Beta-blocker use in systolic heart failure and dilated cardiomyopathy

Predicting maximal oxygen uptake from the 6 min walk test in patients with heart failure

Aims

A cardiopulmonary exercise (CPX) test is considered the gold standard in evaluating maximal oxygen uptake. This study aimed to evaluate the predictive validity of equations provided by Burr et al., Ross et al., Adedoyin et al., and Cahalin et al. in predicting peak VO₂ from 6 min walk test (6MWT) distance in patients with heart failure (HF).

Methods and Results

New York Heart Association Class I–III HF patients performed a maximal effort CPX test and two 6MWTs. Correlations between CPX VO_{2 peak} and the predicted VO_{2 peak}, coefficient of determination (R²), and mean absolute percentage error (MAPE) scores were calculated. P‐values were set at 0.05. A total of 106 participants aged 62.5 ± 11.5 years completed the tests. The mean VO_{2 peak} from CPX testing was 16.4 ± 3.9 mL/kg/min, and the mean 6MWT distance was 419.2 ± 93.0 m. The predicted mean VO_{2 peak} (mL/kg/min) by Burr et al., Ross et al., Adedoyin et al., and Cahalin et al. was 22.8 ± 8.8, 14.6 ± 2.1, 8.30 ± 1.4, and 16.6 ± 2.8. A significant correlation was observed between the CPX test VO_{2 peak} and predicted values. The mean difference (0.1 mL/kg/min), R² (0.97), and MAPE (0.14) values suggest that the Cahalin et al. equation provided the best predictive validity.

Conclusions

The equation provided by Cahalin et al. is simple and has a strong predictive validity, and researchers may use the equation to predict mean VO_{2 peak} in patients with HF. Based on our observation, equations to predict individual maximal oxygen uptake should be used cautiously.

Myocardial energetics in heart failure

It has become common sense that the failing heart is an "engine out of fuel". However, undisputable evidence that, indeed, the failing heart is limited by insufficient ATP supply is currently lacking. Over the last couple of years, an increasingly complex picture of mechanisms evolved that suggests that potentially metabolic intermediates and redox state could play the more dominant roles for signaling that eventually results in left ventricular remodeling and contractile dysfunction. In the pathophysiology of heart failure, mitochondria emerge in the crossfire of defective excitation-contraction coupling and increased energetic demand, which may provoke oxidative stress as an important upstream mediator of cardiac remodeling and cell death. Thus, future therapies may be guided towards restoring defective ion homeostasis and mitochondrial redox shifts rather than aiming solely at improving the generation of ATP.

Beta-Blocker Treatment of Chronic Heart Failure: Comparison of Carvedilol and Metoprolol

Beta blockers have been shown to prolong survival in chronic heart failure. It is currently a matter of debate whether any beta blocker is superior to the other in terms of improving symptoms, left ventricular function, or prognosis. A number of comparative studies have been performed with metoprolol, a beta1-selective second-generation beta blocker, and carvedilol, a nonselective and vasodilatative third-generation beta blocker. This review will focus on the different pharmacological profiles of carvedilol and metoprolol as well as on the clinical consequences derived from these differences. The results indicate that in some studies carvedilol is superior to metoprolol in improving left ventricular ejection fraction. However, because there is no conclusive evidence that carvedilol is superior to metoprolol in terms of prognosis, it is not justified to substitute metoprolol with carvedilol. Comparative data on mortality reduction are not available before termination of the Carvedilol or Metoprolol European Trial. Nevertheless, the different effects of both beta blockers on the beta-adrenergic system have an impact on tolerability and beta-adrenergic responsiveness and thus exercise tolerance in heart-failure patients.

Heart Failure in Older Adults: Providing Nursing Care to Improve Outcomes

Heart failure continues to be a challenge for older patients and their health care providers. This article is based on work by advanced practice nurses in a nursing study funded by the National Institute of Nursing Research of the National Institute of Health. Mary Naylor, RN, PhD at the University of Pennsylvania School of Nursing through grant #1RO1-NR04315 is using a transitional care model to provide advance practice nurse intervention for older adults with heart failure in a randomized controlled trial. Effects of the intervention being addressed include quality of life, functional status, rehospitalizations, and costs of care. Working with the patient in the acute hospital setting and following patients to the home care setting for 3 months, the advance practice nurse develops a visit pattern and intervention plan individual to the patient's needs. Key to a successful intervention plan is the right treatment for systolic versus diastolic failure. Although the patient's symptoms and some physical findings may be similar, the drugs used to treat systolic versus diastolic heart failure are different. Thus the nursing interventions to promote symptom management and avoid rehospitalizations have a different approach. In this article, care of elderly individuals with systolic versus diastolic heart failure is compared and contrasted using physical examination and diagnostic techniques, medication management, and nursing intervention. Case studies of a typical patient with systolic and diastolic heart failure will be used to illustrate the differences in approach to this common group of patients with complex needs.

Effect of beta-adrenoceptor antagonist and angiotensin-converting enzyme inhibitor on hypertension-associated changes in adenylyl cyclase type V messenger RNA expression in spontaneously hypertensive rats

Adenylyl cyclase (AC) messenger RNA (mRNA) expression is decreased in failing hearts. Diminished expressions are accompanied by desensitization of beta-adrenergic signal transduction. Factors contributing to such changes in mRNA expression for the major myocardial isoform AC V are not well established. To assess the contributions of hypertension, left ventricular hypertrophy (LVH), the renin-angiotensin-aldosterone system (RAS), and the sympathetic nervous system to these changes, ventricular expression of AC V mRNA was measured at different ages in spontaneously hypertensive rats (SHRs). In addition, the effects on them of angiotensin-converting enzyme inhibitor and beta-adrenoceptor antagonists were determined. Prior to quantitative Northern blotting at ages 5, 9, or 12 weeks, hemodynamic and morphologic variables were measured in SHRs and Wistar-Kyoto rats (WKYs). The SHRs and WKYs were treated with an angiotensin-converting enzyme inhibitor, enalapril (10 mg/kg/d), or a beta(1)-adrenoceptor antagonist, atenolol (100 mg/kg/d), for 8 weeks preceding Northern analysis. Myocardial AC V mRNA expression increased from 5-12 weeks in both SHRs and WKYs. Expression of AC V mRNA in SHRs increased somewhat less than in WKYs at 9 weeks and significantly less at 12 weeks. This was accompanied by development of LVH and hypertension in SHRs. Blood pressure and left ventricular weight relative to body weight were markedly decreased by enalapril and were moderately decreased by atenolol. Expression of AC V mRNA in SHRs at 12 weeks was normalized equally by enalapril and atenolol to the level of WKYs. Thus AC V mRNA expression increases are blunted in the early stages of LVH in SHRs under the influences of beta(1)-adrenergic signal transduction and the RAS.

Should beta blockers be used in the treatment of hypertension in the elderly?

The lack of benefit and the potential negative side effects of beta blockers are overstated, especially in the elderly. This emphasis has led to recommendations by some investigators that these agents not be used in the management of hypertension in this age group. There are numerous reasons why these recommendations should not be followed. The use of beta blockers in the elderly hypertensive has resulted in a reduction in strokes and congestive heart failure. In addition, it should be emphasized that elderly patients are more likely to have silent coronary artery disease or sustain myocardial infarctions. There is abundant evidence that beta blockers are effective therapy in reducing mortality once a myocardial infarction has occurred. In fact, there is a clear reduction in sudden cardiac death. Furthermore, national statistics document that elderly patients have a prevalence of congestive heart failure that varies from 6%-10%. Multiple studies have now documented that beta blockers are additive to angiotensin-converting enzyme inhibitors in reducing mortality for congestive heart failure. Thus, elderly hypertensive patients may benefit from the use of beta blockers, especially if there is evidence of ischemic heart disease, cardiac arrhythmias, or congestive heart failure.

T-1032, a novel phosphodiesterase type 5 inhibitor, increases the survival of cardiomyopathic hamsters

To evaluate the influence of T-1032 (methyl2-(4-aminophenyl)-1,2-dihydro-1-oxo-7-(2-pyridylmethoxy)-4-(3,4,5-trimethoxyphenyl)-3-isoquinoline carboxylate sulfate), a potent and relatively selective phosphodiesterase 5 inhibitor, on chronic heart failure, we examined the acute hemodynamic profile of T-1032 and its chronic effect on the survival of Bio 14.6 cardiomyopathic hamsters. In the acute study, T-1032 (1, 10, 100 microg/kg) was administered intravenously by means of a dose-escalating procedure in 55-week-old hamsters. T-1032 significantly reduced both the right and left ventricular end-diastolic pressure in a dose-dependent manner. T-1032 modestly reduced the systemic arterial pressure at the highest dose (100 microg/kg i.v.). T-1032 did not change the heart rate or left ventricular dp/dt(max). In the survival study, chronic administration of T-1032 (50 and 500 ppm in a diet) increased survival, and the survival rate was 24.2%, 45.4% and 48.5% in the control, 50 and 500 ppm-treated groups, respectively. The median survival was 55, 58 and 58 weeks in control, 50 and 500 ppm-treated groups, respectively. Analysis of the survival curves revealed that T-1032 (500 ppm) significantly increased the survival of these hamsters (P<0.05 vs. control). It was concluded that T-1032 had beneficial hemodynamic effects on heart failure in Bio 14.6 cardiomyopathic hamsters, and the favorable hemodynamic changes induced by T-1032 were partly related to the increase in the survival of these hamsters. Phosphodiesterase type 5 inhibitors may have therapeutic potential for the treatment of chronic heart failure.

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.

Different intrinsic activities of bucindolol, carvedilol and metoprolol in human failing myocardium

1. Clinical studies have shown different effects of beta-blockers on the beta-adrenergic system, tolerability and outcome in patients with heart failure. 2. The study examines beta-adrenoceptor-G-protein coupling and intrinsic activity of bucindolol, carvedilol and metoprolol in human ventricular myocardium. 3. Radioligand binding studies ([(125)I]-Iodocyanopindolol) were performed in membrane preparations of human failing and nonfailing myocardium. Functional experiments were carried out in isolated muscle preparations of human left ventricular myocardium from failing hearts. 4. Bucindolol and carvedilol bound non-selectively to beta(1)- and beta(2)-adrenoceptors and exerted guanine nucleotide modulatable binding. Metoprolol was 35-fold beta(1)-selective and lacked guanine nucleotide modulatable binding. 5. All beta-blockers antagonized isoprenaline-induced enhancement of contractility. 6. In preparations in which the coupling of the stimulatory G-protein to adenylate cyclase was facilitated by forskolin, bucindolol increased force of contraction in three and decreased it in five experiments. Carvedilol increased force in one and decreased it in six experiments. Metoprolol decreased force in all experiments by 89. 4+/-2.2% (P<0.01 metoprolol vs carvedilol and bucindolol). The negative inotropic effect of metoprolol was antagonized by bucindolol. 7. It is concluded that differences in intrinsic activity can be detected in human myocardium and have an impact on cardiac contractility. In human ventricular myocardium, bucindolol displays substantially higher intrinsic activity than metoprolol and carvedilol. Bucindolol can behave as partial agonist or partial inverse agonist depending on the examined tissue. 8. Differences in intrinsic activity may contribute to differences in beta-adrenoceptor regulation and possibly to differences in tolerability and outcomes of patients with heart failure.

Optimising management of patients with advanced heart failure: the importance of preventing progression

Heart failure is a highly complex, progressive and deadly disease. When incorrectly treated, it results in irreversible structural damage to the myocardium and resists any conventional treatment. This stage has been arbitrarily termed refractory heart failure. However, with timely and sufficiently applied neurohumoral antagonists, progression can be prevented, or at least delayed. In contrast, as soon as heart failure has become moderate or severe due to advanced left ventricular dysfunction, polypharmacy is the rule. Physicians should make every effort to maintain or reconsider optimal neurohumoral antagonist therapy in such patients, even if symptomatic improvement from these agents may be slow. Proper use of diuretics is essential not only for symptom relief but also to achieve full benefit from angiotensin converting enzyme inhibitors and beta-blockers. Digitalis may be particularly indicated in severe heart failure, irrespective of rhythm. Adjunctive regimens can be helpful in specific patients, but evidence of their salutary effects to prolong life is lacking. In the decompensated state, tailoring intravenous therapy to haemodynamic goals followed by (re-)institution of optimal oral therapy is an option. Only if these strategies fail is heart transplantation justified. While waiting for a donor, patients have been bridged with various intravenous agents, most often inotropes, but symptom relief is associated with risk of increased mortality due to these drugs. New hope emerges from drugs interfering with endothelin and the cytokines, and from research into increasing contractility with calcium sensitising agents. Even though these developments follow established routes, they may enable a more effective approach to prevent worsening heart failure in every single patient.

Health outcomes associated with beta-blocker and diltiazem treatment of unstable angina

OBJECTIVE

We compared long-term health outcomes associated with beta-adrenergic blocking agents and diltiazem treatment for unstable angina.

BACKGROUND

No long-term data have been published comparing these two antianginal treatments in this setting.

METHODS

Eligible veterans were discharged from the Veterans Affairs Puget Sound Health Care System (VAPSHCS), Seattle Division, between October 1989 and September 1995 with an unstable angina diagnosis and were prescribed monotherapy beta-blocker or diltiazem treatment at discharge. Medication data were collected from medical records and computerized VAPSHCS outpatient pharmacy files. Follow-up death and coronary artery disease rehospitalization data were collected through 1996. Proportional hazards regression compared survival among diltiazem and beta-blocker users, controlling for patient characteristics with propensity scores.

RESULTS

Two hundred forty-seven veterans (24% on beta-blockers, 76% on diltiazem) were included in this study. There were 54 (22%) deaths during an average follow-up of 51 months. After propensity score adjustment, there was no difference in risk of death comparing diltiazem to beta-blocker treatment (hazards ratios [HR] 1.1; 95% confidence interval [CI] 0.49 to 2.4). Among Washington residents (n=207), there were 146 (71%) coronary artery disease rehospitalizations or deaths during follow-up. After adjustment, there was a nonsignificant increase in risk of rehospitalization or death associated with diltiazem use (HR 1.4; 95% CI 0.80 to 2.4). For both analyses, similar risks were found among veterans without relative contraindications to beta-blockers.

CONCLUSIONS

We found no survival benefit of diltiazem over beta-blocker treatment for unstable angina in this cohort of veterans.

Early reduction in plasma norepinephrine during beta-blocking therapy with metoprolol in chronic heart failure

BACKGROUND

The possible role exerted by modulation of sympathetic outflow in the clinical effects of beta-blockade in chronic heart failure was tested during short- and long-term treatment.

METHODS AND RESULTS

Oral metoprolol (30-150 mg/day) was added to conventional therapy in 14 patients with idiopathic dilated cardiomyopathy, left ventricular ejection fraction (LVEF) of <0.45, and New York Heart Association class II or III. Norepinephrine plasma levels, which are an index of sympathetic activation, decreased by 27.57 +/- 18.03% after 1 month (P < .005), but returned to pretreatment levels after 6 months. LVEF increased by 7.7 +/- 6.0 ejection fraction units after 6 months (P < .005 vs baseline and P < .05 vs 1 month). Long-term beta-blockade resulted in nonsignificant improvements in functional class, symptom score, and oxygen consumption at peak exercise. After 1 month, the reduction in plasma norepinephrine levels and the changes in LVEF were inversely correlated (P < .01). No other correlation emerged during short- or long-term treatment.

CONCLUSION

In conclusion, the reduction in plasma norepinephrine levels during short-term beta-blockade was not proportional to the clinical benefits and may have been attributed to the direct inhibition of sympathetic outflow. The early reduction in circulating norepinephrine levels may decrease cardiac performance through withdrawal of sympathetic support when the favorable effects of beta-blockade have not had time to occur. The role that sympathetic modulation may exert in the long-term clinical benefits of metoprolol deserves further investigation.

Cardiovascular effects of nepicastat (RS-25560-197), a novel dopamine beta-hydroxylase inhibitor

Nepicastat (RS-25560-197) is a novel, selective, and potent inhibitor of dopamine beta-hydroxylase, which modulates catecholamine levels (reduces norepinephrine and elevates dopamine) in cardiovascular tissues. This study was designed to evaluate the cardiovascular effects of nepicastat. Acute oral administration of nepicastat (0.3, 1, 3, 10, and 30 mg/kg) produced attenuation of the pressor and positive chronotropic responses to preganglionic sympathetic nerve stimulation (about twofold to sixfold shift in the frequency-response curve) in pithed spontaneously hypertensive rats (SHRs). In inactin-anesthetized SHRs, the antihypertensive effects of nepicastat (3 mg/kg, i.v.) were accompanied by a significant decrease in renal vascular resistance (38%), a tendency toward an increase in renal blood flow (22%), and no adverse effects on urine output and Na/K excretion. In conscious, unrestrained, telemetry-implanted SHRs, nepicastat (30 and 100 mg/kg/day for 30 days) produced dose-dependent decreases in mean arterial blood pressure (peak decrease of 20 and 42 mm Hg, respectively) without evoking reflex tachycardia. Long-term, concurrent administration of nepicastat (30 mg/kg/day, p.o.) and a subthreshold dose of enalapril (1 mg/kg/day, p.o.) produced greater antihypertensive effects than those produced by nepicastat alone. In normal dogs, nepicastat (5.0 mg/kg, p.o., b.i.d., for 4.5 days) blunted the positive chronotropic and pressor response to tyramine. These findings suggest that nepicastat functionally modulates sympathetic drive to cardiovascular tissues and may be of value in the treatment of cardiovascular disorders associated with overactivation of the sympathetic nervous system such as hypertension and congestive heart failure.