i dysregulation might provide a new therapeutic strategy for DM-related decline in myocardial function.

Abstract 13045: Chronic Beta3-Adrenergic Receptor Antagonist Therapy Rescues Diabetic Cardiomyopathy in a Mouse Model With Type 2 Diabetes: Insights into Cellular Mechanism

Background: Diabetic cardiomyopathy (DCM) leads to progressive decline in cardiac function, increasing the risk for heart failure. There are no known effective prevention approaches or therapeutic strategies. Recent evidence in diabetes mellitus (DM) human and animal hearts suggests that the up-regulation of β 3 -adrenergic receptor (AR)-mediated inhibitory pathway may be responsible for the progression of DCM. However, its precise role is still being debated. We hypothesize that β 3 -AR antagonists (β 3 -ANT) may rescue the detrimental effects of β 3 -AR activation, improve cardiomyocyte function, and preserve normal β-AR regulation, leading to the regression of DCM. Methods: We compared LV myocyte function, [Ca 2+ ] i transient ([Ca 2+ ] iT ) at baseline and responses to β-AR simulation with isoproterenol (ISO,10 -8 M) in 3 groups wild-type female mice over 14 weeks (W):1) Type 2 DM ( T2 ) (n=9), 14 W fed high-fat diet (HFD), but after HFD for 4 W receiving streptozotocin (STZ, 40 mg/kg/day, i.p. 5 days); 2) T2/β 3 -ANT (n=7), T2 mice at 10 W received L-748,337, a selective β 3 -ANT (10 -7 M/kg/day, mini-pump) for 4 W; and 3) Vehicle controls (C) (n=9). Results: Versus C, T2DM was induced in mice received HFD and low dose STZ with significantly elevated blood glucose levels (T2: 388, T2/β 3 -ANT: 369 vs C: 128 mg/dl). In T2, LV myocyte basal function and [Ca 2+ ] iT regulation were impaired measured as significantly decreased myocyte contractility (dL/dt max ) (76.8 vs 135.2 μm/s), relengthening (dR/dt max ) (62.1 vs 113.8 μ m/s) and [Ca 2+ ] iT (0.16 vs 0.21). Furthermore, versus C, in T2 myocytes, ISO-induced increases in dL/dt max (T2: 40% vs C: 58%), dR/dt max (35% vs 54%) and [Ca 2+ ] iT (19% vs 30%) were significantly reduced. By contrary, versus T2, T2/β 3 -ANT myocytes showed normal basal cell contraction (127.8 μm/s), relaxation (109.4 μm/s) and [Ca 2+ ] iT (0.21) with preserved ISO-stimulated positive inotropic effect. Versus C, in T2/β 3 -ANT, ISO caused similar increases in dL/dt max (57%), dR/dt max (52%) and [Ca 2+ ] iT (30%). Conclusion: Chronic β 3 -ANT leads to the preservation of LV myocyte function, [Ca 2+ ] iT , and β-AR responsiveness in a mouse model of type 2 diabetes. Thus, antagonizing β 3 -AR might provide a new therapeutic strategy for DM-related decline in myocardial function.

Targeting MEF2 acetylation improves myocardial recovery and overall survival in mice

Abstract Background Post-myocardial infarct remodeling is a complex process that is strongly associated with the eventual development of heart failure, and involves myocyte hypertrophy, specific alterations in gene expression and mitochondrial metabolism, myocyte death, fibrosis, and incursion of inflammatory mediators. Many of these alterations involve dynamic changes in lysine acetylation (KAc), a key regulatory post-transcriptional modification in the nucleus and cytosol, and can be blocked by small molecules with broad activity against histone deacetylases (HDACi). The downstream targets of HDACi and other KAc modulators remain to be established, and the safety of this class of agent for long-term administration in heart failure is similarly unknown. We recently reported that a small molecule probe (8MI) selectively blocking acetylation of transcription factor MEF2 is effective in preventing and reversing pressure overload hypertrophy in vivo, without altering overall histone acetylation. Hypothesis Treatment with a MEF2-selective KAc modulator will accelerate cardiac functional recovery after myocardial infarction. Methods The left coronary artery was permanently ligated (PCO) in 8–10 week C57BL/6J mice; controls underwent thoracotomy only (Sham). Within each group, half received 8MI (20–100mg/kg) by gavage daily, beginning at 30 min, and half received diluent only (DMSO). Treatment was continued for 31 days with weekly echocardiography. Mice from each group (n=3–6) were euthanized weekly for gross and histological analysis. Separately, mice were subjected to transverse aortic banding (TAC) +/− 8MI. Comparative LV RNASeq data were analysed using Gene Set Enrichment Analysis at 4 weeks, and median survival was determined. Results At 24 hours all PCO vs. Sham mice had reduced ejection fraction (62.1±1.08% vs. 80.9±1.08%), increased LV diastolic dimensions, and decreased systolic wall thickening (n =min. 8 per group, p < E-001). Over 4 weeks, heart weights progressively increased in PCO mice together with lung and liver congestion. 8MI dose-dependently improvedeach of these parameters, with near-normal function and organ weights at 4 weeks in higher-dose groups. 8MI also reduced infarct size, compensatory hypertrophy, and fibrosis at 4 weeks. In parallel, 8MI extended median survival by 1.67-fold after TAC (127.5 vs 76 days, p<0.0001, 8MI vs DMSO). RNASeq +GSEA analysis revealed that 8MI treatment blocked MEF2 target gene induction, while enriching for gene sets Oxidative Phosphorylation and Myc Targets (FDR q values 0.000 and 0.041) compared with DMSO. Conclusion An inhibitor of MEF2 acetylation promoted significant functional and pathological recovery in a mouse model of myocardial infarction, associated with suppression of MEF2-dependent transcription. These findings point to a novel approach to preventing myocardial functional decline, and improving survival, after myocardial injury. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health; Miami Heart Research Institute

Myocardial Functional Decline During Prolonged Ex Situ Heart Perfusion

Myocardial function declines in a time-dependent fashion during ex situ heart perfusion. Cell death and metabolic alterations may contribute to this phenomenon, limiting the safe perfusion period and the potential of ex situ heart perfusion to expand the donor pool. Our aim was to investigate the etiology of myocardial functional decline in ex situ perfused hearts. Cardiac function, apoptosis, effectors and markers of cell death, and metabolic function were assessed in healthy pig hearts perfused for 12 hours. These hearts were perfused in nonworking mode or working mode. Cardiac function declined during ex situ heart perfusion regardless of perfusion mode but was significantly better preserved in the hearts perfused in working mode (11-hour cardiac index/1-hour cardiac index: working mode, 33%; nonworking mode, 10%; p= 0.025). The rate of apoptosis was higher in the ex situ perfused hearts compared with invivo samples (apoptotic cells: invivo, 0.13%; working mode, 0.54%; nonworking mode, 0.88%; p< 0.001), but the absolute values were low and out of proportion to the decline in function in either group. Myocardial dysfunction at the end of the perfusion interval was partially rescued by delivery of a pyruvate bolus. A significant decline in myocardial function occurs over time in hearts preserved ex situ that is out of proportion to the magnitude of myocyte cell deathpresent in dysfunctional hearts. Alterations in myocardial substrate utilization during prolonged ex situheart perfusion may contribute to this phenomenon and represent an avenue to improve donor heart preservation.

Chemotherapy-related cardiotoxicity: are Australian practitioners missing the point?

It has long been established that cardiotoxicity occurs as a result of exposure to certain chemotherapeutics, particularly anthracyclines. Historically, clinicians equate cardiotoxicity with a poor prognosis, in a small percentage of patients and deem long-term surveillance as optional. Emerging evidence suggests that anthracycline cardiotoxicity (ACT) is a life-long risk with an incidence approaching 20%. To elucidate the incidence of anthracycline cardiotoxicity within a current paediatric oncology survivor cohort. Participants were identified through the Haematology-Oncology database at the Royal Children's Hospital, Melbourne. Patients were identified from a retrospective audit of outpatient attendances between January 2008 and December 2015. Patients with a cancer diagnosis exposed to anthracyclines were eligible for the study. Patient demographics and echocardiogram findings were recorded with patients subcategorised according to degree of ACT. More significant ACT defined as fractional shortening (FS) <24% and less significant if FS 24-28% or a decline in baseline ejection fraction of >10%. Two hundred and eighty-six of a total 481 identified patients were eligible for study inclusion. Twenty patients displayed significant ACT with FS <24%. Ten patients had a FS 24-28% and 25 patients with a decline in ejection fraction from baseline of >10%. Overall, 6.6% demonstrated significant cardiac complications, whilst 19.6 % demonstrated some degree of ACT and decline in myocardial function. When stratified for cumulative anthracycline dose, the incidence of severe cardiac dysfunction was 5.1% (<250 mg/m2 ) and 25% (>250 mg/m2 ) CONCLUSION: This study demonstrates, in keeping with modern literature, the higher incidence of anthracycline associated cardiac toxicity and a need for better surveillance and follow up.

(490) - Identification of Hypoxic Cells in Lung Grafts for Future Cell Targeted Therapy for Obliterans Bronchiolitis

Purpose: Ex vivo heart perfusion (EVHP) has been proposed as a means improving heart preservation and expanding the donor pool. Current clinical EVHP protocols involve preservation in an unloaded and non-working state; however, the impact of this approach on the preservation of donor heart function is unknown. We sought to determine if myocardial load during EVHP impacts the preservation of donor heart function. Methods: Donor porcine hearts were perfused ex vivo in a beating state for 12 hours. Loaded hearts (N= 4) were perfused in a working mode (left atrial pressure= 6 mmHg, heart rate= 100 beats/minute) for the entire EVHP interval. Unloaded hearts (N= 4) were briefly transitioned into a working mode at hours 1 (T1), 5 (T5), and 11 (T11) for metabolic and functional assessments, but were otherwise perfused in a resting mode (left atrial pressure= 0 mmHg). Results: Myocardial function (T11 cardiac index (mL/minute/gram): loaded= 6.9±1.0 vs. unloaded= 2.0±1.2, p= 0.02) and mechanical efficiency (T11: loaded= 11±1 vs. unloaded= 2±1 %, p< 0.01) were better preserved in loaded hearts. Myocardial injury (T11 troponin I (ng/mL): loaded= 11.6±0.4 vs. unloaded= 12.1±0.3, p= 0.39) and edema formation (% weight gain: loaded= 14±8 vs. unloaded= 24±3 %, p= 0.15) did not account for these differences. Free fatty acids were rapidly depleted in both groups; however, triglycerides were continually consumed by loaded hearts and secreted by unloaded heats (Figure 1). Conclusion: EVHP in a loaded state improves the preservation of myocardial function. Uncoupling of fatty acid oxidation may contribute to the decline in myocardial function observed in unloaded hearts; however, further research is required to elucidate the mechanism underlying these observations. These results highlight the need for an EVHP device capable of preserving the donor heart in a physiologic working mode.

Duxorubicin-induced cardiotoxicity

The survival rate of cancer patients has greatly increased over the last 20 years. However, to achieve this result, a considerable price has been paid in terms of the side-effects associated with the intensive anticancer treatment. Cardiotoxicity of anticancer drugs is a serious problem. It is defined, by the National Cancer Institute, as the “toxicity that affects the heart.” This definition not only includes a direct effect of the drug on the heart, but also an indirect effect due to enhancement of hemodynamic flow alterations or due to thrombotic events. Cardiotoxicity can develop in a subacute, acute, or chronic manner. The risk for such effects depends upon: cumulative dose, rate of drug administration, mediastinal radiation, advanced age, younger age, female gender, pre-existing heart disease and hypertension. Anthracyclines, such as doxorubicin (DOX), cause serious cardiac side-effects. Acute tachyarrhythmias and acute heart failure (HF) may occur after high doses, but these reactions are now rare due to changed dosage schemes (e.g. slower infusion) with the aim to prevent this. However, the sub-acute or chronic cardiac effects of anthracyclines remain a clinical problem. Clinically, anthracycline induced cardiotoxicity manifests itself as left ventricular failure, which develops insidiously over months to years after completion of the anthracycline based chemotherapy and may result in congestive HF. The mechanism of anthracyclin induced cardiotoxicity is not totally unraveled. It is likely that the decline in myocardial function is related to apoptosis of cardiac myocytes that occurs apparently at random in the myocardium. Anthracyclin induced formation of reactive oxygen species (ROS) in the presence of intracellular iron, impaired homeostasis of intracellular iron and calcium (that may facilitate the apoptosis induced by the ROS) have been put forward as mechanisms. Cardiac protection can be achieved by limitation of the cumulative dose. Further, addition of the antioxidant and iron chelator dexrazoxane to anthracycline therapy has shown to be effective in lowering the incidence of anthracycline induced cardiotoxicity.

Natural History of Cardiomyopathy in Duchenne Muscular Dystrophy and the Effects of Angiotensin-Converting Enzyme Inhibitor with or without -Blocker (S15.003)

Objective: To prospectively examine the natural history of cardiomyopathy (CM) in Duchenne muscular dystrophy (DMD) patients & assess responses to treatment utilizing angiotensin-converting enzyme inhibitors (ACEI) with or without concomitant β-blocker (BB). Background Cardiomyopathy is an invariable consequence of DMD. Suggested treatments include ACEI and/or BB, but few large series are reported. We present 65 DMD patients with CM treated with ACEI or ACEI+BB, including their natural history & therapeutic responses. Design/Methods: Serial echocardiograms were performed and reported for natural history analysis prior to initiation of therapy when available. Adequate ejection fractions (EF) were obtained in 45 patients at initiation of therapy (EF 100 beats/min. Data analyzed using paired t-test & linear regression. Results: Natural history data (n=24) demonstrated decreased EF over time (r2=0.22). At ACEI therapy initiation, the mean age was 14.7 ± 4.4 years & mean EF was 44.3 ± 8.3%. BB therapy was used in 25/45 patients. Mean age for ACEI+BB group was 16.1 ± 3.9 years. Both groups demonstrated significant improvement compared to natural history (p≤0.0001 for ACEI, p Conclusions: Patients with DMD demonstrated gradual decline in myocardial function. Treatment with ACEI or ACEI+BB resulted in significant improvement compared to the natural history. No significant difference was noted in EF improvement between treatment groups. Treatment with ACEI or ACEI+BB can delay progression of CM. Supported by: Data collection was made possible by the Muscular Dystrophy Association & Wellstone Muscular Dystrophy Cooperative Research Center (NIH sponsored) and led to creation of the MDA DMD Clinical Network. Mutational analysis for most patients performed as part of the United Dystrophinopathy Project-supported by NINDS (R01 NS043264)[K.M.F.]. Disclosure: Dr. Thrush has nothing to disclose. Dr. Viollet has nothing to disclose. Dr. Flanigan has received personal compensaiton for activities with AVI Therapeutics, Prosensa Therapeutics, and PTC, Inc. Dr. Flanigan has received research support from PTC Therapeutics. Dr. Mendell has received research support from AVI BioPharmaceuticals Inc. Dr. Allen has nothing to disclose.

Single high-dose intramyocardial administration of erythropoietin promotes early intracardiac proliferation, proves safety and restores cardiac performance after myocardial infarction in rats☆

Various studies demonstrate erythropoietin (EPO) as a cardioprotective growth hormone. Recent findings reveal EPO in addition might induce proliferation cascades inside myocardium. We aimed to evaluate whether a single high-dose intramyocardial EPO administration safely elevates early intracardiac cell proliferation after myocardial infarction (MI). Following permanent MI in rats EPO (3000 U/kg) in MI EPO-treatment group (n=99) or saline in MI control group (n=95) was injected along the infarction border. Intramyocardial EPO injection activated the genes of cyclin D1 and cell division cycle 2 kinase (cdc2) at 24 h after MI (n=6, P<0.05) evaluated by real time-PCR. The number of Ki-67+ intracardiac cells analyzed following immunohistochemistry was significantly enhanced by 45% in the peri-infarction zone at 48 h after EPO treatment (n=6, P<0.001). Capillary density was significantly enhanced by 17% as early as seven days (n=6, P<0.001). After six weeks, left ventricular performance assessed by conductance catheters was restored under baseline and dobutamine induced stress conditions (n=11-14, P<0.05). No thrombus formation was observed in the heart and in distant organs. No deleterious systemic adverse effects were apparent. Single high-dose intramyocardial EPO delivery proved safety and promoted early intracardiac cell proliferation, which might in part have contributed to an attenuated myocardial functional decline.

Central venous oxygen saturation monitoring

It has been established that mixed venous oxygen saturation (Svo2) reflects the balance between systemic oxygen delivery and consumption. Literature indicates that it is a valuable clinical indicator and has good prognostic value early in patient course. This article aims to establish the usefulness of Svo2 as a clinical indicator. A secondary aim was to determine whether central venous oxygen saturation (Scvo2) and Svo2 are interchangeable. Of particular relevance to cardiac nurses is the link between decreased Svo2 and cardiac failure in patients with myocardial infarction, and with decline in myocardial function, clinical shock and arrhythmias. While absolute values Scvo2 and Svo2 are not interchangeable, Scvo2 and Svo2 are equivalent in terms of clinical course. Additionally, Scvo2 monitoring is a safer and less costly alternative to Svo2 monitoring. It can be concluded that continuous Scvo2 monitoring should potentially be undertaken in patients at risk of haemodynamic instability.

Scavenging superoxide selectively in mouse forebrain is associated with improved cardiac function and survival following myocardial infarction

Dysregulation in central nervous system (CNS) signaling that results in chronic sympathetic hyperactivity is now recognized to play a critical role in the pathogenesis of heart failure (HF) following myocardial infarction (MI). We recently demonstrated that adenovirus-mediated gene transfer of cytoplasmic superoxide dismutase (Ad-Cu/ZnSOD) to forebrain circumventricular organs, unique sensory structures that lack a blood-brain barrier and link peripheral blood-borne signals to central nervous system cardiovascular circuits, inhibits both the MI-induced activation of these central signaling pathways and the accompanying sympathoexcitation. Here, we tested the hypothesis that this forebrain-targeted reduction in oxidative stress translates into amelioration of the post-MI decline in myocardial function and increase in mortality. Adult C57BL/6 mice underwent left coronary artery ligation or sham surgery along with forebrain-targeted gene transfer of Ad-Cu/ZnSOD or a control vector. The results demonstrate marked MI-induced increases in superoxide radical formation in one of these forebrain regions, the subfornical organ (SFO). Ad-Cu/ZnSOD targeted to this region abolished the increased superoxide levels and led to significantly improved myocardial function compared with control vector-treated mice. This was accompanied by diminished levels of cardiomyocyte apoptosis in the Ad-Cu/ZnSOD but not the control vector-treated group. These effects of superoxide scavenging with Ad-Cu/ZnSOD in the forebrain paralleled increased post-MI survival rates compared with controls. This suggests that oxidative stress in the SFO plays a critical role in the deterioration of cardiac function following MI and underscores the promise of CNS-targeted antioxidant therapy for the treatment of MI-induced HF.

Matrix metalloproteinase-2 mediates cytokine-induced myocardial contractile dysfunction.

Pro-inflammatory cytokines depress myocardial contractile function by enhancing peroxynitrite production, yet the mechanism by which peroxynitrite does this is unknown. As matrix metalloproteinases (MMPs) can be activated by peroxynitrite and can proteolytically cleave troponin I in hearts, we determined whether this occurs in cytokine-induced myocardial dysfunction. Isolated working rat hearts were perfused with buffer containing interleukin-1 beta, interferon-gamma, and tumor necrosis factor-alpha. Cytokines induced a marked decline in mechanical function during 60-120 min of perfusion. This decline was accompanied by increased myocardial inducible NO synthase activity and perfusate dityrosine (a marker of peroxynitrite), compared to control hearts. Before the decline in mechanical function there was enhanced MMP-2 activity in the perfusate. This was accompanied by decreased tissue levels of MMP-2, tissue inhibitor of matrix metalloproteinases-4 and troponin I in cytokine-treated hearts. The collagen content of the heart was not affected by cytokine treatment. A neutralizing anti-MMP-2 antibody or the MMP inhibitors Ro31-9790 or PD166793 attenuated the decline in myocardial function. Moreover, the MMP-2 antibody prevented the decline in myocardial MMP-2 and troponin I levels. Myocardial contractile dysfunction caused by pro-inflammatory cytokines results in MMP-2 activation and a decline in tissue inhibitor of matrix metalloproteinases-4 in the heart. Troponin I is also a target for the proteolytic action of MMP-2 during acute heart failure triggered by pro-inflammatory cytokines. Inhibition of MMPs may be a novel pharmacological strategy for the treatment of acute inflammatory heart disease.

Respuestas del miocardio al estrés biomecánico

Biomechanical stress of the myocardium is the situation resulting from hypoxia, hypertension, and other forms of myocardial injury, that invariably lead to increased demands for cardiac work and/or loss of functional myocardium. As a consequence of biomechanical stress a number of responses develop involving all the myocardial cells, namely cardiomyocytes. As a result some myocardial phenotypic changes develop that are initially compensatory (i.e., hypertrophy) but which may mediate the eventual decline in myocardial function that occurs with the transition from hypertrophy to failure in conditions of persistent stress (i.e., apoptosis and fibrosis). This review focuses on the steps involved in the response of the myocardium to biomechanical stress and highlights the most recent developments in the molecular mechanisms involved in the development of heart failure.