Long-term beta-blocker vasodilator therapy improves cardiac function in idiopathic dilated cardiomyopathy: a double-blind, randomized study of bucindolol versus placebo

Efficacy of Beta-Blockers and Angiotensin-Converting Enzyme Inhibitors in Non-Ischemic Dilated Cardiomyopathy: A Systematic Review and Meta-Analysis

Background

Non-ischemic dilated cardiomyopathy (NIDCM) is a form of heart failure with a poor prognosis and unclear optimal management. The aim of the study was to systematically review the literature and assess the efficacy and safety of beta-blockers and angiotensin-converting enzyme (ACE) inhibitors in the management of chronic heart failure secondary to NIDCM and explore their putative mechanisms of action.

Methods

Studies from 1990 to 2023 were reviewed using PubMed and EMBASE, focusing on their effects on left ventricular ejection fraction (LVEF) in NIDCM patients, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Results

Beta-blockers showed a significant beneficial effect on LVEF improvement in NIDCM, with an overall effect size of Cohen's d = 1.30, 95% confidence interval (CI) (0.76, 1.84), high heterogeneity (Tau2 = 0.90; Chi2 = 162.05, df = 13, P < 0.00001; I2 = 92%), and a significant overall effect (Z = 4.72, P < 0.00001). ACE inhibitors also showed a beneficial role, but with less heterogeneity (Tau2 = 0.02; Chi2 = 1.09, df = 1, P = 0.30; I2 = 8%) and a nonsignificant overall effect (Z = 1.36, P = 0.17), 95% CI (-0.24, 1.31).

Conclusions

The study highlights the efficacy of carvedilol in improving LVEF in NIDCM patients over ACE inhibitors, recommends beta-blockers as first-line therapy, and advocates further research on ACE inhibitors.

Comparative Efficacy of Different Drugs for the Treatment of Dilated Cardiomyopathy: A Systematic Review and Network Meta-analysis

BACKGROUND AND OBJECTIVE

At present, the therapies of dilated cardiomyopathy concentrated on the symptoms of heart failure and related complications. The study is to evaluate the clinical efficacy of a combination of various conventional and adjuvant drugs in treating dilated cardiomyopathy via network meta-analysis.

METHODS

The study was reported according to the PRISMA 2020 statement. From inception through 27 June 2022, the PubMed, Embase, Cochrane library, and Web of Science databases were searched for randomized controlled trials on medicines for treating dilated cardiomyopathy. The quality of the included studies was evaluated according to the Cochrane risk of bias assessment. R4.1.3 and Revman5.3 software were used for analysis.

RESULTS

There were 52 randomized controlled trials in this study, with a total of 25 medications and a sample size of 3048 cases. The network meta-analysis found that carvedilol, verapamil, and trimetazidine were the top three medicines for improving left ventricular ejection fraction (LVEF). Ivabradine, bucindolol, and verapamil were the top 3 drugs for improving left ventricular end-diastolic dimension (LVEDD). Ivabradine, L-thyroxine, and atorvastatin were the top 3 drugs for improving left ventricular end-systolic dimension (LVESD). Trimetazidine, pentoxifylline, and bucindolol were the top 3 drugs for improving the New York Heart Association classification (NYHA) cardiac function score. Ivabradine, carvedilol, and bucindolol were the top 3 drugs for reducing heart rate (HR).

CONCLUSION

A combination of different medications and conventional therapy may increase the clinical effectiveness of treating dilated cardiomyopathy. Beta-blockers, especially carvedilol, can improve ventricular remodeling, cardiac function, and clinical efficacy in patients with dilated cardiomyopathy (DCM). Hence, they can be used if patients tolerate them. If LVEF and HR do not meet the standard, ivabradine can also be used in combination with other treatments. However, since the quality and number of studies in our research were limited, large sample size, multi-center, and high-quality randomized controlled trials are required to corroborate our findings.

Identification of predictive factors interacting with heart rate reduction for potential beneficial clinical outcomes in chronic heart failure: A systematic literature review and meta-analysis

Background

There is an absence of clinical evidence on what factors modify the effect of heart rate (HR)-reducing treatment on mortality and morbidity in symptomatic heart failure patients with reduced ejection fraction (HFrEF). We performed a Bayesian meta-analysis and meta-regression to identify predictive factors that interact with HR-reducing therapy.

Methods

A systematic review was performed to identify randomized placebo-controlled trials that enrolled symptomatic HFrEF patients. The primary objective was to evaluate how different predictive factors modify the efficacy of HR-reducing therapy on clinical outcomes. Secondary objectives included the evaluation of subgroups stratified by a HR reduction threshold of 10 bpm.

Results

Data from 20 studies were synthesized and HR-reducing therapy was responsible for 16.7 %, 16.4 %, and 21.1 % risk reductions in all-cause mortality, cardiovascular (CV)-related mortality, and rehospitalization due to worsening HF (WHF), respectively. Empirical Bayes meta-regression showed that type 2 diabetes mellitus (T2DM) significantly modified the efficacy of HR-reducing therapy on all-cause mortality (slope = 0.012 in log risk ratio (RR) per 1 %-unit [95 % credible interval (CrI) 0.004, 0.021]) and CV-related mortality (0.01 in log RR per 1 %-unit [95 % CrI 0.0003, 0.0200]). There were insufficient studies to perform a meta-regression when stratifying by a HR reduction threshold of 10 bpm; however, when including all studies, we observed a significant effect modification for rehospitalization due to WHF (p = 0.004).

Conclusions

This meta-analysis focused on the central tenet of HR-reducing therapy and revealed that T2DM is a predictor of HR-reducing treatment effect on all-cause mortality and CV-related mortality in HFrEF patients.

Indications of beta-adrenoceptor blockers in Takotsubo syndrome and theoretical reasons to prefer agents with vasodilating activity

Takotsubo syndrome (TTS) is estimated to account for 1-3% of all patients presenting with suspected ST-segment elevation myocardial infarction. A sudden surge in sympathetic nervous system is considered the cause of TTS. Nonetheless, no specific recommendations have been provided regarding β-blocking therapy. Apart from specific contra-indications (severe LV dysfunction, hypotension, bradycardia and corrected QT interval >500 ms), treatment with a β-blocker seems reasonable until full recovery of LV ejection fraction, though evidence is limited to a few animal studies, case reports or observational studies. In this review, we will reappraise the rationale for β-blocker therapy in TTS and speculate on the pathophysiologic basis for preferring non-selective agents with vasodilating activity over β₁-selective drugs.

α1-adrenoceptor activity of β-adrenoceptor ligands - An expected drug property with limited clinical relevance

Many β-adrenoceptor agonists and antagonists including several clinically used drugs have been reported to also exhibit binding to α₁-adrenoceptors. Such promiscuity within the adrenoceptor family appears to occur more often than off-target effects of drugs in general. It should not be considered surprising based on the amino acid homology among the nine adrenoceptor subtypes including the counter-ions for binding the endogenous catecholamines. When β-adrenoceptor ligands also bind to α₁-adrenoceptors, they almost always act as antagonists, regardless of being agonists or antagonists at the β-adrenoceptor. The α₁-adrenoceptor affinity of β-adrenoceptor ligands in most cases is at least one, and often more log units lower than at their cognate receptor. Consistent evidence from multiple investigators indicates that β-adrenoceptor ligands relatively have the highest affinity for α_1A- and lowest for α_1B-adrenoceptors. While promiscuity among adrenoceptor subtypes causes misleading interpretation of experimental in vitro data, it is proposed based on the law of mass action that α₁-adrenoceptor binding of β-adrenoceptor ligands rarely contributes to the clinical profile of such drugs, particularly if they are agonists at the β-adrenoceptor.

A genotype-directed comparative effectiveness trial of Bucindolol and metoprolol succinate for prevention of symptomatic atrial fibrillation/atrial flutter in patients with heart failure: Rationale and design of the GENETIC-AF trial

BACKGROUND

Few therapies are available for the safe and effective treatment of atrial fibrillation (AF) in patients with heart failure. Bucindolol is a non-selective beta-blocker with mild vasodilator activity previously found to have accentuated antiarrhythmic effects and increased efficacy for preventing heart failure events in patients homozygous for the major allele of the ADRB1 Arg389Gly polymorphism (ADRB1 Arg389Arg genotype). The safety and efficacy of bucindolol for the prevention of AF or atrial flutter (AFL) in these patients has not been proven in randomized trials.

METHODS/DESIGN

The Genotype-Directed Comparative Effectiveness Trial of Bucindolol and Metoprolol Succinate for Prevention of Symptomatic Atrial Fibrillation/Atrial Flutter in Patients with Heart Failure (GENETIC-AF) trial is a multicenter, randomized, double-blinded "seamless" phase 2B/3 trial of bucindolol hydrochloride versus metoprolol succinate, for the prevention of symptomatic AF/AFL in patients with reduced ejection fraction heart failure (HFrEF). Patients with pre-existing HFrEF and recent history of symptomatic AF are eligible for enrollment and genotype screening, and if they are ADRB1 Arg389Arg, eligible for randomization. A total of approximately 200 patients will comprise the phase 2B component and if pre-trial assumptions are met, 620 patients will be randomized at approximately 135 sites to form the Phase 3 population. The primary endpoint is the time to recurrence of symptomatic AF/AFL or mortality over a 24-week follow-up period, and the trial will continue until 330 primary endpoints have occurred.

CONCLUSIONS

GENETIC-AF is the first randomized trial of pharmacogenetic guided rhythm control, and will test the safety and efficacy of bucindolol compared with metoprolol succinate for the prevention of recurrent symptomatic AF/AFL in patients with HFrEF and an ADRB1 Arg389Arg genotype. (ClinicalTrials.govNCT01970501).

A Review of the External Validity of Clinical Trials with Beta-Blockers in Heart Failure

BACKGROUND

Beta-blockers (BBs) are the mainstay prognostic medication for all stages of chronic heart failure (CHF). There are many classes of BBs, each of which has varying levels of evidence to support its efficacy in CHF. However, most CHF patients have one or more comorbid conditions such as diabetes, renal impairment, and/or atrial fibrillation. Patient enrollment to randomized controlled trials (RCTs) often excludes those with certain comorbidities, particularly if the symptoms are severe. Consequently, the extent to which evidence drawn from RCTs is generalizable to CHF patients has not been well described. Clinical guidelines also underrepresent this point by providing generic advice for all patients. The aim of this review is to examine the evidence to support the use of BBs in CHF patients with common comorbid conditions.

METHODS

We searched MEDLINE, PubMed, and the reference lists of reviews for RCTs, post hoc analyses, systematic reviews, and meta-analyses that report on use of BBs in CHF along with patient demographics and comorbidities.

RESULTS

In total, 38 studies from 28 RCTs were identified, which provided data on six BBs against placebo or head to head with another BB agent in ischemic and nonischemic cardiomyopathies. Several studies explored BBs in older patients. Female patients and non-Caucasian race were underrepresented in trials. End points were cardiovascular hospitalization and mortality. Comorbid diabetes, renal impairment, or atrial fibrillation was detailed; however, no reference to disease spectrum or management goals as a focus could be seen in any of the studies. In this sense, enrollment may have limited more severe grades of these comorbidities.

CONCLUSIONS

RCTs provide authoritative information for a spectrum of CHF presentations that support guidelines. RCTs may provide inadequate information for more heterogeneous CHF patient cohorts. Greater Phase IV research may be needed to fill this gap and inform guidelines for a more global patient population.

Pharmacologic Management of Chronic Heart Failure: A Review

Standard drug therapy of systolic heart failure has been evaluated in large-scale randomized clinical trials and includes angiotensin-converting enzyme (ACE) inhibi tors, which should be used as first-line therapy, diuret ics for the management of extracellular fluid volume excess, and digoxin. In combination with ACE inhibitors and diuretics, with or without digoxin, some β-adrener gic receptor blockers attenuate disease progression and improve outcome in mild-to-moderate systolic heart failure. The pharmacologic management of chronic dia stolic heart failure is largely empirical and directed at reducing symptoms. Symptoms caused by increased ventricular filling pressures may be diminished by diuret ics and nitrovasodilators. Some calcium channel antago nists and most β-blockers prolong diastolic filling time by slowing heart rate, thereby improving the symptoms of diastolic heart failure.

Role of echocardiography in the contemporary management of chronic heart failure

Echocardiography is an excellent noninvasive tool for the assessment of ventricular size and both systolic and diastolic function, and it is routinely used in patients with heart failure. This review will discuss the role of echocardiography in heart failure diagnosis, prognostic assessment and in the management of heart failure patients.

Effect of race on left ventricular ejection fraction decline after initial improvement with beta blockers in patients with non-ischemic cardiomyopathy: a retrospective analysis

Background

Although beta blockers (BBs) are established therapy in heart failure, some patients whose left ventricular ejection fraction (LVEF) initially increases on BB therapy experience a subsequent LVEF decline. This study aimed to evaluate the proportion of patients with non-ischemic cardiomyopathy (NICM) whose LVEF declines while on BB therapy and determine important predictors of LVEF decline.

Methods

A retrospective analysis of 238 patients receiving a BB (carvedilol, metoprolol succinate, or tartrate), with an ejection fraction of ≤40 % and NICM, whose LVEF initially rose ≥5 % after 1 year of BB therapy, was conducted. Post-response LVEF decline ≥5 % to a final LVEF of ≤35 % was evaluated within 4 years of BB initiation.

Results

In our study, we had 52 Caucasians (22 %), 78 Hispanics (33 %), and 108 African Americans (45 %). Overall, 32 patients (13.44 %) had post-response LVEF decline. The nadir LVEF of patients with post-response LVEF decline was 25 % (interquartile range 20–27). Compared with others, Hispanics had lower nadir LVEF (22 %, p < 0.001). Important predictors of LVEF decline were Hispanic race (odds ratio (OR) 6.094, p < 0.001), New York Heart Association (NYHA) class (OR 2.287, p < 0.05), baseline LVEF (OR 1.075, p < 0.05), and age (OR 0.933, p < 0.001).

Conclusion

A significant proportion (13.44 %) of NICM patients with LVEF increase over 1 year of BB therapy experienced subsequent LVEF decline. Race, NYHA class, baseline LVEF, and age are important predictors of this decline.

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

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

Treatment of chronic heart failure with β-adrenergic receptor antagonists: a convergence of receptor pharmacology and clinical cardiology

Despite the absence of a systematic development plan, β-blockers have reached the top tier of medical therapies for chronic heart failure. The successful outcome was due to the many dedicated investigators who produced, over a 30-year period, increasing evidence that β-blocking agents should or actually did improve the natural history of dilated cardiomyopathies and heart failure. It took 20 years for supportive evidence to become undeniable, at which time in 1993 the formidable drug development resources of large pharmaceutical companies were deployed into Phase 3 trials. Success then came relatively quickly, and within 8 years multiple agents were on the market in the United States and Europe. Importantly, there is ample room to improve antiadrenergic therapy, through novel approaches exploiting the nuances of receptor biology and/or intracellular signaling, as well as through pharmacogenetic targeting.

Bucindolol: a pharmacogenomic perspective on its use in chronic heart failure

Bucindolol is a non-selective β-adrenergic receptor blocker with α-1 blocker properties and mild intrinsic sympatholytic activity. The Beta-Blocker Evaluation of Survival Trial (BEST), which is the largest clinical trial of bucindolol in patients with heart failure, was terminated prematurely and failed to show an overall mortality benefit. However, benefits on cardiac mortality and re-hospitalization rates were observed in the BEST trial. Bucindolol has not shown benefits in African Americans, those with significantly low ejection fraction and those in NYHA class IV heart failure. These observations could be due to the exaggerated sympatholytic response to bucindolol in these sub-groups that may be mediated by genetic polymorphisms or changes in gene regulation due to advanced heart failure. This paper provides a timely clinical update on the use of bucindolol in chronic heart failure.

Role of β-blocker therapy in pediatric heart failure

Heart failure is becoming an increasingly common and significant problem in the field of pediatric cardiology. The numerous types of cardiomyopathies, and more recently, long-term survival of patients with congenital heart disease, have added to a growing patient population. Over the last several decades, our knowledge base regarding mechanisms of disease and therapeutic intervention in adult patients with heart failure has drastically changed. The most recent and important breakthrough in the pharmacologic treatment of heart failure has been the particular role of β-blocker therapy. This medication has led to significant improvements in survival and symptoms in adults, with less convincing findings in limited studies in pediatrics. The ability to study the benefits of this therapy in patients has been challenging owing to the heterogeneity of the patient population and lack of large sample sizes. However, as we investigate the mechanisms behind the disease process, the differences that exist between disease conditions and ages, and the significant alterations that may exist at the molecular and genetic level, our understanding of β-blocker therapy in pediatric heart failure will improve, and ultimately may lead to patient-specific therapy.

Analysis of randomized controlled trials on the effect of magnitude of heart rate reduction on clinical outcomes in patients with systolic chronic heart failure receiving beta-blockers

Beta blockers improve cardiac function and prolong survival in patients with systolic chronic heart failure (CHF). However, the exact mechanisms underlying these benefits are uncertain. Specifically, it is unclear whether a close relation exists between heart rate (HR) reduction and clinical outcomes with these agents. This hypothesis was therefore tested within randomized controlled trials of beta blockers in systolic CHF. Left ventricular ejection fraction (LVEF) and HR values at baseline and study end were obtained from available beta-blocker randomized clinical trials. The relation between change in HR and all-cause mortality as well as the LVEF was determined using regression analysis. Thirty-five trials, which included 22,926 patients with a mean follow-up duration of 9.6 months, were analyzed for all-cause mortality, the LVEF, and HR. There was a close relation between all-cause annualized mortality rate and HR (adjusted R2 = 0.51, p = 0.004). A strong correlation between change in HR and change in LVEF (adjusted R2 = 0.48, p = 0.000) was also observed. When only trials with >100 patients were included, an even tighter correlation was seen (adjusted R2 = 0.60, p = 0.0004). In conclusion, these analyses indicate that a major contributor to the clinical benefits of beta-blocker therapy in systolic CHF may be the HR-lowering effect of these agents. Therefore, the magnitude of HR reduction may be more important than the achievement of target dose in beta-blocker treatment of systolic CHF.

Beta-blocker use in decompensated heart failure

Despite the current advances in treatment, acute decompensated heart failure accounts for more than 1 million hospital admissions annually. Many of the patients hospitalized are already receiving long-term treatment with beta-blockers. For patients who receive full dose beta-blocker therapy and suffer acute decompensated heart failure, clinicians face two key questions: what to do, if anything, with the dosage of beta-blocker and what is the best way to integrate inotropic and beta-blocker therapies for patients who require inotropes. This article discusses these issues and reviews the available literature. Because these topics have received little systematic evaluation, we also present our clinical approaches to these problems.

A case series of systemic right ventricular dysfunction post atrial switch for simple D-transposition of the great arteries: the impact of beta-blockade

BACKGROUND

Patients with atrial switch (Mustard or Senning) repair of D-transposition of the great arteries (D-TGA) are at increased risk for atrial arrhythmias, systemic right ventricular (RV) dysfunction and late mortality.

OBJECTIVES

To evaluate case series from a single-centre experience with beta-blocker use in adult, post atrial switch, simple D-TGA patients.

METHODS

The Adult Congenital Heart Disease Clinic (Halifax, Nova Scotia) database was used to identify patients with post atrial switch, simple D-TGA. Treatment effect of beta-blockade was evaluated.

RESULTS

Eight patients were treated with beta-blockers for systemic RV dysfunction (n=2), arrhythmia (n=2) or both (n=4). Median follow-up was three years, at which time seven of eight patients were still on beta-blockade. Of those patients with complete data, two of five had improved systemic ventricular dysfunction, two of four had improved tricuspid regurgitation and four of six had improved functional capacity, as determined by history or exercise testing. Beta-blockade was well tolerated in seven of eight patients without any significant clinical deterioration.

CONCLUSIONS

Beta-blockade was used infrequently in patients with a prior Mustard procedure. When beta-blockade was prescribed to patients with a prior atrial switch procedure, the drugs were well tolerated and were associated with trends toward improved symptoms, less tricuspid regurgitation and improved functional status in patients with reduced systemic RV function. These data support the need for a randomized trial of beta-blockade in patients with a previous Mustard or Senning operation and RV dysfunction.

Effect of beta-blocker therapy on functional status in patients with heart failure - A meta-analysis

BACKGROUND

The results of randomised control trials (RCTs) evaluating the effect of beta-blockers on functional status in patients with chronic heart failure are conflicting.

AIM

To perform a systematic review and meta-analysis of RCTs evaluating the effect of beta-blockers on New York Heart Association (NYHA) classification and exercise tolerance in chronic heart failure.

METHODS AND RESULTS

We selected 28 RCTs evaluating beta-blocker versus placebo in addition to ACE inhibitor therapy. Combined results of 23 RCTs showed that beta-blockers improved NYHA class by at least one class with odds ratio (OR) 1.80 (1.33-2.43) p<0.0001. Meta-analysis of 10 RCTs showed a significant prolongation of exercise time by 44.19 (6.62-81.75) s p=0.021. Combining 8 RCTs evaluating the maximal peak oxygen uptake and 9 RCTs evaluating 6-min walk distance showed that beta-blockers had no significant effect compared with placebo, p=0.484, and p=0.730, respectively. Combined results of the 23 RCTs showed significant reducing effect on all cause mortality with OR=0.69 (0.59-0.82) p<0.0001.

CONCLUSION

Chronic use of a beta-blocker in conjunction with ACE inhibitor therapy improves dyspnoea and prolongs exercise tolerance time, but has no significant effect on 6-min walk test or maximal oxygen uptake in patients with heart failure.

A polymorphism within a conserved beta(1)-adrenergic receptor motif alters cardiac function and beta-blocker response in human heart failure

Heterogeneity of heart failure (HF) phenotypes indicates contributions from underlying common polymorphisms. We considered polymorphisms in the beta(1)-adrenergic receptor (beta(1)AR), a beta-blocker target, as candidate pharmacogenomic loci. Transfected cells, genotyped human nonfailing and failing ventricles, and a clinical trial were used to ascertain phenotype and mechanism. In nonfailing and failing isolated ventricles, beta(1)-Arg-389 had respective 2.8 +/- 0.3- and 4.3 +/- 2.1-fold greater agonist-promoted contractility vs. beta(1)-Gly-389, defining enhanced physiologic coupling under relevant conditions of endogenous expression and HF. The beta-blocker bucindolol was an inverse agonist in failing Arg, but not Gly, ventricles, without partial agonist activity at either receptor; carvedilol was a genotype-independent neutral antagonist. In transfected cells, bucindolol antagonized agonist-stimulated cAMP, with a greater absolute decrease observed for Arg-389 (435 +/- 80 vs. 115 +/- 23 fmol per well). Potential pathophysiologic correlates were assessed in a placebo-controlled trial of bucindolol in 1,040 HF patients. No outcome was associated with genotype in the placebo group, indicating little impact on the natural course of HF. However, the Arg-389 homozygotes treated with bucindolol had an age-, sex-, and race-adjusted 38% reduction in mortality (P = 0.03) and 34% reduction in mortality or hospitalization (P = 0.004) vs. placebo. In contrast, Gly-389 carriers had no clinical response to bucindolol compared with placebo. Those with Arg-389 and high baseline norepinephrine levels trended toward improved survival, but no advantage with this allele and exaggerated sympatholysis was identified. We conclude that beta(1)AR-389 variation alters signaling in multiple models and affects the beta-blocker therapeutic response in HF and, thus, might be used to individualize treatment of the syndrome.

An echocardiographic analysis of the long-term effects of carvedilol on left ventricular remodeling, systolic performance, and ventricular filling patterns in dilated cardiomyopathy

BACKGROUND

The long-term clinical benefit of beta blockade is well recognized, but data quantifying long-term effects of beta blockade on remodeling of the left ventricle (LV) is limited.

METHODS

This consecutive series evaluates the long-term response of the LV to the addition of carvedilol to conventional therapy for dilated cardiomyopathy. There were 33 patients who had a LV ejection fraction <45%, LV enlargement and symptomatic heart failure. Quantitative Doppler echocardiography was performed at baseline 6, 12, 24, and 36 months after initiation of carvedilol to evaluate LV ejection fraction, LV volume, wall stress, mass, regional function, and diastolic performance.

RESULTS

Compared to baseline there was a significant and sustained reduction in end-systolic volume and end-systolic wall stress with a corresponding improvement in LV ejection fraction. The LV mass did not decline but relative wall thickness increased toward normal. An analysis of regional wall motion responses showed an improvement in all areas, particularly the apical, septal, and lateral walls that was significantly more frequent in patients with a nonischemic etiology. Filling patterns of the LV remained abnormal throughout the study but changed with therapy suggesting a decline in filling pressures. These changes were sustained for 3 years.

CONCLUSION

(1) The addition of carvedilol to conventional therapy for a dilated cardiomyopathy significantly improves LV ejection fraction and reduces LV end-systolic volume and wall stress for at least 3 years, (2) the response to 6 months of treatment predicts the long-term response, (3) the typical response is partial improvement of the LV, complete return to normal size, and function is uncommon, and (4) abnormalities of LV filling persist in virtually all patients throughout the course of treatment.

The control of adrenergic function in heart failure: therapeutic intervention

Chronic heart failure is characterised by excess adrenergic activity that augurs a poor prognosis. The reasons for increased adrenergic activity are complex and incompletely understood. The circumstantial evidence relating increased activity to adverse outcome is powerful, but not yet conclusive. In normal subjects, autonomic control of the circulation is predominantly under the control of sympatho-inhibitory inputs from the arterial and cardiopulmonary baroreceptors, with a small input from the excitatory ergo- and chemo-receptors. In heart failure, the situation is reversed, with loss of the restraining input from the baroreceptors and an increase in the excitatory inputs, resulting in excessive adrenergic activity. The circumstantial evidence linking neuroendocrine activation with poor outcome coupled with the clinical success of inhibition of the renin-angiotensin-aldosterone system has long suggested that inhibition of adrenergic activity might be beneficial in heart failure. There is a number of potential ways of achieving this. Improved treatment of heart failure itself may reduce sympathetic drive. There is an interplay between angiotensin II, aldosterone and the sympathetic nervous system, and thus RAAS antagonists, such as angiotensin converting enzyme inhibitors and spironolactone could directly reduce sympathetic activation. Exercise rehabilitation may similarly reduce sympathetic activity.Recently, beta-adrenergic receptor antagonists have been conclusively shown to improve symptoms, reduce hospitalisations and increase survival. However, the demonstration that central reduction of sympathetic activity with agents such as moxonidine increases morbidity and mortality suggests that we do not properly understand the role of sympathetic activation in the pathophysiology of heart failure.

PPAR-gamma agonist rosiglitazone ameliorates ventricular dysfunction in experimental chronic mitral regurgitation

Previously we reported that the beneficial effects of beta-adrenergic blockade in chronic mitral regurgitation (MR) were in part due to induction of bradycardia, which obviously affects myocardial energy requirements. From this observation we hypothesized that part of the pathophysiology of MR may involve faulty energy substrate utilization, which in turn might lead to potentially harmful lipid accumulation as observed in other models of heart failure. To explore this hypothesis, we measured triglyceride accumulation in the myocardia of dogs with chronic MR and then attempted to enhance myocardial metabolism by chronic administration of the peroxisome proliferator-activated receptor (PPAR)-gamma agonist rosiglitazone. Cardiac tissues were obtained from three groups of dogs that included control animals, dogs with MR for 3 mo without treatment, and dogs with MR for 6 mo that were treated with rosiglitazone (8 mg/day) for the last 3 mo of observation. Hemodynamics and contractile function (end-systolic stress-strain relationship, as measured by K index) were assessed at baseline, 3 mo of MR, and 6 mo of MR (3 mo of the treatment). Lipid accumulation in MR (as indicated by oil red O staining score and TLC analysis) was marked and showed an inverse correlation with the left ventricular (LV) contractility. LV contractility was significantly restored after PPAR therapy (K index: therapy, 3.01 +/- 0.11*; 3 mo MR, 2.12 +/- 0.34; baseline, 4.01 +/- 0.29; ANOVA, P = 0.038; *P < 0.05 vs. 3 mo of MR). At the same time, therapy resulted in a marked reduction of intramyocyte lipid. We conclude that 1) chronic MR leads to intramyocyte myocardial lipid accumulation and contractile dysfunction, and 2) administration of the PPAR-gamma agonist rosiglitazone ameliorates MR-induced LV dysfunction accompanied by a decline in lipid content.

Failure of benefit and early hazard of bucindolol for Class IV heart failure

OBJECTIVES

The risks and benefits of beta-blockade with bucindolol were assessed in heart failure (HF) patients with Class IV symptoms within the Beta-blocker Evaluation of Survival Trial (BEST).

BACKGROUND

beta-blockade is accepted therapy for mild to moderate HF, but its safety and efficacy in advanced HF have not been established.

METHODS

BEST recruited 2708 HF patients; of these, 226 with Class IV symptoms (n=114 randomized to bucindolol, n=112 to placebo) formed the basis of this study. All-cause death, HF hospitalization, and drug discontinuations occurring early during therapy (< or =6 months) and overall during follow-up were assessed. Compared with Class III, Class IV patients were older and had higher plasma norepinephrine levels, prevalence of coronary disease, S3 gallops, and lower ejection fractions, but characteristics of the 2 Class IV treatment groups were similar.

RESULTS

During a mean of 1.6 years, 49% Class IV patients died, and 54% were hospitalized for HF. Bucindolol increased the combined endpoint of death or HF hospitalization within the first 6 months (hazard ratio [HR]=1.7, 95% confidence interval [CI]=1.1-2.7) and did not result in benefit overall (HR=1.2, 95% CI=0.9-1.6). HF hospitalization alone within 6 months was increased by bucindolol (HR=1.7), and an early adverse trend for death was seen (HR=1.6) with no benefit overall (HR=1.1). Bucindolol was discontinued more frequently than placebo for worsening HF (11% versus 4%) and hypotension (3% versus 0%).

CONCLUSIONS

Class IV HF patients in BEST were at high risk. Bucindolol did not reduce death or HF hospitalization and was associated with early hazard.

Switching between beta blockers in heart failure patients: rationale and practical considerations

The clinical benefit of beta blockade has been proven in a variety of pathologic settings, including hypertension, angina pectoris, acute- and post-myocardial infarction, and congestive heart failure. However, beta blockers do not all share the same clinical outcomes with respect to efficacy or safety in many of these conditions. This is especially true in HF, where differences in reverse remodeling and effects on the periphery may be important differentiating factors leading to improved efficacy. In fact, beta blockers are a heterogeneous group of agents with respect to pharmacology, receptor biology, hemodynamic effects, and tolerability. As cardiovascular disease progresses, the issue of switching from one b blocker to another is an important consideration as to how to optimize the effectiveness of adrenergic blockade. Because of the differences among beta blockers, switching should be conducted in a manner that takes into account pharmacologic differences. For example, the similarities and differences of receptor subtype blockade of the two agents and the potential effects of ancillary properties. Two protocols for switching between carvedilol, a third-generation nonselective agent with vasodilation through alpha1 blockade, and a beta1-selective agent (e.g., metoprolol, atenolol) are described to simplify the process and maximize the safety and tolerability of this procedure. The optimal selection and use of adrenergic-blocking agents in the cardiovascular continuum will assist in providing improved management while minimizing safety and tolerability concerns.

A comparative analysis of the results from 4 trials of β-blocker therapy for heart failure: BEST, CIBIS-II, MERIT-HF, and COPERNICUS

BACKGROUND

Recent large randomized, controlled trials (BEST [Beta-blocker Evaluation of Survival Trial], CIBIS-II [Cardiac Insufficiency Bisoprolol Trial II], COPERNICUS [Carvedilol Prospective Randomized Cumulative Survival Study], and MERIT-HF [Metoprolol Randomized Intervention Trial in Congestive Heart Failure]) have addressed the usefulness of beta-blockade in the treatment of advanced heart failure. CIBIS-II, COPERNICUS, and MERIT-HF have shown that beta-blocker treatment with bisoprolol, carvedilol, and metoprolol XL, respectively, reduce mortality in advanced heart failure patients, whereas BEST found a statistically nonsignificant trend toward reduced mortality with bucindolol. We conducted a post hoc analysis to determine whether the response to beta-blockade in BEST could be related to differences in the clinical and demographic characteristics of the study populations. We generated a sample from BEST to resemble the patient cohorts studied in CIBIS-II and MERIT-HF to find out whether the response to beta-blocker therapy was similar to that reported in the other trials. These findings are further compared with COPERNICUS, which entered patients with more severe heart failure.

METHODS

To achieve conformity with the entry criteria for CIBIS-II and MERIT-HF, the BEST study population was adjusted to exclude patients with systolic blood pressure <100 mm Hg, heart rate <60 bpm, and age >80 years (exclusion criteria employed in those trials). The BEST comparison subgroup (BCG) was further modified to more closely reflect the racial demographics reported for patients enrolled in CIBIS-II and MERIT-HF. The association of beta-blocker therapy with overall survival and survival free of cardiac death, sudden cardiac death, and progressive pump failure in the BCG was assessed.

RESULTS

In the BCG subgroup, bucindolol treatment was associated with significantly lower risk of death from all causes (hazard ratio (HR)=0.77 [95% CI=0.65, 0.92]), cardiovascular death (HR=0.71 [0.58, 0.86]), sudden death (HR=0.77 [0.59, 0.999]), and pump failure death (HR=0.64 [0.45, 0.91]).

CONCLUSIONS

Although not excluding the possibility of differences resulting from chance alone or to different properties among beta-blockers, this study suggests the possibility that different heart failure population subgroups may have different responses to beta-blocker therapy.

Beta-blockade in chronic heart failure: does it work in everyone?

Chronic heart failure continues to exact a heavy burden on society due to high morbidity and mortality, in spite of advances in management. Beta-adrenergic blockade, by the suppression of sympathetic activity, attenuates the adverse ventricular remodeling seen in heart failure, and decreases mortality and hospitalization rates. Recently reported trials, meta-analyses, and sub-analyses extend the benefit of beta-blockade to severe heart failure, women, elderly patients, and African Americans. In addition, recent data also indicate the cost-effectiveness of beta-blockade in combating this deadly disease. These data indicate the strength of evidence for the use of beta-blockade for most patients with chronic heart failure.

Is depressed myocyte contractility centrally involved in heart failure?

This review examines the evidence for and against the hypothesis that abnormalities in cardiac contractility initiate the heart failure syndrome and drive its progression. There is substantial evidence that the contractility of failing human hearts is depressed and that abnormalities of basal Ca2+ regulation and adrenergic regulation of Ca2+ signaling are responsible. The cellular and molecular defects that cause depressed myocyte contractility are not well established but seem to culminate in abnormal sarcoplasmic reticulum uptake, storage, and release. There are also strong links between Ca2+ regulation, Ca2+ signaling pathways, hypertrophy, and heart failure that need to be more clearly delineated. There is not substantial direct evidence for a causative role for depressed contractility in the initiation and progression of human heart failure, and some studies show that heart failure can occur without depressed myocyte contractility. Stronger support for a causal role for depressed contractility in the initiation of heart failure comes from animal studies where maintaining or improving contractility can prevent heart failure. Recent clinical studies in humans also support the idea that beneficial heart failure treatments, such as beta-adrenergic antagonists, involve improved contractility. Current or previously used heart failure treatments that increase contractility, primarily by increasing cAMP, have generally increased mortality. Novel heart failure therapies that increase or maintain contractility or adrenergic signaling by selectively modulating specific molecules have produced promising results in animal experiments. How to reliably implement these potentially beneficial inotropic therapies in humans without introducing negative side effects is the major unanswered question in this field.

Titration of beta-blockers in heart failure. How to maximize benefit while minimizing adverse events

Data from large clinical trials indicate that beta-blocker therapy can be successfully initiated and adjusted upward in most patients with stable chronic heart failure who already take standard heart failure therapy. Such therapy typically includes ACE inhibitors, diuretics, and digoxin. With optimal titration and maintenance strategies, beta-blockers are effective and well tolerated in these patients. It is recommened that all patients with clinically stable mild to moderate chronic heart failure (NYHA class II or III), no contraindications to beta-blocker use, and an LVEF less than 40% should be treated with beta-blockers. Based on the results of recent clinical trials on heart failure, beta-blocker therapy should be initiated at a low dose and slowly tirtrated upward as tolerated. A patient's heart failure should be stable for at least 2 weeks before the dose is adjusted upward. Slow titration facilitates maximal tolerability. In primary care practice, physicians should apply titration strategies and target dosed that have been demonstrated to reduce morbidity and mortality in clinical trials. Although worsening heart failure or other adverse events occur in a minority of patients who take beta-blockers, these effects can be managed by adjusting the dose of ACE inhibitor or diuretic, or both, or by temporarily withholding the beta-clocker. Currently, professional treatment guidelines recommend beta-blocker therapy in combination with ACE inhibitors an diuretics as the standard of care in the treatment of heart failure.

Beta-blockers in chronic heart failure: considerations for selecting an agent

Patients with chronic heart failure have increased sympathetic nervous system activity that contributes to deterioration of cardiovascular function over time. Long-term beta-blocker therapy prevents such deterioration through inhibition of this neurohormonal pathway. The impressive survival data collected from several large studies have made beta-blockers a component of standard therapy for New York Heart Association class II to III heart failure. Although there are differences in the pharmacological properties of the beta-blockers shown to improve morbidity and mortality in heart failure, there is little evidence to suggest that such properties constitute any major advantages in clinical outcome. Carvedilol and extended-release metoprolol succinate are 2 beta-blockers currently approved in the United States for the treatment of patients with heart failure. Both agents have shown similar risk reductions in overall and cause-specific mortality; however, no outcome data from a comparative trial are available to support the use of one agent over the other. Regardless of the agent chosen, appropriate dosing and titration of beta-blockers are essential for successful therapy.

Differential effects of the angiotensin-converting enzyme inhibitor lisinopril versus the beta-adrenergic receptor blocker atenolol on hemodynamics and left ventricular contractile function in experimental mitral regurgitation

OBJECTIVES

The goal of this study was to determine the therapeutic efficacy of angiotensin-converting enzyme (ACE) inhibitors and beta-adrenergic receptor blockers in experimental chronic mitral regurgitation (MR), gaining knowledge using methods difficult to apply in humans.

BACKGROUND

Both ACE inhibitors and beta-blockers are cornerstones in the treatment of human congestive heart failure. However, the roles of these treatments for chronic MR is unclear.

METHODS

Mitral regurgitation was created in 11 closed-chest dogs. Three months after the creation, the ACE inhibitor lisinopril 20 mg was given orally daily. After three months of lisinopril therapy, the beta-blocker atenolol was added to lisinopril for another three months. Atenolol was begun at a dose of 12.5 mg daily and increased gradually to 100 mg daily. Hemodynamics and left ventricular (LV) function were assessed throughout the study.

RESULTS

Regurgitant fraction was consistently >50% over the course of this study. Pulmonary capillary wedge pressure and LV end-diastolic pressure were significantly increased after three months of MR and decreased during both lisinopril and the combined therapy in which it was not different from baseline. Left ventricular contractility measured by the end-systolic stiffness constant was depressed from 3.66 +/- 0.20 to 2.65 +/- 0.12 (p < 0.05) at three months of MR and rose insignificantly after lisinopril treatment (2.99 +/- 0.17). When atenolol was added, it rose significantly and returned to normal (3.50 +/- 0.22, p < 0.05).

CONCLUSIONS

Although lisinopril significantly reduced preload, its effect on LV contractility was insignificant in experimental MR. Conversely, atenolol, when added to lisinopril, achieved maximum hemodynamic benefit and also restored LV contractility.

Bucindolol displays intrinsic sympathomimetic activity in human myocardium

BACKGROUND

Most clinical studies have shown that beta-adrenergic receptor antagonists improve long-term survival in heart failure patients. Bucindolol, a nonselective beta-receptor blocker, however, failed to reduce heart failure mortality in a recent large clinical trial. The reasons for this failure are not known. Bucindolol has partial agonist properties in rat myocardium, but whether it has agonist activity in human heart is controversial. To address this, we measured the ability of bucindolol to increase cAMP accumulation in human myocardium.

METHODS AND RESULTS

Myocardial strips ( approximately 1 mm(3)) obtained from rat and nonfailing human hearts were confirmed to be viable for > or = 48 hours in normoxic tissue culture by MTT assay and histology. Freshly isolated strips were exposed to beta-adrenergic antagonists and agonists and assayed for cAMP. In both rat and human strips, the full beta-adrenergic agonist isoproterenol raised cAMP levels by >2.5-fold at 15 minutes. Carvedilol and propranolol had no effect on basal cAMP levels, whereas metoprolol reduced basal cAMP by approximately 25%. In contrast, bucindolol and xamoterol increased cAMP levels in a concentration-dependent manner in both rat and human myocardium (maximum 1.64+/-0.25-fold and 2.00+/-0.27-fold over control, respectively, P<0.01 for human tissue).

CONCLUSIONS

Bucindolol exhibits approximately 60% of the beta-adrenergic agonist activity of xamoterol in normal human myocardial tissue.

Impact of beta-blocker treatment on the prognostic value of currently used risk predictors in congestive heart failure

OBJECTIVES

This prospective study tested the impact of beta-blocker treatment on currently used risk predictors in congestive heart failure (CHF).

BACKGROUND

Given the survival benefit obtained by beta-blockade, risk stratification by factors established in the "pre-beta-blocker era" may be questioned.

METHODS

The study included 408 patients who had CHF with left ventricular ejection fraction (LVEF) <45%, all treated with an angiotensin-converting enzyme inhibitor or angiotensin type 1 receptor antagonist, who were classified into those receiving a beta-blocker (n = 165) and those who were not (n = 243). In all patients, LVEF, peak oxygen consumption (peakVO(2)), plasma norepinephrine (NE) and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were determined.

RESULTS

Although the New York Heart Association functional class (2.2 +/- 0.7 vs. 2.3 +/- 0.7), peakVO(2) (14.4 +/- 5.2 ml/min per kg vs. 14.4 +/- 5.5 ml/min per kg) and NT-proBNP (337 +/- 360 pmol/l vs. 434 +/- 538 pmol/l) were similar in the groups with and without beta-blocker treatment, the group with beta-blocker treatment had a lower heart rate (68 +/- 30 beats/min vs. 76 +/- 30 beats/min), lower NE (1.7 +/- 1.2 nmol/l vs. 2.5 +/- 2.2 nmol/l) and higher LVEF (24 +/- 10% vs. 21 +/- 9%; all p < 0.05). Within one year, 34% of patients without beta-blocker treatment, but only 16% of those with beta-blocker treatment (p < 0.001), reached the combined end point, defined as hospital admission due to worsening CHF and/or cardiac death. A beneficial effect of beta-blocker treatment was most obvious in the advanced stages of CHF, because the end-point rates were markedly lower (all p < 0.05) in the group with beta-blocker treatment versus the group without it, as characterized by peakVO(2) <10 ml/min per kg (26% vs. 64%), LVEF < or = 20% (25% vs. 45%), NE >2.24 nmol/l (18% vs. 40%) and NT-proBNP >364 pmol/l (27% vs. 45%), although patients with beta-blocker treatment received only 37 +/- 21% of the maximal recommended beta-blocker dosages.

CONCLUSIONS

The prognostic value of variables used for risk stratification of patients with CHF is markedly influenced by beta-blocker treatment. Therefore, in the beta-blocker era, a re-evaluation of the selection criteria for heart transplantation is warranted.

Carvedilol in the failing heart

Patients with chronic heart failure due to left ventricular systolic dysfunction of ischemic or nonischemic etiology have shown improvement in morbidity and mortality with carvedilol therapy. In patients with symptomatic (New York Heart Association class II-IV) heart failure, carvedilol improves left ventricular ejection fraction and clinical status, and slows disease progression, reducing the combined risk of mortality and hospitalization. Despite the overwhelming evidence for their benefit, there continues to be a large treatment gap between those who would derive benefit and those who actually receive the drug. In this article, the pharmacology, clinical trial evidence, and the potential differences between carvedilol and other beta blockers are discussed. Carvedilol provides powerful therapy in the treatment of chronic heart failure caused by a variety of etiologies and in a wide array of clinical settings.

Nonselective versus selective beta-adrenergic receptor blockade in congestive heart failure: differential effects on sympathetic activity

BACKGROUND

Activation of the sympathetic nervous system has important prognostic implications in chronic heart failure. Nonselective versus selective beta-adrenergic receptor antagonists may have differential effects on norepinephrine release from nerve terminals mediated by prejunctional beta(2)-adrenergic receptors.

METHODS AND RESULTS

Thirty-six patients with chronic heart failure were randomized to the nonselective beta-blocker carvedilol or the selective beta-blocker metoprolol (double-blind). Measurements of hemodynamics and cardiac and systemic norepinephrine spillover as well as microneurographic recordings of muscle sympathetic nerve traffic were made before and after 4 months of therapy. In the carvedilol group (n=17), there were significant reductions in both total body (-1.7+/-0.5 nmol/min, P<0.01) and cardiac norepinephrine spillover (-87+/-29 pmol/min, P<0.01). By contrast, in the metoprolol group (n=14), there were no significant changes in total body or cardiac norepinephrine spillover. Responses in the carvedilol group were significantly different from those observed in the metoprolol group (P<0.05). Both agents caused a reduction in heart rate and increases in pulse pressure, although mean arterial pressure did not change. Importantly, microneurographic measures of sympathetic nerve traffic to skeletal muscle did not change in either group.

CONCLUSIONS

Therapy with carvedilol caused significant decreases in systemic and cardiac norepinephrine spillover, an indirect measure of norepinephrine release. Such changes were not observed in patients treated with metoprolol. There was no effect of either agent on sympathetic efferent neuronal discharge to skeletal muscle. These findings suggest that carvedilol, a nonselective beta-blocker, caused its sympathoinhibitory effect by blocking peripheral, prejunctional beta-adrenergic receptors.