Right Ventricular Ejection Fraction and Beta-Blocker Effect in Heart Failure With Reduced Ejection Fraction

BACKGROUND

A low right ventricular ejection fraction (RVEF) is a marker of poor outcomes in patients with heart failure with reduced ejection fraction (HFrEF). Beta-blockers improve outcomes in HFrEF, but whether this effect is modified by RVEF is unknown.

METHODS AND RESULTS

Of the 2798 patients in Beta-Blocker Evaluation of Survival Trial (BEST), 2008 had data on baseline RVEF (mean 35%, median 34%). Patients were categorized into an RVEF of less than 35% (n = 1012) and an RVEF of 35% or greater (n = 996). We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) within each RVEF subgroup and formally tested for interactions between bucindolol and RVEF. The effect of bucindolol on all-cause mortality in 2008 patients with baseline RVEF (HR 0.88, 95% CI 0.75-1.02) is consistent with that in 2798 patients in the main trial (HR 0.90, 95% CI 0.78-1.02). Bucindolol use was associated with a lower risk of all-cause mortality in patients with an RVEF of 35% or greater (HR 0.70, 95% CI 0.55-0.89), but not in those with an RVEF of less than 35% (HR 1.02, 95% CI 0.83-1.24, P for interaction = .022). Similar variations were observed for cardiovascular mortality (P for interaction = .009) and sudden cardiac death (P for interaction = .018), but not for pump failure death (P for interaction = .371) or HF hospitalization (P for interaction = .251).

CONCLUSIONS

The effect of bucindolol on mortality in patients with HFrEF was modified by the baseline RVEF. If these hypothesis-generating findings can be replicated using approved beta-blockers in contemporary patients with HFrEF, then RVEF may help to risk stratify patients with HFrEF for optimization of beta-blocker therapy.

Bucindolol Decreases Atrial Fibrillation Burden in Patients With Heart Failure and the ADRB1 Arg389Arg Genotype

[Figure: see text].

Bucindolol for the Maintenance of Sinus Rhythm in a Genotype-Defined HF Population: The GENETIC-AF Trial

OBJECTIVES

The purpose of this study was to compare the effectiveness of bucindolol with that of metoprolol succinate for the maintenance of sinus rhythm in a genetically defined heart failure (HF) population with atrial fibrillation (AF).

BACKGROUND

Bucindolol is a beta-blocker whose unique pharmacologic properties provide greater benefit in HF patients with reduced ejection fraction (HFrEF) who have the beta₁-adrenergic receptor (ADRB1) Arg389Arg genotype.

METHODS

A total of 267 HFrEF patients with a left ventricular ejection fraction (LVEF) <0.50, symptomatic AF, and the ADRB1 Arg389Arg genotype were randomized 1:1 to receive bucindolol or metoprolol therapy and were up-titrated to target doses. The primary endpoint of AF or atrial flutter (AFL) or all-cause mortality (ACM) was evaluated by electrocardiogram (ECG) during a 24-week period.

RESULTS

The hazard ratio (HR) for the primary endpoint was 1.01 (95% confidence interval [CI]: 0.71 to 1.42), but trends for bucindolol benefit were observed in several subgroups. Precision therapeutic phenotyping revealed that a differential response to bucindolol was associated with the interval of time from the initial diagnoses of AF and HF to randomization and with the onset of AF relative to that of the initial HF diagnosis. In a cohort whose first AF and HF diagnoses were <12 years prior to randomization, in which AF onset did not precede HF by more than 2 years (n = 196), the HR was 0.54 (95% CI: 0.33 to 0.87; p = 0.011).

CONCLUSIONS

Pharmacogenetically guided bucindolol therapy did not reduce the recurrence of AF/AFL or ACM compared to that of metoprolol therapy in HFrEF patients, but populations were identified who merited further investigation in future phase 3 trials.

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.

Nebivolol, bucindolol, metoprolol and carvedilol are devoid of intrinsic sympathomimetic activity in human myocardium

1. The present study investigated whether or not there may be differences in the direct cardiac actions of the novel, highly beta(1)-selective adrenoceptor antagonist nebivolol (NEB) in comparison to metoprolol (MET), bisoprolol (BIS), carvedilol (CAR) and bucindolol (BUC) in human myocardium (n=9). 2. The rank order of beta(1)-selectivity as judged by competition experiments to (3)H-CGP 12.1777 in the presence of CGP 207.12 A (300 nmol l(-1), K(i)beta(2)) or ICI 118.551 (50 nmol l(-1), K(i)beta(1)) were NEB(K(i)beta(2)/K(i)beta(1): 40.7) > BIS(15.6) > MET(4.23) > CAR(0.73) > BUC(0.49). 3. The rank order of the negative inotropic potency of the beta-adrenoceptor antagonists measured in left ventricular trabeculae (dilated cardiomyopathy, DCM) as judged by the concentration needed to induce a 50% decrease in isoprenaline (1 micromol l(-1))-stimulated force (IC(50)) was: MET (0.6 micromol l(-1)) > CAR (4.1 micromol l(-1)) > NEB (7.0 micromol l(-1)). 4. NEB, BUC, MET and CAR did not not exert an intrinsic sympathomimetic activity (ISA) as determined by measurements of force development in forskolin (0.3 micromol l(-1)) pre-treated left ventricular trabeculae, nor by measuring adenylate cyclase activity in forskolin (0.3 micromol l(-1))-stimulated assays (crude membranes). This also holds true for radioligand binding assays with or without guanine nucleotide guanyl-5'-yl imidodiphosphate (Gpp(NH)p). 5. Although all studied beta-adrenoceptor antagonists lack intrinsic sympathomimetic activity (ISA), they differ in the beta(1)-selectivity as well as in their direct negative inotropic action. These differences as well as the mode of extracardiac action may have an impact on outcome of patients treated with beta-adrenoceptor antagonists.