Intermittent, ambulatory dobutamine infusions in patients with severe congestive heart failure

Cardiac Myosin Activator Omecamtiv Mecarbil: Novel Treatment for Systolic Heart Failure

Systolic Heart failure is a complex clinical syndrome characterized by a decrease in cardiac contractility and a reduction in organ perfusion. Current pharmacologic inotropes attempt to improve contractility via indirect mechanisms but are limited in terms of safety and effectiveness. Omecamtiv mecarbil is a novel agent in a new class of drugs known as cardiac myosin activators; their unique mechanism of action involves directly activating the enzymatic pathway in the cardiac myocyte as a way to improve ventricular contraction. Preclinical and clinical trials have found that omecamtiv mecarbil improves cardiac contractility without increasing the risk of any of the harmful effects that are associated with the currently available inotropic agents. Omecamtiv mecarbil is a worthwhile advance and patients with systolic heart failure would benefit from pharmacological use of this drug.

Continuous Intravenous Inotropic Support for Advanced Heart Failure: Palliative Considerations

The global prevalence of heart failure (HF) is increasing. Advancements in guideline-directed medical and device therapy have resulted in improved survival. Thus, there are more patients living - and living longer - with advanced HF. Only a small proportion of these patients are deemed appropriate for advanced surgical intervention (mechanical circulatory support or heart transplantation), and even if offered, some may decline such interventions if not aligned with their overall goals and values. Therefore, a growing number of patients with advanced HF receive chronic intravenous inotropic support (CIIS) for palliation of symptoms. Despite increased use, clinical evidence supporting use of palliative inotropes remains limited. However, available data suggest improvements in functional class, health-related quality of life (HRQoL) indicators, symptom burden, hemodynamic parameters, and possibly rehospitalization. While initial concerns regarding increased mortality have been assuaged in the modern era of guideline-directed medical therapy, palliative inotropes are certainly not without burden. Risks of infection and medication-related adverse effects, need for routine laboratory monitoring, frequent dressing changes, and presence of a reliable caregiver must be carefully considered prior to initiation. This review addresses pharmacology, guideline recommendations, benefits and burdens, considerations related to hospice and end-of-life care, and future directions of CIIS in advanced HF care.

The Role of CaMKII Overexpression and Oxidation in Atrial Fibrillation-A Simulation Study

This simulation study aims to investigate how the Calcium/calmodulin-dependent protein kinase II (CaMKII) overexpression and oxidation would influence the cardiac electrophysiological behavior and its arrhythmogenic mechanism in atria. A new-built CaMKII oxidation module and a refitted CaMKII overexpression module were integrated into a mouse atrial cell model for analyzing cardiac electrophysiological variations in action potential (AP) characteristics and intracellular Ca²⁺ cycling under different conditions. Simulation results showed that CaMKII overexpression significantly increased the phosphorylation level of its downstream target proteins, resulting in prolonged AP and smaller calcium transient amplitude, and impaired the Ca²⁺ cycling stability. These effects were exacerbated by extra reactive oxygen species, which oxidized CaMKII and led to continuous high CaMKII activation in both systolic and diastolic phases. Intracellular Ca²⁺ depletion and sustained delayed afterdepolarizations (DADs) were observed under co-existing CaMKII overexpression and oxidation, which could be effectively reversed by clamping the phosphorylation level of ryanodine receptor (RyR). We also found that the stability of RyR release highly depended on a delicate balance between the level of RyR phosphorylation and sarcoplasmic reticulum Ca²⁺ concentration, which was closely related to the genesis of DADs. We concluded that the CaMKII overexpression and oxidation have a synergistic role in increasing the activity of CaMKII, and the unstable RyR may be the key downstream target in the CaMKII arrhythmogenic mechanism. Our simulation provides detailed mechanistic insights into the arrhythmogenic effect of CaMKII overexpression and oxidation, which suggests CaMKII as a promising target in the therapy of atrial fibrillation.

Genetic, clinical, molecular, and pathogenic aspects of the South Asian-specific polymorphic MYBPC3Δ25bp variant

Hypertrophic cardiomyopathy (HCM) is a cardiac genetic disease characterized by ventricular enlargement, diastolic dysfunction, and increased risk for sudden cardiac death. Sarcomeric genetic defects are the predominant known cause of HCM. In particular, mutations in the myosin-binding protein C gene (MYBPC3) are associated with ~ 40% of all HCM cases in which a genetic basis has been established. A decade ago, our group reported a 25-base pair deletion in intron 32 of MYBPC3 (MYBPC3Δ25bp) that is uniquely prevalent in South Asians and is associated with autosomal dominant cardiomyopathy. Although our studies suggest that this deletion results in left ventricular dysfunction, cardiomyopathies, and heart failure, the precise mechanism by which this variant predisposes to heart disease remains unclear. Increasingly appreciated, however, is the contribution of secondary risk factors, additional mutations, and lifestyle choices in augmenting or modifying the HCM phenotype in MYBPC3Δ25bp carriers. Therefore, the goal of this review article is to summarize the current research dedicated to understanding the molecular pathophysiology of HCM in South Asians with the MYBPC3Δ25bp variant. An emphasis is to review the latest techniques currently applied to explore the MYBPC3Δ25bp pathogenesis and to provide a foundation for developing new diagnostic strategies and advances in therapeutics.

Pathogenesis and pathophysiology of heart failure with reduced ejection fraction: translation to human studies

Heart failure represents the end result of different pathophysiologic processes, which culminate in functional impairment. Regardless of its aetiology, the presentation of heart failure usually involves symptoms of pump failure and congestion, which forms the basis for clinical diagnosis. Pathophysiologic descriptions of heart failure with reduced ejection fraction (HFrEF) are being established. Most commonly, HFrEF is centred on a reactive model where a significant initial insult leads to reduced cardiac output, further triggering a cascade of maladaptive processes. Predisposing factors include myocardial injury of any cause, chronically abnormal loading due to hypertension, valvular disease, or tachyarrhythmias. The pathophysiologic processes behind remodelling in heart failure are complex and reflect systemic neurohormonal activation, peripheral vascular effects and localised changes affecting the cardiac substrate. These abnormalities have been the subject of intense research. Much of the translational successes in HFrEF have come from targeting neurohormonal responses to reduced cardiac output, with blockade of the renin-angiotensin-aldosterone system (RAAS) and beta-adrenergic blockade being particularly fruitful. However, mortality and morbidity associated with heart failure remains high. Although systemic neurohormonal blockade slows disease progression, localised ventricular remodelling still adversely affects contractile function. Novel therapy targeted at improving cardiac contractile mechanics in HFrEF hold the promise of alleviating heart failure at its source, yet so far none has found success. Nevertheless, there are increasing calls for a proximal, 'cardiocentric' approach to therapy. In this review, we examine HFrEF therapy aimed at improving cardiac function with a focus on recent trials and emerging targets.

Current Status of Inotropes in Heart Failure

Inotropes are medications that improve the contractility of the heart and are used in patients with low cardiac output or evidence of end-organ dysfunction. Since their initial discovery, inotropes have held promise in alleviating symptoms and potentially increasing longevity in such patients. Decades of intensive study have further elucidated the benefits and risks of using inotropes. In this article, the authors discuss the history of inotropes, their indications, mechanism of action, and current guidelines pertaining to their use in heart failure. The authors provide insight into their appropriate use and related shortcomings and the practical aspects of inotrope use.

Ambulatory Inotrope Infusions in Advanced Heart Failure: A Systematic Review and Meta-Analysis

OBJECTIVES

This study sought to systematically review the available evidence of risks and benefits of ambulatory intravenous inotrope therapy in advanced heart failure (HF).

BACKGROUND

Ambulatory inotrope infusions are sometimes offered to patients with advanced Stage D HF; however, an understanding of the relative risks and benefits is lacking.

METHODS

On August 7, 2016, we searched SCOPUS, Web of Science, Ovid EMBASE, and Ovid MEDLINE for studies of long-term use of intravenous inotropes in outpatients with advanced HF. Meta-analysis was performed using random effects models.

RESULTS

A total of 66 studies (13 randomized controlled trials and 53 observational studies) met inclusion criteria. Most studies were small and at high risk for bias. Pooled rates of death (41 studies), all-cause hospitalization (15 studies), central line infection (13 studies), and implantable cardioverter-defibrillator shocks (3 studies) of inotropes were 4.2, 22.2, 3.6, and 2.4 per 100 person-months follow-up, respectively. Improvement in New York Heart Association (NYHA) functional class was greater in patients taking inotropes than in controls (mean difference of 0.60 NYHA functional classes; 95% confidence interval [CI]: 0.22 to 0.98; p = 0.001; 5 trials). There was no significant difference in mortality risk in those taking inotropes compared with controls (pooled risk ratio: 0.68; 95% CI: 0.40 to 1.17; p = 0.16; 9 trials). Data were too limited to pool for other outcomes or to stratify by indication (i.e., bridge-to-transplant or palliative).

CONCLUSIONS

High-quality evidence for the risks and benefits of ambulatory inotrope infusions in advanced HF is limited, particularly when used for palliation. Available data suggest that inotrope therapy improves NYHA functional class and does not impact survival.

The Role of Positive Inotropic Drugs in the Treatment of Older Adults with Heart Failure and Reduced Ejection Fraction

Positive inotropic drugs have long been studied for their potential benefits in patients with heart failure and reduced ejection fraction (HFrEF). Although there has been an extensive amount of research about the clinical effects of these drugs in general, few studies examined their effect in older patients. Therefore, there is little or no evidence to guide the use of positive inotropes in older patients with HFrEF. However, recommendations from national heart failure guidelines may be generalized to older HFrEF patients on an individual basis, taking into consideration the basic geriatric principles of pharmacotherapy: start low and go slow.

Retinoid acid-induced microRNA-31-5p suppresses myogenic proliferation and differentiation by targeting CamkIIδ

BACKGROUND

We previously reported that Wnt5a/CaMKIIδ (calcium/calmodulin-dependent protein kinase II delta) pathway was involved in the embryonic tongue deformity induced by excess retinoic acid (RA). Our latest study found that the expression of miR-31-5p, which was predicted to target the 3'UTR of CamkIIδ, was raised in the RA-treated embryonic tongue. Thus, we hypothesized that the excess RA regulated Wnt5a/CaMKIIδ pathway through miR-31-5p in embryonic tongue.

METHODS

C2C12 myoblast line was employed as an in vitro model to examine the suppression of miR-31-5p on CamkIIδ expression, through which RA impaired the myoblast proliferation and differentiation in embryonic tongue.

RESULTS

RA stimulated the expression of miR-31-5p in both embryonic tongue and C2C12 myoblasts. Luciferase reporter assay confirmed that the 3'UTR of CamkIIδ was a target of miR-31-5p. MiR-31-5p mimics disrupted CamkIIδ expression, C2C12 proliferation and differentiation as excess RA did, while miR-31-5p inhibitor partially rescued these defects in the presence of RA.

CONCLUSIONS

Excess RA can stimulate miR-31-5p expression to suppress CamkIIδ, which represses the proliferation and differentiation of tongue myoblasts.

New developments in the pharmacotherapeutic management of heart failure in elderly patients: concerns and considerations

INTRODUCTION

Heart failure (HF) remains a major public health problem worldwide, affecting approximately 23 million patients, and is predominantly a disease of the elderly population. Elderly patients mostly suffer from HF with preserved ejection fraction (HFpEF), which often presents with multiple co-morbidities and they require multiple medical treatments. This, together with the heterogeneous phenotype of HFpEF, makes it a difficult syndrome to diagnose and treat. Areas covered: Although HF is most abundant in the elderly, this group is still underrepresented in clinical trials, which results in the lack of evidence-based medical regimens. The current review has focused on new potential therapies for this poorly studied population. The focus will be on several classes of drugs currently recommended or might be expected soon. These will include sacubitril/valsartan (former LCZ696), Omecamtiv mecarbil, Vericiguat, Ivabradine, mineralocorticoid receptor antagonists (MRAs) and potassium binders. Expert opinion: We discuss promising new treatments and hypothesize that personalized approaches will be needed to treat elderly patients optimally. Medical doctors should not only focus on HF therapy, but comorbidities and polypharmacy should also influence therapeutic decision making. Furthermore, the importance of quality of life as a management endpoint should not be underestimated in the frail elderly.

Quality of life and long-term mortality in patients with advanced chronic heart failure treated with intermittent low-dose intravenous inotropes in an outpatient setting

AIMS

There are limited data on the effect of low-dose, intermittent inotropic therapy in an outpatient setting on the quality of life (QOL) in patients with advanced refractory heart failure (HF) symptoms. We aimed to analyse the effect of this treatment modality on QOL and subsequent survival.

METHODS AND RESULTS

The study population comprised 287 consecutive patients with advanced refractory HF symptoms who were treated with low-dose, intravenous intermittent inotropic therapy in the HF Day Care Service at Sheba Medical Centre between September 2000 and September 2012. All patients completed a baseline Minnesota Living with Heart Failure Questionnaire (MLWHFQ), and 137 (48%) completed a 1 year follow-up questionnaire. MLWHFQ scores' means ranged from 0 (better QOL) to 5 (worse QOL). Mean age was 68 ± 12, 86% were men, 77% had ischaemic cardiomyopathy, and the mean left ventricle ejection fraction (LVEF) was 26% ± 13. The mean baseline MLWHFQ score was 3.1 (±1), while the mean at 1 year of treatment was of 2.7 (±1.1), indicating an overall improvement in QOL associated with intermittent low-dose inotrope therapy (p < 0.01). Multivariate analysis showed that younger age, non-ischaemic cardiomyopathy, and worse renal function were independently associated with improvement in QOL at 1 year. Improvement in QOL was not associated with a significant survival benefit during subsequent follow-up.

CONCLUSIONS

In patients with advanced refractory HF symptoms, treatment with low-dose, intermittent intravenous inotropes in an outpatient setting is associated with significant improvement in QOL. However, improvement in QOL in this population does not appear to affect subsequent long-term survival.

Ivabradine treatment prevents dobutamine-induced increase in heart rate in patients with acute decompensated heart failure

BACKGROUND

Ivabradine is a heart rate (HR)-lowering agent acting by inhibiting the If-channel. Dobutamine does increase the HR and has some deleterious effects on myocardium. So, we aimed to evaluate whether ivabradine treatment blunts a dobutamine-induced increase in HR.

METHODS

The main study population consisted of 58 acute decompensated heart failure patients requiring inotropic support with left-ventricular ejection fraction below 35%, who were randomized to ivabradine (n = 29) or control (n = 29). All patients underwent Holter recording for 6 h and then dobutamine was administered at incremental doses of 5, 10 and 15 μg/kg/min, with 6-h steps. Holter recording was continued during dobutamine infusion. Ivabradine 7.5 mg was given at the initiation of dobutamine and readministered at 12 h of infusion. Also, a nonrandomized beta-blocker group with 15 patients receiving beta-blocker was included in the analysis. Control and beta-blocker groups did not receive ivabradine.

RESULTS

In the control group, mean HR gradually and significantly increased at each step of dobutamine infusion (81 ± 11, 90 ± 16, 97 ± 14 and 101 ± 16 b.p.m., respectively; P = 0.001), whereas no significant increase in HR was observed in the ivabradine group (82 ± 17, 82 ± 15, 85 ± 14 and 83 ± 12 b.p.m., respectively; P = 0.439). Mean HR was also found to significantly increase during dobutamine infusion in the beta-blocker group (75 ± 13, 82 ± 13, 86 ± 14 and 88 ± 13 b.p.m., respectively; P = 0.001). The median increase in HR from baseline was significantly higher in the control group compared to those in the ivabradine group (5 vs. 2 b.p.m.; P = 0.007 at first step, 13 vs. 5 b.p.m.; P = 0.001 at second step and 18 vs. 6 b.p.m.; P = 0.0001 at third step of dobutamine, respectively).

CONCLUSIONS

Ivabradine treatment prevents dobutamine-induced increase in HR and may be useful in reducing HR-related adverse effects of dobutamine.

Omecamtiv mecarbil: a new cardiac myosin activator for the treatment of heart failure

INTRODUCTION

Current available inotropic agents increase cardiac contractility, but are associated with myocardial ischemia, arrhythmias, and mortality. A novel selective cardiac myosin activator, omecamtiv mecarbil (CK-1827452/ AMG-423) is a small molecule that activates the sarcomere proteins directly, resulting in prolonged systolic ejection time and increased cardiac contractility.

AREAS COVERED

This paper discusses the chemistry, pharmacokinetics, clinical efficacy and safety of omecamtiv mecarbil. Omecamtiv mecarbil represents a novel therapeutic approach to directly improve cardiac function and is therefore proposed as a potential new treatment of patients with systolic heart failure. The authors review results of previous studies investigating the effect of omecamtiv mecarbil in heart failure animal models, healthy volunteers, and patients with acute and chronic systolic heart failure.

EXPERT OPINION

Results of phase I and phase II studies demonstrate that omecamtiv mecarbil is safe and well tolerated both as an intravenous and oral formulation. In healthy volunteers and chronic systolic heart failure patients, administration of omecamtiv mecarbil resulted in a concentration-dependent increase of left ventricular ejection time, ejection fraction, fractional shortening, and stroke volume. The first results of a double-blind, randomized, placebo-controlled phase IIb dose-finding study with the oral formulation of omecamtiv mecarbil demonstrated beneficial effects on cardiac function and N-terminal pro-brain natriuretic peptide levels. This study will provide essential dosing information for the requisite phase III trials which will investigate whether the beneficial effects of omecamtiv mecarbil translate into improved clinical outcomes.

Ischemia-modified albumin levels in patients with acute decompensated heart failure treated with dobutamine or levosimendan: IMA-HF study

OBJECTIVE

Ischemia-modified albumin (IMA) is a sensitive biomarker of myocardial ischemia. However, data on IMA levels in acute heart failure (HF) are still lacking. In this study, we aimed to evaluate serum IMA levels in acute decompensated HF and the effects of dobutamine and levosimendan treatments on IMA levels.

METHODS

This was a prospective, multicenter study that included 70 patients hospitalized with acute decompensated HF and left ventricular ejection fraction < 35%. Blood samples for IMA measurements were obtained on admission and 24-48 h after the initiation of HF therapy. Twenty-nine patients were treated with standard HF therapy, 18 received levosimendan, and 23 received dobutamine in addition to standard of care. A single serum specimen was also collected from 32 healthy individuals each. IMA concentrations were measured by the albumin cobalt binding colorimetric assay, and the results were given in absorbance units (AU). Independent and paired sample t-tests, Mann-Whitney U test, and Wilcoxon signed-rank test were used for the analysis.

RESULTS

In patients with acute decompensated HF, the serum concentration of IMA was significantly higher than those of healthy subjects (0.894 ± 0.23 AU vs. 0.379 ± 0.08 AU, p < 0.001). Overall, the IMA levels significantly decreased after 24-48 h of HF therapy (0.894 ± 0.23 AU and 0.832 ± 0.18 AU, p = 0.013). Furthermore, the IMA levels were also found to significantly decrease with standard HF therapy (1.041 ± 0.28 vs. 0.884 ± 0.15 AU, p = 0.041), with levosimendan (0.771 ± 0.18 vs. 0.728 ± 0.18 AU, p = 0.046) and also with dobutamine (0.892 ± 0.18 vs. 0.820 ± 0.13 AU, p = 0.035).

CONCLUSION

Patients with acute decompensated HF had elevated IMA levels, and appropriate HF therapy significantly reduced the serum IMA levels. Dobutamine or levosimendan did not increase the IMA levels, suggesting a lower potential in inducing myocardial ischemia when used in recommended doses.

Inotropes do not increase mortality in advanced heart failure

Inotrope use is one of the most controversial topics in the management of heart failure. While the heart failure community utilizes them and recognizes the state of inotrope dependency, retrospective analyses and registry data have overwhelmingly suggested high mortality, which is logically to be expected given the advanced disease states of those requiring their use. Currently, there is a relative paucity of randomized control trials due to the ethical dilemma of creating control groups by withholding inotropes from patients who require them. Nonetheless, results of such trials have been mixed. Many were also performed with agents no longer in use, on patients without an indication for inotropes, or at a time before automatic cardio-defibrillators were recommended for primary prevention. Thus, their results may not be generalizable to current clinical practice. In this review, we discuss current indications for inotrope use, specifically dobutamine and milrinone, depicting their mechanisms of action, delineating their patterns of use in clinical practice, defining the state of inotrope dependency, and ultimately examining the literature to ascertain whether evidence is sufficient to support the current view that these agents increase mortality in patients with heart failure. Our conclusion is that the evidence is insufficient to link inotropes and increased mortality in low output heart failure.

New insights into the roles of Xin repeat-containing proteins in cardiac development, function, and disease

Since the discovery of Xin repeat-containing proteins in 1996, the importance of Xin proteins in muscle development, function, regeneration, and disease has been continuously implicated. Most Xin proteins are localized to myotendinous junctions of the skeletal muscle and also to intercalated discs (ICDs) of the heart. The Xin gene is only found in vertebrates, which are characterized by a true chambered heart. This suggests that the evolutionary origin of the Xin gene may have played a key role in vertebrate origins. Diverse vertebrates including mammals possess two paralogous genes, Xinα (or Xirp1) and Xinβ (or Xirp2), and this review focuses on the role of their encoded proteins in cardiac muscles. Complete loss of mouse Xinβ (mXinβ) results in the failure of forming ICD, severe growth retardation, and early postnatal lethality. Deletion of mouse Xinα (mXinα) leads to late-onset cardiomyopathy with conduction defects. Molecular studies have identified three classes of mXinα-interacting proteins: catenins, actin regulators/modulators, and ion-channel subunits. Thus, mXinα acts as a scaffolding protein modulating the N-cadherin-mediated adhesion and ion-channel surface expression. Xin expression is significantly upregulated in early stages of stressed hearts, whereas Xin expression is downregulated in failing hearts from various human cardiomyopathies. Thus, mutations in these Xin loci may lead to diverse cardiomyopathies and heart failure.

Efficacy and limitations of oral inotropic agents for the treatment of chronic heart failure

The heart failure guideline in Japan has stated the necessity of investigating the role of oral inotropic agents in patients with chronic heart failure (CHF), which are clinically available only in Japan. A total of 1,846 consecutive patients with heart failure (mean: 69.5 years old, 1,279 males) treated at our institute from November 2009 to August 2010 were investigated retrospectively. Thirty-one patients (1.84%) who had taken oral inotropic agents (pimobendan 27, docarpamine 6, and denopamine 4) were extracted for this study, and the efficacy and limitations of the treatments were analyzed. Following the oral inotropic treatment, the NYHA functional class (P = 0.017), cardiothoracic ratio (P = 0.002) and B-type natriuretic peptide levels (P = 0.011) were significantly improved, and the number of emergency room (ER) visits (P < 0.001) and hospitalizations (P < 0.001) were significantly reduced. The nonsurviving patients (n = 7/31, 22.6%) were significantly older (P = 0.02) and tended to have a larger cardiothoracic ratio (P = 0.084) compared with the survivors. An absence of concomitant beta-blocker therapy was significantly associated with a worse prognosis (oneyear mortality 2/21 versus 5/10, log rank, P = 0.011). Oral inotropic agents brought about improvements in the clinical parameters of CHF and a reduction in ER visits and hospitalizations. However, concomitant beta-blocker therapy should be considered for patients receiving oral inotropic treatment.

A Memory Molecule, Ca(2+)/Calmodulin-Dependent Protein Kinase II and Redox Stress; Key Factors for Arrhythmias in a Diseased Heart

Arrhythmias can develop in various cardiac diseases, such as ischemic heart disease, cardiomyopathy and congenital heart disease. It can also contribute to the aggravation of heart failure and sudden cardiac death. Redox stress and Ca²⁺ overload are thought to be the important triggering factors in the generation of arrhythmias in failing myocardium. From recent studies, it appears evident that Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a central role in the arrhythmogenic processes in heart failure by sensing intracellular Ca²⁺ and redox stress, affecting individual ion channels and thereby leading to electrical instability in the heart. CaMKII, a multifunctional serine/threonine kinase, is an abundant molecule in the neuron and the heart. It has a specific property as "a memory molecule" such that the binding of calcified calmodulin (Ca²⁺/CaM) to the regulatory domain on CaMKII initially activates this enzyme. Further, it allows autophosphorylation of T287 or oxidation of M281/282 in the regulatory domain, resulting in sustained activation of CaMKII even after the dissociation of Ca²⁺/CaM. This review provides the understanding of both the structural and functional properties of CaMKII, the experimental findings of the interactions between CaMKII, redox stress and individual ion channels, and the evidences proving the potential participation of CaMKII and oxidative stress in the diverse arrhythmogenic processes in a diseased heart.

Calmodulin-dependent protein kinase II: linking heart failure and arrhythmias

Understanding relationships between heart failure and arrhythmias, important causes of suffering and sudden death, remains an unmet goal for biomedical researchers and physicians. Evidence assembled over the past decade supports a view that activation of the multifunctional Ca(2+) and calmodulin-dependent protein kinase II (CaMKII) favors myocardial dysfunction and cell membrane electrical instability. CaMKII activation follows increases in intracellular Ca(2+) or oxidation, upstream signals with the capacity to transition CaMKII into a Ca(2+) and calmodulin-independent constitutively active enzyme. Constitutively active CaMKII appears poised to participate in disease pathways by catalyzing the phosphorylation of classes of protein targets important for excitation-contraction coupling and cell survival, including ion channels and Ca(2+) homeostatic proteins, and transcription factors that drive hypertrophic and inflammatory gene expression. This rich diversity of downstream targets helps to explain the potential for CaMKII to simultaneously affect mechanical and electrical properties of heart muscle cells. Proof-of-concept studies from a growing number of investigators show that CaMKII inhibition is beneficial for improving myocardial performance and for reducing arrhythmias. We review the molecular physiology of CaMKII and discuss CaMKII actions at key cellular targets and results of animal models of myocardial hypertrophy, dysfunction, and arrhythmias that suggest CaMKII inhibition may benefit myocardial function while reducing arrhythmias.

Positive inotropes in heart failure: a review article

Increasing myocardial contractility has long been considered a big help for patients with systolic heart failure, conferring an augmented haemodynamic profile in terms of higher cardiac output, lower cardiac filling pressure and better organ perfusion. Though concerns have been raised over the safety issues regarding the clinical trials of different inotropes in hearts with systolic dysfunction, they still stand as a main therapeutic strategy in many centres dealing with such patients. They must be used as short in duration, low in dose and stopped as early as possible. Evidence-based guidelines have provided clinicians with valuable data for better applying inotropes in heart failure patients. In this paper, the authors address clinical trials with different agents used for increasing cardiac contractility in heart failure patients. Furthermore, the authors focus on recent guidelines on making the most out of inotropes in heart failure patients.

In vivo natriuretic peptide reporter assay identifies chemical modifiers of hypertrophic cardiomyopathy signalling

AIMS

Despite increased understanding of the fundamental biology regulating cardiomyocyte hypertrophy and heart failure, it has been challenging to find novel chemical or genetic modifiers of these pathways. Traditional cell-based methods do not model the complexity of an intact cardiovascular system and mammalian models are not readily adaptable to chemical or genetic screens. Our objective was to create an in vivo model suitable for chemical and genetic screens for hypertrophy and heart failure modifiers.

METHODS AND RESULTS

Using the developing zebrafish, we established that the cardiac natriuretic peptide genes (nppa and nppb), known markers of cardiomyocyte hypertrophy and heart failure, were induced in the embryonic heart by pathological cardiac stimuli. This pathological induction was distinct from the developmental regulation of these genes. We created a luciferase-based transgenic reporter line that accurately modelled the pathological induction patterns of the zebrafish nppb gene. Utilizing this reporter line, we were able to show remarkable conservation of pharmacological responses between the larval zebrafish heart and adult mammalian models.

CONCLUSION

By performing a focused screen of chemical agents, we were able to show a distinct response of a genetic model of hypertrophic cardiomyopathy to the histone deacetylase inhibitor, Trichostatin A, and the mitogen-activated protein kinase kinase 1/2 inhibitor, U0126. We believe this in vivo reporter line will offer a unique approach to the identification of novel chemical or genetic regulators of myocardial hypertrophy and heart failure.

Disruption of adenylyl cyclase type V does not rescue the phenotype of cardiac-specific overexpression of Galphaq protein-induced cardiomyopathy

Adenylyl cyclase (AC) is the principal effector molecule in the β-adrenergic receptor pathway. AC(V) and AC(VI) are the two predominant isoforms in mammalian cardiac myocytes. The disparate roles among AC isoforms in cardiac hypertrophy and progression to heart failure have been under intense investigation. Specifically, the salutary effects resulting from the disruption of AC(V) have been established in multiple models of cardiomyopathy. It has been proposed that a continual activation of AC(V) through elevated levels of protein kinase C could play an integral role in mediating a hypertrophic response leading to progressive heart failure. Elevated protein kinase C is a common finding in heart failure and was demonstrated in murine cardiomyopathy from cardiac-specific overexpression of G(αq) protein. Here we assessed whether the disruption of AC(V) expression can improve cardiac function, limit electrophysiological remodeling, or improve survival in the G(αq) mouse model of heart failure. We directly tested the effects of gene-targeted disruption of AC(V) in transgenic mice with cardiac-specific overexpression of G(αq) protein using multiple techniques to assess the survival, cardiac function, as well as structural and electrical remodeling. Surprisingly, in contrast to other models of cardiomyopathy, AC(V) disruption did not improve survival or cardiac function, limit cardiac chamber dilation, halt hypertrophy, or prevent electrical remodeling in G(αq) transgenic mice. In conclusion, unlike other established models of cardiomyopathy, disrupting AC(V) expression in the G(αq) mouse model is insufficient to overcome several parallel pathophysiological processes leading to progressive heart failure.

The case for hypoglycaemia as a proarrhythmic event: basic and clinical evidence

Recent clinical studies show that hypoglycaemia is associated with increased risk of death, especially in patients with coronary artery disease or acute myocardial infarction. This paper reviews data from cellular and clinical research supporting the hypothesis that acute hypoglycaemia increases the risk of malignant ventricular arrhythmias and death in patients with diabetes by generating the two classic abnormalities responsible for the proarrhythmic effect of medications, i.e. QT prolongation and Ca(2+) overload. Acute hypoglycaemia causes QT prolongation and the risk of ventricular tachycardia by directly suppressing K(+) currents activated during repolarisation, a proarrhythmic effect of many medications. Since diabetes itself, myocardial infarction, hypertrophy, autonomic neuropathy and congestive heart failure also cause QT prolongation, the arrhythmogenic effect of hypoglycaemia is likely to be greatest in patients with pre-existent cardiac disease and diabetes. Furthermore, the catecholamine surge during hypoglycaemia raises intracellular Ca(2+), thereby increasing the risk of ventricular tachycardia and fibrillation by the same mechanism as that activated by sympathomimetic inotropic agents and digoxin. Diabetes itself may sensitise myocardium to the arrhythmogenic effect of Ca(2+) overload. In humans, noradrenaline (norepinephrine) also lengthens action potential duration and causes further QT prolongation. Finally, both hypoglycaemia and the catecholamine response acutely lower serum K(+), which leads to QT prolongation and Ca(2+) loading. Thus, hypoglycaemia and the subsequent catecholamine surge provoke multiple, interactive, synergistic responses that are known to be proarrhythmic when associated with medications and other electrolyte abnormalities. Patients with diabetes and pre-existing cardiac disease may therefore have increased risk of ventricular tachycardia and fibrillation during hypoglycaemic episodes.

Pulmonary hypertension in chronic heart failure

The presence of PH in patients who suffer from CHF is common and predicts a poor outcome. However, precise definitions for PH associated with left heart disease, or 'out-of-proportion' PH as well as standardised vasodilator testing protocols are lacking. Moreover, apart from single-centre observations no large-scale trial to date has demonstrated a long-term benefit from pulmonary vasoactive drugs. As a result, there are currently no consensus recommendations for the treatment of PH in the presence of CHF. Off-label use of specific vasodilators in this patient population is discouraged. In a majority of cases, treatment of the underlying left heart disease leads to a decrease in pulmonary pressures. In light of novel agents to treat PH, trials that specifically address 'out-of-proportion' PH in CHF patients are warranted.

Low-dose oral enoximone enhances the ability to wean patients with ultra-advanced heart failure from intravenous inotropic support: results of the oral enoximone in intravenous inotrope-dependent subjects trial

BACKGROUND

We determined whether low-dose oral enoximone could wean patients with ultra-advanced heart failure (UA-HF) from intravenous (i.v.) inotropic support. Chronic parenteral inotropic therapy in UA-HF is costly and requires an indwelling catheter. An effective and safe oral inotrope would have value.

METHODS

In this placebo-controlled study, 201 subjects with UA-HF requiring i.v. inotropic therapy were randomized to enoximone or placebo. Subjects receiving intermittent i.v. inotropes were administered study medication of 25 or 50 mg 3 times a day (tid). Subjects receiving continuous i.v. inotropes were administered 50 or 75 mg tid for 1 week, which was reduced to 25 or 50 mg tid. The ability of subjects to remain alive and free of inotropic therapy was assessed for up to 182 days.

RESULTS

Thirty days after weaning, 51 (51%) subjects on placebo and 62 (61.4%) subjects in the enoximone group were alive and free of i.v. inotropic therapy (unadjusted primary end point P = 0.14, adjusted for etiology P = .17). At 60 days, the wean rate was 30% in the placebo group and 46.5% in the enoximone group (unadjusted P = .016) Kaplan-Meier curves demonstrated a trend toward a decrease in the time to death or reinitiation of i.v. inotropic therapy over the 182-day study period (hazard ratio 0.76 [95% CI 0.55-1.04]) and a reduction at 60 days (0.62 [95% CI 0.43-0.89], P = .009) and 90 days (0.69 [95% CI 0.49-0.97], P = .031) after weaning in the enoximone group.

CONCLUSIONS

Although there was no benefit over placebo in weaning patients from i.v. inotropes from 0 to 30 days, the EMOTE data suggest that low-dose oral enoximone can be used to wean a modest percentage of subjects from i.v. inotropic support for up to 90 days after initiation of therapy.

Inotropic drugs and neurohormonal antagonists in the treatment of HF in the elderly

Heart failure (HF) is the most common reason for hospital admission among individuals over age 65 years and results in more than 1 million admissions each year. The overall annual death rate for HF is approximately 20%. HF results from decreased contractile function of the heart, and neurohormonal dysregulation plays a major part in the morbidity and mortality of the heart. The purpose of this article is to review recent studies on inotropic drugs and neurohormonal antagonists used in the treatment of patients who have HF, especially the elderly.

Effects of levosimendan on myocardial infarct size and hemodynamics in a closed-chest porcine ischemia-reperfusion model

INTRODUCTION

Levosimendan is a positive inotropic drug with vasodilator action and proposed myocardioprotective properties. In a canine model, levosimendan increased coronary collateral flow and reduced myocardial infarct size (IS). We investigated the effect of levosimendan on IS and hemodynamics in the closed-chest porcine ischemia-reperfusion model, which is devoid of coronary collaterals.

METHODS

Infusion with levosimendan (0.2 microg/kg/min following a bolus of 24 microg/kg) or saline was initiated 30 min prior to ischemia in anaesthetized pigs (n = 10 in both groups). Balloon occlusion of the left anterior descending coronary artery for 45 min was followed by 2 1/2 h of reperfusion. Hemodynamics were monitored with a Swan-Ganz catheter and a left ventricular pressure micromanometer. Left ventricular systolic and diastolic function was estimated by dP/dt(max) and tau, respectively. Myocardial area at risk (AAR) and IS were assessed in vivo by myocardial perfusion imaging (MPI) and ex vivo by histopathology (fluorescein staining for AAR, tetrazolium staining for IS).

RESULTS

Prior to ischemia, levosimendan improved left ventricular systolic and diastolic function with coincident preload and afterload reduction. Cardiac output increased by 10 +/- 4% (p = 0.04), dP/dt(max) by 15 +/- 5% (p = 0.01). Pulmonary capillary wedge pressure decreased by 18 +/- 3% (p = 0.04), tau by 11 +/- 2% (p = 0.001), and mean arterial pressure by 11 +/- 2% (p < 0.001). A similar trend was observed during ischemia-reperfusion. The ratio of IS/AAR was not reduced by levosimendan compared to saline as evaluated by histopathology (76 +/- 4% vs. 64 +/- 7%, p = 0.12) and by MPI (94 +/- 2% vs. 87 +/- 5%, p = 0.14).

CONCLUSION

Levosimendan improves hemodynamics but does not reduce IS in an ischemia-reperfusion model without coronary collaterals.

The Second Follow-up Serial Infusions of Nesiritide (FUSION II) trial for advanced heart failure: study rationale and design

BACKGROUND

Patients with persistently symptomatic advanced heart failure have limited treatment options after appropriate use of standard evidence-based therapies. Current recommendations from the American College of Cardiology/American Heart Association guidelines for treatment of stage C/D heart failure beyond standard therapy include ventricular replacement, investigational agents, and palliative interventions. Given the elevated risk of this patient population, additional treatment options seem warranted. Natriuretic peptides are protean compounds that provoke vasodilation, natriuresis, neurohormonal antagonism, and reverse remodeling, but they have an uncertain risk-benefit profile affecting serum creatinine and clinical events. In the pilot, open-label FUSION I trial, the adjunctive administration of nesiritide with standard therapy for patients with advanced heart failure, was demonstrated to have a neutral effect on outcomes with no evidence of increased risk. Within a prespecified subset of high-risk patients, a potential signal of benefit on a combined end point of mortality and cardiovascular hospitalization was identified.

STUDY DESIGN

FUSION II is a 900-patient randomized, placebo-controlled, double-blind, phase IIb trial designed to further assess the safety, efficacy, and optimal dosing frequency of outpatient nesiritide for advanced heart failure. The primary end point is a composite of all-cause mortality and cardiorenal hospitalization.

CONCLUSIONS

If a confirmatory signal of benefit is identified in FUSION II, a definitive phase III mortality/quality of life trial will be warranted. Additional issues related to the influence of disease management, the logistics of outpatient parenteral therapy administration, and future iterations of natriuretic peptide therapy will need to be investigated.

The use of levosimendan in comparison and in combination with dobutamine in the treatment of decompensated heart failure

Levosimendan is a new calcium sensitizer with inotropic and vasodilatory actions mediated by the sensitization of contractile proteins to calcium, opening of potassium channels and inhibition of phosphodiesterase-3. Its alternative mechanisms of action to those of other traditional inotropes provide a new approach in the management of decompensated heart failure. In contrast to dobutamine, levosimendan does not increase myocardial oxygen demand and, therefore, it is thought to have a lower potential to induce increases in myocardial ischemia and cardiac arrhythmias. The commonly used inotropic agent dobutamine increases myocardial contractility at the expense of increased myocardial oxygen consumption and, therefore, it can result in poor outcomes. Although dobutamine may also have favorable hemodynamic and symptomatic effects, levosimendan has been shown to be superior to dobutamine in increasing cardiac output and decreasing pulmonary capillary wedge pressure in patients with decompensated heart failure. In the presence of concomitant beta-blocker therapy, these favorable effects were present or even more pronounced during treatment with levosimendan, but not dobutamine. However, the mortality benefit of levosimendan observed in earlier trials has not been confirmed in recent, larger clinical trials. A distinct advantage of levosimendan over dobutamine is its prolonged hemodynamic effects, which last for up to 7-9 days. There are more data on the safety of levosimendan in ischemic patients than with any other inotropic drug and, therefore, levosimendan seems to be safe and effective in patients with ischemic heart disease when used at the recommended doses. Despite advances in heart failure therapy, many patients experience clinical deterioration, or do not respond to a single inotropic drug. Increasing evidence suggests the use of levosimendan in combination with dobutamine in patients with decompensated heart failure that is refractory to dobutamine alone.

Inotropic drugs and neurohormonal antagonists in the treatment of HF in the elderly

HF (HF) is the most common reason for hospital admission among individuals over age 65 years and results in more than 1 million admissions each year. The overall annual death rate for HF is approximately 20%. HF results from decreased contractile function of the heart, and neurohormonal dysregulation plays a major part in the morbidity and mortality of the heart. The purpose of this article is to review recent studies on inotropic drugs and neurohormonal antagonists used in the treatment of patients who have HF, especially the elderly.

Outpatient continuous parenteral inotropic therapy as bridge to transplantation in children with advanced heart failure

BACKGROUND

Advanced heart failure in children is associated with high morbidity and mortality and is often refractory to standard medical therapy. The purpose of this study was to review our institutional experience with the use of outpatient parenteral inotropic therapy (PIT) for advanced chronic heart failure in children.

METHODS AND RESULTS

We reviewed the medical records of all patients treated with PIT as outpatients. Seven patients received outpatient PIT from 2/99 to 1/05 (mean age was 14.6 years +/- 3.7). Median duration of therapy was 10 weeks (range 4-84 weeks). The mean number of emergency department visits per patient was greater before starting PIT than after starting PIT (2.3 +/- 1.8 versus 1.1 +/- 2.2, P < .05). The mean number of hospital admissions from exacerbation of heart failure symptoms decreased after starting PIT (2.1 +/- 1.3 versus 0.6 +/- 0.8, P < .05). Mean EF% in patients with systolic dysfunction improved while on therapy (30 +/- 14% before versus 39 +/- 16% after, P < .05). There was 1 death and 5 complications in 2 patients. Six patients were successfully bridged to transplantation.

CONCLUSION

Outpatient continuous parenteral inotropic therapy may serve as a successful bridge to cardiac transplantation in selected pediatric outpatients.

Contemporary Issues in the Pharmacologic Management of Acute Heart Failure

Acute heart failure is an evolving syndrome that continues to be defined by ongoing studies and registries. It is associated with significant morbidity and mortality and places a huge economic burden on health care systems. Improved understanding of the underlying pathophysiologic processes has prompted interest into understanding the implications of current and future pharmacologic management strategies beyond hemodynamics. Diuretics, vasodilators, and inotropes remain the mainstays of therapy with several new classes of agents on the horizon. Clinicians should understand the rationale for use and limitations of each therapy to maximize benefit and cost-effectiveness, while minimizing the potential for adverse outcomes.

Rationale and design of the enoximone clinical trials program

BACKGROUND

Chronic heart failure is a disease syndrome characterized in its advanced stages by a poor quality of life, frequent hospitalizations, and a high risk of mortality. In advanced and ultra-advanced chronic heart failure, many treatment options, such as cardiac transplantation and mechanical devices, are severely limited by availability and cost. Short-term Phase II clinical trials suggest that low-dose oral inotropic therapy with enoximone may improve hemodynamics and exercise capacity, without adversely affecting mortality, in selected subjects with advanced chronic heart failure. Based on these data, the ability of enoximone to deliver safe and efficacious palliative treatment of advanced/ultra-advanced chronic heart failure is being evaluated in Phase III clinical trials.

METHODS AND RESULTS

The Enoximone Clinical Trials Program is a series of 4 clinical trials designed to evaluate the safety and efficacy of oral enoximone in advanced chronic heart failure. ESSENTIAL I and II (The Studies of Oral Enoximone Therapy in Advanced Heart Failure) will investigate the effects of oral enoximone on all-cause mortality and cardiovascular hospitalization, submaximal exercise capacity, and quality of life in subjects with New York Heart Association Class III/IV chronic heart failure. EMOTE (Oral Enoximone in Intravenous Inotrope-Dependent Subjects) will evaluate the potential of oral enoximone to wean subjects with ultra-advanced chronic heart failure from chronic intravenous inotropic therapy to which they have been shown to be dependent. EMPOWER (Enoximone Plus Extended-Release Metoprolol Succinate in Subjects with Advanced Chronic Heart Failure) will explore the potential of enoximone to increase the tolerability of continuous release metoprolol in subjects shown previously to be hemodynamically intolerant to beta-blocker treatment.

CONCLUSION

These studies are Phase III, multicenter, randomized, double-blinded, placebo-controlled trials designed to test the general hypothesis that chronic oral administration of low doses of enoximone can produce beneficial effects in subjects with advanced or ultra-advanced chronic heart failure.

Calcium sensitizer agents: a new class of inotropic agents in the treatment of decompensated heart failure

The clinician's primary objective in treating a patient with decompensated heart failure is rapid and effective stabilization. This goal often is achieved through the use of inotropic support. Classic inotropic agents (beta-adrenergic agonists and phosphodiesterase III inhibitors) can provide short-term hemodynamic benefits, but their long-term use has been correlated with poor survival rates. Calcium sensitizers comprise a new drug class that offers hemodynamic and symptomatic improvements without increasing cAMP and intracellular calcium concentrations. These agents enhance contractility without a concurrent increase in the risk of cardiac events and thus represent a significant improvement over classic positive inotropic agents. Levosimendan is the most potent calcium sensitizer to date, exhibiting a unique dual mechanism of action that combines a positive inotropic action mediated via calcium sensitization and a vasodilator property via ATP-dependent potassium channels. Available clinical data suggest that calcium sensitizer agents represent a promising class of inotropic agents in a field that has seen few advances in recent decades.

The impact of arrhythmias in acute heart failure

BACKGROUND

Arrhythmias are common in chronic heart failure and affect outcomes. The incidence and significance of new arrhythmias in acute heart failure, however, are largely unknown.

METHODS AND RESULTS

The Outcomes of a Prospective Trial of Intravenous Milrinone for Exacerbations study randomized 949 patients with decompensated heart failure to receive intravenous milrinone or placebo. In the study, patients were divided into 2 groups based on the occurrence of a new arrhythmic event during their index hospitalization and analyzed for outcome. There were 59 new arrhythmic events occurring in 6% of the population. Of these, 49% were atrial fibrillation/flutter. The primary endpoint of days hospitalized for cardiovascular causes within 60 days after randomization was 30.9+/-22.7 for those in the arrhythmia group and 11.3+/-12.7 days for those with no arrhythmias (P=.0001). Mortality during index hospitalization was 26% in the arrhythmia group and 1.8% in the no arrhythmia group (P=.001). Death or hospitalization at 60 days was also worse in the arrhythmia group (35 versus 8.2%, P=.0001; 57 versus 34%, P=.001, respectively). Cox proportional hazard analysis identified new arrhythmias as an independent risk factor for the primary endpoint and death at 60 days.

CONCLUSION

New arrhythmia during an exacerbation of heart failure identifies a high-risk group with higher intrahospital and 60-day morbidity and mortality.

Home continuous positive inotropic infusion as a bridge to cardiac transplantation in patients with end-stage heart failure

BACKGROUND

The clinical use of positive inotropic therapy at home in patients awaiting cardiac transplantation has not been reported since United Network for Organ Sharing (UNOS) regulations were changed to allow home infusions in Status 1B patients.

METHODS

We observed 21 consecutive patients with UNOS 1B status during positive inotropic therapy at home. We used hemodynamic monitoring at the initiation of therapy to optimize dosing. We selected for home therapy patients with stable clinical status and improved functional capacity during inotropic treatment. Implantable cardioverter defibrillators were placed in all but 1 patient before discharge.

RESULTS

Initial positive inotropic therapy included dobutamine in 12 patients (mean dose, 4.5 mcg/kg/min; range, 2.5-7.5 mcg/kg/min), milrinone in 8 patients (mean dose, 0.44 mcg/kg/min; range, 0.375-0.55 mcg/kg/min), and dopamine at a dose of 3 mcg/kg/min in 1 patient. Patients had improved functional capacity (New York Heart Association Class 3.7 +/- 0.1 to 2.4 +/- 0.2, p < 0.01), improved renal function (serum creatinine, 1.5 +/- 0.1 to 1.3 +/- 0.1, p < 0.01), improved resting hemodynamics, and decreased number of hospitalizations during positive inotropic infusion therapy when compared with pre-treatment baseline. Implantable cardioverter defibrillator discharges were infrequent (0.19 per 100 patient days of follow-up). Actuarial survival to transplantation at 6 and 12 months was 84%.

CONCLUSIONS

Continuous positive inotropic therapy at home was safe and was associated with decreased health care costs in selected patients awaiting cardiac transplantation.

Effect of levosimendan on balance between ATP production and consumption in isolated perfused guinea-pig heart before ischemia or after reperfusion

Levosimendan is a novel drug developed for treatment of decompensated heart failure. Levosimendan is a calcium sensitizer that increases contractile force of the myocardium by enhancing the sensitivity of myofilaments to calcium without increasing intracellular calcium concentration. The present study was carried out to investigate whether levosimendan induces any changes in the phosphorylation potential (ie, the balance between ATP production and consumption) in the normal heart and in the post-ischemic heart while exerting its positive inotropic effect. We show that 0.1 microM levosimendan increased the left ventricle developed pressure in the pre-ischemic and in the post ischemic hearts by 16 and 18% respectively, and the +dP/dt by 16 and 19%, respectively. At that concentration levosimendan did not cause any effect on the phosphorylation potential (1 x 10(5) M(-1) and 0.2 x 10(5) M(-1) in the pre-ischemic and post-ischemic heart, respectively) as assessed by P-NMR, although an increased beating rate (13%) and oxygen consumption (10%) was observed when adding the drug post-ischemically. Our findings are consistent with the results of a recent clinical trial (RUSSLAN), which showed that levosimendan does not induce ischemia and reduces the risk of worsening heart failure and death, in patients with left ventricular failure complicating acute myocardial infarction.