Restoring function in failing hearts: the effects of beta blockers

Dioxygen and Metabolism; Dangerous Liaisons in Cardiac Function and Disease

The heart must consume a significant amount of energy to sustain its contractile activity. Although the fuel demands are huge, the stock remains very low. Thus, in order to supply its daily needs, the heart must have amazing adaptive abilities, which are dependent on dioxygen availability. However, in myriad cardiovascular diseases, “fuel” depletion and hypoxia are common features, leading cardiomyocytes to favor low-dioxygen-consuming glycolysis rather than oxidation of fatty acids. This metabolic switch makes it challenging to distinguish causes from consequences in cardiac pathologies. Finally, despite the progress achieved in the past few decades, medical treatments have not improved substantially, either. In such a situation, it seems clear that much remains to be learned about cardiac diseases. Therefore, in this review, we will discuss how reconciling dioxygen availability and cardiac metabolic adaptations may contribute to develop full and innovative strategies from bench to bedside.

A histamine H₂ receptor blocker ameliorates development of heart failure in dogs independently of β-adrenergic receptor blockade

Histamine has a positive inotropic effect on ventricular myocardium and stimulation of histamine H₂ receptors increases the intracellular cAMP level via Gs protein, as dose stimulation of β-adrenergic receptors, and worsens heart failure. To test whether a histamine H₂ receptor blocker had a beneficial effect in addition to β-adrenergic receptor blockade, we investigated the cardioprotective effect of famotidine, a histamine H₂ receptor blocker, in dogs receiving a β-blocker. We induced heart failure in dogs by rapid ventricular pacing (230 beats/min). Animals received no drugs (control group), famotidine (1 mg/kg daily), carvedilol (0.1 mg/kg daily), or carvedilol plus famotidine. Both cardiac catheterization and echocardiography were performed before and 4 weeks after the initiation of pacing. Immunohistochemical studies showed the appearance of mast cells and histamine in the myocardium after 4 weeks of pacing. In the control group, the left ventricular ejection fraction (LVEF) was decreased after 4 weeks compared with before pacing (71 ± 2 vs. 27 ± 2%, p < 0.05) and mean pulmonary capillary wedge pressure (PCWP) was increased (8 ± 1 vs. 19 ± 3 mmHg). Famotidine ameliorated the decrease of LVEF and increase of PCWP, while the combination of carvedilol plus famotidine further improved both parameters compared with the carvedilol groups. These beneficial effects of famotidine were associated with a decrease of the myocardial cAMP level. Histamine H₂ receptor blockade preserves cardiac systolic function in dogs with pacing-induced heart failure, even in the presence of β-adrenergic receptor blockade. This finding strengthens the rationale for using histamine H₂ blockers in the treatment of heart failure.

Increasing cardiac contractility after myocardial infarction exacerbates cardiac injury and pump dysfunction

RATIONALE

Myocardial infarction (MI) leads to heart failure (HF) and premature death. The respective roles of myocyte death and depressed myocyte contractility in the induction of HF after MI have not been clearly defined and are the focus of this study.

OBJECTIVES

We developed a mouse model in which we could prevent depressed myocyte contractility after MI and used it to test the idea that preventing depression of myocyte Ca(2+)-handling defects could avert post-MI cardiac pump dysfunction.

METHODS AND RESULTS

MI was produced in mice with inducible, cardiac-specific expression of the β2a subunit of the L-type Ca(2+) channel. Myocyte and cardiac function were compared in control and β2a animals before and after MI. β2a myocytes had increased Ca(2+) current; sarcoplasmic reticulum Ca(2+) load, contraction and Ca(2+) transients (versus controls), and β2a hearts had increased performance before MI. After MI, cardiac function decreased. However, ventricular dilation, myocyte hypertrophy and death, and depressed cardiac pump function were greater in β2a versus control hearts after MI. β2a animals also had poorer survival after MI. Myocytes isolated from β2a hearts after MI did not develop depressed Ca(2+) handling, and Ca(2+) current, contractions, and Ca(2+) transients were still above control levels (before MI).

CONCLUSIONS

Maintaining myocyte contractility after MI, by increasing Ca(2+) influx, depresses rather than improves cardiac pump function after MI by reducing myocyte number.

Depression in chronic heart failure: novel pathophysiological mechanisms and therapeutic approaches

Depression is four to five times as common in chronic heart failure (CHF) patients as in the general population, may confer a higher risk of developing CHF in susceptible populations, and is significantly related to higher hospital readmission rates and increased mortality in established CHF. This effect may be mediated via the pathophysiological mechanisms that are shared between CHF and depression, including increased hypothalamic-pituitary-adrenal function, sympathoadrenal hyperactivity, diminished heart-rate variability and excessive pro-inflammatory cytokine activation. Each of these pathways of linkage represents a potential therapeutic target to improve outcome in CHF. This paper reviews the recent investigational observations that clarify the direct effects of antidepressants on immune functions, as well as the indirect effects of anticytokine pharmacological agents on depressive symptoms in CHF. With recent evidence suggesting that selective serotonin re-uptake inhibitors improve survival after myocardial infarction in patients with depression, diagnosis and treatment of this comorbidity may beneficially affect the functional capacity and prognosis of CHF patients.

Increasing longevity by decreasing sympathetic stress--early beta receptor blockade pharmacotherapy

Consideration regarding human aging and sympathetic nervous system activity suggests that old age represents a hyperadrenergic state. With advancing age the sympathetically mediated stress on the body, specifically the cardiovascular system, may outweigh the benefits an intact sympathetic nervous system conveys for short-term survival. Beta blockers temper the effects of the sympathetic nervous system by slowing heart rate and decreasing blood pressure. Recently, beta blockers have been shown to improve outcome and survival following surgery and myocardial infarction, have beneficial effects in patients with heart failure, and may have an antiatherosclerotic effect. We propose that instituting beta receptor blockade pharmacotherapy at an early age will increase longevity by countering the adverse effects of sympathetically mediated stress.

Psychosocial issues in patients with congestive heart failure

Psychosocial issues are important variables that need to be addressed in patients with congestive heart failure (CHF). Unfortunately, these issues are often overlooked. Depression and lack of social support have been shown to have a negative impact on patients with CHF. Patients with CHF who are depressed or who lack social support have been shown to have increased morbidity and hospital readmission rates, to be less adherent to their medical regimen, and to have an overall increase in cost of care. The variables are often interrelated, as high levels of social support may lessen the impact of depression on mortality. In addition, certain biologic factors may influence the impact of psychosocial factors in patients with CHF. This review addresses the effects of depression, treatment adherence, and social support in patients with CHF and suggests interventions targeted to these problems. Health care professionals must assess these issues in all patients with CHF, address their specific needs, and intervene appropriately when warranted.

Left ventricular systolic dysfunction and nonischemic cardiomyopathy

Heart failure is a devastating chronic and progressive cardiac disorder affecting millions of Americans annually. Identifying the cause and initiating treatment early is the key to attempting to slow the progression of the condition. Recommended therapy is treatment with angiotensin-converting enzyme (ACE) inhibitors, diuretics, digoxin, beta blockers, and in patients with symptomatic class III and IV heart failure, the addition of aldactone.

Measurement of left ventricular dimensions and function in patients with dilated cardiomyopathy

Studies on medical therapy in heart failure are focused on changes of left ventricular (LV) dimensions and function. These changes may be small, requiring a large study group. We measured LV parameters (LV volumes, LV ejection fraction (LV-EF), and left ventricular mass (LVM)) with two-dimensional echocardiography (2D-echo) and magnetic resonance imaging (MRI) in 50 patients. Based on the difference between the measurements, we determined the variance of the results and calculated the sample sizes needed to detect changes of baseline values. For the calculated and measured parameters we found significant differences between the two techniques: LV-EF and LVM were higher in 2D-echo, and LV dimensions were comparable. The sample size to detect relevant changes from baseline with MRI was significantly (P < 0.01) smaller than in 2D-echo. We conclude that MRI is superior in clinical studies on left ventricular dimensional and functional changes, since measurements are more reproducible and the required sample size is substantially smaller, thereby reducing costs.

Choosing initial antihypertensive drug therapy for the uncomplicated hypertensive patient

Choosing the initial antihypertensive drug for the uncomplicated hypertensive patient is an important and frequent event for the primary care physician. Patients' first experience with antihypertensive drug therapy will likely affect their long-term perception of hypertension treatment. The choice should be made on the basis of sound scientific data and from the patient's perspective and needs. The drug should be taken once a day, should have proven efficacy in hypertension control and cardiovascular morbidity and mortality reduction, and should have as few side effects as possible. Low-dose thiazide diuretics meet this description, although the need to monitor electrolytes may make them less than ideal. The angiotensin II receptor antagonist class, with side-effects similar to those of placebo in controlled trials, is the most attractive from the patient's perspective, although outcome trial data do not yet exist proving that hypertension treatment with angiotensin II receptor antagonists reduces cardiovascular events. The angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists, with their low side-effect profiles and unique effects on vascular remodeling, are attractive second choices to combine with a diuretic if needed, although low-dose diuretic/Beta blocker combinations have also been shown to lower blood pressure with minimal side effects. At present, ensuring adequate long-term hypertension control is the most important aspect of hypertensive care, and which antihypertensive drug(s) the physician chooses can greatly affect the hypertensive patient's ability to achieve and to maintain long-term blood pressure control. (c)2001 by Le Jacq Communications, Inc.

Treatment of congestive heart failure--current status of use of digitoxin

Digitalis glycosides exert a positive inotropic effect, i.e. an increase in myocardial contractility associated with a prolongation of relaxation period, and glycosides lower the heart rate (negative chronotropic), impede stimulus conduction (negative dromotropic) and promote myocardial excitability (positive bathmotropic). They seem to influence the activities of both the vagal and the sympathetic systems. Digitalis glycosides that belong to different substance classes are closely comparable concerning pharmacodynamics but differ substantially in regard to pharmacokinetics. Digoxin and its derivatives are less lipophilic, show lower protein binding and shorter half-life, are mainly eliminated via the kidney and accumulate rather rapidly in cases of insufficient kidney function. Digitoxin is highly lipophilic and extensively bound to plasma proteins, has a longer half-life, is mainly eliminated in the metabolized state via urine and faeces and does not accumulate in kidney dysfunction. As a result of a more stable pharmacokinetic profile, the incidence of toxic side effects seems to be lower with digitoxin than with digoxin. Since the beginning of the 1990s, the antagonists of the RAAS qualified as the standard treatment for congestive heart failure, often in combination with diuretics, vasodilators or beta-antagonists. However, the important role of digitalis glycosides as therapeutic comedication or alternative was never denied, especially in atrial fibrillation with tachycardia. The PROVED and RADIANCE trials proved a detrimental effect of the withdrawal of digoxin therapy on exercise capacity, left-ventricular ejection fraction and clinical symptoms. The DIG trial revealed that digoxin comedication in sinus rhythm patients with congestive heart failure was associated with a lower morbidity (as taken from death or hospitalization because of worsening heart failure) and an unchanged overall mortality--being a unique feature among the available inotropic drugs. Comparable studies for digitoxin have not yet been performed but, because of its higher pharmacological stability, it might well be associated with even more advantages in this regard than digoxin.

Pressure-volume relationships in pediatric systolic and diastolic heart failure

The left ventricular pressure-volume relationship has been used to examine ventricular systolic and diastolic function as well as to evaluate myocardial energetics and ventricular-vascular coupling. Preload, afterload and contractility can be separately examined using indices derived from simultaneous pressure and volume measurement. Due to the development of new instrumentation and diagnostic tools, these techniques now can be more readily applied to the evaluation of patients in heart failure. Indices of function can be examined on-line during diagnostic cardiac catheterization. Pharmacologic interventions can be evaluated using these methods, allowing for assessment of therapeutic interventions. Medical therapy can be optimized during these studies, allowing more effective and individualized treatment.

Improvement in left ventricular function in response to carvedilol is accompanied by attenuation of neurohumoral activation in patients with dilated cardiomyopathy

BACKGROUND

We sought to evaluate whether improvement in ejection fraction (EF) with carvedilol therapy is accompanied by improvement in neurohumoral factors.

METHODS AND RESULTS

Forty-two patients with dilated cardiomyopathy were given carvedilol for 3 to 5 months. Changes in EF, plasma atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and norepinephrine levels were determined. Iodine-123 metaiodobenzylguanidine (MIBG) images were also obtained before and after carvedilol therapy. Myocardial uptake of MIBG was calculated as the heart to mediastinal activity ratio (H/M). Storage and release of MIBG was calculated as percent myocardial MIBG washout rate (WR). We divided patients into 2 groups: 27 responders whose EF increased by more than 5% and 15 nonresponders whose EF increased by 5% or less. EF of responders increased by 15 +/- 5% and that of nonresponders by 1 +/- 4%. Although MIBG image-derived indexes of nonresponders remained unchanged, the delayed H/M (1.91 +/- 0.34 v 2.24 +/- 0.53, P < .01) and WR (49 +/- 11 v 39 +/- 9%, P < .01) of responders improved, respectively. The plasma ANP (51 +/- 50 v 27 +/- 24 pg/mL, P < .01) and BNP (194 +/- 197 v 49 +/- 62 pg/mL, P < .01) levels of responders decreased. The degree of changes in the plasma BNP level correlated with changes in EF (r = -.698, P < .01).

CONCLUSION

The improvement in EF with carvedilol therapy was proved to be accompanied by an improvement in neurohumoral factors.

Management of heart failure among very old persons living in long-term care: has the voice of trials spread? The SAGE Study Group

BACKGROUND

Increasing prevalence, use of health services, and number of deaths have made congestive heart failure (CHF) a new epidemic in the United States. Yet there are no adequate data to guide treatment of the more typical and complex cases of patients who are very old and frail.

METHODS

Using the SAGE database, we studied the cases of 86,094 patients with CHF admitted to any of the 1492 long-term care facilities of 5 states from 1992 through 1996. We described their clinical and functional characteristics and their pharmacologic treatment to verify agreement with widely approved guidelines. We evaluated age- and sex-related differences, and we determined predictors of receiving an angiotensin-converting enzyme (ACE) inhibitor by developing a multiple logistic regression model.

RESULTS

The mean age of the population was 84.9 +/- 8 years. Eighty percent of the patients 85 years of age or older were women. More than two thirds of patients underwent frequent hospitalizations related to CHF in the year preceding admission to a long-term care facility. Coronary heart disease and hypertension were the most common causes. Half of the patients received digoxin and 45% a diuretic, regardless of background cardiovascular comorbidities. Only 25% of patients had a prescription for ACE inhibitors. The presence of cardiovascular comorbidity, already being a recipient of a large number of medications, a previous hospitalization for CHF, and admission to the facility in recent years were associated with an increased likelihood of receiving an ACE inhibitor. The presence of severe physical limitation was inversely related to use of ACE inhibitors, as were a series of organizational factors related to the facilities.

CONCLUSIONS

Patients in long-term care who have CHF little resemble to those enrolled in randomized trials. This circumstance may explain, at least in part, the divergence from pharmacologic management consensus guidelines. Yet the prescription of ACE inhibitors varies significantly across facilities and depends on organizational characteristics.

beta-Blockers in congestive heart failure

Recent advances in the understanding of the basic mechanisms underlying congestive heart failure (CHF) have focused on the role of neurohormonal activation. Chronic adrenergic overstimulation is directly toxic to myocardial cells, impairs function, causes peripheral vasoconstriction and may induce programmed cell death via apoptosis. beta-Adrenergic blockade can interrupt this pathological process. Accumulating evidence now points to a clear role for beta-blocking agents in the management of heart failure, reducing both the morbidity and mortality associated with CHF. This report will review the recent clinical trials supporting the use of beta-blockers in CHF, briefly highlight some practical considerations in the use of these drugs in patients with CHF and discuss several areas of controversy in which further study is needed.

Medical and surgical therapy for cardiac remodeling

Ventricular remodeling refers to changes in ventricular geometry, volume, mass, and myocellular structure in response to myocardial injury or alteration in loading conditions. Although initially adaptive as a consequence of the initial damage to the myocardium, progressive ventricular remodeling is ultimately a maladaptive process that is associated with significant cardiovascular morbidity and mortality. Treatment with an aim to halt or reverse remodeling with mainly two classes of medications, angiotensin-converting enzyme inhibitors and beta-adrenergic blockers, has been shown to improve the long-term outcome. The role of pharmacologic and surgical therapy in remodeling is evolving and may have an important impact on the development of new directions of therapy for heart failure, myocardial infarction, and hypertension.