Istaroxime, a potential anticancer drug in prostate cancer, exerts beneficial functional effects in healthy and diseased human myocardium

The current gold standard for prostate cancer treatment is androgen deprivation therapy and antiandrogenic agents. However, adverse cardiovascular events including heart failure can limit therapeutic use. Istaroxime, which combines Na⁺-K⁺-ATPase (NKA) inhibition with sarco/endoplasmic reticulum Ca²⁺-ATPase 2a (SERCA2a) stimulation, has recently shown promising anti-neoplastic effects in prostate cancer (PC) models and may also improve cardiac function. Considering the promising anticancer effects of istaroxime, we aimed to assess its functional effects on human myocardium.

Omecamtiv mecarbil activates ryanodine receptors from canine cardiac but not skeletal muscle

Due to the limited results achieved in the clinical treatment of heart failure, a new inotropic strategy of myosin motor activation has been developed. The lead molecule of myosin activator agents is omecamtiv mecarbil, which binds directly to the heavy chain of the cardiac β-myosin and enhances cardiac contractility by lengthening the lifetime of the acto-myosin complex and increasing the number of the active force-generating cross-bridges. In the absence of relevant data, the effect of omecamtiv mecarbil on canine cardiac ryanodine receptors (RyR 2) has been investigated in the present study by measuring the electrical activity of single RyR 2 channels incorporated into planar lipid bilayer. When applying 100nM Ca²⁺ concentration on the cis side ([Ca²⁺]_cis) omecamtiv mecarbil (1-10µM) significantly increased the open probability and opening frequency of RyR 2, while the mean closed time was reduced. Mean open time was increased moderately by 10µM omecamtiv mecarbil. When [Ca²⁺]_cis was elevated to 322 and 735nM, the effect of omecamtiv mecarbil on open probability was evident only at higher (3-10µM) concentrations. All effects of omecamtiv mecarbil were fully reversible upon washout. Omecamtiv mecarbil (up to 10µM) had no effect on the open probability of RyR 1, isolated from either canine or rabbit skeletal muscles. It is concluded that the direct stimulatory action of omecamtiv mecarbil on RyR 2 has to be taken into account when discussing the mechanism of action or the potential side effects of the compound.

New pharmacological approaches in heart failure therapy: developments and possibilities

There have been few major breakthroughs in heart failure (HF) drug therapies in recent years yet HF morbidity and mortality remain high, and there is a clear need for further research. Several newer agents that appear promising in Phase I and II trials do not progress to show clinical benefit in later trials. Part of the failure to find new therapies may lie in flawed trial design compounded by the need for ever-increasing patient numbers in order to prove outcome benefit. We summarize some of the most recent and promising medical therapies for HF.

Direct Myosin Activation by Omecamtiv Mecarbil for Heart Failure with Reduced Ejection Fraction

Myosin is the indispensable molecular motor that utilizes chemical energy to produce force for contraction within the cardiac myocyte. Myosin activity is gated by intracellular calcium levels which are regulated by multiple upstream signaling cascades that can be altered for clinical utility using inotropic medications. In contrast to clinically available cardiac inotropes, omecamtiv mecarbil is a novel direct myosin activator developed to augment left ventricular systolic function without the undesirable secondary effects of altered calcium homeostasis. Its identification and synthesis followed high-throughput screening of a reconstituted sarcomere, deliberate optimization, exquisite biochemical evaluation, and subsequently promising effects in animal models were demonstrated. Physiologically, it prolonged the duration of left ventricular systole in animal models, healthy adults, and patients with heart failure with reduced ejection fraction (HFrEF) without changing the velocity of pressure development, as assessed in animal models. It has been formulated for both intravenous and oral administration, and in both acute and chronic settings produced similar alterations in the duration of systole associated with beneficial increases in cardiac output, improvements in left ventricular volumes, and reductions in heart rate and often of natriuretic peptides. Small, asymptomatic increases in troponin were also observed in the absence of clinically evident ischemia. Clinically, the question remains as to whether the possible harm of this minimal troponin release is outweighed by the potential benefits of reduced neurohormonal activation, increased stroke volume and cardiac output, and improved ventricular remodeling in patients treated with omecamtiv mecarbil. The resolution of this question is being addressed by a phase III outcomes trial of this potential novel therapy for heart failure.

Chronic Oral Study of Myosin Activation to Increase Contractility in Heart Failure (COSMIC-HF): a phase 2, pharmacokinetic, randomised, placebo-controlled trial

BACKGROUND

Impaired contractility is a feature of heart failure with reduced ejection fraction. We assessed the pharmacokinetics and effects on cardiac function and structure of the cardiac myosin activator, omecamtiv mecarbil.

METHODS

In this randomised, double-blind study, done at 87 sites in 13 countries, we recruited patients with stable, symptomatic chronic heart failure and left ventricular ejection fraction 40% or lower. Patients were randomly assigned equally, via an interactive web response system, to receive 25 mg oral omecamtiv mecarbil twice daily (fixed-dose group), 25 mg twice daily titrated to 50 mg twice daily guided by pharmacokinetics (pharmacokinetic-titration group), or placebo for 20 weeks. We assessed the maximum concentration of omecamtiv mecarbil in plasma (primary endpoint) and changes in cardiac function and ventricular diameters. This trial is registered with ClinicalTrials.gov, number NCT01786512.

FINDINGS

From March 17, 2014, to March 5, 2015, we enrolled 150 patients in the fixed-dose omecamtiv mecarbil group and 149 in the pharmacokinetic-titration and placebo groups. Mean maximum concentration of omecamtiv mecarbil at 12 weeks was 200 (SD 71) ng/mL in the fixed-dose group and 318 (129) ng/mL in the pharmacokinetic-titration group. For the pharmacokinetic-titration group versus placebo group at 20 weeks, least square mean differences were as follows: systolic ejection time 25 ms (95% CI 18-32, p<0·0001), stroke volume 3·6 mL (0·5-6·7, p=0·0217), left ventricular end-systolic diameter -1·8 mm (-2·9 to -0·6, p=0·0027), left ventricular end-diastolic diameter -1·3 mm, (-2·3 to 0·3, p=0·0128), heart rate -3·0 beats per min (-5·1 to -0·8, p=0·0070), and N-terminal pro B-type natriuretic peptide concentration in plasma -970 pg/mL (-1672 to -268, p=0·0069). The frequency of adverse clinical events did not differ between groups.

INTERPRETATION

Omecamtiv mecarbil dosing guided by pharmacokinetics achieved plasma concentrations associated with improved cardiac function and decreased ventricular diameter.

FUNDING

Amgen.

Molecular inotropy mediated by cardiac miR-based PDE4D/PRKAR1α/phosphoprotein signaling

Molecular inotropy refers to cardiac contractility that can be modified to affect overall heart pump performance. Here we show evidence of a new molecular pathway for positive inotropy by a cardiac-restricted microRNA (miR). We report enhanced cardiac myocyte performance by acute titration of cardiac myosin-embedded miR-208a. The observed positive effect was independent of host gene myosin effects with evidence of negative regulation of cAMP-specific 3',5'-cyclic phosphodiesterase 4D (PDE4D) and the regulatory subunit of PKA (PRKAR1α) content culminating in PKA-site dependent phosphorylation of cardiac troponin I (cTnI) and phospholamban (PLN). Further, acute inhibition of miR-208a in adult myocytes in vitro increased PDE4D expression causing reduced isoproterenol-mediated phosphorylation of cTnI and PLN. Next, rAAV-mediated miR-208a gene delivery enhanced heart contractility and relaxation parameters in vivo. Finally, acute inducible increases in cardiac miR-208a in vivo reduced PDE4D and PRKAR1α, with evidence of increased content of several complementary miRs harboring the PDE4D recognition sequence. Physiologically, this resulted in significant cardiac cTnI and PLN phosphorylation and improved heart performance in vivo. As phosphorylation of cTnI and PLN is critical to myocyte function, titration of miR-208a represents a potential new mechanism to enhance myocardial performance via the PDE4D/PRKAR1α/PKA phosphoprotein signaling pathway.

Pharmacological reasons that may explain why randomized clinical trials have failed in acute heart failure syndromes

Acute heart failure (AHF) represents a clinical challenge as it encloses a heterogeneous group of syndromes (AHFS) with different pathophysiology, clinical presentations, prognosis and response to therapy. In the last 25years multiple therapeutic targets have been identified and numerous new drugs were evaluated but, up to now, all failed to demonstrate a consistent benefit on clinical outcomes. Moreover, a repeated finding has been the poor correlation between the encouraging results of preclinical and early clinical trials and the lack of effect on outcomes observed in phase III trials. We review several possible pharmacological reasons that may explain the lack of success to develop new drugs and the pharmacological challenges to overcome in the future to develop new more effective and safer drugs for the treatment of AHFS.

Acute Treatment With Omecamtiv Mecarbil to Increase Contractility in Acute Heart Failure: The ATOMIC-AHF Study

BACKGROUND

Omecamtiv mecarbil (OM) is a selective cardiac myosin activator that increases myocardial function in healthy volunteers and in patients with chronic heart failure.

OBJECTIVES

This study evaluated the pharmacokinetics, pharmacodynamics, tolerability, safety, and efficacy of OM in patients with acute heart failure (AHF).

METHODS

Patients admitted for AHF with left ventricular ejection fraction ≤40%, dyspnea, and elevated plasma concentrations of natriuretic peptides were randomized to receive a double-blind, 48-h intravenous infusion of placebo or OM in 3 sequential, escalating-dose cohorts.

RESULTS

In 606 patients, OM did not improve the primary endpoint of dyspnea relief (3 OM dose groups and pooled placebo: placebo, 41%; OM cohort 1, 42%; cohort 2, 47%; cohort 3, 51%; p = 0.33) or any of the secondary outcomes studied. In supplemental, pre-specified analyses, OM resulted in greater dyspnea relief at 48 h (placebo, 37% vs. OM, 51%; p = 0.034) and through 5 days (p = 0.038) in the high-dose cohort. OM exerted plasma concentration-related increases in left ventricular systolic ejection time (p < 0.0001) and decreases in end-systolic dimension (p < 0.05). The adverse event profile and tolerability of OM were similar to those of placebo, without increases in ventricular or supraventricular tachyarrhythmias. Plasma troponin concentrations were higher in OM-treated patients compared with placebo (median difference at 48 h, 0.004 ng/ml), but with no obvious relationship with OM concentration (p = 0.95).

CONCLUSIONS

In patients with AHF, intravenous OM did not meet the primary endpoint of dyspnea improvement, but it was generally well tolerated, it increased systolic ejection time, and it may have improved dyspnea in the high-dose group. (Acute Treatment with Omecamtiv Mecarbil to Increase Contractility in Acute Heart Failure [ATOMIC-AHF]; NCT01300013).

Effects of Combined Milrinone and Levosimendan Treatment on Systolic and Diastolic Function During Postischemic Myocardial Dysfunction in a Porcine Model

It is not known whether there are positive or negative interactions on ventricular function when a calcium-sensitizing inotrope is added to a phosphodiesterase inhibitor in the clinical setting of acute left ventricular (LV) dysfunction. We hypothesized that when levosimendan is added to milrinone treatment, there will be synergetic inotropic and lusitropic effects. This was tested in an anesthetized porcine postischemic global LV injury model, where ventricular pressures and volumes (conductance volumetry) were measured. A global ischemic injury was induced by repetitive left main stem coronary artery occlusions. Load-independent indices of LV function were assessed before and after ventricular injury, after milrinone treatment, and finally after addition of levosimendan to the milrinone treatment. Nonparametric, within-group comparisons were made. The protocol was completed in 12 pigs, 7 of which received the inotrope treatment and 5 of which served as controls. Milrinone led to positive lusitropic effects seen by improvement in tau after myocardial stunning. The addition of levosimendan to milrinone further increased lusitropic state. The latter effect could however not be attributed solely to levosimendan, since lusitropic state also improved spontaneously in time-matched controls at the same rate during the corresponding period. When levosimendan was added to milrinone infusion, there was no increase in systolic function (preload recruitable stroke work) compared to milrinone treatment alone. We conclude that in this model of postischemic LV dysfunction, there appears to be no clear improvement in systolic or diastolic function after addition of levosimendan to established milrinone treatment but also no negative effects of levosimendan in this context.

Review of novel therapeutic targets for improving heart failure treatment based on experimental and clinical studies

Heart failure (HF) is a major public health priority due to its epidemiological transition and the world's aging population. HF is typified by continuous loss of contractile function with reduced, normal, or preserved ejection fraction, elevated vascular resistance, fluid and autonomic imbalance, and ventricular dilatation. Despite considerable advances in the treatment of HF over the past few decades, mortality remains substantial. Pharmacological treatments including β-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone antagonists have been proven to prolong the survival of patients with HF. However, there are still instances where patients remain symptomatic, despite optimal use of existing therapeutic agents. This understanding that patients with chronic HF progress into advanced stages despite receiving optimal treatment has increased the quest for alternatives, exploring the roles of additional pathways that contribute to the development and progression of HF. Several pharmacological targets associated with pathogenesis of HF have been identified and novel therapies have emerged. In this work, we review recent evidence from proposed mechanisms to the outcomes of experimental and clinical studies of the novel pharmacological agents that have emerged for the treatment of HF.

Relative bioavailability, food effect, and safety of the single-dose pharmacokinetics of omecamtiv mecarbil following administration of different modified-release formulations in healthy subjects

Objective: Omecamtiv mecarbil is a novel small molecule that directly activates cardiac myosin and increases cardiac contractility without increasing cardiac myocyte intracellular calcium. This study evaluated the relative bioavailability, food effect, and safety of several modified-release (MR) formulations of omecamtiv mecarbil. Methods: This was a phase 1, randomized, open-label, 4-way crossover, incomplete block-design study evaluating 5 MR formulations of omecamtiv mecarbil vs. an immediate-release (IR) formulation. Materials: Healthy subjects were randomized to 1 of 30 possible sequences: within each sequence, subjects were assigned to receive a single 25-mg dose of 2 of the 6 possible formulations in the fasting and/or fed states. Results: 65 subjects were screened and enrolled; 5 were replacement subjects. Pharmacokinetic and safety data were analyzed from 62 and 63 subjects in the fasting and fed states, respectively. Compared with the IR formulation, median t_max was longer (0.5 vs. 2 – 10 hours), and mean C_max was lower for all 5 MR formulations (262 vs. 34 – 78 ng/mL); t_1/2,z was similar (18 – 21 hours). The relative bioavailability was high (> 75%) for three MR formulations but lower (< 65%) for the other two. Overall, the effect of food on omecamtiv mecarbil pharmacokinetics was minimal for four of the MR formulations. The pharmacokinetics of the inactive metabolites M3 and M4 were similar across all formulations. Conclusions: The relative bioavailability of omecamtiv mecarbil was high (> 75%) for 3 of the five MR formulations. Food had a marginal, nonclinically meaningful effect on the pharmacokinetics of the MR formulations of omecamtiv mecarbil.

[Modern drug therapy in cardiovascular intensive care medicine]

Vasoactive drugs and inotropes are important in the hemodynamic management of patients with cardiogenic shock despite modest volume administration. Currently, the concept of cardiac relief is pursued in the treatment of acute heart failure. In this article we present the use of different drugs in the intensive care unit for acute heart failure and cardiogenic shock. In acute heart failure catecholamines are only used during the transition from heart failure to cardiogenic shock. Here, the therapeutic concept of ventricular unloading is more sought after. This can be achieved by the use of diuretics, nitrates, levosimendan (inodilatator), or in the future serelaxin. The hemodynamic management in cardiogenic shock occurs after moderate volume administration with dobutamine to increase inotropy. If no adequate perfusion pressures are achieved, norepinephrine can be administered as a vasopressor. If there is still no sufficient increase in cardiac output, the inodilatator levosimendan can be used. Levosimendan instead of phosphodiesterase inhibitors in this case is preferable. The maxim of hemodynamic management in cardiogenic shock is the transient use of inotropes and vasopressors in the lowest dose possible and only for as long as necessary. This means that one should continuously check whether the dose can be reduced. There are no mortality data demonstrating the utility of hemodynamic monitoring based on objective criteria—but it makes sense to use inotropes and vasopressors sparingly.

Rationally engineered Troponin C modulates in vivo cardiac function and performance in health and disease

Treatment for heart disease, the leading cause of death in the world, has progressed little for several decades. Here we develop a protein engineering approach to directly tune in vivo cardiac contractility by tailoring the ability of the heart to respond to the Ca(2+) signal. Promisingly, our smartly formulated Ca(2+)-sensitizing TnC (L48Q) enhances heart function without any adverse effects that are commonly observed with positive inotropes. In a myocardial infarction (MI) model of heart failure, expression of TnC L48Q before the MI preserves cardiac function and performance. Moreover, expression of TnC L48Q after the MI therapeutically enhances cardiac function and performance, without compromising survival. We demonstrate engineering TnC can specifically and precisely modulate cardiac contractility that when combined with gene therapy can be employed as a therapeutic strategy for heart disease.

Designing proteins to combat disease: Cardiac troponin C as an example

Throughout history, muscle research has led to numerous scientific breakthroughs that have brought insight to a more general understanding of all biological processes. Potentially one of the most influential discoveries was the role of the second messenger calcium and its myriad of handling and sensing systems that mechanistically control muscle contraction. In this review we will briefly discuss the significance of calcium as a universal second messenger along with some of the most common calcium binding motifs in proteins, focusing on the EF-hand. We will also describe some of our approaches to rationally design calcium binding proteins to palliate, or potentially even cure cardiovascular disease. Considering not all failing hearts have the same etiology, genetic background and co-morbidities, personalized therapies will need to be developed. We predict designer proteins will open doors for unprecedented personalized, and potentially, even generalized medicines as gene therapy or protein delivery techniques come to fruition.

The myosin activator omecamtiv mecarbil: a promising new inotropic agent

Heart failure became a leading cause of mortality in the past few decades with a progressively increasing prevalence. Its current therapy is restricted largely to the suppression of the sympathetic activity and the renin-angiotensin system in combination with diuretics. This restrictive strategy is due to the potential long-term adverse effects of inotropic agents despite their effective influence on cardiac function when employed for short durations. Positive inotropes include inhibitors of the Na⁺/K⁺ pump, β-receptor agonists, and phosphodiesterase inhibitors. Theoretically, Ca²⁺ sensitizers may also increase cardiac contractility without resulting in Ca²⁺ overload; nevertheless, their mechanism of action is frequently complicated by other pleiotropic effects. Recently, a new positive inotropic agent, the myosin activator omecamtiv mecarbil, has been developed. Omecamtiv mecarbil binds directly to β-myosin heavy chain and enhances cardiac contractility by increasing the number of the active force-generating cross-bridges, presumably without major off-target effects. This review focuses on recent in vivo and in vitro results obtained with omecamtiv mecarbil, and discusses its mechanism of action at a molecular level. Based on clinical data, omecamtiv mecarbil is a promising new tool in the treatment of systolic heart failure.

Novel Perspectives in Redox Biology and Pathophysiology of Failing Myocytes: Modulation of the Intramyocardial Redox Milieu for Therapeutic Interventions-A Review Article from the Working Group of Cardiac Cell Biology, Italian Society of Cardiology

The prevalence of heart failure (HF) is still increasing worldwide, with enormous human, social, and economic costs, in spite of huge efforts in understanding pathogenetic mechanisms and in developing effective therapies that have transformed this syndrome into a chronic disease. Myocardial redox imbalance is a hallmark of this syndrome, since excessive reactive oxygen and nitrogen species can behave as signaling molecules in the pathogenesis of hypertrophy and heart failure, leading to dysregulation of cellular calcium handling, of the contractile machinery, of myocardial energetics and metabolism, and of extracellular matrix deposition. Recently, following new interesting advances in understanding myocardial ROS and RNS signaling pathways, new promising therapeutical approaches with antioxidant properties are being developed, keeping in mind that scavenging ROS and RNS tout court is detrimental as well, since these molecules also play a role in physiological myocardial homeostasis.

Early detection of nonneurologic organ failure in patients with severe traumatic brain injury: Multiple organ dysfunction score or sequential organ failure assessment?

Objective:

The aim of this study is to compare the discriminant function of multiple organ dysfunction score (MODS) and sequential organ failure assessment (SOFA) components in predicting the Intensive Care Unit (ICU) mortality and neurologic outcome.

Materials and Methods:

A descriptive–analytic study was conducted at a level I trauma center. Data were collected from patients with severe traumatic brain injury admitted to the neurosurgical ICU. Basic demographic data, SOFA and MOD scores were recorded daily for all patients. Odd's ratios (ORs) were calculated to determine the relationship of each component score to mortality, and area under receiver operating characteristic (AUROC) curve was used to compare the discriminative ability of two tools with respect to ICU mortality.

Results:

The most common organ failure observed was respiratory detected by SOFA of 26% and MODS of 13%, and the second common was cardiovascular detected by SOFA of 18% and MODS of 13%. No hepatic or renal failure occurred, and coagulation failure reported as 2.5% by SOFA and MODS. Cardiovascular failure defined by both tools had a correlation to ICU mortality and it was more significant for SOFA (OR = 6.9, CI = 3.6–13.3, P < 0.05 for SOFA; OR = 5, CI = 3–8.3, P < 0.05 for MODS; AUROC = 0.82 for SOFA; AUROC = 0.73 for MODS). The relationship of cardiovascular failure to dichotomized neurologic outcome was not significant statistically. ICU mortality was not associated with respiratory or coagulation failure.

Conclusion:

Cardiovascular failure defined by either tool significantly related to ICU mortality. Compared to MODS, SOFA-defined cardiovascular failure was a stronger predictor of death. ICU mortality was not affected by respiratory or coagulation failures.

A Randomized Blinded Study of the Left Ventricular Myocardial Performance Index Comparing Epinephrine to Levosimendan following Cardiopulmonary Bypass

BACKGROUND

The objective was to evaluate the effect of epinephrine and levosimendan on the left ventricle myocardial performance index in patients undergoing on-pump coronary artery by-pass grafting (CABG).

METHODS

In a double-blind, randomized clinical trial, 81 patients (age: 45-65 years) of both genders were randomly divided to receive either epinephrine at a dosage of 0.06 mcg.kg(1).min(-1) (epinephrine group, 39 patients) or levosimendan at 0.2 mcg.kg(1).min(-1) (levosimendan group, 42 patients) during the rewarming of cardiopulmonary by-pass (CPB). Hemodynamic data were collected 30 minutes after tracheal intubation, before chest open (pre-CPB) and 10 minutes after termination of protamine (post-CPB). As the primary outcome, we evaluated the left ventricle myocardial performance index by the Doppler echocardiography. The myocardial performance index is the sum of the isovolumetric contraction time and the isovolumetric relaxation time, divided by the ejection time. Secondary outcomes were systolic and diastolic evaluations of the left ventricle and postoperative troponin I and MB-CK levels.

RESULTS

Of the 81 patients allocated to the research, we excluded 2 patients in the epinephrine group and 6 patients in the levosimendan group because they didn't wean from CPB in the first attempt. There was no statistical difference between the groups in terms of patient characteristics, risk factors, or CPB time. The epinephrine group had a lower left ventricle myocardial performance index (p = 0.0013), higher cardiac index (p = 0.03), lower systemic vascular resistance index (p = 0.01), and higher heart rate (p = 0.04) than the levosimendan group at the post-CPB period. There were no differences between the groups in diastolic dysfunction. The epinephrine group showed higher incidence of weaning from CPB in the first attempt (95% vs 85%, p = 0.0001) when compared to the levosimendan group and the norepinephrine requirement was higher in the levosimenandan group than epinephrine group (16% vs. 47%; p = 0.005) in post-CPB period. Twenty-four hours after surgery, the plasma levels of troponin I (epinephrine group: 4.5 ± 5.7 vs. levosimendan group: 2.5 ± 3.2 g/dl; p = 0.09) and MB-CK (epinephrine group: 50.7 ± 31 vs. levosimendan group: 37 ± 17.6 g/dl; p = 0.08) were not significantly different between the two groups.

CONCLUSION

When compared to levosimendan, patients treated with epinephrine had a lower left ventricle myocardial performance index in the immediate post-CPB period, encouraging an efficient weaning from CPB in patients undergoing on-pump CABG.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01616069.

Liver Enzymes and Uric acid in Acute Heart Failure

BACKGROUND

Acute heart failure (AHF) is defined as the new onset or recurrence of gradual or rapidly worsening signs and symptoms of heart failure, requiring urgent or emergent therapy.

OBJECTIVES

This study attempts to assess the association of liver function tests (LFT) and uric acid level with in hospital outcome and echocardiography parameters, in patients with acute decompensated heart failure.

PATIENTS AND METHODS

A total of 100 patients (aged 16 - 90 years, 60% men) admitted with AHF were enrolled. LFTs and uric acid levels were assessed on first day and before discharge, and patients were followed for 3 months.

RESULTS

In-hospital outcomes were considered. Mean Left Ventricular Ejection Fraction (LVEF) was 35% (20 - 45%). Mean Uric acid level was 8.4 mg/dL, significantly higher than chronic HF and normal groups (P < 0.02). Elevated liver enzymes were seen in 52% patients, mostly (87%) in transaminases. Liver enzymes were decreased in 85% patients before discharge. LFT and uric acid levels were inversely and significantly correlated with LVEF on echocardiography (P = 0.02), but not with diastolic parameters. Although there was no significant correlation between uric acid level and in-hospital mortality, risk of intubation and rehospitalization in 3 months, enzyme levels increased in these groups. Increased aspartate transaminase (AST level) was associated with inotrope infusion in AHF patients (42 vs. 82 mg/dL, P = 0.03).

CONCLUSIONS

Abnormal transaminases and uric acid levels are seen in AHF patients. Increased AST levels may be a predictor of the need for inotrope during hospital course in these patients.

Population pharmacokinetic-pharmacodynamic modeling of omecamtiv mecarbil, a cardiac myosin activator, in healthy volunteers and patients with stable heart failure

Data from 3 clinical trials of omecamtiv mecarbil in healthy volunteers and patients with stable heart failure (HF) were analyzed using a nonlinear mixed-effects model to investigate omecamtiv mecarbil's pharmacokinetics and relationship between plasma concentration and systolic ejection time (SET) and Doppler-derived left ventricular outflow tract stroke volume (LVOTSV). Omecamtiv mecarbil pharmacokinetics were described by a linear 2-compartment model with a zero-order input rate for intravenous administration and first-order absorption for oral administration. Oral absorption half-life was 0.62 hours, and absolute bioavailability was estimated as 90%; elimination half-life was approximately 18.5 hours. Variability in pharmacokinetic parameters was not explained by patient baseline characteristics. Omecamtiv mecarbil plasma concentration was directly correlated with increases in SET and LVOTSV between healthy volunteers and patients with HF. The maximum increase from baseline in SET (delta SET) estimated by an Emax model was 137 milliseconds. LVOTSV increased linearly from baseline by 1.6 mL per 100 ng/mL of omecamtiv mecarbil. Model-based simulations for several immediate-release oral dose regimens (37.5, 50, and 62.5 mg dosed every 8, 12, and 24 hours) showed that a pharmacodynamic effect (delta SET ≥20 milliseconds) could be maintained in the absence of excessive omecamtiv mecarbil plasma concentrations.

Acute decompensated heart failure update

Acute decompensated heart failure (ADHF) continues to increase in prevalence and is associated with substantial mortality and morbidity including frequent hospitalizations. The American Heart Association is predicting that more than eight million Americans will have heart failure by 2030 and that the total direct costs associated with the disease will rise from $21 billion in 2012 to $70 billion in 2030. The increase in the prevalence and cost of HF is primarily the result of shifting demographics and a growing population. Although many large, randomized, controlled clinical trials have been conducted in patients with chronic heart failure, it was not until recently that a growing number of studies began to address the management of ADHF. It is the intent of this review to update the clinician regarding the evaluation and optimal management of ADHF.

Nitroxyl (HNO) for treatment of acute heart failure

The loss of contractile function is a hallmark of heart failure. Although increasing intracellular Ca(2+) is a possible strategy for improving contraction, current inotropic agents that achieve this by raising intracellular cAMP levels, such as β-agonists and phosphodiesterase inhibitors, are generally deleterious when administered as long-term therapy due to arrhythmia and myocardial damage. Nitroxyl donors have been shown to improve cardiac function in normal and failing dogs, and in isolated cardiomyocytes they increase fractional shortening and Ca(2+) transients, independently from cAMP/PKA or cGMP/PKG signaling. Instead, nitroxyl targets cysteines in the EC-coupling machinery and myofilament proteins, reversibly modifying them to enhance Ca(2+) handling and myofilament Ca(2+) sensitivity. Phase I-IIa trials with CXL-1020, a novel pure HNO donor, reported declines in left and right heart filling pressures and systemic vascular resistance, and increased cardiac output and stroke volume index. These findings support the concept of nitroxyl donors as attractive agents for the treatment of acute decompensated heart failure.

High-throughput screening for modulators of cellular contractile force

When cellular contractile forces are central to pathophysiology, these forces comprise a logical target of therapy. Nevertheless, existing high-throughput screens are limited to upstream signalling intermediates with poorly defined relationships to such a physiological endpoint. Using cellular force as the target, here we report a new screening technology and demonstrate its applications using human airway smooth muscle cells in the context of asthma and Schlemm's canal endothelial cells in the context of glaucoma. This approach identified several drug candidates for both asthma and glaucoma. We attained rates of 1000 compounds per screening day, thus establishing a force-based cellular platform for high-throughput drug discovery.

Inhaled Milrinone After Left Ventricular Assist Device Implantation

BACKGROUND

Proven strategies to reduce right ventricular (RV) dysfunction after continuous-flow left ventricular assist device (CF-LVAD) implantation are lacking. We sought to evaluate the tolerability, feasibility, efficacy, and pharmacokinetics of inhaled milrinone (iMil) delivery after CF-LVAD implantation.

METHODS AND RESULTS

We prospectively evaluated fixed-dose nebulized iMil delivered into a ventilator circuit for 24 hours in 10 postoperative CF-LVAD (Heartmate-II) patients. Tolerability (arrhythmias, hypotension, and hypersensitivity reaction), efficacy (hemodynamics), pharmacokinetics (plasma milrinone levels), and cost data were collected.Mean age was 56 ± 9 years, 90% were male, and mean INTERMACS profile was 2.5 ± 0.8. No new atrial arrhythmia events occurred, although 3 (30%) ventricular tachycardia (1 nonsustained, 2 sustained) events occurred. Sustained hypotension, drug hypersensitivity, death, or need for right ventricular assist device were not observed. Invasive mean pulmonary arterial pressure from baseline to during iMil therapy was improved (P = .017). Mean plasma milrinone levels (ng/mL) at baseline, and 1, 4, 8, 12, and 24 hours were 74.2 ± 35.4, 111.3 ± 70.9, 135.9 ± 41.5, 205.0 ± 86.7, 176.8 ± 61.3 187.6 ± 105.5, respectively. Reduced institutional cost was observed when iMil was compared with nitric oxide therapy over 24 hours ($165.29 vs $1,944.00, respectively).

CONCLUSIONS

iMil delivery after CF-LVAD implantation was well tolerated, feasible, and demonstrated favorable hemodynamic, pharmacokinetic, and cost profiles. iMil therapy warrants further study in larger clinical trials.

Design and synthesis of new dihydrotestosterone derivative with positive inotropic activity

There are several reports which indicate that some steroid derivatives have inotropic activity; nevertheless, the cellular site and mechanism of action of steroid derivatives at cardiovascular level is very confusing. In order, to clarify these phenomena in this study, two dihydrotestosterone derivatives (compounds 5 and 10) were synthesized with the objective of to evaluate its biological activity on left ventricular pressure and characterize their molecular mechanism. In the first stage, the Langendorff technique was used to measure changes on perfusion pressure and coronary resistance in an isolated rat heart model in absence or presence of the steroid derivatives. Additionally, to characterize the molecular mechanism involved in the inotropic activity induced by the compound 5 was evaluated by measuring left ventricular pressure in absence or presence of following compounds; nifedipine, flutamide, indomethacin, prazosin, isoproterenol, propranolol and metoprolol. The results showed that the compound 5 significantly increased the perfusion pressure and coronary resistance in comparison with dihydrotestosterone, compound 10 and the control conditions. Other data indicate that 5 increase left ventricular pressure in a dose-dependent manner (0.001-100 nM); nevertheless, this phenomenon was significantly inhibited only by propranolol or metoprolol at a dose of 1 nM. These data suggest that positive inotropic activity induced by the compound 5 is through β1-adrenergic receptor however, this effect was independent of cAMP levels. This phenomenon is a particularly interesting because the positive inotropic activity induced by this steroid derivative involves a molecular mechanism different in comparison with other positive inotropic drugs.

Abnormalities of capillary microarchitecture in a rat model of coronary ischemic congestive heart failure

The aim of the present study is to explore the role of capillary disorder in coronary ischemic congestive heart failure (CHF). CHF was induced in rats by aortic banding plus ischemia-reperfusion followed by aortic debanding. Coronary arteries were perfused with plastic polymer containing fluorescent dye. Multiple fluorescent images of casted heart sections and scanning electric microscope of coronary vessels were obtained to characterize changes in the heart. Cardiac function was assessed by echocardiography and in vivo hemodynamics. Stenosis was found in all levels of the coronary arteries in CHF. Coronary vasculature volume and capillary density in remote myocardium were significantly increased in CHF compared with control. This occurred largely in microvessels with a diameter of ≤3 μm. Capillaries in CHF had a tortuous structure, while normal capillaries were linear. Capillaries in CHF had inconsistent diameters, with assortments of narrowed and bulged segments. Their surfaces appeared rough, potentially indicating endothelial dysfunction in CHF. Segments of main capillaries between bifurcations were significantly shorter in length in CHF than in control. Transiently increasing preload by injecting 50 μl of 30% NaCl demonstrated that the CHF heart had lower functional reserve; this may be associated with congestion in coronary microcirculation. Ischemic coronary vascular disorder is not limited to the main coronary arteries, as it occurs in arterioles and capillaries. Capillary disorder in CHF included stenosis, deformed structure, proliferation, and roughened surfaces. This disorder in the coronary artery architecture may contribute to the reduction in myocyte contractility in the setting of heart failure.

Ligand orientation in a membrane-embedded receptor site revealed by solid-state NMR with paramagnetic relaxation enhancement

Paramagnetic relaxation-enhanced solid-state NMR reveals a ouabain analogue with an inverted orientation in the Na,K-ATPase inhibitory site.

Abnormal Ca(2+) cycling in failing ventricular myocytes: role of NOS1-mediated nitroso-redox balance

SIGNIFICANCE

Heart failure (HF) results from poor heart function and is the leading cause of death in Western society. Abnormalities of Ca(2+) handling at the level of the ventricular myocyte are largely responsible for much of the poor heart function.

RECENT ADVANCES

Although studies have unraveled numerous mechanisms for the abnormal Ca(2+) handling, investigations over the past decade have indicated that much of the contractile dysfunction and adverse remodeling that occurs in HF involves oxidative stress.

CRITICAL ISSUES

Regrettably, antioxidant therapy has been an immense disappointment in clinical trials. Thus, redox signaling is being reassessed to elucidate why antioxidants failed to treat HF.

FUTURE DIRECTIONS

A recently identified aspect of redox signaling (specifically the superoxide anion radical) is its interaction with nitric oxide, known as the nitroso-redox balance. There is a large nitroso-redox imbalance with HF, and we suggest that correcting this imbalance may be able to restore myocyte contraction and improve heart function.

Pharmacogenetics of cardiac inotropy

The ability to stimulate cardiac contractility is known as positive inotropy. Endogenous hormones, such as adrenaline and several natural or synthetic compounds possess this biological property, which is invaluable in the modern cardiovascular therapy setting, especially in acute heart failure or in cardiogenic shock. A number of proteins inside the cardiac myocyte participate in the molecular pathways that translate the initial stimulus, that is, the hormone or drug, into the effect of increased contractility (positive inotropy). Genetic variations (polymorphisms) in several genes encoding these proteins have been identified and characterized in humans with potentially significant consequences on cardiac inotropic function. The present review discusses these polymorphisms and their effects on cardiac inotropy, along with the individual pharmacogenomics of the most important positive inotropic agents in clinical use today. Important areas for future investigations in the field are also highlighted.

Progress in gene therapy for heart failure

Recent advances in our understanding of the pathophysiology of myocardial dysfunction in the setting of congestive heart failure have created a new opportunity in developing nonpharmacological approaches to treatment. Gene therapy has emerged as a powerful tool in targeting the molecular mechanisms of disease by preventing the ventricular remodeling and improving bioenergetics in heart failure. Refinements in vector technology, including the creation of recombinant adeno-associated viruses, have allowed for safe and efficient gene transfer. These advancements have been coupled with evolving delivery methods that include vascular, pericardial, and direct myocardial approaches. One of the most promising targets, SERCA2a, is currently being used in clinical trials. The recent success of the Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease phase 2 trials using adeno-associated virus 1-SERCA2a in improving outcomes highlights the importance of gene therapy as a future tool in treating congestive heart failure.

Computer-aided drug discovery approach finds calcium sensitizer of cardiac troponin

In the fight against heart failure, therapeutics that have the ability to increase the contractile power of the heart are urgently needed. One possible route of action to improve heart contractile power is increasing the calcium sensitivity of the thin filament. From a pharmaceutical standpoint, calcium sensitizers have the distinct advantage of not altering cardiomyocyte calcium levels and thus have lower potential for side-effects. Small chemical molecules have been shown to bind to the interface between cTnC and the cTnI switch peptide and exhibit calcium-sensitizing properties, possibly by stabilizing cTnC in an open conformation. Building on existing structural data of a known calcium sensitizer bound to cardiac troponin, we combined computational structure-based virtual screening drug discovery methods and solution NMR titration assays to identify a novel calcium sensitizer 4-(4-(2,5-dimethylphenyl)-1-piperazinyl)-3-pyridinamine (NSC147866) which binds to cTnC and the cTnC-cTnI147-163 complex. Its presence increases the affinity of switch peptide to cTnC by approximately a factor of two. This action is comparable to that of known levosimendan analogues.

Cardiac myosin binding protein-C: a novel sarcomeric target for gene therapy

Through its ability to interact with both the thick and thin filament proteins within the sarcomere, cardiac myosin binding protein-C (cMyBP-C) regulates the contractile properties of the myocardium. The central regulatory role of cMyBP-C in heart function is emphasized by the fact that a large proportion of inherited hypertrophic cardiomyopathy cases in humans are caused by mutations in cMyBP-C. The primary dysfunction in cMyBP-C-related cardiomyopathies is likely to be abnormal myofilament contractile function; however, currently, there are no effective therapies for ameliorating these contractile defects. Thus, there is a compelling need to design novel therapies to restore normal contractile function in cMyBP-C-related cardiomyopathies. To this end, concepts gleaned from various structural, functional, and biochemical studies can now be utilized to engineer cMyBP-C proteins that, when incorporated into the sarcomere, can significantly improve contractile function. In this review, we discuss the rationale for cMyBP-C-based gene therapies that can be utilized to treat contractile dysfunction in inherited and acquired cardiomyopathies.

HNO enhances SERCA2a activity and cardiomyocyte function by promoting redox-dependent phospholamban oligomerization

AIMS

Nitroxyl (HNO) interacts with thiols to act as a redox-sensitive modulator of protein function. It enhances sarcoplasmic reticular Ca(2+) uptake and myofilament Ca(2+) sensitivity, improving cardiac contractility. This activity has led to clinical testing of HNO donors for heart failure. Here we tested whether HNO alters the inhibitory interaction between phospholamban (PLN) and the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) in a redox-dependent manner, improving Ca(2+) handling in isolated myocytes/hearts.

RESULTS

Ventriculocytes, sarcoplasmic reticulum (SR) vesicles, and whole hearts were isolated from control (wildtype [WT]) or PLN knockout (pln(-/-)) mice. Compared to WT, pln(-/-) myocytes displayed enhanced resting sarcomere shortening, peak Ca(2+) transient, and blunted β-adrenergic responsiveness. HNO stimulated shortening, relaxation, and Ca(2+) transient in WT cardiomyocytes, and evoked positive inotropy/lusitropy in intact hearts. These changes were markedly blunted in pln(-/-) cells/hearts. HNO enhanced SR Ca(2+) uptake in WT but not pln(-/-) SR-vesicles. Spectroscopic studies in insect cell microsomes expressing SERCA2a±PLN showed that HNO increased Ca(2+)-dependent SERCA2a conformational flexibility but only when PLN was present. In cardiomyocytes, HNO achieved this effect by stabilizing PLN in an oligomeric disulfide bond-dependent configuration, decreasing the amount of free inhibitory monomeric PLN available.

INNOVATION

HNO-dependent redox changes in myocyte PLN oligomerization relieve PLN inhibition of SERCA2a.

CONCLUSIONS

PLN plays a central role in HNO-induced enhancement of SERCA2a activity, leading to increased inotropy/lusitropy in intact myocytes and hearts. PLN remains physically associated with SERCA2a; however, less monomeric PLN is available resulting in decreased inhibition of the enzyme. These findings offer new avenues to improve Ca(2+) handling in failing hearts.

Nitroxyl (HNO): A novel approach for the acute treatment of heart failure

BACKGROUND

The nitroxyl (HNO) donor, Angeli's salt, exerts positive inotropic, lusitropic, and vasodilator effects in vivo that are cAMP independent. Its clinical usefulness is limited by chemical instability and cogeneration of nitrite which itself has vascular effects. Here, we report on effects of a novel, stable, pure HNO donor (CXL-1020) in isolated myoctyes and intact hearts in experimental models and in patients with heart failure (HF).

METHODS AND RESULTS

CXL-1020 converts solely to HNO and inactive CXL-1051 with a t1/2 of 2 minutes. In adult mouse ventricular myocytes, it dose dependently increased sarcomere shortening by 75% to 210% (50-500 μmol/L), with a ≈30% rise in the peak Ca(2+) transient only at higher doses. Neither inhibition of protein kinase A nor soluble guanylate cyclase altered this contractile response. Unlike isoproterenol, CXL-1020 was equally effective in myocytes from normal or failing hearts. In anesthetized dogs with coronary microembolization-induced HF, CXL-1020 reduced left ventricular end-diastolic pressure and myocardial oxygen consumption while increasing ejection fraction from 27% to 40% and maximal ventricular power index by 42% (both P<0.05). In conscious dogs with tachypacing-induced HF, CXL-1020 increased contractility assessed by end-systolic elastance and provided venoarterial dilation. Heart rate was minimally altered. In patients with systolic HF, CXL-1020 reduced both left and right heart filling pressures and systemic vascular resistance, while increasing cardiac and stroke volume index. Heart rate was unchanged, and arterial pressure declined modestly.

CONCLUSIONS

These data show the functional efficacy of a novel pure HNO donor to enhance myocardial function and present first-in-man evidence for its potential usefulness in HF.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT01096043, NCT01092325.

Positive inotropic agents in myocardial ischemia-reperfusion injury: a benefit/risk analysis

Positive inotropic agents should be used judiciously when managing surgical patients with acute myocardial ischemia–reperfusion injury, as use of these inotropes is not without potential adverse effects.

A pig model of the preterm neonate: anthropometric and physiological characteristics

BACKGROUND

Large animal models are an essential tool in the development of rationally-based new clinical therapies for preterm infants. We provide a description of the newborn pig as a model of the preterm neonate in terms of growth parameters, physiology and the requirement for intensive care over a range of gestational ages.

METHODS

Twenty-nine litters of piglets (n = 298) were delivered by caesarean section at six timepoints during gestation from 91d to 113d (term = 115d). Two groups, at 91 and 97d gestation, also received maternal glucocorticoid treatment. At four of these timepoints, piglets (n = 79) were ventilated, sedated and monitored using standard neonatal intensive care techniques for up to 8 h in various experimental protocols.

RESULTS

Body weight increased from mean 697 g (SD 193) at 91d gestation to 1331 g (SD 368) at 113d gestation. Piglets delivered at 97d gestation were able to be resuscitated and kept alive for at least 8 h on respiratory support after surfactant administration. Maternal glucocorticoid treatment 48 h and 24 h hours prior to delivery reduced the requirement for ventilator support and improved cardiovascular stability.

CONCLUSION

The pig provides a relevant model for the study of human preterm physiology and for investigation of novel therapies to improve outcomes.

A case of riata® dual coil defibrillator lead failure in a patient with ventricular fibrillation

A 50-year-old man, who underwent a procedure for an implantable cardioverter defibrillator (ICD), visited the outpatient department of our clinic after suffering multiple ICD shocks. The ICD interrogation revealed recurrent shock due to a high frequency of noise that is sensed by the device as ventricular fibrillation. Chest radiography revealed a significant split in the insulation of the lead allowing the inner wire to protrude. We considered the removal of the failed lead, but the removal of ICD lead is potentially a high risk procedure, so we cut and capped a proximal part of the failed lead and inserted a new lead. This is the first report of a St. Jude Riata® dual coil defibrillator lead failure with clinical and radiologic evidence of a defect in lead insulation in Korea.