Prospective, randomized comparison of effect of long-term treatment with metoprolol or carvedilol on symptoms, exercise, ejection fraction, and oxidative stress in heart failure

Initiation and use of beta-blockers in class IV heart failure

Treatment of patients with heart failure caused by left ventricular systolic dysfunction using b-adrenergic receptor antagonists (or b-blockers) results in improvements in symptoms, hemodynamics, left ventricular remodeling, morbidity, and mortality. Most patients studied in prospective, randomized placebo-controlled trials have had New York Heart Association (NYHA) functional class II or III symptoms. The efficacy of b-blockers in treating NYHA class IV patients is not as well-established. This review summarizes the published experience regarding the use of b-blockers in patients with advanced heart failure. Although treatment requires considerable care, the data support attempts at initiation of b-blockers in this group of patients.

Beta-blockers in heart failure: Is more better?

Therapies that modulate the sympathetic nervous system and renin-angiotensin-aldosterone system reduce morbidity and mortality in patients with heart failure. However, they are grossly underused in clinical practice; when used, the doses prescribed are substantially smaller than the target doses used in the large-scale studies that established their utility. Whether these suboptimal doses are as effective in reducing morbidity and mortality is largely unknown. This review focuses on the relationship between the dose of b-blockers and their effect on clinical outcomes. Because direct dose comparisons of b-blockers are limited, we draw upon a broader spectrum of clinical trials across the cardiovascular continuum that involved neurohormonal modulators to address the question, "Is more better?"

Ventricular remodeling in heart failure and the effect of beta-blockade

Left ventricular (LV) remodeling has an important role in the progression of cardiovascular disease. An understanding of the process of LV remodeling has led to greater knowledge of the pathophysiology of heart failure. Drug therapies that slow or reverse the remodeling process seem to have favorable natural history effects in short-term and long-term therapy. Angiotensin-converting enzyme (ACE) inhibitors have been associated with a significant reduction in mortality, and the effect of beta-blockers on the remodeling process has now been studied across much of the spectrum of severity in patients with heart failure. beta-Blockade seems to add favorable and independent effects on the post-myocardial infarction remodeling process over and above those of ACE inhibitors. A combination of both drugs shows the greatest reduction in mortality (ie, the most favorable reverse remodeling). Differences in their effect on remodeling have been recently shown among the beta-blockers. Several studies and a meta-analysis suggest that carvedilol may be more favorable to outcome, having the most effect on LV remodeling.

Commentary on the Carvedilol or Metoprolol European Trial (COMET)

beta-Adrenergic blockade is commonly and successfully used to treat chronic heart failure. Until recently, few data were available on which to base selection of a particular beta-blocking agent. The Carvedilol or Metoprolol European Trial (COMET) provides evidence that beta-blockers are not interchangeable. The trial compared carvedilol, a nonselective beta-blocker with alpha-adrenergic blocking and numerous ancillary activities, with metoprolol tartrate. In comparison to metoprolol tartrate, significant reductions in all-cause mortality and cardiovascular mortality were observed with carvedilol. These data indicate that cardiovascular benefit may be obtained from switching patients from metoprolol tartrate to carvedilol.

Pharmacology of carvedilol

Carvedilol is a third-generation, neurohormonal antagonist with multiple activities. It blocks both beta(1)- and beta(2)-adrenergic receptors, enhances vasodilation via alpha(1)-adrenergic blockade, and, at high concentrations, has ion channel-blocking activities. Carvedilol lacks sympathomimetic activity. In addition to these well-known properties, carvedilol has a number of ancillary activities, including antioxidant, anti-inflammatory, and antiapoptotic properties. Together, they contribute to the clinical efficacy of carvedilol in a broad spectrum of patient types and may also confer a range of cardioprotective benefits.

Beta-adrenergic receptor blockade and the angiotensin-converting enzyme deletion polymorphism in patients with chronic heart failure

BACKGROUND

Beta-adrenergic receptor blockade is an established treatment of chronic heart failure (HF). Previous studies have suggested a potential pharmacogenetic interaction between beta-blocker therapy and the angiotensin-converting enzyme (ACE) I/D polymorphism in patients with HF.

AIMS

We designed this study to analyze changes in myocardial function of HF patients in response to beta-blocker therapy as a function of the ACE I/D polymorphism.

METHODS AND RESULTS

We studied 199 consecutive patients with chronic HF not treated with beta-blockers. Before initiation of beta-blockers and 3 months after the maximal tolerated dose was reached, patients underwent echocardiography, radionuclide angiography, and a cardiopulmonary exercise test. We extracted genomic DNA from white blood cells and determined the ACE I/D polymorphism. Thirty-five (18%) patients had the II genotype, 86 (43%) the ID genotype and 78 (39%) the DD genotype. A significant and similar improvement in left ventricular ejection fraction (LVEF) was observed in II (from 0.30+/-0.10 to 0.41+/-0.13; P<0.0001), ID (from 0.29+/-0.11 to 0.39+/-0.13; P<0.0001) and DD patients (from 0.31+/-0.11 to 0.40+/-0.13; P<0.0001). Peak Vo(2) before and after beta-blockade was similar among the three groups. The proportion of responders to beta-blockers (patients without cardiac events during titration who had an increase in LVEF >5% after beta-blockers) was similar among the three groups (II: 65.9%%, ID: 60.6%%, DD: 65.9%; P=NS). During a median follow-up of 933 days, there was no evidence for any effect of ACE I/D polymorphism on cardiac survival.

CONCLUSIONS

We observed no evidence of pharmacogenetic interaction between the ACE I/D polymorphism and the effects of beta-blockade on LVEF and other prognostic parameters in patients with chronic HF. Our results support the initiation of beta-blockers in HF patients with the II or the ID genotype as well as in those with the DD genotype.

Selective versus nonselective beta-blockade for heart failure therapy: are there lessons to be learned from the COMET trial?

The recently reported COMET trial found that the beta1/beta2/alpha1 receptor blocking agent carvedilol given in a relatively high beta1-receptor blocking dose regimen was superior in mortality reduction to immediate release metoprolol given in a relatively low beta1-receptor blocking dose schedule. We analyze the problems with the trial design of COMET from the standpoint of comparing 2 therapeutic agents at different positions on a common dose-response curve, and discuss the theoretical reasons why postjunctional adrenergic receptor blockade that is in addition to beta1-receptor antagonism will likely produce only minimal or no incremental benefit in chronic heart failure.

Efficacy of amiodarone treatment on cardiac symptom, function, and sympathetic nerve activity in patients with dilated cardiomyopathy: comparison with beta-blocker therapy

BACKGROUND

Amiodarone, which is an antiarrhythmic drug used to treat life-threatening arrhythmias, is effective in patients with chronic heart failure. However, its effectiveness compared with beta-blockers has not yet been reported.

METHODS AND RESULTS

In 30 patients (mean age, 57 +/- 13 years) with dilated cardiomyopathy, we compared 15 patients receiving amiodarone (group A) with 15 patients receiving metoprolol (group B). Before and after 1 year of treatment, cardiac iodine 123 metaiodobenzylguanidine uptake was assessed from the total defect score, heart-to-mediastinum activity ratio based on delayed images, and washout rate. New York Heart Association class and echocardiographic left ventricular ejection fraction were also assessed. In both groups the total defect score decreased (from 25 +/- 11 to 16 +/- 10 in group A, P <.01; from 26 +/- 10 to 18 +/- 11 in group B, P <.01), the heart-to-mediastinum activity ratio increased (from 1.63 +/- 0.16 to 1.81 +/- 0.29 in group A, P <.01; from 1.63 +/- 0.21 to 1.85 +/- 0.3 in group B, P <.01), and the washout rate decreased (from 51% +/- 12% to 38% +/- 14% in group A, P <.01; from 48% +/- 11% to 37% +/- 8% in group B, P <.01). Left ventricular ejection fraction increased (from 30% +/- 9% to 42% +/- 11% in group A, P <.01; from 26% +/- 7% to 46% +/- 16% in group B, P <.01) and New York Heart Association functional class improved (from 3.1 +/- 0.5 to 1.8 +/- 0.7 in group A, P <.01; from 2.9 +/- 0.5 to 1.7 +/- 0.6 in group B, P <.01).

CONCLUSION

Amiodarone treatment can improve cardiac symptom, function, and sympathetic nerve activity, as evaluated by I-123 metaiodobenzylguanidine imaging in patients with dilated cardiomyopathy, which improves to a similar extent with beta-blocker treatment.

Cardioprotective effects of carvedilol on acute autoimmune myocarditis: anti-inflammatory effects associated with antioxidant property

Carvedilol, a new β-blocker with antioxidant properties, has been shown to be cardioprotective in experimental models of myocardial damage. We investigated whether carvedilol protects against experimental autoimmune myocarditis (EAM) because of its suppression of inflammatory cytokines and its antioxidant properties. We orally administered a vehicle, various doses of carvedilol, racemic carvedilol [ R(+)-carvedilol, an enantiomer of carvedilol without β-blocking activity], metoprolol, or propranolol to rats with EAM induced by porcine myosin for 3 wk. Echocardiographic study showed that the three β-blockers, except R(+)-carvedilol, suppressed left ventricular fractional shortening and decreased heart rates to the same extent. Carvedilol and R(+)-carvedilol, but not metoprolol or propranolol, markedly reduced the severity of myocarditis at the two different doses and suppressed thickening of the left ventricular posterior wall in rats with EAM. Only carvedilol suppressed myocardial mRNA expression of inflammatory cytokines and IL-1β protein expression in myocarditis. In addition, carvedilol and R(+)-carvedilol decreased myocardial protein carbonyl contents and myocardial thiobarbituric acid-reactive substance products in rats with EAM. The in vitro study showed that carvedilol and R(+)-carvedilol suppressed IL-1β production in LPS-stimulated U937 cells and that carvedilol and R(+)-carvedilol, but not metoprolol or propranolol, suppressed thiobarbituric acid-reactive substance products in myocardial membrane challenged by oxidative stress. It was also confirmed that probucol, an antioxidant, ameliorated EAM in vivo. Carvedilol protects against acute EAM in rats, and the superior cardioprotective effect of carvedilol compared with metoprolol and propranolol may be due to suppression of inflammatory cytokines associated with the antioxidant properties in addition to the hemodynamic modifications.

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.

Measurement of carvedilol in plasma by high-performance liquid chromatography with electrochemical detection

Carvedilol is a beta/alpha1-adrenoceptor blocker. A sensitive method for measuring plasma levels of carvedilol in human administrated low doses is needed since its plasma concentration is low. We measured carvedilol and carvedilol M21-aglycon using high-performance liquid chromatography (HPLC) with electrochemical detection. The amperometric detector was operated at 930 mV versus Ag/AgCl. Mean coefficients of variation (n = 5) for carvedilol and M21-aglycon were 4.0 and 7.7% (intra) and 6.1 and 6.7% (inter), respectively. The lower limit of quantification for each analyte was 0.10 ng/ml (signal-to-noise ratio = 3). This lower limit of quantification for carvedilol was sufficient for clinical use.

Beta-blockers for chronic heart failure: surviving longer but feeling better?

Beta-blockers, as determined by four landmark placebo-controlled studies, impart a significant survival advantage to the chronic heart failure population. What ancillary benefits might be expected from beta-blockade, in terms of symptom relief and improvement in exercise capacity, is less clear. This situation in part reflects the heterogeneity of tools used to quantify quality of life and exercise performance as well as factors concerning the statistical handling of symptom and exercise data. In this review we explore the methodology and results of over 20 trials of carvedilol, metoprolol and bisoprolol where quality of life and measures of exercise capacity were end-points. A consistent message relating to a benefit from beta-blockade on these outcomes was elusive but the finding that patients on beta-blockers did at least as well as patients prescribed placebo was a unanimous verdict. There remains a dearth of data to help identify those patients that are at high risk of adverse events from beta-blocker therapy.

Effects of angiotensin receptor blockade on haemodynamics and gene expression after myocardial infarction

INTRODUCTION

Despite the fact that congestive heart failure (CHF) remains the most common disease in the developed world and has been extensively studied, there is little known about the molecular and cellular mechanisms of cardiac dysfunction. Angiotensin has been implicated as a mediator of cardiac injury; however, the mechanisms of its action have not been delineated. The objective of this study was to examine the relationship between the haemodynamic and molecular events during cardiac dysfunction and the role of the angiotensin system.

STUDY DESIGN

We examined the effects of the angiotensin receptor blocker, valsartan, on changes in the haemodynamic and gene expression patterns in a postmyocardial infarction model in the rat.

METHODS

Myocardial infarction (MI) was induced in rats by coronary artery ligation. Cardiac haemodynamics were monitored using echocardiography. Gene expression profiles after myocardial infarction were identified using Affymetrix Genechip oligonucleotide arrays.

RESULTS

Myocardial contractility, as assessed by cardiac output and left ventricle (LV) fraction of shortening, was reduced in untreated animals by week 3 after MI (p < 0.05 versus baseline), and preserved with valsartan treatment as observed by the nonsignificant changes versus baseline. LV dilatation, as demonstrated by increases in LV systolic and diastolic diameters, developed by week 3 in untreated animals (p < 0.05 versus baseline) while valsartan-treated animals were protected and showed no significant increases in diameter size compared with baseline. LV hypertrophy, as shown by LV posterior wall thickness, was more profound in untreated animals (p < 0.05 versus baseline) than in those treated with valsartan at weeks 3 and 4. Changes in gene expression at 4 weeks after MI included those encoding muscle-specific genes, fibrous tissue proliferation, immune response and various others. Treatment with valsartan reversed these changes in 67% of overexpressed genes and 83% of underexpressed genes.

CONCLUSION

Angiotensin receptor blockade with valsartan was found to protect cardiac function, and this beneficial effect was accompanied by a reversal of changes in gene expression induced by MI.

Should beta-blockers be used for the treatment of pediatric patients with chronic heart failure?

In multiple clinical trials, beta-blockers have been shown to significantly improve morbidity and mortality in adults with chronic congestive heart failure, but there is little reported experience with their use in children. Heart failure involves activation of the adrenergic nervous system and other neurohumoral systems in order to maintain cardiovascular homeostasis. These compensatory mechanisms have been shown to cause myocardial damage with chronic activation, which has been hypothesized to be a major contributing factor to the clinical deterioration of adults with heart failure. Studies have demonstrated inhibition of this neurohumoral response and concomitant clinical benefits with beta-blockers. Consequently, beta-blockers have evolved to become an important part of comprehensive medical therapy for congestive heart failure in adults. Pediatric heart failure represents an entirely different spectrum of disease, caused more commonly by congenital heart disease than cardiomyopathy. Surgical palliation and correction are important components of pediatric heart failure therapy, and residual, postsurgical cardiac lesions can lead to chronic heart failure. Although neurohumoral activation in children is similar to that in adults with heart failure, there are important differences from adults in physiology and developmental changes that are especially observed in infants. Current published clinical experience with beta-blocker use in children with heart failure is limited to case series with relatively small numbers of patients. Nevertheless, these series show consistent symptomatic improvement, and improvement in ventricular systolic function in patients with cardiomyopathies and congenital heart disease, similar to findings in adults. Adverse effects were common and many patients in these studies had adverse outcomes (death and/or need for transplantation). One study has noted differences in pharmacokinetics in children compared with adults. However, a multicenter, randomized controlled trial to evaluate carvedilol in pediatric heart failure from systolic ventricular dysfunction is currently ongoing and should help to clarify the efficacy and tolerability of carvedilol in children.

Expanding role of beta-blockade in the management of chronic heart failure

Although recent advances have been made in the treatment of heart failure, this disease continues to result in significant morbidity and mortality. Among the negative effects associated with progression of heart failure are decline in myocardial reserve, decreased exercise tolerance, decreased contractile function, and altered cardiac gene expression. Guidelines recommend neurohormonal antagonists for treatment and stress the importance of angiotensin-converting enzyme inhibition and beta-blockade in reversing the cardiac remodeling process. beta-Blockade slows or reverses the adverse effects resulting from chronic adrenergic stimulation. Traditionally, beta-blockers were reserved for mild-to-moderate heart failure, based on evidence from large, randomized clinical trials showing their positive effects on myocardial function and clinical outcomes. More recently, clinical data reveal that the agents can be expanded to patients with severe heart failure and those with left ventricular systolic dysfunction after myocardial infarction. Individual beta-blocking agents vary in their pharmacology and dosing requirements. These variations may influence treatment decisions and affect clinical measurements of left ventricular function and ventricular remodeling.

PKA phosphorylation activates the calcium release channel (ryanodine receptor) in skeletal muscle: defective regulation in heart failure

The type 1 ryanodine receptor (RyR1) on the sarcoplasmic reticulum (SR) is the major calcium (Ca2+) release channel required for skeletal muscle excitation-contraction (EC) coupling. RyR1 function is modulated by proteins that bind to its large cytoplasmic scaffold domain, including the FK506 binding protein (FKBP12) and PKA. PKA is activated during sympathetic nervous system (SNS) stimulation. We show that PKA phosphorylation of RyR1 at Ser2843 activates the channel by releasing FKBP12. When FKB12 is bound to RyR1, it inhibits the channel by stabilizing its closed state. RyR1 in skeletal muscle from animals with heart failure (HF), a chronic hyperadrenergic state, were PKA hyperphosphorylated, depleted of FKBP12, and exhibited increased activity, suggesting that the channels are "leaky." RyR1 PKA hyperphosphorylation correlated with impaired SR Ca2+ release and early fatigue in HF skeletal muscle. These findings identify a novel mechanism that regulates RyR1 function via PKA phosphorylation in response to SNS stimulation. PKA hyperphosphorylation of RyR1 may contribute to impaired skeletal muscle function in HF, suggesting that a generalized EC coupling myopathy may play a role in HF.

Beta-blockers for heart failure: why, which, when, and where

Beta-blockers are a highly effective treatment for patients with all grades of heart failure secondary to LV systolic dysfunction. Beta-blockers are best deployed as a form of tertiary prevention in heart failure but have a very limited role for the treatment of a heart failure crisis. Physicians and patients need to understand the time course of the effects of beta-blocker therapy. The initial effects are often neutral or adverse, though the benefits, at least of carvedilol, may be apparent within days in patients with severe heart failure. Benefits accumulate gradually over a period of weeks to months. Some patience, perseverance, and education are required in order to allow patients to reap the full benefits of beta-blocker therapy for this malignant disease. Initiation of treatment early in the course of the disease maximizes the effectiveness and acceptance of therapy. Trials are under way to determine whether the benefits of beta-blockers extend to patients over 80 years of age and to those with preserved LV systolic function. It is likely that important differences exist between beta-blockers in terms of their clinical benefit, though whether differences exist between the agents that have been reported to be effective so far awaits the outcome of a large clinical trial. It is unclear whether the target doses of beta-blockers currently recommended are optimal.

Anti-oxidative properties of beta-blockers and angiotensin-converting enzyme inhibitors in congestive heart failure

BACKGROUND

Chronic elevation of plasma catecholamines and sympathetic stimulation in chronic heart failure (CHF) leads to increased production of free radicals, and so possibly to endothelial damage/dysfunction and atheroma formation. Abnormal oxidative stress may therefore be related to some of the high mortality and morbidity in CHF. The objective of the present prospective open study was to compare the effects of beta-blockers and ACE inhibitors in relation to oxidative stress and endothelial damage in CHF.

METHODS

We studied 66 outpatients with CHF: 46 patients were established on an ACE inhibitor and were then started on a beta-blocker, and 20 patients not previously on ACE-inhibitors were started on lisinopril. Baseline levels of the measured parameters were compared to 22 healthy control subjects. Serum lipid hydroperoxides (LHP) and total antioxidant capacity (TAC) were determined as indices of oxidative damage and antioxidant defence, and plasma von Willebrand factor (vWf) as an index of endothelial damage/dysfunction.

RESULTS

Baseline indices for the measures of oxidative damage and endothelial function in the 66 CHF patients were significantly higher than healthy control subjects [median LHP 7.5 (5.9-12.6) vs. 4.8 micromol/l, P=0.0022; TAC 428 (365-567) vs. 336 Trollox Eq. Units, P=0.0005; mean vWf 134+/-27 vs. 89+/-23 IU/dl, P<0.0001]. Following 3 months of maintenance therapy with beta-blockers, there was significant reduction in LHP levels, but not TAC or vWf. ACE inhibitor therapy also significantly reduced vWf levels, but failed to have any statistically significant effects on LHP or TAC.

CONCLUSION

This pilot study suggests that oxidative stress in CHF may be due to increased free radical production or inefficient free radical clearance by scavengers. beta-Blockers, but not ACE inhibitors, reduced lipid peroxidation in patients with CHF. No relation was demonstrated between a reduction in oxidative damage and endothelial damage/dysfunction.

Differential effects of carvedilol and atenolol on plasma noradrenaline during exercise in humans

AIMS

Evidence of long-term beneficial effects of beta-blockers on mortality and morbidity in patients with heart failure has been demonstrated in recent randomized trials. However, not all beta-blockers are identical. Carvedilol, a nonselective beta- and alpha-adrenergic blocker, can potentially blunt the release of noradrenaline by blocking presynaptic beta2-adrenergic receptors. To test this hypothesis, we have compared the effects of carvedilol and atenolol on plasma noradrenaline during exercise in healthy young volunteers.

METHODS

This study investigated the differential effects of 2 weeks pretreatment with carvedilol 25 mg day(-1) and atenolol 50 mg day(-1) on plasma noradrenaline at rest and during exercise on a treadmill in a double-blind randomized crossover study, involving 12 healthy male volunteers (mean age 21.6 +/- 0.3 years).

RESULTS

Haemodynamic parameters at rest and during exercise were not significantly different in either carvedilol or atenolol pretreatment groups. However, carvedilol pretreatment significantly blunted the increase in plasma noradrenaline during exercise [393.8 +/- 51.7 pg ml(-1) (pretreatment) to 259.7 +/- 21.2 pg ml(-1) (post-treatment)], when compared with atenolol [340.4 +/- 54.6 pg ml(-1) (pretreatment) to 396.2 +/- 32.0 pg ml(-1) (post-treatment)]. The difference between carvedilol and atenolol (95% confidence interval) was -145.2, -351.0, P < 0.05.

CONCLUSIONS

We have demonstrated that carvedilol but not atenolol significantly blunted the increase in plasma noradrenaline during exercise. These findings may suggest a sympathoinhibitory effect of carvedilol that may enhance its ability to attenuate the cardiotoxicity associated with adrenergic stimulation in patients with 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.

Intermediate effects of treatment with metoprolol or carvedilol in children with left ventricular systolic dysfunction

The use of beta-blocking agents in adults with congestive heart failure has been shown to improve symptoms and outcome; however, experience in pediatric patients with left ventricular systolic dysfunction is limited. We identified 12 pediatric patients treated with beta-blocking agents for left ventricular systolic dysfunction and reviewed echocardiographic indices of left ventricular systolic performance prior to initiation of beta-blocker therapy and at intermediate follow-up. Left ventricular fractional shortening and ejection fraction increased significantly from baseline to intermediate follow-up (13 +/- 4% to 21 +/- 8% [p = 0.01] and 26 +/- 8% to 41 +/- 17% [p = 0.04], respectively). When added to conventional therapy, beta-blocker therapy resulted in an increase in ejection-phase indices of left ventricular systolic performance at intermediate follow-up in pediatric patients with systolic dysfunction.

[Persistence of oxidative stress after heart transplantation: a comparative study of patients with heart transplant versus chronic stable heart failure]

INTRODUCTION AND OBJECTIVE

Chronic heart failure (CHF) is associated with oxidative stress. Heart transplantation, an important therapeutic alternative in these patients, could reduce oxidative stress by improving cardiac function. Our aim was to evaluate post-heart transplantation oxidative stress.

PATIENTS AND METHOD

We studied three experimental groups: a) heart transplant recipients without evidence of rejection (n = 11); b) NYHA class III CHF patients (n = 19), and c) healthy control subjects (n = 14). Oxidative stress was assessed by measuring plasma malondialdehyde levels (MDA), and determining the enzymatic activities of glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD).

RESULTS

The demographic characteristics of the three groups were similar. Mean time from transplantation was 20.0 4.8 months. Mean MDA plasma levels in heart transplantation and CHF patients were significantly higher than in normal subjects (3.35 0.8; 3.27 1.7 y 0.9 0.3 microM, respectively). GSH-Px activity increased after transplantation compared to control subjects (0.40 0.06 and 0.33 0.05 U/g Hb, respectively), but not the CHF group. A significant decrease in SOD activity was found in the heart transplant vs. CHF group (0.44 0.1 vs. 0.87 0.6 U/mg Hb). There were no differences in CAT values between heart transplant and CHF patients.

CONCLUSION

These findings demonstrated the presence of permanent oxidative stress in patients who have undergone heart transplantation, characterized by an increase in MDA and a decrease in SOD activity, despite an increase in GSH-Px activity.

Effect of carvedilol on microcirculatory and glucose metabolic regulation in patients with congestive heart failure secondary to ischemic cardiomyopathy

In a randomized (2:1), double-blinded design study, we studied 25 patients with congestive heart failure (66 +/- 9 years, ejection fraction 30 +/- 7%) before and after 23-week treatment with the beta blocker carvedilol 25 mg twice daily (n = 17) or placebo (n = 8) in addition to standard therapy. Using dynamic positron emission tomography, myocardial perfusion at rest and perfusion reserve after dipyridamole (0.56 mg/kg/min) were measured. Myocardial glucose uptake and plasma levels of catecholamines were also estimated. Carvedilol treatment reduced the rate-pressure product (8,781 +/- 2,672 vs 6,342 +/- 1,346, p <0.01) and improved ejection fraction (29 +/- 7% vs 37 +/- 11%, p <0.001), whereas no changes were observed in the control group. Perfusion at rest was unchanged in the placebo group (0.81 +/- 0.17 vs 0.86 +/- 0.23 ml/g/min, p = NS), whereas the carvedilol-treated group showed a significant reduction (0.88 +/- 0.26 vs 0.75 +/- 0.16 ml/g/min, p <0.05). Dipyridamole-induced hyperemia was significantly reduced after carvedilol treatment (1.51 +/- 0.45 vs 1.31 +/- 0.51 ml/g/min, p <0.001), whereas myocardial perfusion reserve was unaltered. Carvedilol did not alter myocardial glucose uptake (0.33 +/- 0.14 vs 0.32 +/- 0.12 micromol/g/min, p = NS) or the plasma catecholamines levels. We therefore conclude that in patients with congestive heart failure, carvedilol reduced resting and hyperemic perfusion. No effect on glucose uptake or catecholamine levels was observed. The reduced perfusion at rest must reflect reduced perfusion demand and thereby a higher threshold for myocardial ischemia and protection against myocardial damage or malignant arrhythmia. These effects may serve as a pathophysiologic explanation for the reduced mortality in patients with congestive heart failure who receive carvedilol.

Cardiovascular and renal effects of carvedilol in dogs with heart failure

To determine the acute effects of carvedilol (beta-blocker) on cardiovascular and renal function and its pharmacokinetics in dogs. Fifteen mature mongrel dogs (7-15 kg) of both sexes were used in these experiments. Eight dogs served as controls, and seven dogs served as iatrogenic mitral regurgitation (MR) experimental animals. Carvedilol (0.2, 0.4, and 0.8 mg/kg, P.O.) was administered, and the blood carvedilol concentration was analyzed by reverse-phase high-performance liquid chromatography. The response to isoproterenol or phenylephrine was also evaluated. Isoproterenol (0.025 microg/kg/min) was infused via the saphenous vein for 5 min, and phenylephrine (5 microg/kg) was injected with carvedilol (0.2, 0.4 mg/kg) or placebo for 4 days. The heart rate and arterial blood pressure were measured, and LV fractional shortening was measured by echocardiography. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by intravenous infusion of sodium thiosulfate and sodium para-aminohippurate. Carvedilol (0.2 mg/kg) decreased the heart rate, whereas renal function, arterial blood pressure, and left ventricular contractile function were not affected. Carvedilol (0.4 mg/kg) decreased heart rate, blood pressure, and renal function. The tachycardic response to isoproterenol was significantly diminished for 36 hr by 0.4 mg/kg carvedilol. Carvedilol 0.2 mg/kg inhibited this effect for 24 hr. Thus, it is necessary to titrate the dosage of carvedilol, it should be initiated at less than 0.2 mg/kg and titrated up to 0.4 mg/kg for heart failure dogs.

Carvedilol therapy in pediatric patients with congestive heart failure: a study investigating clinical and pharmacokinetic parameters

OBJECTIVE

Our purpose was to evaluate the clinical effect of carvedilol among pediatric patients with congestive heart failure (CHF) who did not respond to standard therapy and to assess the pharmacokinetics of carvedilol among these children.

METHODS

In this prospective, open intervention trial with blinded interpretation of selected end points, patients with CHF who did not improve on standard therapy, including digoxin, angiotensin-converting enzyme inhibitors, and diuretics, were treated with oral carvedilol in a ramped dosing scheme. Clinical parameters (ejection fraction, fractional shortening, and modified Ross score) were assessed before initiation of treatment and monthly for 6 months. Pharmacokinetic profiles of carvedilol were determined over the first 12-hour period after the initial dose in study patients, and for comparison, in 9 healthy adult volunteers.

RESULTS

Fifteen patients (aged 6 weeks to 19 years) were enrolled in the study, including 10 patients with dilated cardiomyopathy and 5 with CHF secondary to congenital heart disease. All 15 patients tolerated carvedilol for the duration of the trial, and all achieved maximum target dosing. After 6 months of carvedilol therapy, ejection fraction increased (36% vs 54%; P <.05) and modified Ross Score improved (5 +/- 2 vs 3 +/- 3; P <.05). Elimination half-life was about 50% shorter in pediatric CHF patients compared with healthy adult volunteers (2.9 vs 5.2 hours; P <.05).

CONCLUSIONS

Pediatric patients with CHF not responding to standard therapy may benefit from oral carvedilol treatment. The observed increased elimination of carvedilol in children suggests that optimal dosing strategies need to be further defined among the pediatric population.

Reimbursement claims analysis of outcomes with carvedilol and metoprolol

OBJECTIVE

To compare resource use and costs in heart failure (HF) patients receiving metoprolol, a selective beta1-receptor blocker, with carvedilol, which blocks beta1-, beta2-, and alpha1-adrenergic receptors, by use of a retrospective reimbursement-claims analysis.

METHODS

Resource use and cost data were extracted for patients diagnosed with HF and treated with carvedilol or metoprolol for 6 months after the initiation of the respective therapy, by use of claims submitted to 6 healthcare plans. A modified Charlson index was used to assess comorbidity. Stepwise logistic regression was used to measure the influence of treatment on hospitalization.

RESULTS

Claims from 139 carvedilol and 106 metoprolol patients showed that carvedilol patients experienced significantly fewer total hospitalizations (36.0% vs. 62.3%, respectively; p < 0.001) and emergency department visits (23.7% vs. 42.5%, respectively; p = 0.002) and a trend for fewer HF-related (7.9% vs. 14.2%, respectively; NS) and cardiac-related hospitalizations (15.1% vs. 24.5%, respectively; NS). Treatment with carvedilol was associated with a significant decrease in the risk of any hospitalization (adjusted odds ratio 0.35, 95% CI 0.20 to 0.63; p <0.001). Higher pharmacy costs (mean $1677 vs. $1322; p <0.001) and lower total costs (mean $8100 vs. $14475; p = 0.025) were observed in carvedilol-treated compared with metoprolol-treated patients, respectively.

CONCLUSIONS

Compared with metoprolol, the more comprehensive adrenergic blockade achieved with carvedilol may translate into greater clinical benefits in patients with HF. Despite higher pharmacy costs, lower total costs were observed in carvedilol-treated patients.

The oxidative stress hypothesis of congestive heart failure: radical thoughts

There is extensive experimental evidence from in vitro and animal experiments that congestive heart failure (CHF) is a state of oxidative stress. Moreover, in animal models, the development of CHF is accompanied by changes in the antioxidant defense mechanisms of the myocardium as well as evidence of oxidative myocardial injury. This has led to the hypothesis that oxidative stress may be a mechanism of disease progression in CHF. Indeed, many patients consume antioxidant supplements making the assumption that no harm will result and, possibly, that this therapy will yield some clinical benefits. The focus of this review is to examine the oxidative stress hypothesis of CHF as it pertains to humans. To date, human studies that have sought evidence for a role of oxidative stress in patients with CHF have fallen short of providing strong support for this hypothesis. Studies that have demonstrated an association between oxidant stress and CHF are small and are hindered by methodologic limitations that diminish the impact of their conclusions. Randomized trials of antioxidant supplementation for CHF are scarce, and to our knowledge no study yet convincingly demonstrates any benefit from consuming antioxidant supplements. Therefore, the available evidence is insufficient to support or negate the oxidative stress hypothesis of CHF and the use of antioxidants cannot be recommended as a specific therapy for this condition.

Dose-related effects of metoprolol on heart rate and pharmacokinetics in heart failure

BACKGROUND

The pharmacokinetics and pharmacodynamics of immediate-release (IR) metoprolol, 50 mg 3 times daily, were compared with those of different doses of controlled-release/extended-release metoprolol (CR/XL) given once daily.

METHODS AND RESULTS

Fifteen patients with chronic heart failure were randomized to a 3-way crossover study to receive metoprolol IR 50 mg 3 times daily, CR/XL 100 mg once daily, and CR/XL 200 mg once daily for 7 days. On the seventh day of each treatment, serial plasma samples were drawn and standardized exercise tests and a 24-hour Holter recording were performed. Metoprolol IR 50 mg produced peak plasma levels comparable to those observed for CR/XL 200 mg (285 v 263 nmol/L). The difference in mean 24-hour heart rate between CR/XL 100 mg and IR 50 mg was 1.0 bpm (95% confidence interval [CI]), -2.9 to 4.9; NS) compared with -3.8 bpm (95% CI, -7.6 to -0.04; P = .048) between CR/XL 200 mg and IR 50 mg. Submaximal exercise heart rate was lower for patients receiving CR/XL 200 mg than those receiving IR 50 mg. No difference in tolerance or exercise performance was observed between treatment regimens.

CONCLUSIONS

Peak plasma levels produced by metoprolol 200 mg CR/XL were similar to those of 50 mg IR. Metoprolol CR/XL 200 mg was associated with a more pronounced suppression of heart rate than metoprolol IR 50 mg. It is suggested that patients can safely be switched from multiple dosing of metoprolol IR 50 mg to a once-daily dose of metoprolol CR/XL.

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.

Comparative left ventricular functional and neurohumoral effects of chronic treatment with carvedilol versus metoprolol in patients with dilated cardiomyopathy

The efficacy of treating dilated cardiomyopathy with metoprolol was compared with that of carvedilol. Metoprolol was administered to 29 patients, and carvedilol to 62. Patients who could not be dosed with up to 40 mg daily of metoprolol or 20 mg daily of carvedilol were defined as intolerant. As well as the tolerability of these beta-blockers, the effects on left ventricular end-diastolic dimension (LVDd), fractional shortening (FS), plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations, the delayed heart and mediastinum (H/M) ratio determined from metaiodobenzylguanidine imaging were compared. Drug intolerance occurred in 24% of patients in the metoprolol group and 19% in the carvedilol group. Among the drug-tolerant patients, LVDd, FS and plasma BNP concentration improved in both groups and to the same degree. Only 25% of drug-tolerant patients in the metoprolol group had a delayed H/M ratio below 1.9 compared with 57% in the carvedilol group. Both metoprolol and carvedilol, when tolerated, improve cardiac function and neurohumoral factors to the same degree. However, carvedilol is preferable to metoprolol for patients with a low delayed H/M ratio.

Long-term effect of atenolol on ejection fraction, symptoms, and exercise variables in patients with advanced left ventricular dysfunction

AIMS

We recently reported a beneficial clinical effect of atenolol, a beta(1) selective adrenergic antagonist, in 100 ambulatory heart failure patients with low left ventricular ejection fraction (LVEF, <or=25%) who were receiving background therapy with 40 mg/day enalapril. In this sub-study, we investigated the effects of atenolol vs placebo on LVEF, New York Heart Association (NYHA) class, workload, and peak oxygen consumption (Vo(2)).

METHODS AND RESULTS

We included 43 patients (23 receiving atenolol, 20 receiving placebo) who had similar entry characteristics. We evaluated LVEF once a year and evaluated workload, pVO(2), and NYHA class before and after 6, 12, and 24 months. Repeated measures of analysis of variance were used for comparison of serial measurements. After 2 years, both atenolol (18% +/- 5% vs 36% +/- 18%, p < 0.05) and placebo (18% +/- 5% vs 23% +/- 5%, p < 0.05) increased LVEF, with a more pronounced effect of atenolol (p = 0.02), which also changed NYHA class distribution more favorably over time (p < 0.05). Workload and peak Vo(2) increased after atenolol (110 +/- 47 vs 140 +/- 48 watts, p < 0.05, and 18 +/- 5 vs 21 +/- 5 ml/kg/min, p < 0.05) but not after placebo (100 +/- 35 vs 110 +/- 38 watts, p < 0.05, between groups and 17 +/- 4 vs 19 +/- 7 ml/kg/min, not significant, between groups).

CONCLUSIONS

In patients with advanced heart failure who tolerate long-term atenolol vs placebo treatment added to high-dose enalapril for 2 years without cardiac events, systolic left ventricular function is markedly improved. These patients experience greater relief of symptoms and increased exercise tolerance.

Lack of evidence for peripheral alpha(1)- adrenoceptor blockade during long-term treatment of heart failure with carvedilol

OBJECTIVES

The purpose of this study was to determine whether carvedilol's alpha(1)-adrenoceptor antagonism persists during long-term therapy of patients with congestive heart failure (CHF).

BACKGROUND

Carvedilol and metoprolol differ in that carvedilol also antagonizes beta(2)- and alpha(1)-adrenoceptors. We hypothesized that in contrast to metoprolol, carvedilol would increase calf vascular conductance (CVC), blunt neurally mediated vasoconstriction and attenuate neuroeffector transfer function gain.

METHODS

We randomized 36 patients with CHF (age 55 +/- 1 years, ejection fraction 19 +/- 1%, means +/- SE) to either drug. Blood pressure (BP), heart rate, muscle sympathetic nerve activity (MSNA) and CVC were assessed before and after four months of treatment. The variability of BP and MSNA was determined using fast Fourier transformation.

RESULTS

Paired data were obtained in 23 (carvedilol, 13; metoprolol, 10) subjects. Both beta-blockers decreased heart rate, but neither affected mean BP or CVC (carvedilol: 0.016 +/- 0.002 to 0.018 +/- 0.003 U; metoprolol: 0.020 +/- 0.002 to 0.020 +/- 0.004 U). Isometric handgrip exercise (30% of maximum) increased heart rate, mean BP and MSNA. The calf vasoconstrictor response to handgrip exercise was not affected by carvedilol (from 16 +/- 6 resistance U to 25 +/- 10 resistance U, NS). The gain of the transfer of oscillations in MSNA into BP under resting conditions was not attenuated by carvedilol.

CONCLUSIONS

Carvedilol did not increase CVC, blunt the calf vasoconstrictor response to handgrip or attenuate the gain of the neuroeffector transfer function, indicating the absence of functionally important peripheral alpha(1)-adrenoceptor antagonism during long-term treatment of CHF.

To anticoagulate or not to anticoagulate patients with cardiomyopathy

The current published literature does not indicate whether the long-term effect of anticoagulant or antiplatelet therapy contributes to mortality reduction in patients with LV dysfunction. Evaluating patients for personal risk for emboli or for ischemic coronary artery events may influence the choice of therapies. As more is learned about the mechanisms of drug effects in different populations, physicians may be better able to direct appropriate therapies. Until that time, one must weigh the risks and benefits of each drug alone and in combination. In NYHA class IV patients, the risk for thrombosis owing to spontaneous clotting increases as does the adverse potential of warfarin and the adverse effects of inhibiting prostaglandin mediated vasodilation by aspirin. In NYHA class I and II patients, the quality of life and convenience of multidrug therapy is weighed against the devastating effect of a major stroke. In less symptomatic patients, the long-term risk for acute coronary events may be higher than previously identified. This would suggest that all patients with depressed LV function should be on some type of antiplatelet or anticoagulant therapy. The current WATCH study will provide much needed information about the outcome differences between these agents. Conclusions based on available data include the following: Heart failure is increasing in incidence and prevalence. Atherosclerotic disease is an important causative factor for the development of heart failure or may be a comorbid condition in these patients. There is a measurable rate of stroke in patients with heart failure, although the cause of death in large studies is more often owing to sudden death or progressive heart failure. Sudden death may be from new ischemic events, asystole, or from ventricular tachyarrhythmias. In patients with heart failure, not all strokes are cardioembolic in origin. The benefits and risks of warfarin may be increased as the EF worsens or heart failure functional class declines. The interactions of aspirin and ACE inhibitors have been best evaluated for the hemodynamic effects. There may be additional factors hitherto not studied. The hemodynamic effect of ACE inhibitors may be more important in NYHA classes III and IV than in less symptomatic patients. Warfarin use has clear indications for patients in atrial fibrillation with mechanical prosthetic valves, in hypercoagulable states, and with a previous history of embolization. Aspirin is inexpensive and commonly available, but its use must be evaluated and articulated by the prescribing physician. The current multicenter prospective trials will provide much needed guidance on this subject. The ongoing trials do not have a placebo arm, however, indicating a consensus among clinicians that patients with cardiomyopathy should be on an antiplatelet or anticoagulant drug until further data emerge.

Prospective crossover comparison of carvedilol and metoprolol in patients with chronic heart failure

OBJECTIVES

This study investigates the effects of a change of beta-adrenergic blocking agent treatment from metoprolol to carvedilol and vice versa in patients with heart failure (HF).

BACKGROUND

Beta-blockers improve ventricular function and prolong survival in patients with HF. It has recently been suggested that carvedilol has more pronounced effects on left ventricular ejection fraction (LVEF) compared with metoprolol. It is uncertain whether a change from one beta-blocker to the other is safe and leads to any change of left ventricular function.

METHODS

Forty-four patients with HF due to ischemic (n = 17) or idiopathic cardiomyopathy (n = 27) that had responded well to long-term treatment with either metoprolol (n = 20) or carvedilol (n = 24) were switched to an equivalent dose of the respective other beta-blocker. Before and six months after crossover of treatment, echocardiography, radionuclide ventriculography and dobutamine stress echocardiography were performed.

RESULTS

Six months after crossover of beta-blocker treatment, LVEF had further improved with both carvedilol and metoprolol (carvedilol: 32 +/- 3% to 36 +/- 4%; metoprolol: 27 +/- 4% to 30 +/- 5%; both p < 0.05 vs. baseline), without interindividual differences. There were no changes in either New York Heart Association functional class or any other hemodynamic parameters at rest. Dobutamine stress echocardiography revealed a more pronounced increase of heart rate after dobutamine infusion in metoprolol- compared with carvedilol-treated patients. After dobutamine infusion, LVEF increased in the carvedilol- but not in the metoprolol-treated group.

CONCLUSIONS

When switching treatment from one beta-blocker to the other, improvement of LVEF in patients with HF is maintained. Despite similar long-term effects on hemodynamics at rest, beta-adrenergic responsiveness is different in both treatments.

Differing beta-blocking effects of carvedilol and metoprolol

BACKGROUND

Metoprolol is a beta(1)-selective beta-adrenergic antagonist while carvedilol is a non-selective beta-blocker with additional blockades of alpha(1)-adrenoceptors. Administration of metoprolol has been shown to cause up-regulation of beta-adrenoceptor density and to decrease nocturnal melatonin release, whereas carvedilol lacks these typical effects of beta-blocking drugs.

AIMS

To compare beta-blocking effects of metoprolol and carvedilol when applied orally in healthy subjects.

METHODS

We investigated the effects of single oral doses of clinically recommended amounts of metoprolol (50, 100 and 200 mg) and carvedilol (25, 50 and 100 mg) to those of a placebo in a randomised, double-blind, cross-over study in 12 healthy male volunteers. Two hours after oral administration of the drugs heart rate and blood pressure were measured at rest, after 10 min of exercise, and after 15 min of recovery.

RESULTS

Metoprolol tended to decrease heart rate during exercise (-21%, -25% and -24%) to a greater extent than carvedilol (-16%, -16% and -18%). At rest, increasing doses of metoprolol caused decreasing heart rates (62, 60 and 58 beats/min) whereas increasing doses of carvedilol caused increasing heart rates (62, 66 and 69 beats/min), 50 and 100 mg carvedilol failed to differ significantly from the placebo (71 beats/min).

CONCLUSIONS

We conclude that clinically recommended doses of carvedilol cause a clinically relevant beta-blockade in humans predominantly during exercise where it appears to be slightly (although not significantly) less effective than metoprolol. On the other hand, the effects of carvedilol on heart rate at rest appear rather weak, particularly in subjects with a low sympathetic tone. This might be caused by a reflex increase on sympathetic drive secondary to peripheral vasodilation resulting from the alpha-blocking effects of the drug. These results might be helpful in explaining why carvedilol, in contrast to metoprolol, may fail to cause up-regulation of beta-adrenoceptor density and does not decrease nocturnal melatonin release. This, in turn, may be a reason for the weak side-effects of carvedilol resulting from the beta-blockade. In addition, our data might be of interest in the interpretation of the forthcoming results of the COMET trial, although it has to be emphasised that they were derived from healthy subjects and, therefore, cannot be directly extrapolated to patients with heart failure.

Mediators of chronic heart failure: how drugs work

OBJECTIVE

To critically review the pathophysiology of chronic heart failure at the neurohormonal level, and discuss the effect of present and future therapeutic options on these neurohormones.

DATA SOURCES

A MEDLINE search (1986-November 2000) was used to identify important primary literature and reviews. Additional references were obtained from these articles.

DATA SYNTHESIS

Chronic heart failure is a common, progressive disorder with high morbidity and mortality. Progression is due in large part to several redundant neurohormonal responses. The neurohormones include angiotensin II, norepinephrine, aldosterone, endothelin-1, arginine vasopressin, and tumor necrosis factor. These responses are initially adaptive, but become maladaptive in the long term, impairing the function of the heart, vasculature, and kidneys. Counter-regulatory hormones, such as bradykinin and natriuretic peptides, are insufficient to offset the adverse effects of the other neurohormones. Most drugs used to treat chronic heart failure, such as angiotensin-converting enzyme inhibitors, beta-adrenergic antagonists, and spironolactone, achieve their benefits through altering the neurohormonal pathways. New agents that affect more or different neurohormones may soon be available.

CONCLUSIONS

Multiple agents are required for treatment of chronic heart failure, as no single agent can counteract all of the various adverse pathways. The appropriate prescription and use of such inherently complex regimens require significant physician and patient education.

Beneficial effect of carvedilol on heart rate response to exercise in digitalised patients with heart failure in atrial fibrillation due to idiopathic dilated cardiomyopathy

Fourteen digitalised patients diagnosed with heart failure (NYHA Functional class II) with idiopathic dilated cardiomyopathy in chronic established atrial fibrillation were administered carvedilol in addition to their anti-heart failure medications in an attempt to improve their heart rate control. Fourteen matched patients who did not receive carvedilol acted as control subjects. Patients treated with carvedilol showed significantly reduced resting heart rates (10-36%), maximal heart rates on exercise (5-20%) and an increased exercise time (2-30%) on treadmill stress tests (all P=0.001). Ventricular ectopic activity was also diminished. This was associated with symptomatic improvement in effort intolerance and palpitations. NYHA functional class, left ventricular dimensions and ejection fractions did not improve during the study period of 3 months. Thus, addition of carvedilol to digoxin had a beneficial effect on exercise tolerance in patients with idiopathic dilated cardiomyopathy in atrial fibrillation by virtue of an improved heart rate control both at rest and on exercise. Carvedilol was well tolerated despite impaired myocardial function.

Effect of metoprolol CR/XL on exercise tolerance in chronic heart failure - a substudy to the MERIT-HF trial

BACKGROUND

Beta-blockade usually causes a slight reduction in exercise capacity among healthy subjects, while more variable results have been observed in chronic heart failure (CHF), probably related to patients studied, methods and agent used. The effect of metoprolol controlled release/extended release (CR/XL) on peak oxygen uptake (peak VO(2)) in this patient population has not previously been investigated.

AIMS

We examined the effect of long-term treatment with the selective beta(1)-receptor blocker metoprolol CR/XL once daily on exercise capacity in patients with CHF.

METHODS

Ninety-four patients (70 males and 24 females; mean age 63.6+/-10.6 years) with chronic symptomatic heart failure in New York Heart Association (NYHA) functional class II-IV, and with ejection fraction <or=40%, stabilized on optimum standard therapy were randomized to metoprolol CR/XL or placebo in a double-blind trial. Exercise capacity was evaluated by peak VO(2) at baseline, after 3 months and at the end of study (mean follow-up 11.4+/-0.4 months).

RESULTS

Compared with placebo metoprolol CR/XL produced a significant decrease in heart rate by 11 beats/min at rest and 18 beats/min at peak exercise. There was a tendency for a temporal decline in peak VO(2) after 3 months of therapy in both groups, but altogether peak VO(2) remained unchanged from baseline with no difference between the groups at 1 year.

CONCLUSIONS

In patients with moderate to severe CHF, 11.4 months of beta(1)-blockade with metoprolol CR/XL had no effect on exercise capacity when compared with placebo or baseline.