A trial of the beta-blocker bucindolol in patients with advanced chronic heart failure

The autonomic nervous system and heart failure

The pathophysiology of heart failure (HF) is characterized by hemodynamic abnormalities that result in neurohormonal activation and autonomic imbalance with increase in sympathetic activity and withdrawal of vagal activity. Alterations in receptor activation from this autonomic imbalance may have profound effects on cardiac function and structure. Inhibition of the sympathetic drive to the heart through β-receptor blockade has become a standard component of therapy for HF with a dilated left ventricle because of its effectiveness in inhibiting the ventricular structural remodeling process and in prolonging life. Several devices for selective modulation of sympathetic and vagal activity have recently been developed in an attempt to alter the natural history of HF. The optimal counteraction of the excessive sympathetic activity is still unclear. A profound decrease in adrenergic support with excessive blockade of the sympathetic nervous system may result in adverse outcomes in clinical HF. In this review, we analyze the data supporting a contributory role of the autonomic functional alterations on the course of HF, the techniques used to assess autonomic nervous system activity, the evidence for clinical effectiveness of pharmacological and device interventions, and the potential future role of autonomic nervous system modifiers in the management of this syndrome.

Medication management of chronic heart failure in older adults

Heart failure (HF) is a common problem in older adults. Individuals aged 65 years or older are at a higher risk for developing HF, especially diastolic HF or HF with preserved ejection fraction (HFpEF). HF can be seen in up to 20 % of adults aged 85 years or older. In contrast to middle-aged (40-64 years) HF patients, multiple cardiac, non-cardiac and geriatric syndrome co-morbidities are seen in elderly HF patients. Additionally, age-related changes in pharmacokinetics and pharmacodynamics influence medication therapy. Hence, the management of older patients with HF is challenging and treatment should be modified in the light of the above-mentioned conditions. This article discusses the current evidence for medication management in both systolic HF or HF with reduced ejection fraction (HFrEF) and HFpEF, noting, however, the limited data for HFpEF and HFrEF in those 80 years of age or older. The objective of this article is to discuss evidence-based and outcomes-driven pharmacologic management strategies for chronic HF in the older adults for whom functional and other patient-centered outcomes might be more than or as important as clinical outcomes. Optimal management would be expected to help to reduce illness burden, reduce mortality and hospitalizations, and improve function and quality of life.

Pharmacological Treatment of Patients with Chronic Systolic Heart Failure

Chronic heart failure is characterised by neuroendocrine activation as an attempt of the body to maintain pump function of the heart and blood pressure for the perfusion of peripheral tissues. While this neuroendocrine activation is beneficial in the short term, it induces maladaptive remodeling of the heart with continuous deterioration of left ventricular function. Accordingly, pharmacological treatment of patients with heart failure aims at protecting the heart from this neuroendocrine activation, which is represented in particular by the sympathetic nervous and the renin-angiotensin-aldosterone systems. While this concept is based on evidence from numerous large randomised placebo-controlled studies in patients with systolic heart failure, about half of the patients with heart failure have preserved systolic function, and most studies antagonising neuroendocrine activation were not successful in these latter patients. Here, we review the pathophysiological changes that occur in patients with heart failure and provide an overview on the mechanisms and clinical evidence of currently applied pharmacological treatment in patients with systolic heart failure.

GNAS gene variants affect β-blocker-related survival after coronary artery bypass grafting

BACKGROUND

Cardiac overexpression of the β-adrenoreceptor (βAR)-coupled stimulatory G-protein subunit Gαs enhances inotropic responses to adrenergic stimulation and improves survival in mice under βAR blockade. The authors recently identified three common haplotypes in the GNAS gene encoding Gαs, with the greatest Gαs protein expression and signal transduction in haplotype *3 carriers and less in haplotype *2 and *1 carriers. The authors tested the hypothesis that these GNAS variants result in altered mortality in patients after coronary artery bypass graft surgery, particularly in those receiving βAR blockade.

METHODS

This prospective analysis included 1,627 European ancestry patients undergoing primary coronary artery bypass graft surgery. Patients were genotyped for two GNAS haplotype tagging single-nucleotide polymorphisms defining three major haplotypes. Up to 5-yr all-cause mortality was estimated using a Cox proportional hazard model; hazard ratios and 95% CIs were calculated while adjusting for demographics, clinical covariates, and the new EuroSCORE II.

RESULTS

Univariate analysis revealed haplotype-dependent 5-yr mortality rates (*1/*1: 18.9%, *2/*1: 13.7%, *2/*2: 9.3%, *3/*1: 10.6%, *3/*2: 9.1%, and *3/*3: 9.6%; P = 0.0006). After adjustment for other predictors of death, homozygote haplotype *1 carriers showed a doubled risk for death (hazard ratio, 2.2; 95% CI, 1.2 to 3.8; P = 0.006). Considering only patients receiving βAR blockers (n = 1,267), the adjusted risk of death even tripled (hazard ratio, 3.0; 95% CI, 1.5 to 6.1; P = 0.002).

CONCLUSIONS

GNAS haplotypes independently associate with an increased risk of death after primary coronary artery bypass graft surgery. These results are most pronounced in patients receiving βAR blockers, strengthening the rationale for personalized treatment, to decrease medication side effects and improve outcomes.

Race contributes to beta-blocker efficacy in pediatric patients with arrhythmias

In African-American (AA) adults, β-blockers (BB) have been reported to be less efficacious treating cardiac disease compared with whites (CAUC). This has been attributed to genetic polymorphisms of β-receptors. It is unknown if racial differences affect response to BB in pediatric patients with arrhythmias. AA and CAUC ≤ 18 years of age were included if they underwent treadmill stress testing while receiving metoprolol, atenolol, nadolol, or carvedilol. Patient demographics, resting heart rate (HR), maximum HR, and BB variables were collected. CAUC patients were matched on a 2:1 basis by age and sex to AA patients. Patients were blunted if HR was <90 % of maximum predicted HR for same-age patients on a modified Bruce protocol treadmill stress test. Long-term follow-up for breakthrough arrhythmias was documented. 78 patients were included (26 AA, 52 CAUC). No differences were noted in demographics, medication dose, BB or arrhythmia type, or baseline, maximal, or % HR change (p = not significant [NS]). On univariate analysis, fewer AA achieved a blunted HR during treadmill testing compared with CAUC (65 vs. 86%, p = 0.03). On multivariate analysis, AA were less likely to have an HR blunted by BB (OR 0.18, 95% confidence interval [CI] 0.04-0.75, p = 0.02) compared with CAUC. During the 1-year follow-up period, AA trended toward having one (58 vs. 40%, p = 0.14) or multiple instances (38 vs. 26%, p = 0.26) of breakthrough arrhythmia on cardiac Holter monitor testing. Race appears to affect the efficacy of BB therapy in pediatric patients with arrhythmias. Future studies to identify genetic polymorphisms in this patient subset are necessary.

β-Blockers

Objective: To review the pharmacology, pharmacokinetics, and pharmacodynamic properties of commonly used β-blockers (atenolol, carvedilol, metoprolol succinate, metoprolol tartrate, and nebivolol). Data Sources: A MEDLINE literature search (1966-May 2013) was performed using the following key terms: hypertension, β-blockers, atenolol, carvedilol, metoprolol tartrate, metoprolol succinate, nebivolol, pharmacology, pharmacodynamics, pharmacokinetics, blood pressure, metabolic, lipid, central aortic pressure, diabetes, and insulin resistance. References from publications reviewed were included. Study Selection and Data Extraction: English-language articles identified were reviewed. Animal studies and studies in patients for a primary diagnosis of coronary artery disease were excluded. Data Synthesis: β-Blockers are no longer recommended first-line therapy for primary hypertension, based on data showing that β-blockers are inferior to other antihypertensives and no better than placebo, in spite of provision of blood pressure reduction. Because atenolol is the β-blocker used in 75% of these studies, uncertainty about widespread application to all β-blockers exists. Different pharmacological and physiological properties, both within β-blockers and compared with other antihypertensives, may explain divergent effects. Evidence shows that β-blockers have a truncated effect on central aortic pressure, an independent predictor of cardiovascular events, compared with other antihypertensive classes; differences within the class may exist, but the evidence is inconclusive. Metabolic effects differ within the β-blocker class, with evidence that carvedilol causes less metabolic dysregulation. Conclusion: Emerging evidence reveals physiological differences within the β-blocker class and in comparison to other antihypertensives. These differences provide insight into the diverse clinical effects β-blockers provide in cardiovascular disease.

Ligand bias prevents class equality among beta-blockers

β-Blockers are used for a wide range of diseases from hypertension to glaucoma. In some diseases/conditions all β-blockers are effective, while in others only certain subgroups are therapeutically beneficial. The best-documented example for only a subset of β-blockers showing clinical efficacy is in heart failure, where members of the class have ranged from completely ineffective, to drugs of choice for treating the disease. Similarly, β-blockers were tested in murine asthma models and two pilot clinical studies. A different subset was found to be effective for this clinical indication. These findings call into question the current system of classifying these drugs. To consider 'β-blockers', as a single class is misleading when considering their rigorous pharmacological definition and their appropriate clinical application.

Pharmacogenetics: implications of race and ethnicity on defining genetic profiles for personalized medicine

Pharmacogenetics is being used to develop personalized therapies specific to subjects from different ethnic or racial groups. To date, pharmacogenetic studies have been primarily performed in trial cohorts consisting of non-Hispanic white subjects of European descent. A "bottleneck" or collapse of genetic diversity associated with the first human colonization of Europe during the Upper Paleolithic period, followed by the recent mixing of African, European, and Native American ancestries, has resulted in different ethnic groups with varying degrees of genetic diversity. Differences in genetic ancestry might introduce genetic variation, which has the potential to alter the therapeutic efficacy of commonly used asthma therapies, such as β2-adrenergic receptor agonists (β-agonists). Pharmacogenetic studies of admixed ethnic groups have been limited to small candidate gene association studies, of which the best example is the gene coding for the receptor target of β-agonist therapy, the β2-adrenergic receptor (ADRB2). Large consortium-based sequencing studies are using next-generation whole-genome sequencing to provide a diverse genome map of different admixed populations, which can be used for future pharmacogenetic studies. These studies will include candidate gene studies, genome-wide association studies, and whole-genome admixture-based approaches that account for ancestral genetic structure, complex haplotypes, gene-gene interactions, and rare variants to detect and replicate novel pharmacogenetic loci.

Nebivolol: vasodilator properties and evidence for relevance in treatment of cardiovascular disease

β-adrenergic blocking agents, a pharmacologically diverse class of cardiovascular medications, are recommended as first-line treatment for patients with hypertension and concomitant structural heart disease, and for angina and heart failure. Many within-class differences exist, from pharmacokinetics and pharmacodynamics to ancillary effects, such as intrinsic sympathomimetic activity, antiarrhythmic activity, α-1 adrenergic receptor blockade affinity, and direct vasodilation. Nebivolol is a third-generation, β1 selective, long acting β-blocker, which causes direct vasodilation via endothelium-dependent nitric oxide stimulation. The vasodilatory actions of nebivolol might result in clinical effects with some distinct properties. Differences from other β-blockers might include improvement of endothelial function, enhancement of forward flow in muscular resistance arteries, maintenance of exercise tolerance, and overall improved tolerability, side effect profile, and adherence. Nebivolol has been shown to be a clinically effective β-blocker for treatment as initial or add-on therapy for systemic hypertension, as an antianginal agent, and as therapy for patients with heart failure. These properties position nebivolol as a treatment option for patients with hypertension and/or structural heart disease, although its precise role in the therapeutic armamentarium remains to be clarified.

Carvedilol: use in chronic heart failure

Carvedilol is a beta-adrenergic antagonist with vasodilatory properties (alpha1-antagonism), which has been extensively evaluated in the treatment of patients with heart failure. In patients with chronic heart failure carvedilol improves left-ventricular (LV) ejection fraction over 6 to 12 months of treatment, and attenuates LV remodelling. Large-scale randomised, placebo controlled trials involving more than 4000 patients with chronic heart failure have demonstrated that carvedilol improves survival and reduces hospitalizations. Comparative studies with metoprolol in patients with heart failure have suggested that carvedilol may be associated with greater survival benefit although differences in the preparation of metoprolol have left uncertainty in this area. Carvedilol has a high safety profile and the clinical benefits appear maintained across a wide range of patients with comorbidities such as diabetes and renal failure. Carvedilol has also been shown to attenuate LV remodeling and improve clinical outcomes in patients with LV dysfunction and/or heart failure following acute myocardial infarction. As a result of these data, carvedilol is recommended for treatment of patients with heart failure in heart-failure guidelines. This evidence-based treatment should be widely implemented to ensure that patients with heart failure receive appropriate medical therapy.

Pharmacogenomics of heart failure

The combination of angiotensin-converting enzyme (ACE) inhibitors and β-adrenergic receptor (βAR) blockers remains the essential component of heart failure (HF) pharmacotherapy. However, individual patient responses to these pharmacotherapies vary widely. The variability in response cannot be explained entirely by clinical characteristics, and genetic variation may play a role. The purpose of this chapter is to examine the current knowledge in the field of beta-blocker and ACE inhibitor pharmacogenetics in HF. β-blocker and ACE inhibitor pharmacogenetic studies performed in patients with HF were identified from the PubMed database from 1966 to July 2011. Thirty beta-blocker and 10 ACE inhibitor pharmacogenetic studies in patients with HF were identified.The ACE deletion variant was associated with greater survival benefit from ACE inhibitors and beta-blockers compared with the ACE insertion. Ser49 in the β1AR, the insertion in the α2CAR, and Gln41 in G protein-coupled receptor (GPCR) kinase (GRK)-5 are associated with greater survival benefit from β-blockers, compared with Gly49, the deletion, and Leu41, respectively. However, many of these associations have not been validated. The HF pharmacogenetic literature is still in its very early stages, but there are promising candidate genetic variants that may identify which HF patients are most likely to benefit from beta-blockers and ACE inhibitors and patients that may require additional therapies.

A novel approach to drug development in heart failure: towards personalized medicine

Evidence-based treatment has succeeded in improving clinical outcomes in heart failure. Nevertheless, morbidity, mortality, and the economic burden associated with the syndrome remain unsatisfactorily high. Most landmark heart failure studies included broad study populations, and thus current recommendations dictate standardized, universal therapy. While most patients included in recent trials benefit from this background treatment, exceeding this already significant gain has proven to be a challenge. The early identification of responders and nonresponders to treatment could result in improved therapeutic effectiveness, while reduction of unnecessary exposure may limit harmful and unpleasant side effects. In this review, we examine the potential value of currently available information on differential responses to heart failure therapy-a first step toward personalized medicine in the management of heart failure.

New advances in beta-blocker therapy in heart failure

The use of β-blockers (BB) in heart failure (HF) has been considered a contradiction for many years. Considering HF simply as a state of inadequate systolic function, BB were contraindicated because of their negative effects on myocardial contractility. Nevertheless, evidence collected in the past years have suggested that additional mechanisms, such as compensatory neuro-humoral hyperactivation or inflammation, could participate in the pathogenesis of this complex disease. Indeed, chronic activation of the sympathetic nervous system, although initially compensating the reduced cardiac output from the failing heart, increases myocardial oxygen demand, ischemia and oxidative stress; moreover, high catecholamine levels induce peripheral vasoconstriction and increase both cardiac pre- and after-load, thus determining additional stress to the cardiac muscle (1). As a consequence of such a different view of the pathogenic mechanisms of HF, the efficacy of BB in the treatment of HF has been investigated in numerous clinical trials. Results from these trials highlighted BB as valid therapeutic tools in HF, providing rational basis for their inclusion in many HF treatment guidelines. However, controversy still exists about their use, in particular with regards to the selection of specific molecules, since BB differ in terms of adrenergic β-receptors selectivity, adjunctive effects on α-receptors, and effects on reactive oxygen species and inflammatory cytokines production. Further concerns about the heterogeneity in the response to BB, as well as the use in specific patients, are matter of debate among clinicians. In this review, we will recapitulate the pharmacological properties and the classification of BB, and the alteration of the adrenergic system occurring during HF that provide a rationale for their use; we will also focus on the possible molecular mechanisms, such as genetic polymorphisms, underlying the different efficacy of molecules belonging to this class.

The effect of preoperative β-blocker use and race on long-term survival after coronary artery bypass grafting

OBJECTIVE

To date, racial differences in the long-term survival of coronary artery bypass grafting (CABG) patients who receive preoperative β-blockers have not been specifically examined. The purpose of this study was to examine the effect of preoperative β-blockers on long-term survival among black CABG patients and to compare the magnitude of this effect with white patients.

DESIGN

A retrospective cohort study.

SETTING

A tertiary referral heart hospital.

PARTICIPANTS

13,354 patients undergoing CABG between 1992 and 2011.

MEASUREMENTS AND MAIN RESULTS

Hazard ratios (HR) and 95% confidence intervals (CI) were computed using a Cox regression model. A total of 1,448 (62%) black and 6,094 (55%) white patients had a history of preoperative β-blocker use. Among black patients, those receiving β-blockers survived longer than those not receiving β-blockers (adjusted HR = 0.77, 95% CI = 0.67-0.88). The survival advantage was comparable to that observed among white patients (adjusted HR = 0.88, 95% CI = 0.82-0.93).

CONCLUSION

Black CABG patients benefited from preoperative β-blockers and the magnitude of the effect was comparable to that among white patients.

Systematic review of genuine versus spurious side-effects of beta-blockers in heart failure using placebo control: recommendations for patient information

BACKGROUND

Patients trying life-preserving agents such as beta-blockers may be discouraged by listings of harmful effects provided in good faith by doctors, drug information sheets, and media. We systematically review the world experience of side-effect information in blinded, placebo-controlled beta-blockade in heart failure. We present information for a physician advising a patient experiencing an unwanted symptom and suspecting the drug.

METHODS

We searched Medline for double-blinded randomized trials of beta-blocker versus placebo in heart failure reporting side-effects. We calculated, per 100 patients reporting the symptom on beta-blockade, how many would have experienced it on placebo: the "proportion of symptoms non-pharmacological".

RESULTS

28 of the 33 classically-described side-effects are not significantly more common on beta-blockers than placebo. Of the 100 patients developing dizziness on beta-blockers, 81 (95% CI 73-89) would have developed it on placebo. For diarrhoea this proportion is 82/100 (70-95), and hyperglycaemia 83/100 (68-98). For only two side-effects is this under half (i.e. predominantly due to beta-blocker): bradycardia (33/100, CI 21-44) and intermittent claudication (41/100, 2-81). At least 6 so-called side-effects are less common on beta-blocker than placebo, including depression (reduced by 35%, p<0.01) and insomnia (by 27%, p=0.01).

CONCLUSIONS

Clinicians might reconsider whether it is scientifically and ethically correct to warn a patient that a drug might cause them a certain side-effect, when randomized controlled trials show no significant increase, or indeed a significant reduction. A better informed consultation could, in patients taking beta-blockers, alleviate suffering. In patients who might otherwise not take the drug, it might prevent deaths.