Antioxidant properties of carvedilol and metoprolol in heart failure: a double-blind randomized controlled trial

Role of carvedilol in atrial fibrillation: insights from clinical trials

Atrial fibrillation affects approximately 2 million people in the United States and is a common comorbidity among patients with heart failure. Clinical studies indicate that the benefits of the beta-blocker carvedilol in patients with heart failure extend to patients with heart failure complicated by atrial fibrillation. The results of the Carvedilol in Atrial Fibrillation Evaluation (CAFE) trial provide support that carvedilol has incremental benefit when added to digoxin for the management of atrial fibrillation in patients with heart failure. Additional recent studies suggest that carvedilol may be useful in managing postsurgical atrial fibrillation and also may prevent recurrence of atrial fibrillation among patients who undergo cardioversion.

Carvedilol: a review of its use in chronic heart failure

Carvedilol (Dilatrend) blocks beta(1)-, beta(2)- and alpha(1)-adrenoceptors, and has antioxidant and antiproliferative effects. Carvedilol improved left ventricular ejection fraction (LVEF) in patients with chronic heart failure (CHF) in numerous studies. Moreover, significantly greater increases from baseline in LVEF were seen with carvedilol than with metoprolol in a double-blind, randomised study and in a meta-analysis. Carvedilol also reversed or attenuated left ventricular remodelling in patients with CHF and in those with left ventricular dysfunction after acute myocardial infarction (MI). Combined analysis of studies in the US Carvedilol Heart Failure Trials Program (patients had varying severities of CHF; n = 1094) revealed that mortality was significantly lower in carvedilol than in placebo recipients. In addition, the risk of hospitalisation for any cardiovascular cause was significantly lower with carvedilol than with placebo. Mortality was significantly lower with carvedilol than with metoprolol in patients with mild to severe CHF in the Carvedilol Or Metoprolol European Trial (COMET) [n = 3029]. The Carvedilol Prospective Randomised Cumulative Survival (COPERNICUS) trial (n = 2289) demonstrated that compared with placebo, carvedilol was associated with significant reductions in all-cause mortality and the combined endpoint of death or hospitalisation for any reason in severe CHF. All-cause mortality was reduced in patients who received carvedilol in addition to conventional therapy compared with those who received placebo plus conventional therapy in the Carvedilol Post-Infarct Survival Control in LV Dysfunction (CAPRICORN) trial (enrolling 1959 patients with left ventricular dysfunction following acute MI). Carvedilol was generally well tolerated in patients with CHF. Adverse events associated with the alpha- and beta-blocking effects of the drug occurred more commonly with carvedilol than with placebo, whereas placebo recipients were more likely to experience worsening heart failure. In conclusion, carvedilol blocks beta(1)-, beta(2)- and alpha(1)-adrenoceptors and has a unique pharmacological profile. It is thought that additional properties of carvedilol (e.g. antioxidant and antiproliferative effects) contribute to its beneficial effects in CHF. Carvedilol improves ventricular function and reduces mortality and morbidity in patients with mild to severe CHF, and should be considered a standard treatment option in this setting. Administering carvedilol in addition to conventional therapy reduces mortality and attenuates myocardial remodelling in patients with left ventricular dysfunction following acute MI. Moreover, mortality was significantly lower with carvedilol than with metoprolol in patients with mild to severe CHF, suggesting that carvedilol may be the preferred beta-blocker.

Do β-blockers prolong survival in heart failure only by inhibiting the β1-receptor? A perspective on the results of the COMET trial

Experimental and clinical studies indicate that carvedilol exerts multiple antiadrenergic effects in addition to beta(1)-receptor blockade, but the prognostic importance of these actions has long been debated. This controversy has now been substantially advanced by the results of the recently completed Carvedilol Or Metoprolol European Trial (COMET), which showed that carvedilol (25 mg twice daily) reduced mortality by 17% when compared with metoprolol (50 mg twice daily), P=.0017--a result that was consistent with the differences seen across earlier controlled trials with beta-blockers in survivors of an acute myocardial infarction and in patients with chronic heart failure. Questions have been raised about the interpretation of these findings in view of the fact that the trial did not use the dose or formulation of metoprolol that was shown to prolong life in a placebo-controlled trial (ie, Metoprolol CR/XL [Controlled Release] Randomized Intervention Trial in Heart Failure). Pharmacokinetic and pharmacodynamic analyses, however, indicate that the dosing regimen of metoprolol selected for use in the COMET trial produces a magnitude and time course of beta(1)-blockade during a 24-hour period that is similar to the dose of carvedilol targeted for use in the trial. These analyses suggest that the observed difference in the mortality effects of metoprolol and carvedilol is not related to a difference in the magnitude or time course of their beta(1)-blocking effects but instead reflect antiadrenergic effects of carvedilol in addition to beta(1)-blockade.

Comparison of effectiveness of carvedilol versus metoprolol or atenolol for atrial fibrillation appearing after coronary artery bypass grafting or cardiac valve operation

A retrospective review of 115 patients who underwent cardiac surgery demonstrated a marked reduction in postoperative atrial fibrillation (8% vs 32%, p <0.05) in patients who received carvedilol versus metoprolol or atenolol immediately after surgery. A prospective study examining the possibility of carvedilol's greater efficacy in preventing postoperative atrial fibrillation appears warranted.

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.

Present and future pharmacotherapy for heart failure

The pharmacotherapy currently recommended by the American College of Cardiology and the American Heart Association for heart failure (HF) is a diuretic, an angiotensin-converting enzyme inhibitor (ACEI), a beta-adrenoceptor antagonist and (usually) digitalis. This current treatment of HF may be improved by optimising the dose of ACEI used, as increasing the dose of lisinopril increases its benefits in HF. Selective angiotensin receptor-1 (AT(1)) antagonists are effective alternatives for those who cannot tolerate ACEIs. AT(1) antagonists may also be used in combination with ACEIs, as some studies have shown cumulative benefits for the combination. In addition to being used in Stage IV HF patients, in whom it has a marked benefit, spironolactone should be studied in less severe HF and in the presence of beta-blockers. The use of carvedilol, extended-release metoprolol and bisoprolol should be extended to severe HF patients as these agents have been shown to decrease mortality in this group. The ancillary properties of carvedilol, particularly antagonism at prejunctional beta -adrenoceptors, may give it additional benefits to selective beta(1)-adrenoceptor antagonists. Celiprolol and bucindolol are not the beta-blockers of choice in HF, as they do not decrease mortality. Although digitalis does not reduce mortality, it remains the only option for a long-term positive inotropic effect, as the long-term use of the phosphodiesterase inhibitors is associated with increased mortality. The calcium sensitising drug levosimendan may be useful in the hospital treatment of decompensated HF to increase cardiac output and improve dyspnoea and fatigue. The antiarrhythmic drug amiodarone should probably be used in patients at high risk of arrhythmic or sudden death, although this treatment may soon be superseded by the more expensive implanted cardioverter defibrillators, which are probably more effective and have fewer side effects. The natriuretic peptide nesiritide has recently been introduced for the hospital treatment of decompensated HF. Novel drugs that may be beneficial in the treatment of HF include the vasopeptidase inhibitors and the selective endothelin-A receptor antagonists but these require much more investigation. However, disappointing results have been obtained in a large clinical trial of the tumour necrosis factor alpha antagonist etanercept, where no likelihood of a difference between placebo and etanercept was observed. Small clinical trials with recombinant growth hormone to thicken ventricles in dilated cardiomyopathy have given variable results.

Attenuation of hypertension, cardiomyocyte hypertrophy, and myocardial fibrosis by beta-adrenoceptor blockers in rats under long-term blockade of nitric oxide synthesis

The effects of propranolol and atenolol were investigated on arterial hypertension, cardiomyocyte hypertrophy, and ventricular ischaemic lesions induced by an 8-week treatment with the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 20 mg/rat per day) in Wistar rats. Propranolol and atenolol (30 mg/rat per day each) were given in the drinking water concomitantly to L-NAME. Treatment with L-NAME induced marked arterial hypertension and cardiomyocyte hypertrophy, both of which were significantly reduced by propranolol and atenolol. A marked repairing fibrosis was also observed in L-NAME-treated rats and this was significantly attenuated in animals receiving the beta-blockers. In L-NAME group, 33% mortality was observed, whereas all the animals from the other groups survived. Our study demonstrates that propranolol and atenolol reduce arterial hypertension, cardiomyocyte hypertrophy and myocardial fibrosis induced by L-NAME, suggesting that beta-blockers are of beneficial value in treatment of vascular and cardiac alterations caused by chronic nitric oxide deficiency.