Acute heart failure: inotropic agents and their clinical uses

Structures, Photoresponse Properties, and Biological Activity of Dicyano-Substituted 4-Aryl-2-pyridone Derivatives

Described in this work is the synthesis of a novel dicyano-substituted N-2-aminoethyl-4-(3-pyridinyl)-2-pyridone organic compound (1) that is characterized by several spectroscopic methods. Compound (1) was utilized for the preparation of its perchlorate (2), chloride (3), and bromide (4) salts. Single-crystal X-ray structures of these three salts were determined, and noncovalent weak interactions involving the aromatic rings, anions, and water molecules in (2-4) were investigated in detail. Solid-state UV-vis spectrum of the reported compounds (1-4) was utilized to calculate their optical band gaps, which clearly indicated that they belong to the semiconductor family. Under illumination condition, the magnitudes of electrical properties of (1) and its salts (2-4) improve remarkably although the improvement differs from salt to salt and the result was analyzed theoretically. Salt (2) was tested for its DNA binding ability.

Elucidation of the Strongest Predictors of Cardiovascular Events in Patients with Heart Failure

BACKGROUND

In previous retrospective studies, we identified the 50 most influential clinical predictors of cardiovascular outcomes in patients with heart failure (HF). The present study aimed to use the novel limitless-arity multiple-testing procedure to filter these 50 clinical factors and thus yield combinations of no more than four factors that could potentially predict the onset of cardiovascular events. A Kaplan-Meier analysis was used to investigate the importance of the combinations.

METHODS

In a multi-centre observational trial, we prospectively enrolled 213 patients with HF who were hospitalized because of exacerbation, discharged according to HF treatment guidelines and observed to monitor cardiovascular events. After the observation period, we stratified patients according to whether they experienced cardiovascular events (rehospitalisation or cardiovascular death).

FINDINGS

Among 77,562 combinations of fewer than five clinical parameters, we identified 151 combinations that could potentially explain the occurrence of cardiovascular events. Of these, 145 combinations included the use of inotropic agents, whereas the remaining 6 included the use of diuretics without bradycardia or tachycardia, suggesting that the high probability of cardiovascular events is exclusively determined by these two clinical factors. Importantly, Kaplan-Meier curves demonstrated that the use of inotropes or of diuretics without bradycardia or tachycardia were independent predictors of a markedly worse cardiovascular prognosis.

INTERPRETATION

Patients treated with either inotropic agents or diuretics without bradycardia or tachycardia were at a higher risk of cardiovascular events. The uses of these drugs, regardless of heart rate, are the strongest clinical predictors of cardiovascular events in patients with HF.

A highly efficient magnetic solid acid nanocatalyst for the synthesis of new bulky heterocyclic compounds

Fe₃O₄nanoparticles were coated with 3-aminopropyltriethoxysilane and further chemically modified with maleic anhydride to generate Fe₃O₄@APTES·MAH NPs. Then some new bulky heterocyclic compounds were synthesized using this catalyst.

Lipid emulsion rapidly restores contractility in stunned mouse cardiomyocytes: a comparison with therapeutic hypothermia

OBJECTIVES

Cooling following cardiac arrest can improve survival significantly. However, delays in achieving target temperature may decrease the overall benefits of cooling. Here, we test whether lipid emulsion, a clinically approved drug reported to exert cardioprotection, can rescue heart contractility in the setting of delayed cooling in stunned mouse cardiomyocytes.

DESIGN

Cell culture study.

SETTING

Academic research laboratory.

SUBJECTS

Cardiomyocytes isolated from 1- to 2-day-old C57BL6 mice.

INTERVENTIONS

Cardiomyocytes were exposed to 30 minutes of ischemia followed by 90 minutes of reperfusion and 10 minutes of isoproterenol with nine interventions: 1) no additional treatment; 2) intraischemic cooling at 32 °C initiated 10 minutes prior to reperfusion; 3) delayed cooling started 20 minutes after reperfusion; 4) lipid emulsion + delayed cooling; 5) lipid emulsion (0.25%) administered at reperfusion; 6) lipid emulsion + intraischemic cooling; 7) delayed lipid emulsion; 8) lipid emulsion + delayed cooling + Akt inhibitor (API-2, 10 µM); and 9) lipid emulsion + delayed cooling + Erk inhibitor (U0126, 10 µM). Inhibitors were given to cells 1 hour prior to ischemia.

MEASUREMENTS AND MAIN RESULTS

Contractility was recorded by real-time phase-contrast imaging and analyzed with pulse image velocimetry in MATLAB (Mathworks, Natick, MA). Ischemia diminished cell contraction. The cardioprotective effect of cooling was diminished when delayed but was rescued by lipid emulsion. Further, lipid emulsion on its own improved recovery of the contractility to a greater extent as intraischemic cooling. However, cotreatment of lipid emulsion and intraischemic cooling did not further improve the recovery compared to either treatment alone. Furthermore, Akt and Erk inhibitors blocked lipid emulsion-induced protection.

CONCLUSIONS

Lipid emulsion improved contractility and rescued contractility in the context of delayed cooling. This protective effect required Akt and Erk signaling. Lipid emulsion might serve as a treatment or adjunct to cooling in ameliorating myocardial ischemia/reperfusion injury.

Clinical and molecular genetics of the phosphodiesterases (PDEs)

Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that have the unique function of terminating cyclic nucleotide signaling by catalyzing the hydrolysis of cAMP and GMP. They are critical regulators of the intracellular concentrations of cAMP and cGMP as well as of their signaling pathways and downstream biological effects. PDEs have been exploited pharmacologically for more than half a century, and some of the most successful drugs worldwide today affect PDE function. Recently, mutations in PDE genes have been identified as causative of certain human genetic diseases; even more recently, functional variants of PDE genes have been suggested to play a potential role in predisposition to tumors and/or cancer, especially in cAMP-sensitive tissues. Mouse models have been developed that point to wide developmental effects of PDEs from heart function to reproduction, to tumors, and beyond. This review brings together knowledge from a variety of disciplines (biochemistry and pharmacology, oncology, endocrinology, and reproductive sciences) with emphasis on recent research on PDEs, how PDEs affect cAMP and cGMP signaling in health and disease, and what pharmacological exploitations of PDEs may be useful in modulating cyclic nucleotide signaling in a way that prevents or treats certain human diseases.

Are the different patterns of stress-induced (Takotsubo) cardiomyopathy explained by regional mechanical overload and demand: supply mismatch in selected ventricular regions?

Takotsubo cardiomyopathy (TCM) or stress-induced cardiomyopathy is an increasingly recognized syndrome characterized by severe regional left ventricular dysfunction in the absence of an explanatory coronary lesion. TCM may lead to lethal complications but is completely reversible if the patient survives the acute phase. The pathogenesis of TCM and the mechanism behind this remarkable recovery are unknown. Plasma levels of catecholamine are elevated in many TCM patients and exogenously administered catecholamine induces TCM-like cardiac dysfunction in both humans and rats. A catecholamine excess increases myocardial metabolic demand by increasing the force of contraction as well as the heart rate, and also alters cardiac depolarization patterns. We propose that an altered spatiotemporal pattern of cardiac contraction and excessive force of contraction may lead to a redistribution of wall stresses in the left ventricle. This redistribution of wall stress causes regional mechanical overload of regions where wall tension becomes disproportionately great and renders these cardiomyocytes "metabolically insufficient". In other words, these cardiomyocytes experience a demand: supply mismatch on the basis of excessive metabolic demand. In order to prevent the death of these cardiomyocytes and to prevent excessive wall tension from developing in neighboring regions, a protective metabolic shutdown occurs in the affected cardiomyocytes. This metabolic shutdown, i.e., acute down regulation of non-vital cellular functions, serves to protect the affected regions from necrosis and explains the apparently complete recovery observed in TCM. We propose that this phenomenon may share important characteristics with phenomena such as ischemic conditioning, stunning and hibernation. In this manuscript, we discuss our hypothesis in the context of available knowledge and discuss important experiments that would help to corroborate or refute the hypothesis.

A review of the pharmacology and clinical uses of pimobendan

OBJECTIVE

To review the pharmacology, research developments, and clinical uses of pimobendan

DATA SOURCES

Original research articles and clinical studies from 1984 to August 2011.

VETERINARY DATA SYNTHESIS

Pimobendan is approved for use in dogs for the treatment of congestive heart failure (CHF) secondary to chronic valvular heart disease (CVHD) and dilated cardiomyopathy (DCM). Expert-based veterinary guidelines recommend the use of pimobendan in the management of acute, hospital-based therapy for patients with CHF attributable to CVHD.

CONCLUSIONS

The use of pimobendan, an inodilator with phosphodiesterase 3 (PDE3) inhibitory and calcium-sensitizing properties, is regarded as a component of the standard of care in the management of dogs with CHF secondary to both DCM and CVHD. Further studies are warranted to confirm the safety and efficacy of pimobendan for the off-label use of this drug in asymptomatic CVHD, pulmonary arterial hypertension, asymptomatic myocardial diseases, CHF from all other causes and in cats with CHF.

Phosphodiesterase type 3A regulates basal myocardial contractility through interacting with sarcoplasmic reticulum calcium ATPase type 2a signaling complexes in mouse heart

RATIONALE

cAMP is an important regulator of myocardial function, and regulation of cAMP hydrolysis by cyclic nucleotide phosphodiesterases (PDEs) is a critical determinant of the amplitude, duration, and compartmentation of cAMP-mediated signaling. The role of different PDE isozymes, particularly PDE3A vs PDE3B, in the regulation of heart function remains unclear.

OBJECTIVE

To determine the relative contribution of PDE3A vs PDE3B isozymes in the regulation of heart function and to dissect the molecular basis for this regulation.

METHODS AND RESULTS

Compared with wild-type littermates, cardiac contractility and relaxation were enhanced in isolated hearts from PDE3A(-/-), but not PDE3B(-/-), mice. Furthermore, PDE3 inhibition had no effect on PDE3A(-/-) hearts but increased contractility in wild-type (as expected) and PDE3B(-/-) hearts to levels indistinguishable from PDE3A(-/-). The enhanced contractility in PDE3A(-/-) hearts was associated with cAMP-dependent elevations in Ca(2+) transient amplitudes and increased sarcoplasmic reticulum (SR) Ca(2+) content, without changes in L-type Ca(2+) currents of cardiomyocytes, as well as with increased SR Ca(2+)-ATPase type 2a activity, SR Ca(2+) uptake rates, and phospholamban phosphorylation in SR fractions. Consistent with these observations, PDE3 activity was reduced ≈8-fold in SR fractions from PDE3A(-/-) hearts. Coimmunoprecipitation experiments further revealed that PDE3A associates with both SR calcium ATPase type 2a and phospholamban in a complex that also contains A-kinase anchoring protein-18, protein kinase type A-RII, and protein phosphatase type 2A.

CONCLUSIONS

Our data support the conclusion that PDE3A is the primary PDE3 isozyme modulating basal contractility and SR Ca(2+) content by regulating cAMP in microdomains containing macromolecular complexes of SR calcium ATPase type 2a-phospholamban-PDE3A.

Regulation of murine cardiac function by phosphodiesterases type 3 and 4

Cyclic nucleotide phosphodiesterases (PDEs) encompass a large group of enzymes that regulate intracellular levels of two-second messengers, cAMP and cGMP, by controlling the rates of their degradation. More than 60 isoforms, subdivided into 11 gene families (PDE1-11), exist in mammals with at least six families (PDE1-5 and PDE8) identified in mammalian hearts. The two predominant families implicated in regulating contraction strength of the heart are PDE3 and PDE4. Studies using transgenic models in combination with family-specific PDE inhibitors have demonstrated that PDE3A, PDE4B, and PDE4D isoforms regulate cardiac contractility by modulating cAMP levels in various subcellular compartments. These studies have further uncovered contributions of PDE4B and PDE4D in preventing ventricular arrhythmias.

Beneficial effects of SR33805 in failing myocardium

AIMS

SR33805, a potent Ca(2+) channel blocker, increases cardiac myofilament Ca(2+) sensitivity in healthy rat cardiomyocytes. Therefore, the aim of the present study was to evaluate the effects of SR33805 on contractile properties in ischaemic failing hearts after myocardial infarction (MI) in vivo and in vitro at the cellular level.

METHODS AND RESULTS

The effect of SR33805 (10 µM) was tested on the excitation-contraction coupling of cardiomyocytes isolated from rat with end-stage heart failure. Cell shortening and Ca(2+) transients were measured in intact cardiomyocytes, while contractile properties were determined in Triton X-100 permeabilized myocytes. Acute treatment with SR33805 restored the MI-altered cell shortening without affecting the Ca(2+) transient amplitude, suggesting an increase of myofilament Ca(2+) sensitivity in MI myocytes. Indeed, a SR33805-induced sensitization of myofilament activation was found to be associated with a slight increase in myosin light chain-2 phosphorylation and a more significant decrease on troponin I (TnI) phosphorylation. Decreased TnI phosphorylation was related to inhibition of protein kinase A activity by SR33805. Finally, administration of a single intra-peritoneal bolus of SR33805 (20 mg/kg) improved end-systolic strain and fractional shortening of MI hearts.

CONCLUSION

The present study indicates that treatment with SR33805 improved contractility of ischaemic failing hearts after MI in the rat by selectively modulating the phosphorylation status of sarcomeric regulatory proteins, which then sensitized the myofilaments to Ca(2+). Our results gave a proof of concept that manipulation of the Ca(2+) sensitivity of sarcomeric regulatory proteins can be used to improve contractility of a failing heart.

Modeling cardiac β-adrenergic signaling with normalized-Hill differential equations: comparison with a biochemical model

Background

New approaches are needed for large-scale predictive modeling of cellular signaling networks. While mass action and enzyme kinetic approaches require extensive biochemical data, current logic-based approaches are used primarily for qualitative predictions and have lacked direct quantitative comparison with biochemical models.

Results

We developed a logic-based differential equation modeling approach for cell signaling networks based on normalized Hill activation/inhibition functions controlled by logical AND and OR operators to characterize signaling crosstalk. Using this approach, we modeled the cardiac β₁-adrenergic signaling network, including 36 reactions and 25 species. Direct comparison of this model to an extensively characterized and validated biochemical model of the same network revealed that the new model gave reasonably accurate predictions of key network properties, even with default parameters. Normalized Hill functions improved quantitative predictions of global functional relationships compared with prior logic-based approaches. Comprehensive sensitivity analysis revealed the significant role of PKA negative feedback on upstream signaling and the importance of phosphodiesterases as key negative regulators of the network. The model was then extended to incorporate recently identified protein interaction data involving integrin-mediated mechanotransduction.

Conclusions

The normalized-Hill differential equation modeling approach allows quantitative prediction of network functional relationships and dynamics, even in systems with limited biochemical data.

Combination therapy with beta-adrenergic receptor antagonists and phosphodiesterase inhibitors for chronic heart failure

Abstract Rational use of phosphodiesterase inhibitors represents an ongoing controversy in contemporary pharmacotherapy for heart failure. In randomized clinical trials, phosphodiesterase inhibitors increased cardiac output at the expense of worsening the rates of sudden cardiac death and cardiovascular mortality. Preliminary findings from ongoing clinical and preclinical investigations of phosphodiesterase activity suggest that combined use of phosphodiesterase inhibitors with beta-adrenergic antagonists may prevent these adverse outcomes. Compartmentation of cyclic adenosine 3',5'-monophosphate signaling may prove critical in determining myocardial response to combination therapy.

Cardiac Ca2+ signaling and Ca2+ sensitizers

The role of Ca2+ in cardiac excitation-contraction (E-C) coupling has been established by simultaneous measurements of contractility and Ca2+ transients by means of aequorin in intact myocardium and Ca2+ sensitive fluorescent dyes in single myocytes. The E-C coupling process can be classified into 3 processes: upstream (Ca2+ mobilization), central (Ca2+ binding to troponin C) and downstream mechanism (thin filament regulation and crossbridge cycling). These mechanisms are regulated differentially by various inotropic interventions. Positive force-frequency relationship and effects of beta-adrenoceptor stimulation, phosphodiesterase 3 inhibitors and digitalis are essentially exerted via upstream mechanism. Alpha-adrenoceptor stimulation, endothelin-1, angiotensin II, and clinically available Ca2+ sensitizers, such as levosimendan and pimobendan, act by a combination of the upstream and central/downstream mechanism. The Frank-Starling mechanism and effects of Ca2+ sensitizers such as EMD 57033 and Org 30029 are primarily induced via the central/downstream mechanism. Whereas the upstream and central mechanisms are markedly suppressed in failing myocytes and under acidotic conditions, Ca2+ sensitizers such as EMD 57033 and Org 30029 can induce cardiotonic effects under such conditions. Ca2+ sensitizers have high therapeutic potential for the treatment of contractile dysfunction in congestive heart failure and ischemic heart diseases, because they have energetic advantages and less risk of Ca2+ overload and can maintain effectiveness under pathological conditions.

Comparative effects of levosimendan, OR-1896, OR-1855, dobutamine, and milrinone on vascular resistance, indexes of cardiac function, and O2consumption in dogs

Levosimendan enhances cardiac contractility via Ca2+sensitization and induces vasodilation through the activation of ATP-dependent K+and large-conductance Ca2+-dependent K+channels. However, the hemodynamic effects of levosimendan, as well as its metabolites, OR-1896 and OR-1855, relative to plasma concentrations achieved, are not well defined. Thus levosimendan, OR-1896, OR-1855, or vehicle was infused at 0.01, 0.03, 0.1, and 0.3 μmol·kg−1·30 min−1, targeting therapeutic to supratherapeutic concentrations of total levosimendan (62.6 ng/ml). Results were compared with those of the β1-agonist dobutamine and the phosphodiesterase 3 inhibitor milrinone. Peak concentrations of levosimendan, OR-1896, and OR-1855 were 455 ± 21, 126 ± 6, and 136 ± 6 ng/ml, respectively. Levosimendan and OR-1896 produced dose-dependent reductions in mean arterial pressure (−31 ± 2 and −42 ± 3 mmHg, respectively) and systemic resistance without affecting pulse pressure, effects paralleled by increases in heart rate; OR-1855 produced no effect at any dose tested. Dobutamine, but not milrinone, increased mean arterial pressure and pulse pressure (17 ± 2 and 23 ± 2 mmHg, respectively). Regarding potency to elicit reductions in time to peak pressure and time to systolic pressure recovery: OR-1896 > levosimendan > milrinone > dobutamine. Levosimendan and OR-1896 elicited dose-dependent increases in change in pressure over time (118 ± 10 and 133 ± 13%, respectively), concomitant with reductions in left ventricular end-diastolic pressure and ejection time. However, neither levosimendan nor OR-1896 produced increases in myocardial oxygen consumption at inotropic and vasodilatory concentrations, whereas dobutamine increased myocardial oxygen consumption (79% above baseline). Effects of the levosimendan and OR-1896 were limited to the systemic circulation; neither compound produced changes in pulmonary pressure, whereas dobutamine produced profound increases (74 ± 13%). Thus levosimendan and OR-1896 are hemodynamically active in the anesthetized dog at concentrations observed clinically and elicit cardiovascular effects consistent with activation of both K+channels and Ca2+sensitization, whereas OR-1855 is inactive on endpoints measured in this study.

Inotropic, chronotropic, and arrhythmogenic effects of dopamine on the isolated working heart of rabbit

Some improvements of Kodama's method for perfusing the isolated rabbit heart in its working mode were made. Increases in the right and left atrium pressure, together with an increase in the pulmonary artery pressure, were observed to occur immediately after the start of venous return, and then all of the increased pressures were found to remain at each constant level. In these stable states, the administration of dopamine (DA) into the perfusate was found to produce dose-related increases in contractile activities. In the preparations denervated with reserpine or 6-hydroxydopamine, in which tyramine (Ty) produced no response, the inotropic effectiveness of DA did not differ from that in the normal ones. On the other hand, responses to noradrenaline (NA) were found to increase significantly after the denervation. DA produced a dose-related increase in heart rates in the normal preparation, and this effect was greatly suppressed in the denervated preparations, suggesting that the primary chronotropic effect of DA is an indirect one via the release of NA from the sympathetic nerve terminals. Arrhythmogenic effects of NA, Ty or DA were also observed in these preparations. At all the doses tested, the incidence rates by NA were as high as 50% or more, the type of arrhythmia being recognized as atrial or ventricular extrasystole from the ECG analysis. On the other hand, the rates by DA were relatively low, less than 34%. From a comparison of the incidence rates between the normal and denervated preparations, this effect of DA was considered to be primarily an indirect one.

Tuning cardiac performance in ischemic heart disease and failure by modulating myofilament function

The cardiac myofilaments are composed of highly ordered arrays of proteins that coordinate cardiac contraction and relaxation in response to the rhythmic waves of [Ca(2+)] during the cardiac cycle. Several cardiac disease states are associated with altered myofilament protein interactions that contribute to cardiac dysfunction. During acute myocardial ischemia, the sensitivity of the myofilaments to activating Ca(2+) is drastically reduced, largely due to the effects of intracellular acidosis on the contractile machinery. Myofilament Ca(2+) sensitivity remains compromised in post-ischemic or "stunned" myocardium even after complete restoration of blood flow and intracellular pH, likely because of covalent modifications of or proteolytic injury to contractile proteins. In contrast, myofilament Ca(2+) sensitivity can be increased in chronic heart failure, owing in part to decreased phosphorylation of troponin I, the inhibitory subunit of the troponin regulatory complex. We highlight, in this paper, the central role of the myofilaments in the pathophysiology of each of these distinct disease entities, with a particular focus on the molecular switch protein troponin I. We also discuss the beneficial effects of a genetically engineered cardiac troponin I, with a histidine button substitution at C-terminal residue 164, for a variety of pathophysiologic conditions, including hypoxia, ischemia, ischemia-reperfusion and chronic heart failure.

Could Ca2+ sensitizers rescue patients from chronic congestive heart failure?

Attempts to ameliorate cardiac contractile dysfunction by Ca(2+) mobilizers, such as catecholamines, phosphodiesterase (PDE) inhibitors and digitalis, play an important role in pharmacotherapy for congestive heart failure (CHF), but these agents possess disadvantages in causing Ca(2+) overload resulting in arrhythmogenicity and damage to cardiomyocytes. Ca(2+) sensitizers that act directly on contractile proteins are free from the risk of Ca(2+) overload and they could improve haemodynamic parameters with minimum increase in energy expenditure even under pathological conditions, including acidosis and stunned myocardium. Beneficial effects of levosimendan (that acts by combination of Ca(2+) sensitization and PDE inhibition) on CHF due to hypertensive cardiomyopathy in Dahl/Rapp rats as reported in this issue demonstrate the potential of oral levosimendan in long-term treatment of chronic CHF. Since chronic CHF in clinical settings is much more complex, careful analysis of clinical outcomes will be required to establish the therapeutic relevance of Ca(2+) sensitizers in the treatment of chronic CHF.