Critical differences among beta-adrenoreceptor antagonists in myocardial failure: debating the MERIT of COMET

Comparison of new-onset post-operative atrial fibrillation between patients receiving carvedilol and metoprolol after off-pump coronary artery bypass graft surgery

OBJECTIVE

Post-operative atrial fibrillation (POAF) is a common complication of coronary artery bypass graft (CABG) surgery. Previous studies suggest carvedilol is more effective than metoprolol in preventing POAF in on-pump CABG. This study investigated if the same benefit would be seen in off-pump CABG.

METHODS

This single-center, retrospective review compared rates of new-onset POAF between adult patients who received carvedilol and metoprolol after off-pump CABG surgery. Safety endpoints included hypotension, bradycardia, dyspnea, and the composite. Multivariate logistic regression was conducted to identify associations between demographics, potential confounders, and beta-blocker dose and POAF. Kaplan-Meier plots and Cox proportional-hazards models examined differences in time-to-event for POAF.

RESULTS

134 patients were included (34 carvedilol and 100 metoprolol). The mean age was 63 years, 70.9% were male, 85% had history of hypertension, 3.7% had history of heart failure with reduced ejection fraction, and 38.8% were taking beta blockers prior to admission. POAF developed in 2 patients (5.8%) in the carvedilol group and 24 patients (24.0%) in the metoprolol group (odds ratio 0.17 [95% CI 0.03-0.83], p = 0.023). Safety endpoints occurred in 10 carvedilol (29.4%) and 44 metoprolol (44.0%) patients (p = 0.134). Hypotension and dyspnea rates were similar between groups; bradycardia occurred more commonly among metoprolol-treated patients (p = 0.040). Time-to-event analyses revealed a hazard ratio = 0.22 (95% CI 0.05-0.93, p = 0.040) for carvedilol use.

CONCLUSIONS

In this single-center, retrospective study of off-pump CABG patients, carvedilol was associated with reduced POAF risk and enhanced safety compared to metoprolol.

Cardiac α1A-adrenergic receptors: emerging protective roles in cardiovascular diseases

α1-Adrenergic receptors (ARs) are catecholamine-activated G protein-coupled receptors (GPCRs) that are expressed in mouse and human myocardium and vasculature, and play essential roles in the regulation of cardiovascular physiology. Though α1-ARs are less abundant in the heart than β1-ARs, activation of cardiac α1-ARs results in important biologic processes such as hypertrophy, positive inotropy, ischemic preconditioning, and protection from cell death. Data from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) indicate that nonselectively blocking α1-ARs is associated with a twofold increase in adverse cardiac events, including heart failure and angina, suggesting that α1-AR activation might also be cardioprotective in humans. Mounting evidence implicates the α1A-AR subtype in these adaptive effects, including prevention and reversal of heart failure in animal models by α1A agonists. In this review, we summarize recent advances in our understanding of cardiac α1A-ARs.

Vidarabine, an anti-herpesvirus agent, prevents catecholamine-induced arrhythmias without adverse effect on heart function in mice

Sympathetic activation causes clinically important arrhythmias including atrial fibrillation (AF) and ventricular tachyarrhythmia. Although the usefulness of β-adrenergic receptor blockade therapy is widely accepted, its multiple critical side effects often prevent its initiation or continuation. The aim of this study is to determine the advantages of vidarabine, an adenylyl cyclase (AC)-targeted anti-sympathetic agent, as an alternative treatment for arrhythmia. We found that vidarabine, which we identified as a cardiac AC inhibitor, consistently shortens AF duration and reduces the incidence of sympathetic activation-induced ventricular arrhythmias. In atrial and ventricular myocytes, vidarabine inhibits adrenergic receptor stimulation-induced RyR2 phosphorylation, sarcoplasmic reticulum (SR) Ca²⁺ leakage, and spontaneous Ca²⁺ release from SR, the last of which has been considered as a potential arrhythmogenic trigger. Moreover, vidarabine also inhibits sympathetic activation-induced reactive oxygen species (ROS) production in cardiac myocytes. The pivotal role of vidarabine's inhibitory effect on ROS production with regard to its anti-arrhythmic property has also been implied in animal studies. In addition, as expected, vidarabine exerts an inhibitory effect on AC function, which is more potent in the heart than elsewhere. Indexes of cardiac function including ejection fraction and heart rate were not affected by a dosage of vidarabine sufficient to exert an anti-arrhythmic effect. These findings suggest that vidarabine inhibits catecholamine-induced AF or ventricular arrhythmia without deteriorating cardiac function in mice.

Comparing the therapeutic effects of carvedilol and metoprolol on prevention of atrial fibrillation after coronary artery bypass surgery, a double-blind study

BACKGROUND

Atrial Fibrillation (AF) is a common complication after open heart surgery and is frequently associated with increased hospital stay, complications, and mortality rates. The effect of β-blockers on prevention of supraventricular arrhythmias has been confirmed in several prospective randomized studies.

OBJECTIVES

This clinical trial aimed to compare the preventive effects of carvedilol and metoprolol on occurrence of AF after CABG surgery.

PATIENTS AND METHODS

This prospective, double-blind, randomized clinical trial was conducted on 150 patients (55 females, 95 males; mean age: 59 ± 10 years) who underwent CABG surgery. The patients with no contraindication for β-blocker use were randomly divided into two groups of carvedilol and metoprolol Tartarate (n = 75). Treatment with β-blocker was started on the first postoperative day (metoprolol, 25 mg BD; carvedilol, 6.25 mg, BD) and the dosage was regulated according to the patients' hemodynamic response. All the patients were monitored 5 days after the surgery and incidence of AF and other complications was recorded in both groups.

RESULTS

AF was detected in 18 patients in the carvedilol group and 21 patients in the metoprolol group (P = 0.577). The results of Fisher Exact test showed no significant relationship between the type of the drug and the occurrence of AF (P < 0.05). Nevertheless, the prevalence of AF was higher in the renal failure group. AF was mostly recorded on the second and third days after the surgery. The results showed an association between old age and higher occurrence of AF. AF was recorded in 11 patients (14%) in the metoprolol group and 9 ones (12%) in the carvedilol group, with Left Ventricle Ejection Fraction (LVEF) being between 35% and 45% (P = 0.587). However, no significant difference was found between the two groups in this regard.

CONCLUSIONS

In the patients with sufficient ejection fraction, no difference was observed in using carvedilol or metoprolol in prevention of post-CABG AF. Yet, given the anti-oxidant and anti- inflammatory effects of carvedilol, it might be more beneficial in comparison to metoprolol, particularly in the patients with lower ejection fractions or heart failure.

Carvedilol for prevention of atrial fibrillation after cardiac surgery: a meta-analysis

BACKGROUND

Postoperative atrial fibrillation (POAF) remains the most common complication after cardiac surgery. Current guidelines recommend β-blockers to prevent POAF. Carvedilol is a non-selective β-adrenergic blocker with anti-inflammatory, antioxidant, and multiple cationic channel blocking properties. These unique properties of carvedilol have generated interest in its use as a prophylaxis for POAF.

OBJECTIVE

To investigate the efficacy of carvedilol in preventing POAF.

METHODS

PubMed from the inception to September 2013 was searched for studies assessing the effect of carvedilol on POAF occurrence. Pooled relative risk (RR) with 95% confidence interval (CI) was calculated using random- or fixed-effect models when appropriate. Six comparative trials (three randomized controlled trials and three nonrandomized controlled trials) including 765 participants met the inclusion criteria.

RESULTS

Carvedilol was associated with a significant reduction in POAF (relative risk [RR] 0.49, 95% confidence interval [CI] 0.37 to 0.64, p<0.001). Subgroup analyses yielded similar results. In a subgroup analysis, carvedilol appeared to be superior to metoprolol for the prevention of POAF (RR 0.51, 95% CI 0.37 to 0.70, p<0.001). No evidence of heterogeneity was observed.

CONCLUSIONS

In conclusion, carvedilol may effectively reduce the incidence of POAF in patients undergoing cardiac surgery. It appeared to be superior to metoprolol. A large-scale, well-designed randomized controlled trial is needed to conclusively answer the question regarding the utility of carvedilol in the prevention of POAF.

Anti-inflammatory and pro-angiogenic effects of beta blockers in a canine model of chronic ischemic cardiomyopathy: comparison between carvedilol and metoprolol

There is controversy regarding the superiority of carvedilol (C) over metoprolol (M) in congestive heart failure. We hypothesized that C is superior to M in chronic ischemic cardiomyopathy because of its better anti-inflammatory and pro-angiogenic effects. In order to test our hypothesis we used a chronic canine model of multivessel ischemic cardiomyopathy where myocardial microcatheters were placed from which interstitial fluid was collected over time to measure leukocyte count and cytokine levels. After development of left ventricular dysfunction, the animals were randomized into four groups: sham (n = 7), placebo (n = 8), M (n = 11), and C (n = 10), and followed for 3 months after treatment initiation. Tissue was examined for immunohistochemistry, oxidative stress, and capillary density. At 3 months both rest and stress wall thickening were better in C compared to the other groups. At the end of 3 months of treatment end-systolic wall stress also decreased the most in C. Similarly resting myocardial blood flow (MBF) improved the most in C as did the stress endocardial/epicardial MBF. Myocardial interstitial fluid showed greater attenuation of leukocytosis with C compared to M, which was associated with less fibrosis and oxidative stress. C also had higher IL-10 level and capillary density. In conclusion, in a chronic canine model of multivessel ischemic cardiomyopathy we found 3 months of C treatment resulted in better resting global and regional function as well as better regional function at stress compared to M. These changes were associated with higher myocardial levels of the anti-inflammatory cytokine IL-10 and less myocardial oxidative stress, leukocytosis, and fibrosis. Capillary density and MBF were almost normalized. Thus in the doses used in this study, C appears to be superior to M in a chronic canine model of ischemic cardiomyopathy from beneficial effects on inflammation and angiogenesis. Further studies are required for comparing additional doses of these drugs.

Pediatric heart failure therapy with beta-adrenoceptor antagonists

Management of chronic heart failure in pediatrics has been altered by the adult literature showing improvements in mortality and hospitalization rates with the use of beta-adrenoceptor antagonists (beta-blockers) for routine therapy of all classes of ischemic and non-ischemic heart failure. Many pediatric heart failure specialists have incorporated these agents into their routine management of pediatric heart failure related to dilated cardiomyopathy or ventricular dysfunction in association with congenital heart disease. Retrospective and small prospective case series have shown encouraging improvements in cardiac function and symptoms, but interpretation has been complicated by the high rate of spontaneous recovery in pediatric patients. A recently completed pediatric double-blind, randomized, placebo-controlled clinical trial showed no difference between placebo and two doses of carvedilol over a 6-month period of follow-up, with significant improvement of all three groups over the course of evaluation. Experience with adults has suggested that only certain beta-blockers, including carvedilol, bisoprolol, nebivolol, and metoprolol succinate, should be used in the treatment of heart failure and that patients with high-grade heart failure may derive the most benefit. Other studies surmise that early or prophylactic use of these medications may alter the risk of disease progression in some high-risk subsets, such as patients receiving anthracyclines or those with muscular dystrophy. This article reviews these topics using experience as well as data from all the recent pediatric studies on the use of beta-blockers to treat congestive heart failure, especially when related to systolic ventricular dysfunction.

Carvedilol versus Metoprolol for the Prevention of Atrial Fibrillation After Off-Pump Coronary Bypass Surgery: Rationale and Design of the Carvedilol or Metoprolol Post-Revascularization Atrial Fibrillation Controlled Trial (COMPACT)

BACKGROUND

Postoperative new-onset atrial fibrillation (AF) remains the most common complication of coronary artery bypass graft surgery. Postoperative AF carries the risk of hemodynamic instability, increases the risk of thromboembolic events, and has a significant economic impact. Current guidelines recommend treatment with beta-blockers to prevent AF; information, however, is limited regarding the relative efficacy of beta-blocking agents. Carvedilol is a non-selective adrenergic blocker with anti-inflammatory, antioxidant, and multiple cationic channel blocking properties. These unique properties of carvedilol have generated interest in its use as a prophylaxis for postoperative AF.

MATERIALS AND METHODS

We hypothesize that carvedilol will be more effective than metoprolol, a conventional beta(1)-selective antagonist, in suppressing newly developed AF following off-pump coronary artery bypass (OPCAB) surgery. We have designed the Carvedilol or Metoprolol Post-Revascularization Atrial Fibrillation Controlled Trial (COMPACT) to test our hypothesis in a multi-center, open-label, randomized, and controlled trial. A total of at least 650 patients will be randomized to receive an initial oral dose of either 5 mg of carvedilol twice per day or 20 mg of metoprolol tartrate three times per day following surgery. The dose of each beta-blocker will be increased to the maximum tolerated dose. The primary endpoint is the incidence of new-onset AF during the first 7 days after surgery.

CONCLUSIONS

The COMPACT is the first multi-center, randomized, controlled trial to directly compare two different beta-blockers in patients following surgical coronary revascularization. Results of this trial will help to guide physicians in choosing appropriate medications following OPCAB surgery.

Nebivolol

Nebivolol is a third-generation beta-adrenoceptor antagonist. It differs from other beta-adrenoceptor antagonists as it combines highly selective beta(1)-adrenoceptor antagonist properties with nitric oxide-mediated vasodilatory actions and beneficial effects on endothelial function. Nebivolol is approved in Europe and several other countries for the treatment of essential hypertension and in Europe for the treatment of stable mild or moderate chronic heart failure (CHF) in addition to standard therapies in elderly patients aged >or=70 years. Nebivolol is an effective antihypertensive agent and is well tolerated in patients with hypertension. The drug also effectively decreased the composite endpoint of mortality and cardiovascular hospital admission in elderly patients with CHF and was generally well tolerated in this population. Nebivolol should be considered as an alternative first-line treatment option for patients with uncomplicated mild to moderate essential hypertension and in elderly patients with CHF.