Chronic therapy with metoprolol attenuates cardiomyocyte apoptosis in dogs with heart failure

Global Research Trends on Ventricular Remodeling: A Bibliometric Analysis From 2012 to 2022

Ventricular remodeling is the progressive pathologic change of the original substance and morphology of the ventricle caused by various injuries and has attracted increasing attention in the past decade. This study aims to conduct a bibliometric analysis of articles on ventricular remodeling published in the Web of Science Core Collection database from 2012 to 2022 to understand the current research state in the field of ventricular remodeling and provide insights for clinicians and researchers. As a result, a total of 1710 articles on ventricular remodeling were included. Annual publications have been gradually increasing and have remained at a high level over the past 10 years. The United States of America contributed the most publications, followed by China. Circulation was the most mainstream and authoritative journal focusing on ventricular remodeling. Research hotspot analysis suggested that myocardial infarction was the primary risk factor for ventricular remodeling, and emerging risk factor studies have focused on pulmonary hypertension, aortic stenosis, and diabetes. The mechanisms in the pathogenesis of ventricular remodeling were mainly closely associated with inflammation, apoptosis, oxidative stress, and myocardial fibrosis. Intensive investigation of the interactions between different mechanisms might be a future research direction. In terms of treatment, cardiac resynchronization therapy was a hot topic of research. These findings can help researchers grasp the research status of ventricular remodeling and determine future research directions.

Management of Chronic Congestive Heart Failure Caused by Myxomatous Mitral Valve Disease in Dogs: A Narrative Review from 1970 to 2020

Simple Summary

Myxomatous mitral valve disease (MMVD) is the most common acquired cardiovascular disease in dogs. The progression of the disease and the increasing severity of valvular regurgitation cause a volume overload of the left heart, leading to left atrial and ventricular remodeling and congestive heart failure (CHF). The treatment of chronic CHF secondary to MMVD in dogs has not always been the same over time. In the last fifty years, the drugs utilized have considerably changed, as well as the therapeutic protocols. Some drugs have also changed their intended use. An analysis of the literature concerning the therapy of chronic heart failure in dogs affected by this widespread degenerative disease is not available; a synthesis of the published literature on this topic and a description of its current state of art are needed. To the authors’ knowledge, a review of this topic has never been published in veterinary medicine; therefore, the aim of this study is to overview the treatments of chronic CHF secondary to MMVD in dogs from 1970 to 2020 using the general framework of narrative reviews.

Abstract

The treatment of chronic congestive heart failure (CHF), secondary to myxomatous mitral valve disease (MMVD) in dogs, has considerably changed in the last fifty years. An analysis of the literature concerning the therapy of chronic CHF in dogs affected by MMVD is not available, and it is needed. Narrative reviews (NRs) are aimed at identifying and summarizing what has been previously published, avoiding duplications, and seeking new study areas that have not yet been addressed. The most accessible open-access databases, PubMed, Embase, and Google Scholar, were chosen, and the searching time frame was set in five decades, from 1970 to 2020. The 384 selected studies were classified into categories depending on the aim of the study, the population target, the pathogenesis of MMVD (natural/induced), and the resulting CHF. Over the years, the types of studies have increased considerably in veterinary medicine. In particular, there have been 43 (24.29%) clinical trials, 41 (23.16%) randomized controlled trials, 10 (5.65%) cross-over trials, 40 (22.60%) reviews, 5 (2.82%) comparative studies, 17 (9.60%) case-control studies, 2 (1.13%) cohort studies, 2 (1.13%) experimental studies, 2 (1.13%) questionnaires, 6 (3.40%) case-reports, 7 (3.95%) retrospective studies, and 2 (1.13%) guidelines. The experimental studies on dogs with an induced form of the disease were less numerous (49–27.68%) than the studies on dogs affected by spontaneous MMVD (128–72.32%). The therapy of chronic CHF in dogs has considerably changed in the last fifty years: in the last century, some of the currently prescribed drugs did not exist yet, while others had different indications.

A fresh look at coronary microembolization

Mechanical stress from haemodynamic perturbations or interventional manipulation of epicardial coronary atherosclerotic plaques with inflammatory destabilization can release particulate debris, thrombotic material and soluble substances into the coronary circulation. The physical material obstructs the coronary microcirculation, whereas the soluble substances induce endothelial dysfunction and facilitate vasoconstriction. Coronary microvascular obstruction and dysfunction result in patchy microinfarcts accompanied by an inflammatory reaction, both of which contribute to progressive myocardial contractile dysfunction. In clinical studies, the benefit of protection devices to retrieve atherothrombotic debris during percutaneous coronary interventions has been modest, and the treatment of microembolization has mostly relied on antiplatelet and vasodilator agents. The past 25 years have witnessed a relative proportional increase in non-ST-segment elevation myocardial infarction in the presentation of acute coronary syndromes. An associated increase in the incidence of plaque erosion rather than rupture has also been recognized as a key mechanism in the past decade. We propose that coronary microembolization is a decisive link between plaque erosion at the culprit lesion and the manifestation of non-ST-segment elevation myocardial infarction. In this Review, we characterize the features and mechanisms of coronary microembolization and discuss the clinical trials of drugs and devices for prevention and treatment.

Cardioprotective effect of garlic extract in isoproterenol-induced myocardial infarction in a rat model: assessment of pro-apoptotic caspase-3 gene expression

Background

Myocardial Infarction (MI), also known as heart attack, is one of the most common cardiovascular diseases. Although certain drugs or mechanical means are used, day by day natural products such as herbs and spices based MI treatment is getting much popularity over the drugs or mechanical means for their pharmacological effects and have low or no side effects. This study was designed to assess the cardio-protective effect of methanolic extract of Bangladeshi multi clove garlic (Allium sativum) cultivar, a highly believed spice having cardioprotective activity, against isoproterenol (ISO) induced MI through cardiac histopathology as well as cardiac apoptotic caspase-3 gene expression study in female Wistar albino rats. Four groups containing 35 rats treated with respective agents like distill water / garlic extract (200 mg/kg-body-weight/day) up to 28 days and normal saline / ISO (100 mg/kg-body-weight/day) on 29th and 30th day were sacrificed (two rats/group/sacrifice) on the day 31, 46 and 61 and collecting the heart, cardiac histology and gene expression analysis were performed.

Results

ISO induced MI rats pretreated with garlic extract revealed up regulated expression of the cardiac apoptotic caspase-3 gene at the initial stage but finally the expressions gradually getting down regulated along with gradual improving the cardiac damage caused by apoptosis. Furthermore, only garlic extract pretreated rats were found undamaged cardioarchitecture and normal expressions of this gene.

Conclusions

These findings suggested that garlic extract confers having significant cardioprotective effect and consuming this spice with regular diet may reduce the risk of MI.

Repair of Adult Mammalian Heart After Damages by Oral Intake of Gu Ben Pei Yuan San

Adult mammalian heart repair after myocardial damage is highly inefficient due to the post-mitotic nature of cardiomyocytes. Interestingly, in traditional Chinese medicine (TCM), there are reported effective treatments of myocardial infarction (MI) and heart failure in adult humans by oral intake of a TCM concoction named Gu Ben Pei Yuan San (GBPYS), which is composed of Panax ginseng, velvet antler, Gekko gecko Linnaeus tail, human placenta, Trogopterus dung, Panax notoginseng, and amber. We fed mice with GBPYS after myocardial damages through everyday self-feeding. We then examined the effect of everyday oral intake of GBPYS on improving cardiac function and myocardial repair in adult mice after apical resection or MI. We found that long-term oral intake of GBPYS significantly improved cardiac function after myocardial damages in adult mice. BrdU, phospho-histone 3, and AuroraB staining indicated increased cell proliferation at the border zone of MI after TCM feeding. GBPYS feeding reduced organ inflammation, induced angiogenesis, and is non-toxic to mice after long-term oral intake. Further, serum derived from TCM-fed MI rats promoted division of both neonatal rat cardiomyocytes and human induced pluripotent stem cell (iPSC)-derived cardiomyocytes in vitro. Oral intake of GBPYS improved heart repair after myocardial damages in adult mice. Our results suggest that there are substances present in GBPYS that help improve adult mammalian heart repair after MI. Also, it could be a good choice of non-invasive alternative therapy for myocardial damages and heart failure after rigorous clinical study in the future.

Heart-Derived Stem Cells in Miniature Swine with Coronary Microembolization: Novel Ischemic Cardiomyopathy Model to Assess the Efficacy of Cell-Based Therapy

A major problem in translating stem cell therapeutics is the difficulty of producing stable, long-term severe left ventricular (LV) dysfunction in a large animal model. For that purpose, extensive infarction was created in sinclair miniswine by injecting microspheres (1.5 × 10⁶ microspheres, 45 μm diameter) in LAD. At 2 months after embolization, animals (n = 11) were randomized to receive allogeneic cardiosphere-derived cells derived from atrium (CDCs: 20 × 10⁶, n = 5) or saline (untreated, n = 6). Four weeks after therapy myocardial function, myocyte proliferation (Ki67), mitosis (phosphor-Histone H3; pHH3), apoptosis, infarct size (TTC), myocyte nuclear density, and cell size were evaluated. CDCs injected into infarcted and remodeled remote myocardium (global infusion) increased regional function and global function contrasting no change in untreated animals. CDCs reduced infarct volume and stimulated Ki67 and pHH3 positive myocytes in infarct and remote regions. As a result, myocyte number (nuclear density) increased and myocyte cell diameter decreased in both infarct and remote regions. Coronary microembolization produces stable long-term ischemic cardiomyopathy. Global infusion of CDCs stimulates myocyte regeneration and improves left ventricular ejection fraction. Thus, global infusion of CDCs could become a new therapy to reverse LV dysfunction in patients with asymptomatic heart failure.

Cardiac Adenylyl Cyclase and Phosphodiesterase Expression Profiles Vary by Age, Disease, and Chronic Phosphodiesterase Inhibitor Treatment

BACKGROUND

Pediatric heart failure (HF) patients have a suboptimal response to traditional HF medications, although phosphodiesterase-3 inhibition (PDE3i) has been used with greater success than in the adult HF population. We hypothesized that molecular alterations specific to children with HF and HF etiology may affect response to treatment.

METHODS AND RESULTS

Adenylyl cyclase (AC) and phosphodiesterase (PDE) isoforms were quantified by means of quantitative real-time polymerase chain reaction in explanted myocardium from adults with dilated cardiomyopathy (DCM), children with DCM, and children with single-ventricle congenital heart disease of right ventricular morphology (SRV). AC and PDE expression profiles were uniquely regulated in each subject group and demonstratde distinct changes in response to chronic PDE3i. There was unique up-regulation of AC5 in adult DCM with PDE3i (fold change 2.415; P = .043), AC2 in pediatric DCM (fold change 2.396; P = .0067), and PDE1C in pediatric SRV (fold change 1.836; P = .032). Remarkably, PDE5A expression was consistently increased across all age and disease groups.

CONCLUSIONS

Unique regulation of AC and PDE isoforms supports a differential molecular adaptation to HF in children compared with adults, and may help identify mechanisms specific to the pathogenesis of pediatric HF. Greater understanding of these differences will help optimize medical therapies based on age and disease process.

Identification, synthesis, isolation and characterization of new impurity in metoprolol tartrate tablets

A new unknown impurity was observed in accelerated stability studies of Metoprolol tartrate tablets. This impurity has been identified, synthesized and characterized through different spectral studies and confirmed as an adduct of lactose and Metoprolol formed by Maillard reaction.

Fargesin as a potential β₁ adrenergic receptor antagonist protects the hearts against ischemia/reperfusion injury in rats via attenuating oxidative stress and apoptosis

Fargesin displayed similar chromatographic retention peak to metoprolol in the cardiac muscle/cell membrane chromatography (CM/CMC) and β1 adrenergic receptor/cell membrane chromatography (β1AR/CMC) models. To provide more biological information about fargesin, we investigated the effects of fargesin on isoproterenol-(ISO-) induced cells injury in the high expression β1 adrenergic receptor/Chinese hamster ovary-S (β1AR/CHO-S) cells and occluding the left coronary artery- (LAD-) induced myocardial ischemia/reperfusion (MI/R) injury in rats. The results in vitro showed that ISO-induced canonical cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) levels were decreased by fargesin in β1AR/CHO-S cells. Fargesin attenuated the serum creatine kinase (CK), lactate dehydrogenase (LDH), and improved histopathological changes of ischemic myocardium compared with the I/R rats. Similar results were obtained with Evans Blue/TTC staining, in which fargesin notably reduced infarct size. Moreover, compared with the I/R group, fargesin increased COX release and the activities of some endogenous antioxidative enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), but suppressed malondialdehyde (MDA), and intracellular ROS release. Additionally, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay demonstrated fargesin suppressed myocardial apoptosis, which may be related to inhibition of caspase-3 activity. Taken together, these results provided substantial evidences that fargesin as a potential β1AR antagonist through cAMP/PKA pathway could protect against myocardial ischemia/reperfusion injury in rats. The underlining mechanism may be related to inhibiting oxidative stress and myocardial apoptosis.

The switching role of β-adrenergic receptor signalling in cell survival or death decision of cardiomyocytes

How cell fate (survival or death) is determined and whether such determination depends on the strength of stimulation has remained unclear. In this study, we discover that the cell fate of cardiomyocytes switches from survival to death with the increase of β-adrenergic receptor (β-AR) stimulation. Mathematical simulations combined with biochemical experimentation of β-AR signalling pathways show that the gradual increment of isoproterenol (a non-selective β₁/β₂-AR agonist) induces the switching response of Bcl-2 expression from the initial increase followed by a decrease below its basal level. The ERK1/2 and ICER-mediated feed-forward loop is the hidden design principle underlying such cell fate switching characteristics. Moreover, we find that β1-blocker treatment increases the survival effect of β-AR stimuli through the regulation of Bcl-2 expression leading to the resistance to cell death, providing new insight into the mechanism of therapeutic effects. Our systems analysis further suggests a novel potential therapeutic strategy for heart disease.

The contribution of signal strength on cell fate decisions is often not reflected in signalling networks. By combining mathematical simulation and biochemical experiments in cultured adult cardiomyocytes, Shin et al. show that the concentration of a β-adrenergic receptor agonist affects the expression of Bcl-2, influencing the balance between cell survival and death.

N-acetylcysteine reduces oxidative stress, nuclear factor‑κB activity and cardiomyocyte apoptosis in heart failure

The roles of oxidative stress on nuclear factor (NF)‑κB activity and cardiomyocyte apoptosis during heart failure were examined using the antioxidant N‑acetylcysteine (NAC). Heart failure was established in Japanese white rabbits with intravenous injections of doxorubicin, with ten rabbits serving as a control group. Of the rabbits with heart failure, 12 were not treated (HF group) and 13 received NAC (NAC group). Cardiac function was assessed using echocardiography and hemodynamic analysis. Myocardial cell apoptosis, apoptosis‑related protein expression, NF‑κBp65 expression and activity, total anti‑oxidative capacity (tAOC), 8‑iso‑prostaglandin F2α (8‑iso‑PGF2α) expression and glutathione (GSH) expression levels were determined. In the HF group, reduced tAOC, GSH levels and Bcl‑2/Bax ratios as well as increased 8‑iso‑PGF2α levels and apoptosis were observed (all P<0.05), which were effects that were attenuated by the treatment with NAC. NF‑κBp65 and iNOS levels were significantly higher and the P‑IκB‑α levels were significantly lower in the HF group; expression of all three proteins returned to pre‑HF levels following treatment with NAC. Myocardial cell apoptosis was positively correlated with left ventricular end-diastolic pressure (LVEDP), NF‑κBp65 expression and 8‑iso‑PGF2α levels, but negatively correlated with the maximal and minimal rates of increase in left ventricular pressure (+dp/dtmax and ‑dp/dtmin, respectively) and the Bcl‑2/Bax ratio (all P<0.001). The 8‑iso‑PGF2α levels were positively correlated with LVEDP and negatively correlated with +dp/dtmax and ‑dp/dtmin (all P<0.001). The present study demonstrated that NAC increased the antioxidant capacity, decreased the NF‑κB activation and reduced myocardial cell apoptosis in an in vivo heart failure model.

Pathological ventricular remodeling: mechanisms: part 1 of 2

Despite declines in heart failure morbidity and mortality with current therapies, rehospitalization rates remain distressingly high, substantially affecting individuals, society, and the economy. As a result, the need for new therapeutic advances and novel medical devices is urgent. Disease-related left ventricular remodeling is a complex process involving cardiac myocyte growth and death, vascular rarefaction, fibrosis, inflammation, and electrophysiological remodeling. Because these events are highly interrelated, targeting a single molecule or process may not be sufficient. Here, we review molecular and cellular mechanisms governing pathological ventricular remodeling.

Beta1-adrenergic receptors promote focal adhesion signaling downregulation and myocyte apoptosis in acute volume overload

Numerous studies demonstrated increased expression of extracellular matrix (ECM) proteins and activation of focal adhesion (FA) signaling pathways in models of pressure overload-induced cardiac hypertrophy. However, little is known about FA signaling in response to volume overload where cardiac hypertrophy is associated with ECM loss. This study examines the role of beta1-adrenergic receptors (β(1)-ARs) in FA signaling changes and myocyte apoptosis induced during acute hemodynamic stress of volume overload. Rats with eccentric cardiac hypertrophy induced after aorto-caval fistula (ACF) develop reduced interstitial collagen content and decreased tyrosine phosphorylation of key FA signaling molecules FAK, Pyk(2) and paxillin along with an increase in cardiac myocyte apoptosis. ACF also increased activation of PTEN, a dual lipid and protein phosphatase, and its interaction with FA proteins. β(1)-AR blockade (extended-release of metoprolol succinate, 100mg QD) markedly attenuated PTEN activation, restored FA signaling and reduced myocyte apoptosis induced by ACF at 2days, but failed to reduce interstitial collagen loss and left ventricular dilatation. Treating cultured myocytes with β(1)-AR agonists or adenoviral expression of β(1)-ARs caused PTEN activation and interaction with FA proteins, thus leading to FA signaling downregulation and myocyte apoptosis. Adenoviral-mediated expression of a catalytically inactive PTEN mutant or wild-type FAK restored FA signaling downregulation and attenuated myocyte apoptosis induced by β(1)-ARs. Collectively, these data show that β(1)-AR stimulation in response to ACF induces FA signaling downregulation through an ECM-independent mechanism. This effect involves PTEN activation and may contribute to adverse cardiac remodeling and function in the course of volume overload.

Therapeutic potential of c-Myc inhibition in the treatment of hypertrophic cardiomyopathy

Investigating the pathophysiological importance of the molecular and mechanical development of cardiomyopathy is critical to find new and broader means of protection against this disease that is increasing in prevalence and impact. The current available treatment options for cardiomyopathy mainly focus on treating symptoms and strive to make the patient more comfortable while preventing progression of disease and sudden death. The proto-oncogene c-Myc (Myc) has been shown to be increased in many different types of heart disease, including hypertrophic cardiomyopathy, before any signs of the disease are present. As the mechanisms of action and multiple pathways of dependent actions of Myc are being dissected by many research groups, inhibition of Myc is becoming an attractive paradigm for prevention and treatment of cardiomyopathy and heart failure. Elucidating the role Myc plays in the development, propagation and perpetuation of cardiomyopathy and heart failure will one day translate into potential therapeutics for cardiomyopathy.

N-acetylglucosamine conjugated to nanoparticles enhances myocyte uptake and improves delivery of a small molecule p38 inhibitor for post-infarct healing

An estimated 985,000 new myocardial infarctions will occur in the USA in 2011. While many will survive the initial insult, the early damage will eventually lead to heart failure for which the only definitive cure is transplantation. Cardiomyocyte (CM) apoptosis is a large contributor to cardiac dysfunction, and although potential therapeutic molecules exist to inhibit apoptotic pathways, drug delivery methods are lacking. This damage is largely regional and thus localized delivery of therapeutics holds great potential; however, CMs are relatively non-phagocytic, which limits existing options that rely on phagocytosis. Recently, the sugar N-acetylglucosamine (GlcNAc) was shown to be bound and internalized by CMs, providing a potential mechanism for drug delivery. Here we demonstrate efficacy of a drug delivery system comprising a drug-loaded biodegradable polyketal nanoparticle that is surface-decorated with GlcNAc. Inclusion of the sugar enhanced uptake by CMs as measured by intracellular activated fluorescence. When delivered in vivo following ischemia-reperfusion injury, GlcNAc-decorated particles loaded with the p38 inhibitor SB239063 reduced apoptotic events and infarct size and improved acute cardiac function. This was in contrast to our published data demonstrating no acute effect of non-sugar-decorated, p38 inhibitor-loaded particles. These data suggest a novel therapeutic option to enhance uptake of drug-loaded nanoparticles to CMs and perhaps reduce the large amount of CM cell death following myocardial injury.

Silencing nox4 in the paraventricular nucleus improves myocardial infarction-induced cardiac dysfunction by attenuating sympathoexcitation and periinfarct apoptosis

RATIONALE

Myocardial infarction (MI)-induced heart failure is characterized by central nervous system-driven sympathoexcitation and deteriorating cardiac function. The paraventricular nucleus (PVN) of the hypothalamus is a key regulator of sympathetic nerve activity and is implicated in heart failure. Redox signaling in the PVN and other central nervous system sites is a primary mechanism of neuro-cardiovascular regulation, and excessive oxidant production by activation of NADPH oxidases (Noxs) is implicated in some neuro-cardiovascular diseases.

OBJECTIVE

We tested the hypothesis that Nox-mediated redox signaling in the PVN contributes to MI-induced sympathoexcitation and cardiac dysfunction in mice.

METHODS AND RESULTS

Real-time PCR revealed that Nox4 was the most abundantly expressed Nox in PVN under basal conditions. Coronary arterial ligation (MI) caused a selective upregulation of this homolog compared to Nox1 and Nox2. Adenoviral gene transfer of Nox4 (AdsiNox4) to PVN (bilateral) attenuated MI-induced superoxide formation in this brain region (day 14) to the same level as that produced by PVN-targeted gene transfer of cytoplasmic superoxide dismutase (AdCu/ZnSOD). MI mice treated with AdsiNox4 or AdCu/ZnSOD in the PVN showed marked improvement in cardiac function as assessed by echocardiography and left ventricular hemodynamic analysis. This was accompanied by significantly diminished sympathetic outflow and apoptosis in the periinfarct region of the heart.

CONCLUSIONS

These results suggest that MI causes dysregulation of Nox4-mediated redox signaling in the PVN, which leads to sympathetic overactivation and a decline in cardiac function. Targeted inhibition of oxidant signaling in the PVN could provide a novel treatment for MI-induced heart failure.

Apoptosis predominates in nonmyocytes in heart failure

The goal of this investigation was to determine the distribution of myocardial apoptosis in myocytes and nonmyocytes in primates and patients with heart failure (HF). Almost all clinical cardiologists and cardiovascular investigators believe that myocyte apoptosis is considered to be a cardinal sign of HF and a major factor in its pathogenesis. However, with the knowledge that 75% of the number of cells in the heart are nonmyocytes, it is important to determine whether the apoptosis in HF is occurring in myocytes or in nonmyocytes. We studied both a nonhuman primate model of chronic HF, induced by rapid pacing 2-6 mo after myocardial infarction (MI), and biopsies from patients with ischemic cardiomyopathy. Dual labeling with a cardiac muscle marker was used to discriminate apoptosis in myocytes versus nonmyocytes. Left ventricular ejection fraction decreased following MI (from 78% to 60%) and further with HF (35%, P < 0.05). As expected, total apoptosis was increased in the myocardium following recovery from MI (0.62 cells/mm(2)) and increased further with the development of HF (1.91 cells/mm(2)). Surprisingly, the majority of apoptotic cells in MI and MI + HF, and in both the adjacent and remote areas, were nonmyocytes. This was also observed in myocardial biopsies from patients with ischemic cardiomyopathy. We found that macrophages contributed the largest fraction of apoptotic nonmyocytes (41% vs. 18% neutrophils, 16% fibroblast, and 25% endothelial and other cells). Although HF in the failing human and monkey heart is characterized by significant apoptosis, in contrast to current concepts, the apoptosis in nonmyocytes was eight- to ninefold greater than in myocytes.

High-sugar diets increase cardiac dysfunction and mortality in hypertension compared to low-carbohydrate or high-starch diets

OBJECTIVE

Sugar consumption affects insulin release and, in hypertension, may stimulate cardiac signaling mechanisms that accelerate left ventricular hypertrophy and the development of heart failure. We investigated the effects of high-fructose or sucrose diets on ventricular function and mortality in hypertensive Dahl salt-sensitive rats.

METHODS

Rats were fed chows that were either high starch (70% starch, 10% fat by energy), high fat (20% carbohydrates, 60% fat), high fructose (61% fructose, 9% starch, 10% fat), or high sucrose (61% sucrose, 9% starch, 10% fat). Hypertension was induced by adding 6% salt to the chow (n = 8-11/group).

RESULTS

After 8 weeks of treatment, systolic blood pressure and left ventricular mass were similarly increased in all rats that were fed high-salt diets. Hypertension caused a switch in mRNA myosin heavy chain isoform from alpha to beta, and this effect was greater in the high-salt sucrose and fructose groups than in starch and fat groups. The cardiac mRNA for atrial natriuretic factor was also increased in all high-salt groups compared to respective controls, with the increase being significantly greater in the hypertensive sucrose fed group. Mortality was greater in the sucrose group (44%) compared to all the other hypertensive groups (12-18%), as was cardiomyocyte apoptosis. Left ventricular ejection fraction was lower in the high-salt sucrose group, which was due to an increase in end-systolic volume, and not increased end-diastolic volume.

CONCLUSION

Diets high in sugar accelerated cardiac systolic dysfunction and mortality in hypertension compared to either a low-carbohydrate/high-fat or high-starch diet.

The effects of nebivolol on apoptosis in a rat infarct model

BACKGROUND

In the present study, nitric oxide (NO) was investigated to see if it mediated effects of nebivolol on apoptosis in the rat myocardial infarction (MI) model.

METHODS AND RESULTS

Rats were divided into 3 groups: sham operated (sham-control), MI-induced (MI-control) and nebivolol treated (MI-nebivolol). The initial dose of nebivolol was administrated intravenously (iv) within 10 min of post-MI reperfusion and continued orally for 28 days. NO mediated effects of nebivolol were assessed either in the early (2(nd) day) or sub-acute (28(th) day) period of MI by histologic, hemodynamic and biologic studies. Left ventricular (LV) pressure changes were prevented with nebivolol (the increase in LV end-diastolic pressure and the decrease in maximum rise and fall rate of LV pressure (+dp/dt and -dp/dt) was significantly less in MI-nebivolol). Total and regional apoptotic indexes were significantly lower in the MI-nebivolol group (10.2 vs 7.1%, respectively on the 2(nd) day; p=0.004). Although plasma nitrite/nitrate, cyclic guanylate cyclase and peroxynitrite concentrations were high both in MI-control and MI-nebivolol groups on the 2(nd) day, these concentrations were decreased to the basal value on the 28(th) day in the MI-nebivolol group.

CONCLUSION

As a result, nebivolol treatment (initially by iv within 10 min of reperfusion and continued orally) reduced the myocardial apoptosis after MI. This beneficial effect of nebivolol is mediated by NO regulation.

Plasma concentration of Fas/Fas ligand and left ventricular function in response to metoprolol in conjunction with standard treatment

Recent studies suggest that cardiac myocyte apoptosis contributes to the progress of CHF (congestive heart failure). In the present study, we tested the hypothesis that metoprolol in conjunction with the standard treatment regime for CHF [an ACE (angiotensin-converting enzyme) inhibitor, diuretics and digoxin] may significantly reduce the plasma concentrations of the apoptotic mediators sFas (soluble Fas) and sFasL (soluble Fas ligand) in patients with CHF. An ELISA was used to determine the plasma concentrations of sFas and sFasL in 106 patients with stable CHF at recruitment. Echocardiography was performed at baseline and after 1 year of treatment with metoprolol in conjunction with the standard treatment regime for CHF (i.e. an ACE inhibitor, diuretics and digoxin). The dose of metoprolol was doubled on a biweekly basis up to 50 mg twice a day or maintained at the maximum tolerated dose. Data after 1 year were available for 92 patients and were analysed. The plasma concentrations of sFas and sFasL in patients with CHF decreased significantly (P<0.01) after 1 year of treatment with metoprolol in conjunction with the standard treatment regime compared with at baseline (5.4±0.2 compared with 3.2±0.1 ng/ml respectively for sFas, and 52.1±2.3 compared with 26.7±1.0 pg/ml respectively for sFasL). Compared with baseline, after 1 year of treatment with metoprolol in conjunction with the standard treatment regime there were significant improvements in LV (left ventricular) ejection fraction (from 32.6±0.9 to 51.5±0.8%; P<0.01), LV end-diastolic dimension (from 69.8±0.6 to 57.7±0.3 mm; P<0.01), LV end-systolic dimension (from 53.9±0.6 to 40.5±0.5 mm; P<0.01), LV end-diastolic volume (from 254.7±5.0 to 164.1±2.2 ml; P<0.01) and LV end-systolic volume (from 142.0±4.2 to 72.2±2.0 ml; P<0.01). In addition, the distance walked in a 6-min walk test increased markedly (P<0.01) from 260.3±5.2 m at baseline to 440.9±5.7 m after 1 year of treatment. In conclusion, we have demonstrated that metoprolol in conjunction with an ACE inhibitor, diuretics and digoxin in patients with CHF can lead to a reverse in LV remodelling potentially through its anti-apoptotic effects.

Mechanisms of disease: apoptosis in heart failure--seeing hope in death

Apoptosis or programmed cell death is an evolutionarily conserved process of cell death, wherein cells die without provoking significant inflammatory response. There is convincing evidence that apoptosis contributes to the progression of heart failure. Apoptosis occurs through a cascade of subcellular events including cytochrome c release into the cytoplasm and activation of proteolytic caspases. Activated caspases lead to fragmentation of cytoplasmic proteins, including contractile apparatus, to a variable extent. It is proposed that the release of cytochrome c from mitochondria and contractile protein loss in living heart muscle cells contributes to systolic dysfunction. Interestingly, despite extensive changes in the cytoplasm, nuclear damage, which is the final event in apoptosis, is rather infrequent in the failing heart. Since the nucleus remains unaffected and the genetic blueprint intact in cells with interrupted apoptosis, these heart muscle cells might be amenable to cytoplasmic reconstitution. This process of 'apoptosis interruptus' could allow development of novel strategies to reverse or attenuate heart failure.

Perioperative management of chronic heart failure

Heart failure (HF) is one of the few cardiac conditions that is increasing. Despite a better understanding of how hormones and other signaling systems underlie the pathophysiology, and despite improved outcomes from pharmacologic therapy, many HF patients receive no effective treatment. Patients with HF commonly require medical diagnosis and management in operating rooms and critical care units; thus anesthesiologists are obliged to remain up-to-date both with advances in outpatient (chronic) medical management and with inpatient treatments for acute exacerbations of HF. Accordingly, we reviewed angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-adrenergic receptor blockers, and aldosterone antagonists because these drugs prolong life and are included in current clinical practice guidelines for treating patients with chronic HF. We also reviewed the implications of chronic HF for patients undergoing surgery and anesthesia and discuss how best to provide intensive treatment for acute exacerbations of symptoms, such as might be caused by excessive intravascular volume, inappropriate drug "holidays," or worsening of the underlying cardiac disease.

Nuclear Cardiology: Present and Future

Nuclear cardiology has made significant advances since the first reports of planar scintigraphy for the evaluation of left ventricular perfusion and function. While the current "state of the art" of gated myocardial perfusion single-photon emission computed tomographic (SPECT) imaging offers invaluable diagnostic and prognostic information for the evaluation of patients with suspected or known coronary artery disease (CAD), advances in the cellular and molecular biology of the cardiovascular system have helped to usher in a new modality in nuclear cardiology, namely, molecular imaging. In this review, we will discuss the current state of the art in nuclear cardiology, which includes SPECT and positron emission tomographic evaluation of myocardial perfusion, evaluation of left ventricular function by gated myocardial perfusion SPECT and gated blood pool SPECT, and the evaluation of myocardial viability with PET and SPECT methods. In addition, we will discuss the future of nuclear cardiology and the role that molecular imaging will play in the early detection of CAD at the level of the vulnerable plaque, the evaluation of cardiac remodeling, and monitoring of important new therapies including gene therapy and stem cell therapy.

Beta1-Adrenergic receptor antagonism abrogates cardioprotective effects of intermittent hypoxia

Adaptation to hypoxia lessens myocardial ischemic injury. This study tested whether hypoxia-induced beta-adrenergic activity mobilizes mechanisms that protect myocardium during subsequent ischemia and reperfusion. Dogs were intermittent hypoxia conditioned (IHC) by a 20 days program of 5-8 daily, 5-10 min cycles of normobaric hypoxia (FIO2 = 9.5-10%), or sham conditioned with normoxic air, and metoprolol (beta1-adrenoceptor antagonist) was administered throughout the IHC program. Twenty-four hours after the last IHC session, the left anterior descending coronary artery (LAD) was occluded for 60 min, and then reperfused for 5 h. Area at risk (AAR) and infarct size (IS) were measured. IHC lowered IS/AAR from 38+/-6% in sham-conditioned dogs to 1.1+/-0.3%, and eliminated ventricular tachycardia (VT) and fibrillation (VF) that occurred in 14 of 17 non-conditioned dogs. Metoprolol blunted IHC-evoked cardioprotection (IS/AAR=27+/-3%), and VT and/or VF occurred in 5 of 6 dogs. Metoprolol did not exacerbate ischemic injury in sham-conditioned dogs (IS/AAR=38+/-2%). Neither IHC nor metoprolol affected hematocrit or LAD collateral blood flow. A single IHC session failed to protect ischemic myocardium (IS/AAR = 36+/-8%), and protection was incomplete after 10 days of IHC (IS/AAR = 13+/-5%), suggesting that de novo protein synthesis was required for protection. Thus, episodic beta1-adrenergic activation during IHC evokes progressive development of powerful resistance to myocardial ischemia.

Differential effects of saturated and unsaturated fatty acid diets on cardiomyocyte apoptosis, adipose distribution, and serum leptin

Fatty acids are the primary fuel for the heart and are ligands for peroxisome proliferator-activated receptors (PPARs), which regulate the expression of genes encoding proteins involved in fatty acid metabolism. Saturated fatty acids, particularly palmitate, can be converted to the proapoptotic lipid intermediate ceramide. This study assessed cardiac function, expression of PPAR-regulated genes, and cardiomyocyte apoptosis in rats after 8 wk on either a low-fat diet [normal chow control (NC); 10% fat calories] or high-fat diets composed mainly of either saturated (Sat) or unsaturated fatty acids (Unsat) (60% fat calories) (n = 10/group). The Sat group had lower plasma insulin and leptin concentrations compared with the NC or Unsat groups. Cardiac function and mass and body mass were not different. Cardiac triglyceride content was increased in the Sat and Unsat groups compared with NC (P < 0.05); however, ceramide content was higher in the Sat group compared with the Unsat group (2.9 +/- 0.2 vs. 1.4 +/- 0.2 nmol/g; P < 0.05), whereas the NC group was intermediate (2.3 +/- 0.3 nmol/g). The number of apoptotic myocytes, assessed by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling staining, was higher in the Sat group compared with the Unsat group (0.28 +/- 0.05 vs. 0.17 +/- 0.04 apoptotic cells/1,000 nuclei; P < 0.04) and was positively correlated to ceramide content (P < 0.02). Both high-fat diets increased the myocardial mRNA expression of the PPAR-regulated genes encoding uncoupling protein-3 and pyruvate dehydrogenase kinase-4, but only the Sat diet upregulated medium-chain acyl-CoA dehydrogenase. In conclusion, dietary fatty acid composition affects cardiac ceramide accumulation, cardiomyocyte apoptosis, and expression of PPAR-regulated genes independent of cardiac mass or function.

Proapoptotic Effects of Caspase-1/Interleukin-Converting Enzyme Dominate in Myocardial Ischemia

Caspase-1/interleukin-converting enzyme (ICE) is a cysteine protease traditionally considered to have importance as an inflammatory mediator, but not as an apoptotic effector. Because of the dual functions of this caspase, the pathophysiological impact of its reported upregulation in hypertrophy and heart failure is not known. Here, the consequences of increased myocardial expression of procaspase-1 were examined on the normal and ischemically injured heart. In unstressed mouse hearts with a 30-fold increase in procaspase-1 content, unprocessed procaspase-1 was well tolerated, without detectable pathology. Cardiomyocyte processing and activation of caspase-1 and caspase-3 occurred after administration of endotoxin or with transient myocardial ischemia. In post-ischemic hearts, procaspase-1 overexpression was associated with strikingly increased cardiac myocyte apoptosis in the peri- and noninfarct regions and with 50% larger myocardial infarctions. Tissue culture studies revealed that procaspase-1 processing/activation is stimulated by hypoxia, and that caspase-1 acts in synergy with hypoxia to stimulate caspase-3 mediated apoptosis without activating upstream caspases. These data demonstrate that the proapoptotic effects of caspase-1 can significantly impact the myocardial response to ischemia and suggest that conditions in which procaspase-1 in the heart is increased may predispose to apoptotic myocardial injury under conditions of physiological stress.

Importance of antioxidant and antiapoptotic effects of β-receptor blockers in heart failure therapy

The present study was carried out to determine whether beneficial effects of carvedilol in congestive heart failure (CHF) are mediated via its β-adrenergic blocking, antioxidant, and/or α-adrenergic blocking action. Rabbits with heart failure induced by rapid cardiac pacing were randomized to receive subcutaneous carvedilol, metoprolol, propranolol plus doxazosin, or placebo pellets for 8 wk and compared with sham-operated rabbits without pacing. We found rapid cardiac pacing produced clinical heart failure, left ventricular dilation, and decline of left ventricular fractional shortening. This was associated with an increase in left ventricular end-diastolic pressure, decrease in left ventricular first derivative of left ventricular pressure, and myocyte hypertrophy. Tissue oxidative stress measured by GSH/GSSG was increased in the heart with increased oxidation product of mitochondrial DNA, 8-oxo-7,8-dihydro-2′-deoxyguanosine, increase of Bax, decrease of Bcl-2, and increase of apoptotic myocytes as measured by anti-single-stranded DNA monoclonal antibody. Administration of carvedilol and metoprolol, which had no effect in sham animals, attenuated cardiac ventricular remodeling, cardiac hypertrophy, oxidative stress, and myocyte apoptosis in CHF. In contrast, propranolol plus doxazosin, which has less antioxidant effects, produced smaller effects on left ventricular function and myocyte apoptosis. In all animals, GSH/GSSG correlated significantly with changes of left ventricular end-diastolic dimension ( r = −0.678, P < 0.0001), fractional shortening ( r = 0.706, P < 0.0001), and apoptotic myocytes ( r = −0.473, P = 0.0001). Thus our findings suggest antioxidant and antiapoptotic actions of carvedilol and metoprolol are important determinants of clinical beneficial effects of β-receptors in the treatment of CHF.

Beta-blockade in the management of systolic dysfunction

The concept that heart failure is simply the consequence of impaired pump function is now outmoded. Congestive heart failure is a neuroendocrine syndrome in with activation of the adrenergic nervous system and specific endocrine pathways is integral to its pathogenesis. It is now clear that chronic increases in adrenergic drive associated with heart failure have detrimental effects on myocardial function. The use of BAAs is now standard therapy for people who develop heart failure caused by systolic dysfunction. Beta-blockade may have a role in the management of dogs with heart failure.

Direct inhibition of type 5 adenylyl cyclase prevents myocardial apoptosis without functional deterioration

Adenylyl cyclase, a major target enzyme of beta-adrenergic receptor signals, is potently and directly inhibited by P-site inhibitors, classic inhibitors of this enzyme, when the enzyme catalytic activity is high. Unlike beta-adrenergic receptor antagonists, this is a non- or uncompetitive inhibition with respect to ATP. We have examined whether we can utilize this enzymatic property to regulate the effects of beta-adrenergic receptor stimulation differentially. After screening multiple new and classic compounds, we found that some compounds, including 1R,4R-3-(6-aminopurin-9-yl)-cyclopentanecarboxylic acid hydroxyamide, potently inhibited type 5 adenylyl cyclase, the major cardiac isoform, but not other isoforms. In normal mouse cardiac myocytes, contraction induced by low beta-adrenergic receptor stimulation was poorly inhibited with this compound, but the induction of cardiac myocyte apoptosis by high beta-adrenergic receptor stimulation was effectively prevented by type 5 adenylyl cyclase inhibitors. In contrast, when cardiac myocytes from type 5 adenylyl cyclase knock-out mice were examined, beta-adrenergic stimulation poorly induced apoptosis. Our data suggest that the inhibition of beta-adrenergic signaling at the level of the type 5 adenylyl cyclase isoform by P-site inhibitors may serve as an effective method to prevent cardiac myocyte apoptosis induced by excessive beta-adrenergic stimulation without deleterious effect on cardiac myocyte contraction.

Prevention and Reversal of LV Remodeling with Neurohormonal Inhibitors

Left ventricular (LV) remodeling refers to alterations in ventricular mass, chamber size, and shape that result from myocardial injury, pressure, or volume overload. Numerous studies have demonstrated that LV remodeling correlates with the incidence of heart failure and death, supporting a causative role for remodeling in heart failure progression. Heart failure trials have shown that neurohormonal antagonists, including angiotensin-converting enzyme (ACE) inhibitors and beta-adrenergic receptor blockers (beta blockers), reduce remodeling in parallel with improved clinical outcomes. Existing data favor using angiotensin II type 1 (AT1) receptor antagonists (or "ARBs"), although their anti-remodeling effects are less well established. Recently, mineralocorticoid receptor antagonists have gained substantial interest based on favorable clinical trial results, although data regarding their effects on remodeling are limited. Thus, an optimal medical regimen to prevent or limit LV remodeling in patients with LV dysfunction should include both an ACE inhibitor and beta-adrenergic receptor antagonist, irrespective of the degree of LV dysfunction and symptom status. For patients intolerant to ACE inhibitors, an AT1 receptor antagonist should be substituted. An aldosterone antagonist should be administered to patients with severe, New York Heart Association class III to IV heart failure who have normal or only mildly impaired renal function, or to those patients with depressed LV function following an acute myocardial infarction. Through the aggressive pharmacologic inhibition of both the renin-angiotensin-aldosterone and sympathetic nervous systems, progressive LV remodeling can be prevented or hindered, thereby favorably altering the natural history of the heart failure syndrome.

Anti-beta(1)-adrenergic receptor antibodies and heart failure: causation, not just correlation

Antibodies specific for the beta(1)-adrenergic receptor are found in patients with chronic heart failure of various etiologies. From work presented in this issue of the JCI, we can now infer that these antibodies actually contribute to the pathogenesis of chronic heart failure. This commentary discusses mechanisms by which these antibodies may engender cardiomyopathy.

From CONSENSUS to CHARM—how do ACEI and ARB produce clinical benefits in CHF?

Two decades of research from CONSENSUS to CHARM using modulators of the renin-angiotensin-aldosterone system (RAAS) in chronic heart failure (CHF) patients have shown convincing clinical benefits, but the majority of clinicians prescribing these drugs are still unclear about what mechanisms are responsible for the observed benefits. Of the candidate mechanisms hitherto proposed, there emerges a theme that best fits the spectrum of known factors from pathophysiology of heart failure to how the drugs enhance longevity of patients. This concept can be summarised as follows: after the onset of heart failure, neurohormones are activated resulting in raised levels of angiotensin, aldosterone and catecholamines, which are all known cardiotoxic agents. Cumulatively over time, they are responsible for accelerated cardiomyocyte attrition, manifesting as a faster reduction of cardiac pumping reserve, leading to worsening heart failure, more neurohormonal activation, thus propagating a vicious cycle spiralling towards an earlier fatality. The vicious cycle can be interrupted by dampening the excessive neurohormonal activities, thereby minimising cardiomyocyte losses and preserving cardiac functional reserve for longer. This culminates in maintenance of a reasonable quality of life and enhanced longevity. Such a mechanistic understanding would enable clinicians to have a better perspective on how to apply data from various clinical trials involving these drugs into clinical practice, to optimise and tailor therapy to the individual patient so that each patient can gain maximal benefits.

Selective versus nonselective beta-blockade for heart failure therapy: are there lessons to be learned from the COMET trial?

The recently reported COMET trial found that the beta1/beta2/alpha1 receptor blocking agent carvedilol given in a relatively high beta1-receptor blocking dose regimen was superior in mortality reduction to immediate release metoprolol given in a relatively low beta1-receptor blocking dose schedule. We analyze the problems with the trial design of COMET from the standpoint of comparing 2 therapeutic agents at different positions on a common dose-response curve, and discuss the theoretical reasons why postjunctional adrenergic receptor blockade that is in addition to beta1-receptor antagonism will likely produce only minimal or no incremental benefit in chronic heart failure.

Selective β1-blockade attenuates post-infarct remodelling without improvement in myocardial energy metabolism and function in rats with heart failure

OBJECTIVE

To investigate in vivo effects of long-term selective beta1-blockade on cardiac energy metabolism, remodelling, function and plasma cytokines in a rat model of post-infarct congestive heart failure (CHF).

METHODS

Myocardial infarction (MI) was induced in male rats by ligation of the left coronary artery. Three different groups of rats were studied, MI rats treated with metoprolol (n=17), MI rats treated with saline (n=14) and sham-operated rats (n=12). The treatment with metoprolol 1 mg/kg/h was initiated in the third week post-infarct for a period of 6 weeks. All rats were investigated non-invasively with volume-selective 31P magnetic resonance spectroscopy and echocardiography for evaluation of left ventricular (LV) energy metabolism, morphology and function. Plasma concentration of IL-1beta and IL-6 and density of beta-adrenergic receptors were analyzed.

RESULTS

Metoprolol attenuated the increase in LV dimensions and volumes. Treatment with metoprolol had no effect on PCr/ATP and LV function. Plasma level of IL-1beta was higher and IL-6 was lower in the metoprolol group. Density of beta-adrenergic receptors was similar in all three groups.

CONCLUSION

Selective beta1-blockade in rats with chronic CHF attenuates post-infarct structural remodelling, without concomitant improvement in myocardial energy metabolism and function. Improvements in myocardial energy metabolism and function do not precede and are not a prerequisite for an anti-remodelling effect of beta1-blockade in the setting of chronic CHF.

What is the role of beta-adrenergic signaling in heart failure?

This review addresses open questions about the role of beta-adrenergic receptors in cardiac function and failure. Cardiomyocytes express all three beta-adrenergic receptor subtypes-beta1, beta2, and, at least in some species, beta3. The beta1 subtype is the most prominent one and is mainly responsible for positive chronotropic and inotropic effects of catecholamines. The beta2 subtype also increases cardiac function, but its ability to activate nonclassical signaling pathways suggests a function distinct from the beta1 subtype. In heart failure, the sympathetic system is activated, cardiac beta-receptor number and function are decreased, and downstream mechanisms are altered. However, in spite of a wealth of data, we still do not know whether and to what extent these alterations are adaptive/protective or detrimental, or both. Clinically, beta-adrenergic antagonists represent the most important advance in heart failure therapy, but it is still debated whether they act by blocking or by resensitizing the beta-adrenergic receptor system. Newer experimental therapeutic strategies aim at the receptor desensitization machinery and at downstream signaling steps.

Left ventricular wall stress as a direct correlate of cardiomyocyte apoptosis in patients with severe dilated cardiomyopathy

BACKGROUND

Apoptosis has been implicated as a possible mechanism in the development of heart failure (HF), but the mechanisms involved remain unclear. In patients with severe dilated cardiomyopathy, we evaluated cardiomyocyte apoptosis in relation to the transmural distribution of Bax and Bcl-2 proteins (2 molecules inhibiting or promoting apoptosis, respectively) and left ventricular wall stresses.

METHODS

We studied the presence and distribution of cardiomyocyte apoptosis in 90 tissue samples obtained from 8 patients who were undergoing left ventricular reduction with the Batista (ventricular remodeling) operation. Apoptosis was assessed in tissue samples taken from the entire left ventricular thickness (subdivided in subepicardial, midmyocardial, and subendocardial sections) with the terminal deoxynucleotidyl transferase mediated dUTP-biotin nick-end labeling (TUNEL) technique and DNA agarose gel electrophoresis. The expression of Bcl-2 and Bax proteins were determined with both Western analysis and immunohistochemistry.

RESULTS

TUNEL-positive cells (apoptotic index) were 2.3% +/- 1.4%. Apoptotic cells were predominantly distributed in the subendocardium, where higher levels of Bax protein were detected. The ratio of Bax to Bcl-2 proteins (Bax/Bcl-2) was similar in the midmyocardium or subepicardium, but increased in the subendocardium, where it was directly related to systolic wall stress (y = 0.009x - 0.629; r2 = 0.85, P <.001). The apoptotic index was also directly related to systolic and end-diastolic stresses calculated from hemodynamic and echocardiographic data (r2 = 0.77, P <.001 and r2 = 0.40, P <.01, respectively).

CONCLUSIONS

In patients with dilated cardiomyopathy, in whom cardiomyocyte apoptosis is an important cause of cell loss, apoptosis is more extensively localized in the subendocardium and strictly related to ventricular wall stresses and the Bax/Bcl-2 ratio.

Myocardial Contractile Reserve by Dobutamine Stress Echocardiography Predicts Improvement in Ejection Fraction With β-Blockade in Patients With Heart Failure

Background— β-Blockers improve survival and reduce hospitalization in chronic heart failure (CHF) by biologically improving left ventricular ejection fraction (LVEF). However, a good predictor of improvement with this therapy has not been identified. This substudy of BEST examined whether myocardial contractile reserve, as determined by dobutamine stress echocardiography, predicts improvement in LVEF.

Methods and Results— Seventy-nine patients with class III/IV CHF underwent dobutamine stress echocardiography before treatment with bucindolol (n=41) or placebo (n=38). Regional wall motion score index (WMSI) was calculated as the sum of the scores in each segment divided by the total number of segments visualized. WMSI was compared with change in LVEF after 3 months of therapy as determined by gated radionuclide scan. Change in WMSI correlated inversely with change in LVEF after 3 months of bucindolol ( r =−0.72, P <0.0001) and was the most significant multivariate predictor of change in LVEF ( P =0.0002). Patients with contractile reserve had demographics similar to those of patients without contractile reserve, including RVEF, LVEF, systolic blood pressure, and CHF duration. However, patients without contractile reserve had higher baseline plasma norepinephrine levels (687±333 versus 420±246 pg/mL, P <0.05) and greater decrease in plasma norepinephrine in response to bucindolol (−249±171 versus −35±277 pg/mL, P <0.05).

Conclusions— This study suggests a direct relationship between contractile reserve and improvement in LVEF with β-blocker therapy in patients with advanced CHF. Patients without contractile reserve have higher resting adrenergic drive, as reflected by plasma norepinephrine, and may experience greater sympatholytic effects from bucindolol.

Right ventricular dilatation after left ventricular acute myocardial infarction is predictive of extremely high peri-infarctual apoptosis at postmortem examination in humans

BACKGROUND

Cardiac remodelling after acute myocardial infarction (AMI) is characterised by molecular and cellular mechanisms involving both left and right ventricles, and biventricular failure identifies patients with an extremely unfavourable prognosis.

AIMS

To assess whether a link exists between increased myocardial apoptotic rates (AR) at sites of recent infarction and patterns of unfavourable cardiac remodelling, such as biventricular enlargement after left ventricular (LV) infarction.

METHODS

Twelve patients with recent AMI involving the LV and not the right ventricle (RV) and with permanent infarct related artery occlusion were selected at necropsy. Gross pathological characteristics, such as LV and RV dilatation, and AR at site of infarction were assessed. Potential false positive results (DNA synthesis and RNA splicing) were excluded from the cell count.

RESULTS

RV enlargement, defined as a tricuspidal ring greater than 120 mm, was found in five cases and was associated with LV dilatation. These patients showed significantly higher AR than the others. When the subjects were divided into three groups according to progressive cardiac remodelling (absence of cardiac dilatation, isolated LV dilatation, and biventricular enlargement), the last group had significantly higher ARs than the other two groups, showing that myocardiocyte apoptosis is increased in more unfavourable forms of cardiac remodelling.

CONCLUSION

Patients with severely unfavourable cardiac remodelling, such as biventricular enlargement, have extremely high myocardiocyte apoptosis at necropsy, even late after LV myocardial infarction, supporting the role of myocardiocyte loss in determining post-infarction adverse remodelling.