Hemodynamic properties of a new-generation positive luso-inotropic agent for the acute treatment of advanced heart failure

Medical therapy of cardiogenic shock: Contemporary use of inotropes and vasopressors

Cardiogenic shock is a primary cardiac disorder that results in both clinical and biochemical evidence of tissue hypoperfusion and can lead to multi-organ failure and death depending on its severity. Inadequate cardiac contractility or cardiac power secondary to acute myocardial infarction remains the most frequent cause of cardiogenic shock, although its contribution has declined over the past two decades, compared with other causes. Despite some advances in cardiogenic shock management, this clinical syndrome is still burdened by an extremely high mortality. Its management is based on immediate stabilization of haemodynamic parameters so that further treatment, including mechanical circulatory support and transfer to specialized tertiary care centres, can be accomplished. With these aims, medical therapy, consisting mainly of inotropic drugs and vasopressors, still has a major role. The purpose of this article is to review current evidence on the use of these medications in patients with cardiogenic shock and discuss specific clinical settings with indications to their use.

Selective SERCA2a activator as a candidate for chronic heart failure therapy

BACKGROUND

The sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA2a) depression substantially contributes to diastolic dysfunction in heart failure (HF), suggesting that SERCA2a stimulation may be a mechanism-based HF therapy. Istaroxime is a drug endowed with both a SERCA2a stimulatory activity and a Na+/K+ pump inhibitory activity for acute HF treatment. Its main metabolite PST3093 shows a more favorable therapeutic profile as compared to the parent drug, but it is still unsuitable for chronic usage. Novel PST3093 derivatives have been recently developed for oral (chronic) HF treatment; compound 8 was selected among them and here characterized.

METHODS

Effects of compound 8 were evaluated in a context of SERCA2a depression, by using streptozotocin-treated rats, a well-known model of diastolic dysfunction. The impact of SERCA2a stimulation by compound 8 was assessed at the cellular level ad in vivo, following i.v. infusion (acute effects) or oral administration (chronic effects).

RESULTS

As expected from SERCA2a stimulation, compound 8 induced SR Ca2+ compartmentalization in STZ myocytes. In-vivo echocardiographic analysis during i.v. infusion and after repeated oral administration of compound 8, detected a significant improvement of diastolic function. Moreover, compound 8 did not affect electrical activity of healthy guinea-pig myocytes, in line with the absence of off-target effects. Finally, compound 8 was well tolerated in mice with no evidence of acute toxicity.

CONCLUSIONS

The pharmacological evaluation of compound 8 indicates that it may be a safe and selective drug for a mechanism-based treatment of chronic HF by restoring SERCA2a activity.

Istaroxime: A Novel Therapeutic Agent for Acute Heart Failure

Acute decompensated heart failure (ADHF) is a multifactorial process that is associated with high morbidity and mortality. Treatment with inotropes can rapidly improve hemodynamic status; however, their use has been associated with increased mortality and incidence of arrhythmias. Istaroxime is a first-in-class intravenous agent currently undergoing clinical trials for acute heart failure. It has the unique mechanism of action of both Na+/K+ ATPase inhibition and sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a stimulation. Notably, its action on sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a improves calcium handling, which is known to be abnormal in heart failure. Clinical trials have shown that istaroxime has beneficial hemodynamic effects; in particular, its ability to increase systolic blood pressure without causing significant increases in heart rate or clinically significant arrhythmias differentiates it from inotropes currently utilized for ADHF treatment, such as milrinone. While initial studies are encouraging, additional trials are needed to assess outcomes and to compare their performance to standard inotropes in patients hospitalized with ADHF. This article will review the relevant preclinical and clinical trials for istaroxime, as well as the relevant pharmacology.

Safety and Efficacy of Istaroxime in Patients With Acute Heart Failure: A Meta-Analysis of Randomized Controlled Trials

The aim of this study was to assess the efficacy and safety of istaroxime in patients with heart failure. Following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines, a search was conducted on the EMBASE and Medline databases to identify articles related to the safety and efficacy of istaroxime in patients with heart failure. The search covered the period from inception to May 31st, 2023, without any restrictions on the year of publication. The search strategy utilized relevant terms such as "istaroxime," "heart failure", "efficacy," and other related terms, along with their corresponding Medical Subject Headings (MeSH) terms. The outcomes assessed in this meta-analysis included the change in left ventricular ejection fraction (LVEF), E to A ratio (a marker of left ventricle function), cardiac index in L/min/m2, systolic blood pressure (SBP) in mmHg, left ventricular end-systolic volume (LVESV) in ml, and left ventricular end-diastolic volume (LVDSV) in ml. For safety analysis, gastrointestinal events and cardiovascular events were assessed. A total of three randomized controlled trials (RCTs) were included in this meta-analysis encompassing 211 patients with heart failure. Pooled analysis showed that istaroxime was effective in increasing LVEF (MD: 1.26, 95% CI: 0.91 to 1.62, p-value: 0.001), reducing E to A ratio (MD: -0.39, 95% CI: -0.60 to -0.19, p-value: 0.001), increasing cardiac index (MD: 0.22, 95% CI: 0.18 to 0.25, p-value: 0.001), reducing LVESV (MD: -11.84, 95% CI: -13.91 to -9.78, p-value: 0.001), reducing LVEDV (MD: -12.25, 95% CI: -14.63 to -9.87, p-value: 0.001) and increasing SBP (MD: 8.41, 95% CI: 5.23 to 11.60, p-value: 0.001) compared to the placebo group. However, risk of gastrointestinal events was significantly higher in patients receiving istaroxime compared to the placebo group (RR: 2.64, 95% CI: 1.53 to 4.57, p-value: 0.0005). These findings support the enhancement of heart function with istaroxime administration, aligning with previous clinical and experimental evidence.

Emerging Therapy for Diabetic Cardiomyopathy: From Molecular Mechanism to Clinical Practice

Diabetic cardiomyopathy is characterized by abnormal myocardial structure or performance in the absence of coronary artery disease or significant valvular heart disease in patients with diabetes mellitus. The spectrum of diabetic cardiomyopathy ranges from subtle myocardial changes to myocardial fibrosis and diastolic function and finally to symptomatic heart failure. Except for sodium–glucose transport protein 2 inhibitors and possibly bariatric and metabolic surgery, there is currently no specific treatment for this distinct disease entity in patients with diabetes. The molecular mechanism of diabetic cardiomyopathy includes impaired nutrient-sensing signaling, dysregulated autophagy, impaired mitochondrial energetics, altered fuel utilization, oxidative stress and lipid peroxidation, advanced glycation end-products, inflammation, impaired calcium homeostasis, abnormal endothelial function and nitric oxide production, aberrant epidermal growth factor receptor signaling, the activation of the renin–angiotensin–aldosterone system and sympathetic hyperactivity, and extracellular matrix accumulation and fibrosis. Here, we summarize several important emerging treatments for diabetic cardiomyopathy targeting specific molecular mechanisms, with evidence from preclinical studies and clinical trials.

The interplay of inflammation, exosomes and Ca2+ dynamics in diabetic cardiomyopathy

Diabetes mellitus is one of the prime risk factors for cardiovascular complications and is linked with high morbidity and mortality. Diabetic cardiomyopathy (DCM) often manifests as reduced cardiac contractility, myocardial fibrosis, diastolic dysfunction, and chronic heart failure. Inflammation, changes in calcium (Ca²⁺) handling and cardiomyocyte loss are often implicated in the development and progression of DCM. Although the existence of DCM was established nearly four decades ago, the exact mechanisms underlying this disease pathophysiology is constantly evolving. Furthermore, the complex pathophysiology of DCM is linked with exosomes, which has recently shown to facilitate intercellular (cell-to-cell) communication through biomolecules such as micro RNA (miRNA), proteins, enzymes, cell surface receptors, growth factors, cytokines, and lipids. Inflammatory response and Ca²⁺ signaling are interrelated and DCM  has been known to adversely affect many of these signaling molecules either qualitatively and/or quantitatively. In this literature review, we have demonstrated that Ca²⁺ regulators are tightly controlled at different molecular and cellular levels during various biological processes in the heart. Inflammatory mediators, miRNA and exosomes are shown to interact with these regulators, however how these mediators are linked to Ca²⁺ handling during DCM pathogenesis remains elusive. Thus, further investigations are needed to understand the mechanisms to restore cardiac Ca²⁺ homeostasis and function, and to serve as potential therapeutic targets in the treatment of DCM.

Istaroxime Metabolite PST3093 Selectively Stimulates SERCA2a and Reverses Disease-Induced Changes in Cardiac Function

Heart failure (HF) therapeutic toolkit would strongly benefit from the availability of ino-lusitropic agents with a favorable pharmacodynamics and safety profile. Istaroxime is a promising agent, which combines Na+/K+ pump inhibition with sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) stimulation; however, it has a very short half-life and extensive metabolism to a molecule named PST3093. The present work aims to investigate whether PST3093 still retains the pharmacodynamic and pharmacokinetic properties of its parent compound. We studied PST3093 for its effects on SERCA2a and Na+/K+ ATPase activities, Ca2+ dynamics in isolated myocytes, and hemodynamic effects in an in vivo rat model of diabetic [streptozotocin (STZ)-induced] cardiomyopathy. Istaroxime infusion in HF patients led to accumulation of PST3093 in the plasma; clearance was substantially slower for PST3093 than for istaroxime. In cardiac rat preparations, PST3093 did not inhibit the Na+/K+ ATPase activity but retained SERCA2a stimulatory activity. In in vivo echocardiographic assessment, PST3093 improved overall cardiac performance and reversed most STZ-induced abnormalities. PST3093 intravenous toxicity was considerably lower than that of istaroxime, and it failed to significantly interact with 50 off-targets. Overall, PST3093 is a "selective" SERCA2a activator, the prototype of a novel pharmacodynamic category with a potential in the ino-lusitropic approach to HF with prevailing diastolic dysfunction. Its pharmacodynamics are peculiar, and its pharmacokinetics are suitable to prolong the cardiac beneficial effect of istaroxime infusion. SIGNIFICANCE STATEMENT: Heart failure (HF) treatment would benefit from the availability of ino-lusitropic agents with favourable profiles. PST3093 is the main metabolite of istaroxime, a promising agent combining Na+/K+ pump inhibition and sarcoplasmic reticulum Ca2+ ATPase2a (SERCA2a) stimulation. PST3093 shows a longer half-life in human circulation compared to istaroxime, selectively activates SERCA2a, and improves cardiac performance in a model of diabetic cardiomyopathy. Overall, PST3093 as a selective SERCA2a activator can be considered the prototype of a novel pharmacodynamic category for HF treatment.

Efficacy of the New Inotropic Agent Istaroxime in Acute Heart Failure

Current therapeutic strategies for acute heart failure (AHF) are based on traditional inotropic agents that are often associated with untoward effects; therefore, finding new effective approaches with a safer profile is dramatically needed. Istaroxime is a novel compound, chemically unrelated to cardiac glycosides, that is currently being studied for the treatment of AHF. Its effects are essentially related to its inotropic and lusitropic positive properties exerted through a dual mechanism of action: activation of the sarcoplasmic reticulum Ca2+ ATPase isoform 2a (SERCA2a) and inhibition of the Na+/K+-ATPase (NKA) activity. The advantages of istaroxime over the available inotropic agents include its lower arrhythmogenic action combined with its capability of increasing systolic blood pressure without augmenting heart rate. However, it has a limited half-life (1 hour) and is associated with adverse effects including pain at the injection site and gastrointestinal issues. Herein, we describe the main mechanism of action of istaroxime and we present a systematic overview of both clinical and preclinical trials testing this drug, underlining the latest insights regarding its adoption in clinical practice for AHF.

Advanced heart failure: guideline-directed medical therapy, diuretics, inotropes, and palliative care

Heart failure (HF) is a major cause of mortality, hospitalizations, and reduced quality of life and a major burden for the healthcare system. The number of patients that progress to an advanced stage of HF is growing. Only a limited proportion of these patients can undergo heart transplantation or mechanical circulatory support. The purpose of this review is to summarize medical management of patients with advanced HF. First, evidence-based oral treatment must be implemented although it is often not tolerated. New therapeutic options may soon become possible for these patients. The second goal is to lessen the symptomatic burden through both decongestion and haemodynamic improvement. Some new treatments acting on cardiac function may fulfil both these needs. Inotropic agents acting through an increase in intracellular calcium have often increased risk of death. However, in the recent Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure (GALACTIC-HF) trial, omecamtiv mecarbil was safe and effective in the reduction of the primary outcome of cardiovascular death or HF event compared with placebo (hazard ratio, 0.92; 95% confidence interval, 0.86-0.99; P = 0.03) and its effects were larger in those patients with more severe left ventricular dysfunction. Patients with severe HF who received omecamtiv mecarbil experienced a significant treatment benefit, whereas patients without severe HF did not (P = 0.005 for interaction). Lastly, clinicians should take care of the end of life with an appropriate multidisciplinary approach. Medical treatment of advanced HF therefore remains a major challenge and a wide open area for further research.

Calcium dysregulation in heart diseases: Targeting calcium channels to achieve a correct calcium homeostasis

Intracellular calcium signaling is a universal language source shared by the most part of biological entities inside cells that, all together, give rise to physiological and functional anatomical units, the organ. Although preferentially recognized as signaling between cell life and death processes, in the heart it assumes additional relevance considered the importance of calcium cycling coupled to ATP consumption in excitation-contraction coupling. The concerted action of a plethora of exchangers, channels and pumps inward and outward calcium fluxes where needed, to convert energy and electric impulses in muscle contraction. All this without realizing it, thousands of times, every day. An improper function of those proteins (i.e., variation in expression, mutations onset, dysregulated channeling, differential protein-protein interactions) being part of this signaling network triggers a short circuit with severe acute and chronic pathological consequences reported as arrhythmias, cardiac remodeling, heart failure, reperfusion injury and cardiomyopathies. By acting with chemical, peptide-based and pharmacological modulators of these players, a correction of calcium homeostasis can be achieved accompanied by an amelioration of clinical symptoms. This review will focus on all those defects in calcium homeostasis which occur in the most common cardiac diseases, including myocardial infarction, arrhythmia, hypertrophy, heart failure and cardiomyopathies. This part will be introduced by the state of the art on the proteins involved in calcium homeostasis in cardiomyocytes and followed by the therapeutic treatments that to date, are able to target them and to revert the pathological phenotype.

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

Simple Summary

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

Abstract

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

SERCA2a stimulation by istaroxime improves intracellular Ca2+ handling and diastolic dysfunction in a model of diabetic cardiomyopathy

Aims 

Diabetic cardiomyopathy is a multifactorial disease characterized by an early onset of diastolic dysfunction (DD) that precedes the development of systolic impairment. Mechanisms that can restore cardiac relaxation improving intracellular Ca²⁺ dynamics represent a promising therapeutic approach for cardiovascular diseases associated to DD. Istaroxime has the dual properties to accelerate Ca²⁺ uptake into sarcoplasmic reticulum (SR) through the SR Ca²⁺ pump (SERCA2a) stimulation and to inhibit Na⁺/K⁺ ATPase (NKA). This project aims to characterize istaroxime effects at a concentration (100 nmol/L) marginally affecting NKA, in order to highlight its effects dependent on the stimulation of SERCA2a in an animal model of mild diabetes.

Methods and results 

Streptozotocin (STZ) treated diabetic rats were studied at 9  weeks after STZ injection in comparison to controls (CTR). Istaroxime effects were evaluated in vivo and in left ventricular (LV) preparations. STZ animals showed (i) marked DD not associated to cardiac fibrosis, (ii) LV mass reduction associated to reduced LV cell dimension and T-tubules loss, (iii) reduced LV SERCA2 protein level and activity and (iv) slower SR Ca²⁺ uptake rate, (v) LV action potential (AP) prolongation and increased short-term variability (STV) of AP duration, (vi) increased diastolic Ca²⁺, and (vii) unaltered SR Ca²⁺ content and stability in intact cells. Acute istaroxime infusion (0.11 mg/kg/min for 15 min) reduced DD in STZ rats. Accordingly, in STZ myocytes istaroxime (100 nmol/L) stimulated SERCA2a activity and blunted STZ-induced abnormalities in LV Ca²⁺ dynamics. In CTR myocytes, istaroxime increased diastolic Ca²⁺ level due to NKA blockade albeit minimal, while its effects on SERCA2a were almost absent.

Conclusions 

SERCA2a stimulation by istaroxime improved STZ-induced DD and intracellular Ca²⁺ handling anomalies. Thus, SERCA2a stimulation can be considered a promising therapeutic approach for DD treatment.

Intravenous Infusion of the β3-Adrenergic Receptor Antagonist APD418 Improves Left Ventricular Systolic Function in Dogs With Systolic Heart Failure

BACKGROUND

Unlike β₁- and β₂-adrenergic receptors (ARs), β₃-AR stimulation inhibits cardiac contractility and relaxation. In the failing left ventricular (LV) myocardium, β₃-ARs are upregulated, and can be maladaptive in the setting of decompensation by contributing to LV dysfunction. This study examined the effects of intravenous infusions of the β₃-AR antagonist APD418 on cardiovascular function and safety in dogs with systolic heart failure (HF).

METHODS AND RESULTS

Three separate studies were performed in 21 dogs with coronary microembolization-induced HF (LV ejection fraction [LVEF] of approximately 35%). Studies 1 and 2 (n = 7 dogs each) were APD418 dose escalation studies (dosing range, 0.35-15.00 mg/kg/h) designed to identify an effective dose of APD418 to be used in study 3. Study 3, the sustained efficacy study, (n = 7 dogs) was a 6-hour constant intravenous infusion of APD418 at a dose of 4.224 mg/kg (0.70 mg/kg/h) measuring key hemodynamic endpoints (e.g., EF, cardiac output, the time velocity integral of the mitral inflow velocity waveform representing early filling to time-velocity integral representing left atrial contraction [Ei/Ai]). Studies 1 and 2 showed a dose-dependent increase of LVEF and Ei/Ai, the latter being an index of LV diastolic function. In study 3, infusion of APD418 over 6 hours increased LVEF from 31 ± 1% to 38 ± 1% (P < .05) and increased Ei/Ai from 3.4 ± 0.4 to 4.9 ± 0.5 (P < .05). Vehicle had no effect on the LVEF or Ei/Ai. In study 3, APD418 had no significant effects on the HR or the systemic blood pressure.

CONCLUSIONS

Intravenous infusions of APD418 in dogs with systolic HF elicit significant positive inotropic and lusitropic effects. These findings support the development of APD418 for the in-hospital treatment of patients with an acute exacerbation of chronic HF.

Effects of Angiotensin-Neprilysin Inhibition in Canines with Experimentally Induced Cardiorenal Syndrome

BACKGROUND

Sacubitril/valsartan (Sac/Val), a combined angiotensin-II receptor blocker (Val) and neprilysin inhibitor (Sac) in a 1:1 molar ratio, was shown to decrease the risk of cardiovascular death or heart failure (HF) hospitalization in patients with HF and reduced left ventricular (LV) ejection fraction. This study examined the effects of Sac/Val on LV structure, function, and bioenergetics, and on biomarkers of kidney injury and kidney function in dogs with experimental cardiorenal syndrome.

METHODS AND RESULTS

Fourteen dogs with cardiorenal syndrome (coronary microembolization-induced HF and renal dysfunction) were randomized to 3 months Sac/Val therapy (100 mg once daily, n = 7) or no therapy (control, n = 7). LV ejection fraction and troponin-I, as well as biomarkers of kidney injury/function including serum creatinine and urinary kidney injury molecule-1 were measured before and at end of therapy and the change (treatment effect change) calculated. Mitochondrial function measures, including the maximum rate of adenosine triphosphate synthesis, were measured in isolated cardiomyocytes at end of therapy. In Sac/Val dogs, the change in ejection fraction increased compared with controls, 6.9 ± 1.4 vs 0.7 ± 0.6%, P < .002, whereas change in troponin I decreased, -0.16 ± 0.03 vs -0.03 ± 0.02 ng/mL, P < .001. Urinary change in kidney injury molecule 1 decreased in Sac/Val-treated dogs compared with controls, -17.2 ± 7.9 vs 7.7 ± 3.0 mg/mL, P < .007, whereas the change in serum creatinine was not significantly different. Treatment with Sac/Val increased adenosine triphosphate synthesis compared with controls, 3240 ± 121 vs 986 ± 84 RLU/µg protein, P < .05.

CONCLUSIONS

In dogs with cardiorenal syndrome, Sac/Val improves LV systolic function, improves mitochondrial function and decreases biomarkers of heart and kidney injury. The results offer mechanistic insights into the benefits of Sac/Val in HF with compromised renal function.

Targeting Ca2 + Handling Proteins for the Treatment of Heart Failure and Arrhythmias

Diseases of the heart, such as heart failure and cardiac arrhythmias, are a growing socio-economic burden. Calcium (Ca²⁺) dysregulation is key hallmark of the failing myocardium and has long been touted as a potential therapeutic target in the treatment of a variety of cardiovascular diseases (CVD). In the heart, Ca²⁺ is essential for maintaining normal cardiac function through the generation of the cardiac action potential and its involvement in excitation contraction coupling. As such, the proteins which regulate Ca²⁺ cycling and signaling play a vital role in maintaining Ca²⁺ homeostasis. Changes to the expression levels and function of Ca²⁺-channels, pumps and associated intracellular handling proteins contribute to altered Ca²⁺ homeostasis in CVD. The remodeling of Ca²⁺-handling proteins therefore results in impaired Ca²⁺ cycling, Ca²⁺ leak from the sarcoplasmic reticulum and reduced Ca²⁺ clearance, all of which contributes to increased intracellular Ca²⁺. Currently, approved treatments for targeting Ca²⁺ handling dysfunction in CVD are focused on Ca²⁺ channel blockers. However, whilst Ca²⁺ channel blockers have been successful in the treatment of some arrhythmic disorders, they are not universally prescribed to heart failure patients owing to their ability to depress cardiac function. Despite the progress in CVD treatments, there remains a clear need for novel therapeutic approaches which are able to reverse pathophysiology associated with heart failure and arrhythmias. Given that heart failure and cardiac arrhythmias are closely associated with altered Ca²⁺ homeostasis, this review will address the molecular changes to proteins associated with both Ca²⁺-handling and -signaling; their potential as novel therapeutic targets will be discussed in the context of pre-clinical and, where available, clinical data.

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.

Effects of Intravenous Infusion of Vepoloxamer on Left Ventricular Function in Dogs with Advanced Heart Failure

PURPOSE

Vepoloxamer (VEPO), a rheologic agent, repairs damaged cell membranes, thus inhibiting unregulated Ca²⁺ entry into cardiomyocytes. This study examined the effects of i.v. infusion of VEPO on LV function in dogs with coronary microembolization-induced heart failure (HF) (LV ejection fraction, EF ~ 30%).

METHODS

Thirty-five HF dogs were studied. Study 1: 21 of 35 dogs were randomized to 2-h infusion of VEPO at dose of 450 mg/kg (n = 7) or VEPO at 225 mg/kg (n = 7) or normal saline (control, n = 7). Hemodynamics were measured at 2 h, 24 h, 1 week, and 2 weeks after infusion. Study 2: 14 HF dogs were randomized to 2-h infusions of VEPO (450 mg/kg, n = 7) or normal saline (control, n = 7). Each dog received 2 infusions of VEPO or saline (pulsed therapy) 3 weeks apart and hemodynamics measured at 24 h, and 1, 2, and 3 weeks after each infusion. In both studies, the change between pre-infusion measures and measures at other time points (treatment effect, Δ) was calculated.

RESULTS

Study 1: compared to pre-infusion, high dose VEPO increased LVEF by 11 ± 2% at 2 h, 8 ± 2% at 24 h (p < 0.05), 8 ± 2% at 1 week (p < 0.05), and 4 ± 2% at 2 weeks. LV EF also increased with low-dose VEPO but not with saline. Study 2: VEPO but not saline significantly increased LVEF by 6.0 ± 0.7% at 2 h (p < 0.05); 7.0 ± 0.7%% at 1 week (p < 0.05); 1.0 ± 0.6% at 3 weeks; 6.0 ± 1.3% at 4 weeks (p < 0.05); and 5.9 ± 1.3% at 6 weeks (p < 0.05).

CONCLUSIONS

Intravenous VEPO improves LV function for at least 1 week after infusion. The benefits can be extended with pulsed VEPO therapy. The results support development of VEPO for treating patients with acute on chronic HF.

Preclinical Studies of Stem Cell Therapy for Heart Disease

As part of the TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes) series to enhance regenerative medicine, here, we discuss the role of preclinical studies designed to advance stem cell therapies for cardiovascular disease. The quality of this research has improved over the past 10 to 15 years and overall indicates that cell therapy promotes cardiac repair. However, many issues remain, including inability to provide complete cardiac recovery. Recent studies question the need for intact cells suggesting that harnessing what the cells release is the solution. Our contribution describes important breakthroughs and current directions in a cell-based approach to alleviating cardiovascular disease.

Istaroxime, a positive inotropic agent devoid of proarrhythmic properties in sensitive chronic atrioventricular block dogs

Current inotropic agents in heart failure therapy associate with low benefit and significant adverse effects, including ventricular arrhythmias. Istaroxime, a novel Na⁺/K⁺-transporting ATPase inhibitor, also stimulates SERCA2a activity, which would confer improved inotropic and lusitropic properties with less proarrhythmic effects. We investigated hemodynamic, electrophysiological and potential proarrhythmic and antiarrhythmic effects of istaroxime in control and chronic atrioventricular block (CAVB) dogs sensitive to drug-induced Torsades de Pointes arrhythmias (TdP). In isolated normal canine ventricular cardiomyocytes, istaroxime (0.3-10 μM) evoked no afterdepolarizations and significantly shortened action potential duration (APD) at 3 and 10 μM. Istaroxime at 3 μg/kg/min significantly increased left ventricular (LV) contractility (dP/dt+) and relaxation (dP/dt-) respectively by 81 and 94% in anesthetized control dogs (n = 6) and by 61 and 49% in anesthetized CAVB dogs (n = 7) sensitive to dofetilide-induced TdP. While istaroxime induced no ventricular arrhythmias in control conditions, only single ectopic beats occurred in 2/7 CAVB dogs, which were preceded by increase of short-term variability of repolarization (STV) and T wave alternans in LV unipolar electrograms. Istaroxime pre-treatment (3 μg/kg/min for 60 min) did not alleviate dofetilide-induced increase in repolarization and STV, and mildly reduced incidence of TdP from 6/6 to 4/6 CAVB dogs. In six CAVB dogs with dofetilide-induced TdP, administration of istaroxime (90 μg/kg/5 min) suppressed arrhythmic episodes in two animals. Taken together, inotropic and lusitropic properties of istaroxime in CAVB dogs were devoid of significant proarrhythmic effects in sensitive CAVB dogs, and istaroxime provides a moderate antiarrhythmic efficacy in prevention and suppression of dofetilide-induced TdP.

Myocardial fibrosis: biomedical research from bench to bedside

Myocardial fibrosis refers to a variety of quantitative and qualitative changes in the interstitial myocardial collagen network that occur in response to cardiac ischaemic insults, systemic diseases, drugs, or any other harmful stimulus affecting the circulatory system or the heart itself. Myocardial fibrosis alters the architecture of the myocardium, facilitating the development of cardiac dysfunction, also inducing arrhythmias, influencing the clinical course and outcome of heart failure patients. Focusing on myocardial fibrosis may potentially improve patient care through the targeted diagnosis and treatment of emerging fibrotic pathways. The European Commission funded the FIBROTARGETS consortium as a multinational academic and industrial consortium with the primary aim of performing a systematic and collaborative search of targets of myocardial fibrosis, and then translating these mechanisms into individualized diagnostic tools and specific therapeutic pharmacological options for heart failure. This review focuses on those methodological and technological aspects considered and developed by the consortium to facilitate the transfer of the new mechanistic knowledge on myocardial fibrosis into potential biomedical applications.

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.

Cardiovascular Pharmacology: An Update and Anesthesia Considerations

Cardiovascular disease remains a leading cause of morbidity and mortality worldwide. The development of therapeutic agents for the treatment of cardiovascular diseases has always been a priority because of the huge potential market for these drugs. These medications should be part of the anesthesiologist's armamentarium because the typical surgical patient is older and has more comorbidities than in the past. This article reviews commonly used cardiovascular medications that are important in managing patients with unstable hemodynamics.

Targeting cardiomyocyte Ca2+ homeostasis in heart failure

Improved treatments for heart failure patients will require the development of novel therapeutic strategies that target basal disease mechanisms. Disrupted cardiomyocyte Ca²⁺ homeostasis is recognized as a major contributor to the heart failure phenotype, as it plays a key role in systolic and diastolic dysfunction, arrhythmogenesis, and hypertrophy and apoptosis signaling. In this review, we outline existing knowledge of the involvement of Ca²⁺ homeostasis in these deficits, and identify four promising targets for therapeutic intervention: the sarcoplasmic reticulum Ca²⁺ ATPase, the Na⁺-Ca²⁺ exchanger, the ryanodine receptor, and t-tubule structure. We discuss experimental data indicating the applicability of these targets that has led to recent and ongoing clinical trials, and suggest future therapeutic approaches.

SERCA2a stimulation by istaroxime: a novel mechanism of action with translational implications

Sarcoplasmic reticular (SR) Ca(2+) -ATPase (SERCA2a) is central to cardiac electrophysiological and mechanical function. It ensures full diastolic relaxation minimizing delayed after-potentials that would otherwise compromise membrane electrophysiological stability, and optimizes SR Ca(2+) refilling and systolic contraction. Previous studies demonstrated that the small molecule agent istaroxime stimulates SERCA2a-ATPase activity, restoring its function in failing hearts, and enhancing indices of mechanical, and SR Ca(2+) release and re-uptake, activity. Ferrandi et al (2013) now elegantly demonstrate its ability to dissociate the phospholamdan (PB) bound to cardiac SERCA2a, thereby removing the inhibitory effect of PB on SERCA2a. This effect was independent of the cAMP/PKA system and modified a specific SERCA2a reaction step. They used SERCA-enriched SR preparations from a rigorously validated and realistic physiological, canine model of cardiac failure with established Na(+) -K(+) -ATPase sensitivity to cardiac glycosides and SR Ca(2+) handling features. These findings potentially translate into a novel management of the major and increasingly important public health challenge of chronic cardiac failure.

LINKED ARTICLE

This article is a commentary on Ferrandi et al., pp. 1849-1861 of volume 169 issue 8. To view this paper visit http://dx.doi.org/10.1111/bph.12278.

Inotropes

Inotropes have been fundamental to resuscitation of acute cardiogenic shock for decades. Heart failure and cardiogenic shock, in severe cases, are syndromes characterized in many patients by a reduction in myocardial contractile force. While inotropes successfully increase cardiac output, their use has been plagued by excessive mortality due to increased tachycardia and myocardial oxygen consumption leading to arrhythmia and myocardial ischemia. There is a pressing need for new inotropic agents that avoid these harmful effects. This review describes the mechanism of action and the clinical utility of some of the older inotropic agents, which are still commonly used, and provides an update for physicians on the development of newer inotropic drugs. The field is rapidly changing, and it is likely that new agents will be designed that improve systolic performance without necessarily increasing the myocardial oxygen consumption.

Istaroxime stimulates SERCA2a and accelerates calcium cycling in heart failure by relieving phospholamban inhibition

BACKGROUND AND PURPOSE

Calcium handling is known to be deranged in heart failure. Interventions aimed at improving cell Ca(2) (+) cycling may represent a promising approach to heart failure therapy. Istaroxime is a new luso-inotropic compound that stimulates cardiac contractility and relaxation in healthy and failing animal models and in patients with acute heart failure (AHF) syndrome. Istaroxime is a Na-K ATPase inhibitor with the unique property of increasing sarcoplasmic reticulum (SR) SERCA2a activity as shown in heart microsomes from humans and guinea pigs. The present study addressed the molecular mechanism by which istaroxime increases SERCA2a activity.

EXPERIMENTAL APPROACH

To study the effect of istaroxime on SERCA2a-phospholamban (PLB) complex, we applied different methodologies in native dog healthy and failing heart preparations and heterologous canine SERCA2a/PLB co-expressed in Spodoptera frugiperda (Sf21) insect cells.

KEY RESULTS

We showed that istaroxime enhances SERCA2a activity, Ca(2) (+) uptake and the Ca(2) (+) -dependent charge movements into dog healthy and failing cardiac SR vesicles. Although not directly demonstrated, the most probable explanation of these activities is the displacement of PLB from SERCA2a.E2 conformation, independently from cAMP/PKA. We propose that this displacement may favour the SERCA2a conformational transition from E2 to E1, thus resulting in the acceleration of Ca(2) (+) cycling.

CONCLUSIONS AND IMPLICATIONS

Istaroxime represents the first example of a small molecule that exerts a luso-inotropic effect in the failing human heart through the stimulation of SERCA2a ATPase activity and the enhancement of Ca(2) (+) uptake into the SR by relieving the PLB inhibitory effect on SERCA2a in a cAMP/PKA independent way.

Current management and future directions for the treatment of patients hospitalized for heart failure with low blood pressure

Although patients hospitalized with heart failure have relatively low in-hospital mortality, the post-discharge rehospitalization and mortality rates remain high despite advances in treatment. Most patients admitted for heart failure have normal or high blood pressure, but 15-25 % have low systolic blood pressure with or without signs and/or symptoms of hypoperfusion. All pharmacological agents known to improve the prognosis of patients with heart failure also reduce blood pressure, and this limits their use in patients with heart failure and low blood pressure (HF-LBP). However, patients with HF-LBP have much higher in-hospital and post-discharge mortality. In these patients, a conceptually important therapeutic target is to improve cardiac output in order to alleviate signs of hypoperfusion. Accordingly, the majority of these patients will require an inotrope as cardiac dysfunction is the cause of their low cardiac output. However, the short-term use of currently available inotropes has been associated with further decreases in blood pressure and increases in heart rate, myocardial oxygen consumption and arrhythmias. Agents that improve cardiac contractility without this undesirable effects should be developed. To the best of our knowledge, the epidemiology, pathophysiology and therapy of patients with HF-LBP have not been addressed thoroughly. In June 2010, a workshop that included scientists and clinicians was held in Rome, Italy. The objectives of this meeting were to (1) develop a working definition for HF-LBP, (2) describe its clinical characteristics and pathophysiology, (3) review current therapies and their limitations, (4) discuss novel agents in development and (5) create a framework for the design and conduct of future clinical trials.

Chronic therapy with a partial adenosine A1-receptor agonist improves left ventricular function and remodeling in dogs with advanced heart failure

BACKGROUND

Adenosine elicits cardioprotection through A1-receptor activation. Therapy with adenosine A1-receptor agonists, however, is limited by undesirable actions of full agonism, such as bradycardia. This study examined the effects of capadenoson (CAP), a partial adenosine A1-receptor agonist, on left ventricular (LV) function and remodeling in dogs with heart failure.

METHODS AND RESULTS

Twelve dogs with microembolization-induced heart failure were randomized to 12 weeks oral therapy with CAP (7.5 mg BID; n=6) or to no therapy (control; n=6). LV end-diastolic and end-systolic volumes, ejection fraction, plasma norepinephrine, and n-terminal pro-brain natriuretic peptide were measured before (pre) and 1 and 12 weeks after therapy (post). LV tissue obtained at post was used to assess volume fraction of interstitial fibrosis, sarcoplasmic reticulum calcium ATPase-2a activity, expression of mitochondria uncoupling proteins (UCP) and glucose transporters (GLUT). In controls, end-diastolic and end-systolic volumes increased and ejection fraction decreased significantly from pre to post (ejection fraction, 30±2 versus 27±1%; P<0.05). In CAP-treated dogs, end-diastolic volume was unchanged; ejection fraction increased significantly after 1 week (36±2 versus 27±2%; P<0.05) with a further increase at post (39±2%; P<0.05), whereas end-systolic volume decreased. CAP significantly decreased volume fraction of interstitial fibrosis, normalized sarcoplasmic reticulum calcium ATPase-2a activity and expression of UCP-2 and UCP-3, and GLUT-1 and GLUT-2 and significantly decreased plasma norepinephrine and n-terminal pro-brain natriuretic peptide.

CONCLUSIONS

In heart failure dogs, CAP improves LV function and prevents progressive remodeling. Improvement of LV systolic function occurs early after initiating therapy. The results support development of partial adenosine A1-receptor agonists for the treatment of chronic heart failure.

Istaroxime: A rising star in acute heart failure

Heart failure in India is a growing epidemic. Around 30 to 40% of patients die from heart failure within one year of receiving the diagnosis. Currently available inotropes have not only failed to show consistent results but are also associated with adverse outcomes. Istaroxime is a novel intravenous agent with luso-inotropic properties that acts by inhibition of Na⁺/K⁺ adenosine triphosphatase and stimulation of sarco/ endoplasmic reticulum calcium ATPase isoform 2. In clinical studies, it significantly decreased left ventricular end diastolic pressure, pulmonary capillary wedge pressure, heart rate and increased systolic blood pressure and cardiac index with no change in neurohormones, renal function or troponin I. Istaroxime is a promising alternative for patients presenting with acute heart failure syndrome for whom the therapeutic options are currently limited.

Chronic istaroxime improves cardiac function and heart rate variability in cardiomyopathic hamsters

PURPOSE

Istaroxime is a new luso-inotropic compound. It exerts inotropic action by reducing Na+/K+-ATPase activity, and simultaneously it stimulates sarcoplasmic reticulum Ca(2+)-ATPase function, thus also inducing lusitropic action. The aim of present study is to assess the effect of chronic istaroxime treatment on cardiac function and heart rate variability in Bio TO.2 Syrian hamster model of progressive heart failure.

METHODS

Bio TO.2 hamsters were daily treated, from 12 to 28 weeks of age, with 30 mg/kg/day oral istaroxime. Age-matched Bio TO.2 and Bio F1B hamsters were treated with vehicle and used as diseased and healthy controls. At the end of treatment, hearts function and autonomic cardiac control were evaluated.

RESULTS

Hearts from vehicle-treated Bio TO.2 when compared with hearts from Bio F1B showed higher heart/body weight ratio, and lower left ventricular systolic pressure (LVSP), positive and negative derivative of LV pressure (dP/dT), coronary flow rate (CFR). Hearts from istaroxime-treated when compared with those of vehicle-treated hamsters, showed the reduction of heart/body weight ratio, and the increase of LVSP, of both positive and negative dP/dT, and of CFR. Autonomic cardiac control, evaluated by HRV analysis, indicated in vehicle-treated Bio TO.2 hamsters, when compared to healthy, a shift towards increased sympathetic and decreased parasympathetic activities. Istaroxime-treatment preserved parasympathetic activity.

CONCLUSIONS

Chronic istaroxime improves cardiac function and heart rate variability in Bio TO.2 Syrian hamster model of progressive heart failure.

Evolving approaches to the management of heart failure with preserved ejection fraction in patients with coronary artery disease

OPINION STATEMENT

Coronary artery disease (CAD) is a major cause of heart failure with preserved ejection fraction (HFpEF). In studies of HFpEF, the reported prevalence of CAD varies widely, which may be the result of inconsistent definitions of CAD, geographic and ethnic differences in CAD burden, varying definitions of HFpEF (including different cutoffs for "preserved ejection fraction"), and differences in study design. Despite these limitations, pooled analysis of prospective HFpEF studies demonstrates that CAD is common in HFpEF, with an estimated prevalence of approximately 50%. Based on available data, patients with signs and symptoms of heart failure who have preserved left ventricular ejection fraction and evidence of CAD (HFpEF-CAD) most likely comprise a distinct etiologic and pathophysiologic subset of HFpEF. Therefore, future clinical trials in HFpEF should a priori stratify by CAD or specifically target patients with CAD, strategies that may improve the disappointing track record of therapies tested in HFpEF. The combination of systematic evaluation and management of CAD in HFpEF, along with promising future therapies for HFpEF-CAD, may lead to improved outcomes for this challenging clinical syndrome.

Myocardial transfection with naked DNA plasmid encoding hepatocyte growth factor prevents the progression of heart failure in dogs

This study examined the effects of localized intramyocardial injections of hepatocyte growth factor (HGF) naked DNA plasmid on the progression of left ventricular (LV) dysfunction and remodeling in dogs with moderate heart failure (HF). Twenty-one dogs with intracoronary microembolization-induced HF [LV ejection fraction (EF) = 35-40%] were randomized into three treatment groups, namely, high-dose HGF plasmid (4.0 mg, n = 7), low-dose HGF plasmid (0.4 mg, n = 7), and sham-operated controls treated with normal saline (n = 7). A total of 10-15 injections of HGF plasmid or saline were made directly into the anterior wall of LV. LV EF and end-systolic volume (ESV) were measured before randomization (pretreatment) and at the end of 3 mo of follow-up (posttreatment). Treatment effect (Δ) was calculated as the change from pre- to posttreatment. Protein expression of sarcoplasmic reticulum (SR) Ca(2+)-cycling proteins was determined in LV tissue obtained from the sites of HGF injection and remote areas. Low-dose HGF attenuated the decline in EF (ΔEF: -3 ± 1 vs. -8 ± 1%, P < 0.05) and the increase in ESV (ΔESV: 6 ± 2 vs. 10 ± 1 ml, P < 0.05) seen in control sham-operated dogs, whereas high-dose HGF significantly increased EF (ΔEF: 4 ± 1 vs. -8 ± 1%, P < 0.05) and prevented the increase in ΔESV (ESV: -1 ± 1 vs. 10 ± 1 ml, P < 0.05) compared with control dogs. Treatment with high- and low-dose HGF improved the expression of the SR Ca(2+)-cycling proteins compared with controls. In conclusion, regional intramyocardial injections of HGF naked DNA plasmid improve regional and global LV function and prevent progressive LV remodeling.

Chronic electrical stimulation of the carotid sinus baroreflex improves left ventricular function and promotes reversal of ventricular remodeling in dogs with advanced heart failure

BACKGROUND

Autonomic abnormalities exist in heart failure and contribute to disease progression. Activation of the carotid sinus baroreflex (CSB) has been shown to reduce sympathetic outflow and augment parasympathetic vagal tone. This study tested the hypothesis that long-term electric activation of the CSB improves left ventricular (LV) function and attenuates progressive LV remodeling in dogs with advanced chronic heart failure.

METHODS AND RESULTS

Studies were performed in 14 dogs with coronary microembolization-induced heart failure (LV ejection fraction ≈25%). Eight dogs were chronically instrumented for bilateral CSB activation using the Rheos System (CVRx Inc, Minneapolis, Minn) and 6 were not and served as controls. All dogs were followed for 3 months, and none received other background therapy. During follow-up, treatment with CSB increased LV ejection fraction 4.0±2.4% compared with a reduction in control dogs of −2.8±1.0% (P<0.05). Similarly, treatment with CSB decreased LV end-systolic volume -2.5±2.7 mL compared with an increase in control dogs of 6.7±2.9 mL (P<0.05). Compared with control, CSB activation significantly decreased LV end-diastolic pressure and circulating plasma norepinephrine, normalized expression of cardiac β(1)-adrenergic receptors, β-adrenergic receptor kinase, and nitric oxide synthase and reduced interstitial fibrosis and cardiomyocyte hypertrophy.

CONCLUSIONS

In dogs with advanced heart failure, CSB activation improves global LV function and partially reverses LV remodeling both globally and at cellular and molecular levels.

Agents with inotropic properties for the management of acute heart failure syndromes. Traditional agents and beyond

Treatment with inotropic agents is one of the most controversial topics in heart failure. Initial enthusiasm, based on strong pathophysiological rationale and apparent empirical efficacy, has been progressively limited by results of controlled trials and registries showing poorer outcomes of the patients on inotropic therapy. The use of these agents remains, however, potentially indicated in a significant proportion of patients with low cardiac output, peripheral hypoperfusion and end-organ dysfunction caused by heart failure. Limitations of inotropic therapy seem to be mainly related to their mechanisms of action entailing arrhythmogenesis, peripheral vasodilation, myocardial ischemia and damage, and possibly due to their use in patients without a clear indication, rather than to the general principle of inotropic therapy itself. This review will discuss the characteristics of the patients with a potential indication for inotropic therapy, the main data from registries and controlled trials, the mechanism of the untoward effects of these agents on outcomes and, lastly, perspectives with new agents with novel mechanisms of action.

Large animal models of heart failure: a critical link in the translation of basic science to clinical practice

Congestive heart failure (HF) is a clinical syndrome, with hallmarks of fatigue and dyspnea, that continues to be highly prevalent and morbid. Because of the growing burden of HF as the population ages, the need to develop new pharmacological treatments and therapeutic interventions is of paramount importance. Common pathophysiologic features of HF include changes in left ventricle structure, function, and neurohormonal activation. The recapitulation of the HF phenotype in large animal models can allow for the translation of basic science discoveries into clinical therapies. Models of myocardial infarction/ischemia, ischemic cardiomyopathy, ventricular pressure and volume overload, and pacing-induced dilated cardiomyopathy have been created in dogs, pigs, and sheep for the investigation of HF and potential therapies. Large animal models recapitulating the clinical HF phenotype and translating basic science to clinical applications have successfully traveled the journey from bench to bedside. Undoubtedly, large animal models of HF will continue to play a crucial role in the elucidation of biological pathways involved in HF and the development and refinement of HF therapies.

Effects of istaroxime on diastolic stiffness in acute heart failure syndromes: results from the Hemodynamic, Echocardiographic, and Neurohormonal Effects of Istaroxime, a Novel Intravenous Inotropic and Lusitropic Agent: a Randomized Controlled Trial in Patients Hospitalized with Heart Failure (HORIZON-HF) trial

BACKGROUND

Istaroxime is a novel intravenous agent with inotropic and lusitropic properties related to inhibition of the Na+/K+ adenosine triphosphatase and stimulation of sarcoplasmic reticulum calcium adenosine triphosphatase activity. We analyzed data from HORIZON-HF, a randomized, controlled trial evaluating the short-term effects of istaroxime in patients hospitalized with heart failure and left ventricular ejection fraction < or = 35% to test the hypothesis that istaroxime improves diastolic stiffness in acute heart failure syndrome.

METHODS

One hundred twenty patients were randomized 3:1 (istaroxime/placebo) to a continuous 6-hour infusion of 1 of 3 doses of istaroxime or placebo. All patients underwent pulmonary artery catheterization and comprehensive 2-dimensional/Doppler and tissue Doppler echocardiography at baseline and at the end of the 6-hour infusion. We quantified diastolic stiffness using pressure-volume analysis and tissue Doppler imaging of the lateral mitral annulus (E').

RESULTS

Baseline characteristics were similar among all groups, with mean age 55 +/- 11 years, 88% men, left ventricular ejection fraction 27% +/- 7%, systolic blood pressure (SBP) 116 +/- 13 mm Hg, and pulmonary capillary wedge pressure (PCWP) 25 +/- 5 mm Hg. Istaroxime administration resulted in an increase in E' velocities, whereas there was a decrease in E' in the placebo group (P = .048 between groups). On pressure-volume analysis, istaroxime decreased end-diastolic elastance (P = .0001). On multivariate analysis, increasing doses of istaroxime increased E' velocity (P = .043) and E-wave deceleration time (P = .001), and decreased E/E' ratio (P = .047), after controlling for age, sex, baseline ejection fraction, change in PCWP, and change in SBP.

CONCLUSIONS

Istaroxime decreases PCWP, increases SBP, and decreases diastolic stiffness in patients with acute heart failure syndrome.

Ranolazine combined with enalapril or metoprolol prevents progressive LV dysfunction and remodeling in dogs with moderate heart failure

Acute intravenous infusion of ranolazine (Ran), an anti-ischemic/antiangina drug, was previously shown to improve left ventricular (LV) ejection fraction (EF) without a concomitant increase in myocardial oxygen consumption in dogs with chronic heart failure (HF). This study examined the effects of treatment with Ran alone and in combination with metoprolol (Met) or enalapril (Ena) on LV function and remodeling in dogs with HF. Dogs (n = 28) with microembolization-induced HF were randomized to 3 mo oral treatment with Ran alone [375 mg twice daily (bid); n = 7], Ran (375 mg bid) in combination with Met tartrate (25 mg bid; n = 7), Ran (375 mg bid) in combination with Ena (10 mg bid; n = 7), or placebo (PL; Ran vehicle bid; n = 7). Ventriculographic measurements of LV end-diastolic volume (EDV) and end-systolic volume (ESV) and LV EF were obtained before treatment and after 3 mo of treatment. In PL-treated dogs, EDV and ESV increased significantly. Ran alone prevented the increase in EDV and ESV seen in the PL group and significantly increased EF, albeit modestly, from 35 +/- 1% to 37 +/- 2%. When combined with either Ena or Met, Ran prevented the increase in EDV, significantly decreased ESV, and markedly increased EF compared with those of PL. EF increased from 35 +/- 1% to 40 +/- 1% with Ran + Ena and from 34 +/- 1% to 41 +/- 1% with Ran + Met. Ran alone or in combination with Ena or Met was also associated with beneficial effects at the cellular level on histomorphometric parameters such as hypertrophy, fibrosis, and capillary density as well as the expression for pathological hypertrophy and Ca2+ cycling genes. In conclusion, Ran prevented progressive LV dysfunction and global and cellular myocardial remodeling, and Ran in combination with Ena or Met improved LV function beyond that observed with Ran alone.

Transient left ventricular apical ballooning and exercise induced hypertension during treadmill exercise testing: is there a common hypersympathetic mechanism?

Objective

To describe two cases of Takotsubo like myocardial contractile pattern during exercise stress test secondary to hypertensive response.

Background

Treadmill exercise testing is known to cause sympathetic stimulation, leading to increased levels of catecholamine, resulting in alteration in vascular tone. Hypertensive response during exercise testing can cause abnormal consequences, resulting in false positive results.

Cases

We present the cases of two patients experiencing apical and basal akinesis during exercise stress echocardiography, in whom normal wall motion response was observed on subsequent pharmacologic stress testing. The first patient developed transient left ventricular (LV) apical akinesis during exercise stress echocardiography. Due to high suspicion that this abnormality might be secondary to hypertensive response, pharmacologic stress testing was performed after three days, which was completely normal and showed no such wall motion abnormality. Qualitative assessment of myocardial perfusion using contrast was also performed, which showed good myocardial blood flow, indicating low probability for significant obstructive coronary artery disease. The second patient developed LV basal akinesis as a result of hypertensive response during exercise testing. Coronary angiogram was not performed in either patient due to low suspicion for coronary artery disease, and subsequently negative stress studies.

Results

Transient stress induced cardiomyopathy can develop secondary to hypertensive response during exercise stress testing.

Conclusion

These cases provide supporting evidence to the hyper-sympathetic theory of left ventricular ballooning syndrome.

Overview of emerging pharmacologic agents for acute heart failure syndromes

BACKGROUND

Several therapies commonly used for the treatment of acute heart failure syndromes (AHFS) present some well-known limitations and have been associated with an early increase in the risk of death. There is, therefore, an unmet need for new pharmacologic agents for the early management of AHFS that may improve both short- and long-term outcomes.

AIM

To review the recent evidence on emerging pharmacologic therapies in AHFS.

METHODS

A systematic search of peer-reviewed publications was performed on MEDLINE, EMBASE and Clinical Trials.gov from January 1990 to August 2007. The results of unpublished or ongoing trials were obtained from presentations at national and international meetings and pharmaceutical industry releases. Bibliographies from these references were also reviewed, as were additional articles identified by content experts.

RESULTS

Cumulative data from large studies and randomised trials suggest that therapies with innovative mechanisms of action may safely and effectively reduce pulmonary congestion or improve cardiac performance in AHFS patients.

CONCLUSION

Some investigational agents for the management of AHFS are able to improve haemodynamics and/or clinical status. In spite of these promising findings, no new agent has demonstrated a clear benefit in terms of long-term clinical outcomes compared to placebo or conventional therapies.

New pharmacologic therapies for acute heart failure

Given the limitations of high-dose diuretics and vasodilators and the increasing literature showing that inotropes, regardless of the dose used, have a detrimental effect on mortality, a variety of new agents are under investigation for the treatment of pulmonary and systemic congestion and restoration of cardiac output in the setting of acute heart failure syndromes. The new therapeutic approach is based on two goals: short-term improvement in symptoms together with long-term improvement of cardiac function. This review describes new agents that are in preclinical and in clinical phases with realistic prospects: anti-endothelin, natriuretic peptides, istaroxime, levosimendan, myosin activators, and vasopressin antagonists. Those new therapeutic strategies aim to act at the cellular level to improve vessel and heart functions, with minimal side effects, together with improved sodium and water balance.

Review of current and investigational pharmacologic agents for acute heart failure syndromes

Acute heart failure syndromes (AHFS) are a major public health problem and present a therapeutic challenge to clinicians. Commonly used agents in the treatment of AHFS include diuretics, vasodilators (eg, nitroglycerin, nitroprusside, nesiritide), and inotropes (eg, dobutamine, dopamine, milrinone). Patients admitted to hospital with AHFS and low cardiac output state (AHFS/LO) represent a subgroup with very high inhospital and postdischarge mortality rates. Most of these patients require intravenous inotropic therapy. However, the use of current intravenous inotropes has been associated with risk for hypotension, atrial and ventricular arrhythmias, and possibly increased postdischarge mortality, particularly in those with coronary artery disease. Consequently, there is an unmet need for new agents to safely improve cardiac performance (contractility and/or active relaxation) in this patient population. This article reviews a selection of current and investigational agents for the treatment of AHFS, with a main focus on the high-risk patient population with AHFS/LO.