A comparison of oral milrinone, digoxin, and their combination in the treatment of patients with chronic heart failure

Symptomatic systolic ventricular failure

Over the past 20 to 30 years there have been significant advances in the management of heart failure related to improved understanding of pathophysiology, better methods of assessment, and improved drug treatments. The aims of treatment have broadened, with increased emphasis on earlier intervention. Clinical research activity in this area has been considerable, increasingly allowing an evidence-based approach to management. Most earlier trials of treatment were relatively short-term, small-group studies with various clinical end points, including severity of symptoms, exercise performance, and left ventricular function assessment; however, increasingly a higher standard of evidence has been required, including a provision of reliable, large-scale mortality trial data. This has been further encouraged, if not mandated, by the relatively recent appreciation that some agents may demonstrate dissociation of treatment effects, possibly dose related, with improved short-term outcomes but adverse effects on survival with prolonged treatment. The general principles of management of congestive heart failure encompass patient evaluation and confirmation of the diagnosis, consideration, and correction of underlying remediable causes and precipitating factors, pharmacological treatment, patient education and counseling, and planned follow-up, as summarized in recently published guidelines. This review focuses primarily on the available randomized controlled clinical trial evidence related to the pharmacological treatment of the clinical congestive heart failure syndrome. Other aspects of management, such as patient education, counseling, and planned follow-up, should be regarded as complementary to pharmacological treatment and important to ensure compliance and optimal long-term outcomes.

Are coronary patients at higher risk with digoxin therapy? An ongoing controversy

Previous reports have yielded contradictory conclusions regarding the safety of digoxin therapy in patients with acute myocardial infarction. The purpose of our study was to determine whether digoxin therapy is associated with increased mortality in patients with chronic coronary artery disease. We analyzed data from 8173 patients who were screened for participation in the Bezafibrate Infarction Prevention (BIP) trial and who survived an acute myocardial infarction at least 6 months prior to the study. Three-year overall mortality of the 451 (15.5%) patients receiving digoxin (according to the judgement of their treating physician) at the time of screening for BIP participation, was 22.4% compared to 8.3% in the patients who did not receive digoxin. Cardiac mortality was 16.2% in the digoxin-treated group, compared to 4.9% in the non-treated patients. The increased risk associated with digoxin remained statistically significant when patients were stratified according to sex, age groups, functional capacity and the presence of hypertension, diabetes or angina. The administration of digoxin to survivors of an acute myocardial infarction in the chronic phase of their disease, is statistically associated with a 30-50% increase in the risk of overall and cardiac mortality during long-term follow-up. A propensity of increased risk of arrhythmias in ischemic coronary patients may explain this finding.

The effects of an angiotensin-converting inhibitor (enalapril) on patients with mild cardiac failure--evaluating cardiac function based on the relationship between daily walking pace and heart rate

BACKGROUND

Heart failure has been evaluated by several methods, the New York Heart Association (NYHA) classification of heart failure based on symptoms being used most frequently. However, the degree of heart failure assessed by these criteria does not always correlate with cardiac function in daily life.

HYPOTHESIS

The aim of the study was to evaluate cardiac function based on the walking pace/heart rate (HR) relationship to assess the effects of enalapril, an angiotensin-converting enzyme inhibitor, in patients with mild to moderate cardiac function.

METHODS

To evaluate cardiac function objectively, we developed a method using a pedometer to count the steps walked while simultaneously recording HR using a Holter electrocardiograph (ECG). Step-count walk rate (WR) was recorded on the magnetic tape of the Holter apparatus, and both HR and walking pace were calculated automatically by the Holter ECG analysis system. Data were determined every hour, and mean pace and HR were plotted along the x and y axes, respectively. The slope of HR x WR was calculated using the least squares method. The slope and the total number of steps were regarded as indicators of cardiac function and quality of life, respectively. We analyzed 36 subjects, consisting of 8 normal volunteers, 8 patients in New York Heart Association (NYHA) class I. 11 in class II, and 9 in class III chronic mild heart failure, during maximal exercise work load by bicycle ergometer; furthermore, fractional shortening of the left ventricle on echocardiogram was determined in 14 patients with chronic mild heart failure and was compared with the slope of HR x WR. Enalapril was administered at a daily dose of 2.5-10 mg for 1-24 months (mean 6 months) in 60 patients to evaluate the effects of this drug on these parameters.

RESULTS

There was a significant inverse relationship between maximal work load and the HR x WR slope, and also between the fractional shortening and the slope, suggesting that the slope may reflect the severity of cardiac dysfunction. Furthermore, the slope decreased significantly from 1.8 +/- 1.26 before enalapril to 1.0 +/- 0.94 (mean +/- standard deviation) after drug administration, while the total number of steps increased significantly from 4842 +/- 3581 to 7804 +/- 4793.

CONCLUSION

The slope of the graph relating step count and HR proved to be a good, objective indicator of cardiac function, and enalapril therapy improved this parameter.

Medical therapy of chronic heart failure. Role of ACE inhibitors and beta-blockers

Heart failure has long been considered to have a progressive downhill course leading inexorably to an early demise. This course often occurs silently, in the absence of any obvious cardiac insults. The reason for this is a combination of cell loss, myocyte dysfunction, impaired energetics, and pathologic remodeling of the chamber. Improved clinical outcome should result from strategies that reduce the biologic signals responsible for myocyte growth, dysfunction, and loss and chamber remodeling. Clinicians should no longer attempt to treat chronic heart failure with pharmacologic growth and remodeling process. In time, it may be possible for the clinician to view the treatment of heart failure largely as a matter of improving the biologic function of the myocardium.

Saterinone, dobutamine, and sodium nitroprusside: comparison of cardiovascular profiles in patients with congestive heart failure

The acute hemodynamic effects of the phosphodiesterase (PDE) III inhibitor saterinone were compared with dobutamine and sodium nitroprusside in 12 patients with idiopathic congestive cardiomyopathy (NYHA III). Hemodynamic measurements were obtained with a Swan-Ganz thermodilution catheter. At the peak of its dose-response curve, saterinone induced an increase in cardiac index (+102%), stroke volume (+97%), and heart rate (+6%), paralleled by a decrease in pulmonary capillary wedge pressure (-46%), right atrial pressure (-51%), pulmonary arterial pressure (systolic -32%, diastolic -45%, mean -38%), systemic blood pressure (systolic -3%, diastolic -13%, mean -9%), systemic vascular resistance (-54%), and pulmonary vascular resistance (-58%). Dobutamine had similar effects on cardiac index (+106%) and stroke volume (+87%) but lacked vasodilatory characteristics. In contrast to dobutamine, both nitroprusside and saterinone demonstrated more pronounced vasodilatory effects. Nitroprusside was less effective on cardiac index (+66%) and stroke volume (+56%) than was saterinone. The double product was markedly increased by dobutamine (+28%), did not change with saterinone treatment (+2%), and decreased with nitroprusside (-10%). This indicates that according to double product, only the application of dobutamine caused a relevant increase in myocardial oxygen consumption. Saterinone was demonstrated to be a safe and potent drug on short-term application; it combines the vasodilating properties of sodium nitroprusside with the positive inotropic effects of dobutamine without major changes in myocardial oxygen consumption.

cAMP-mediated signal transduction and sarcoplasmic reticulum function in heart failure

There is evidence that the effects of beta-adrenergic receptor agonists on myocardial contractility result principally from the phosphorylation of phospholamban by cAMP-dependent protein kinase and the consequent deinhibition of SERCA2 activity and stimulation of sarcoplasmic reticulum Ca2+ transport. An impairment in beta-adrenergic receptor-stimulated cAMP generation, attributable to down-regulation of beta 1-adrenergic receptors and increased activity of G alpha i and G protein-coupled receptor kinase, has long been recognized in failing human myocardium. This impairment is associated with a compartment-specific decrease in sarcoplasmic reticulum cAMP content that may selectively reduce phospholamban phosphorylation. Published and preliminary results indicate that two plausible explanations for this compartment-specific decrease--a reduction in sarcoplasmic reticulum-associated cAMP-dependent protein kinase or an increase in sarcoplasmic reticulum-associated cAMP phosphodiesterase--are unlikely. Instead, there is reason to believe that the selective reduction in beta 1-adrenergic receptor density in failing myocardium is causally related to this compartment-specific decrease in cAMP content through an as-yet-undetermined mechanism. The fact that the modulation of SERCA2 activity by phospholamban is preserved in failing human myocardium offers an opportunity for improvement in the therapy of heart failure.

A case series of hospitalized patients with elevated digoxin levels

PURPOSE

Although there is renewed enthusiasm for the use of digoxin in patients with heart failure, current dosing guidelines are based on a nomogram published in 1974. We studied the incidence of and risk factors for elevated digoxin levels in patients admitted to a community hospital, and compared their dosage regimens to published guidelines.

SUBJECTS AND METHODS

We reviewed the charts of all patients who had serum digoxin levels greater than 2.4 ng/mL during a 6-month period. We collected demographic and clinical data, indications for digoxin use, digoxin dosage, concurrent medications, laboratory data, and clinical and electrocardiographic features of digoxin toxicity.

RESULTS

Of the 1,433 patients with digoxin assays, 115 (8%) patients had elevated levels. Of the 82 patients with complete records and correctly timed digoxin levels, 59 (72%) had electrocardiographic or clinical features of digoxin toxicity. Patients with serum digoxin levels >2.4 ng/mL were slightly older (78 +/- 8 versus 73 +/- 9 years of age; P = 0.12) and had greater serum creatinine levels (3.1 +/- 7.3 versus 1.4 +/- 0.3 mg/dL; P = 0.01) than those with levels < or =2.4 ng/mL. Forty-seven patients had elevated digoxin levels on admission, including 21 patients admitted for digoxin toxicity. Impaired or worsening renal function contributed to high levels in 37 patients, and a drug interaction was a contributory factor in 10 cases. Twenty (43%) of these patients were taking the recommended maintenance dose based on the scheme employed in the Digitalis Investigation Group study. Thirty-five patients developed high digoxin levels while in hospital. In 26 patients, this followed a loading dose of digoxin for the control of rapid atrial fibrillation. Impaired renal function was implicated in all of these patients. Despite the elevated digoxin level, rate control was achieved in only 11 patients of these patients.

CONCLUSIONS

Elevated digoxin levels and clinical toxicity remains a common adverse drug reaction. Elderly patients, particularly those with impaired renal function and low body weights, are at the greatest risk. As published digoxin nomograms often result in toxicity, clinical variables need to be monitored. In patients with congestive heart failure and normal sinus rhythm the potential benefit of digoxin is small; thus, patients should receive a dose that minimizes the risk of toxicity. For patients with new onset atrial fibrillation, other agents may be preferable for rate control.

Innovations in the pharmacologic management of heart failure

Improved understanding of the pathophysiologic course of heart failure has led to many advances in pharmacologic therapy. Angiotensin-converting enzyme inhibitors represent the first effort at targeting neurohormonal activation in chronic heart failure. More recently, beta-adrenergic receptor antagonists have been shown effective in blocking chronic sympathetic nervous system activation. The roles of digoxin and the newer, vasoselective calcium channel blockers in heart failure have been better defined. Other agents targeting the neurohormonal system are under investigation. These include angiotensin-receptor antagonists, aldosterone inhibitors, and endothelin antagonists. Experience with phosphodiesterase inhibitors and adrenergic agents has confirmed the importance of neurohormonal activation in progression of heart failure. Despite angiotensin-converting enzyme inhibitor, diuretic, and digoxin therapy, mortality in heart failure remains high. Careful manipulation of the neurohormonal response to heart failure holds promise for altering the course of the disease.

Clinical predictors of worsening heart failure during withdrawal from digoxin therapy

Previous work provides limited information concerning predictors of clinical deterioration after digoxin withdrawal. We investigated the association between selected baseline clinical characteristics and symptomatic deterioration in two similarly designed trials: Prospective Randomized Study of Ventricular Function and Efficacy of Digoxin (PROVED) and Randomized Assessment of Digoxin and Inhibitors of Angiotensin-Converting Enzyme (RADIANCE). Cox proportional-hazards analysis found the following independent predictors of worsening during follow-up in the combined PROVED and RADIANCE patients: heart failure score, left ventricular ejection fraction, cardiothoracic ratio, use of an angiotensin-converting enzyme inhibitor, use of digoxin, and age. When these factors, except for digoxin use, were tested in the subgroup of patients withdrawn from digoxin, they all were significant independent predictors of worsening heart failure. In contrast, only use of angiotensin-converting enzyme inhibitor predicted deterioration in patients who continued digoxin. Patients with more congestive symptoms, worse ventricular function, greater cardiac enlargement, or who were not taking an angiotensin-converting enzyme inhibitor were significantly more likely to worsen early after digoxin discontinuation than patients without these characteristics.

Restoring function in failing hearts: the effects of beta blockers

Until recently, clinical management of congestive heart failure was purely palliative. The drugs used in patients with failing hearts--digoxin, vasodilators, and positive inotropic agents--improved contractility, reversed hemodynamic abnormalities, and enhanced functional status, but they failed to confer a survival benefit. Indeed, the use of inotropic agents often resulted in excess mortality--a paradox explained in part by the pharmacological properties of these agents, which increase production of cAMP, the intracellular messenger for the beta-adrenergic system. The short-term pharmacological benefits of these drugs may be offset by deleterious long-term biological effects on the heart muscle itself. The use of beta-blockers in heart failure is counterintuitive, given that their initial pharmacological effect is to reduce heart rate and contractility in a faltering heart, thus producing an effect diametrically opposed to that of inotropic agents. However, it is becoming more clear that beta-blocker therapy in patients with heart failure not only improves left ventricular function, but may actually reverse pathological remodeling in the heart. Accumulating clinical evidence indicates that these beneficial changes are the result of secondary biological changes in the myocardium rather than a response to the pharmacological effects of the drugs themselves. Mounting evidence suggest that these agents may prolong survival in patients with heart failure, and ongoing clinical trials may soon confirm these preliminary findings.

Does digoxin still have a role in congestive heart failure?

The role of digoxin in the treatment of congestive heart failure is (CHF) being questioned. Digoxin continues to be the drug of choice for patients with atrial fibrillation in CHF. Large randomised trials have shown that digoxin (in addition to ACE inhibitors and diuretic) is beneficial in CHF due to systolic dysfunction, although it does not reduce mortality. Limited data suggest that digoxin benefit some, but not all patients with CHF due to left to right shunts. Digoxin does not benefit CHF due to diastolic dysfunction and it is not routinely recommended for prematures with patent ductus and CHF. The treatment with digoxin should be individualised.

Pharmacotherapy for systolic dysfunction: a review of randomized clinical trials

Chronic heart failure (HF) is a leading cause of morbidity and mortality in the United States, affecting >4 million people. The increasing prevalence of HF has placed an enormous burden on the US healthcare system. For many patients with cardiovascular disease, HF is the final common pathway. Treatment strategies for HF are aimed at preventing and delaying progression of the disease and ultimately improving survival. This article reviews recent clinical drug trials for HF, including angiotensin-converting enzyme (ACE) inhibitors, angiotensin II antagonists, vasodilators, beta-adrenergic blockers, positive inotropic agents, calcium antagonists, and antiarrhythmics. The benefits and shortcomings of these agents and the study designs are discussed. For patients with left ventricular (LV) systolic dysfunction, ACE inhibitors are the only agents that consistently improved survival and decreased the rate of HF progression. It is likely that beta-adrenergic blockers have the same effect. The syndrome of HF is complex with both peripheral and cardiac factors contributing to disease progression. The addition of a diuretic and/or digoxin is often needed to prevent worsening heart failure. Although an angiotensin II antagonist may also be beneficial in the treatment of HF, further studies are needed to clarify their precise role in the management of this condition. Calcium anatagonists, antiarrhythmics excluding amiodarone, and positive inotropes other than digoxin do not appear to prevent progression of HF nor improve survival. The most common cause of HF in the United States is related to coronary artery disease. Reduction of cardiac risk factors, such as smoking cessation, lowering serum cholesterol with diet and a lipid lowering agent, and blood pressure control, is likely to prevent the development or progression of HF.

[Status of digitalis in therapy of acute and chronic heart failure]

Although supported by more than 200 years of experience and anecdotal clinical evidence, the efficacy of digitalis in the management of heart failure has been questioned until the past decade. The idea to improve contractility of the diseased myocardium with an inotropic agent is fundamental in the management of left ventricular dysfunction. The majority of clinical trials published since 1980, most of which examined patients with mild to moderate heart failure, indicate that digitalis alone or in combination with vasodilators may improve the clinical outcome particular in those patients with more advanced symptoms and poorer left ventricular function. Aside from its action as an inotropic drug the pharmacology and the mechanisms by which digitalis influence the diseased myocardium and peripheral circulation in heart failure has gained more complexity within the last years, raising the idea of other mechanisms that might be involved in its action. Particular for ACE inhibition multiple clinical trials have conclusively demonstrated its impact on survival and morbidity in congestive heart failure. Improvement of clinical outcome as measured in terms of fewer hospitalizations and improvement of symptoms in patients receiving digitalis seems to be comparable to patients receiving beta-blockers additional to diuretics and ACE inhibitors, an entirely different approach to the treatment of heart failure. Despite initial improvement of hemodynamics it now appears that there is no survival benefit found for digitalis in the management of heart failure.

Contribution of phosphodiesterase isozymes to the regulation of the L-type calcium current in human cardiac myocytes

1. To determine the contribution of the various phosphodiesterase (PDE) isozymes to the regulation of the L-type calcium current (ICa(L)) in the human myocardium, we investigated the effect of selective and non-selective PDE inhibitors on ICa(L) in single human atrial cells by use of the whole-cell patch-clamp method. We repeated some experiments in rabbit atrial myocytes, to make a species comparison. 2. In human atrial cells, 100 microM pimobendan increased ICa(L) (evoked by depolarization to +10 mV from a holding potential of -40 mV) by 250.4 +/- 45.0% (n = 15), with the concentration for half-maximal stimulation (EC50) being 1.13 microM. ICa(L) was increased by 100 microM UD-CG 212 by 174.5 +/- 30.2% (n = 10) with an EC50 value of 1.78 microM in human atrial cells. These two agents inhibit PDE III selectively. 3. A selective PDE IV inhibitor, rolipram (1-100 microM), did not itself affect ICa(L) in human atrial cells. However, 100 microM rolipram significantly enhanced the effect of 100 microM UD-CG 212 on ICa(L) (increase with UD-CG 212 alone, 167.9 +/- 33.9, n = 5; increase with the two agents together, 270.0 +/- 52.2%; n = 5, P < 0.05). Rolipram also enhanced isoprenaline (5 nM)-stimulated ICa(L) by 52.9 +/- 9.3% (n = 5) in human atrial cells. 4. In rabbit atrial cells, ICa(L) at +10 mV was increased by 22.1 +/- 9.0% by UD-CG 212 (n = 10) and by 67.4 +/- 12.0% (n = 10) by pimobendan (each at 100 microM). These values were significantly lower than those obtained in human atrial cells (P < 0.0001). Rolipram (1-100 microM) did not itself affect ICa(L) in rabbit atrial cells. However, ICa(L) was increased by 215.7 +/- 65.2% (n = 10) by the combination of 100 microM UD-CG 212 and 100 microM rolipram. This value was almost 10 times larger than that obtained for the effect of 100 microM UD-CG 212 alone. 5. These results imply a species difference: in the human atrium, the PDE III isoform seems dominant, whereas PDE IV may be more important in the rabbit atrium for regulating ICa(L). However, PDE IV might contribute significantly to the regulation of intracellular cyclic AMP in human myocardium when PDE III is already inhibited or when the myocardium is under beta-adrenoceptor-mediated stimulation.

Patients with mild heart failure worsen during withdrawal from digoxin therapy

OBJECTIVES

We investigated whether patients with mild heart failure due to left ventricular systolic dysfunction were at risk of worsening during digoxin withdrawal.

BACKGROUND

Deterioration during digoxin withdrawal is often believed to be restricted to patients with moderate to severe clinical evidence of heart failure. To test this hypothesis, we studied the outcome of patients categorized by treatment assignment and a clinical signs and symptoms heart failure score in two rigorously designed clinical heart failure trials: the Prospective Randomized Study of Ventricular Function and Efficacy of Digoxin (PROVED) and the Randomized Assessment of Digoxin and Inhibitors of Angiotensin-Converting Enzyme (RADIANCE) trial.

METHODS

Potential differences in treatment failure, left ventricular ejection fraction and exercise capacity were evaluated in three groups of patients: those with mild heart failure (score < or = 2) who were withdrawn from digoxin (Dig WD Mild); those with moderate heart failure (score > 2) who were withdrawn from digoxin (Dig WD Moderate); and patients who continued receiving digoxin regardless of heart failure score (Dig Cont).

RESULTS

Heart failure score at randomization did not predict outcome during follow-up in Dig Cont-group patients. Dig WD Mild-group patients were at increased risk of treatment failure and had deterioration of exercise capacity and left ventricular ejection fraction compared with that in Dig Cont-group patients (all p < 0.01). Patients in the Dig WD Moderate group were significantly more likely to experience treatment failure than patients in either the Dig WD Mild or Dig Cont group (both p < 0.05).

CONCLUSIONS

Patients with systolic left ventricular dysfunction were at risk of clinical deterioration after digoxin withdrawal despite mild clinical evidence of congestive heart failure.

Effects of a new cardiotonic phosphodiesterase III inhibitor, olprinone, on cardiohemodynamics and plasma hormones in conscious pigs with heart failure

We examined the effects of a novel phosphodiesterase III inhibitor, olprinone, on the cardiohemodynamics and plasma hormones in conscious pigs with pacing-induced heart failure. After pacing for 5-10 days, cardiac output (CO) decreased from 2.25 +/- 0.17 to 1.67 +/- 0.13 L/min (n = 8, p < 0.01) and stroke volume (SV) decreased from 20.1 +/- 2.1 to 12.0 +/- 1.6 ml (n = 8, p < 0.01), whereas left arterial pressure (LAP) increased from 2.8 +/- 1.2 to 16.7 -/+ 0.9 mm Hg (n = 7, p < 0.001) and systemic vascular resistance (SVR) increased from 38.7 +/- 3.5 to 49.8 +/- 4.2 mm Hg/L/min (n = 8, p < 0.01). Sequential intravenous infusions of 0.03, 0.3, and 3.0 microg/kg/min of olprinone at 30-min intervals to eight pigs caused dose-dependent increases in the decreased CO, SV, and maximal rate of rise in left ventricular pressure (LV dP/dt(max)) and decreased the elevated LAP and SVR. Olprinone at 3.0 microg/kg/min maximally increased CO, SV, and LV dP/dt(max) by 40.0 +/- 10.8% (p < 0.05 vs. vehicle), 25.6 +/- 6.9% (p < 0.05), and 43.9 +/- 11.2% (p < 0.01), respectively, and brought about a slight increase in heart rate and decreases in LAP and SVR, by 35.9 +/- 7.3% (p < 0.001) and 27.9 +/- 4.8% (p < 0.01), respectively. Olprinone did not affect the rate-pressure product. In addition, olprinone produced significant decreases in the plasma levels of atrial natriuretic peptide and cyclic guanosine monophosphate, with no changes in the plasma levels of cyclic adenosine monophosphate and catecholamines or plasma renin activity. These findings indicate that the short-term intravenous infusions of olprinone ameliorated the decreased left ventricular function without affecting myocardial oxygen consumption or the sympathetic nervous system in conscious pigs with heart failure.

Does digoxin provide additional hemodynamic and autonomic benefit at higher doses in patients with mild to moderate heart failure and normal sinus rhythm?

OBJECTIVES

This study sought to examine the hemodynamic and autonomic dose response to digoxin.

BACKGROUND

Previous studies have demonstrated an increase in contractility and heart rate variability with digitalis preparations. However, little is known about the dose-response to digoxin, which has a narrow therapeutic window.

METHODS

Nineteen patients with moderate heart failure and a left ventricular ejection fraction < 0.45 were studied hemodynamically using echocardiography and blood pressure at baseline and after 2 weeks of low dose (0.125 mg daily) and 2 weeks of moderate dose digoxin (0.25 mg daily). Loading conditions were altered with nitroprusside at each study. Autonomic function was studied by assessing heart rate variability on 24-h Holter monitoring and plasma norepinephrine levels during supine rest.

RESULTS

Low dose digoxin provided a significant increase in ventricular performance, but no further increase was seen with the moderate dose. Low dose digoxin reduced heart rate and increased heart rate variability. Moderate dose digoxin produced no additional increase in heart rate variability or reduction in sympathetic activity, as manifested by heart rate, plasma norepinephrine or low frequency/high frequency power ratio. In addition, we did not find that either low or moderate dose digoxin increased parasympathetic activity.

CONCLUSIONS

We conclude that moderate dose digoxin provides no additional hemodynamic or autonomic benefit for patients with mild to moderate heart failure over low dose digoxin. Because higher doses of digoxin may predispose to arrhythmogenesis, lower dose digoxin should be considered in patients with mild to moderate heart failure.

Cardiac and hemodynamic effects of TZC-5665, a novel pyridazinone derivative, and its metabolite in humans and dogs

1. TZC-5665 is a novel pyridazinone derivative with vasodilatory and beta-adrenergic blocking activities and type III phosphodiesterase inhibitory action. 2. In healthy volunteers, TZC-5665 was rapidly absorbed and immediately metabolized. Its main metabolite, M-2, remained at a higher concentration in plasma. Orally administered TZC-5665 reduced end-diastolic left ventricular volume (20.16 ml) and exhibited a tendency to increase ejection fraction (0.04). 3. In dogs, M-2 dose-dependently increased cardiac contractility and reduced both preload and afterload. These effects appeared more potent in the failed heart than in the normal heart. At the same dose (30 micrograms/kg), the effects of M-2 seem to be more potent than those of milrinone. 4. We concluded that TZC-5665 is a useful medication for treating patients with chronic congestive heart failure (CHF) because of the positive inotropic and vasodilating effects due to its active metabolite in addition to its own beta-adrenergic blocking actions.

Dose of digoxin prescribed in the UK compared with France and the USA

BACKGROUND

Two trials in patients with heart failure showed that some patients grew worse if digoxin was withdrawn. The median daily dose of digoxin in these trials was 375 micrograms. We suspected that doses used in the UK were much lower.

METHODS

We studied the prescription of digoxin to 119 patients who were discharged from St George's Hospital, London, UK, in April and May, 1994. We calculated the appropriate digoxin prescription dose by Jelliffe's formula. Appropriate doses were put into a scale of six levels: 62.5 micrograms, 125 micrograms, 187.5 micrograms, 250 micrograms, 375 micrograms, or 500 micrograms. We compared our findings with information from a database of prescription records. These records, gathered during 1993-94, came from the UK (1085 prescriptions). France (1148), and the USA (2303).

FINDINGS

In the St George's Hospital series, the median daily dose of digoxin was 125 micrograms (mean 170 [SD 80] micrograms). The dose was significantly higher in patients who had heart failure than those who did not, by a mean of 40 micrograms. Among the 100 patients for whom appropriate dose was calculated, the dose was as predicted in 28, one level too low in 34, two or more levels too low in 32, and one level too high in six. There was no difference between St George's Hospital and UK practice as a whole (p > 0.05), but the dosage was significantly higher in the USA and France than in the UK (p < 0.001 for both) and significantly higher in France than in the USA (p < 0.001).

INTERPRETATION

Differences in dosage may be correlated to the range of tablet strengths available in each country in our analysis. Underdosing can be detected with certainty only if plasma digoxin concentration is measured. However, our study provides strong circumstantial evidence that many patients in the UK are receiving too little digoxin.

Effects of digoxin on time domain measures of heart rate variability in patients with stable chronic cardiac failure: withdrawal and comparison group studies

The effect on heart rate variability of adding digoxin to a diuretic and ACE inhibitor was studied in patients with chronic stable cardiac failure. Digoxin was found to increase heart rate variability, especially those measures of heart rate variability thought to represent parasympathetic activity. The withdrawal of digoxin led to a decrease in heart rate variability to pre-treatment levels. Whilst digoxin in standard doses does not alter prognosis in chronic cardiac failure, it does have potentially beneficial neurohumoral effects. If the increase in heart rate variability, which represents beneficial neurohumoral modulation, can be divorced from the potentially detrimental effects, perhaps by using smaller doses, then there may be a role for digoxin in the treatment of chronic cardiac failure.

Current and newer approaches in the drug treatment of congestive heart failure

Most patients with chronic congestive heart failure (CHF) are subjected to symptomatic treatment, predominantly with drugs. Over the years, it has become clear that treatment with unloading drugs is probably more beneficial than treatment with inotropic agents. In addition, it has been widely recognized that the neuroendocrine compensatory changes associated with CHF afford and important target for drug treatment. This may also hold for some of the changes in receptor density, such as the downregulation of cardiac beta-adrenoceptors. The present and clearly changing insights into the backgrounds of drugs for the treatment of CHF are critically discussed. Apart from the changing views and appreciation of the currently used drugs (diuretics, ACE inhibitors, digoxin, beta-adrenoceptor agonists), the following new approaches are discussed: beta-blockers, angiotensin II receptor antagonists, ibopamine, calcium antagonists, inhibitors of ANP degradation, vasopression antagonist, vesnarinone, and calcium sensitizers.

Inotropic agents in the treatment of heart failure: despair or hope?

Depression of myocardial contractility plays an important role in the development of heart failure; therefore, intensive interest and passion have been generated to develop cardiotonic agents to improve the contractile function of the failing heart. Inotropic agents that increase cyclic AMP, either by increasing its synthesis or reducing its degradation, exert dramatic short-term hemodynamic benefits, but these acute effects cannot be extrapolated into long-term improvement of the clinical outcome in patients with advanced heart failure. Administration of these agents to an energy-starved failing heart would be expected to increase myocardial energy use and could accelerate disease progression. The role of digitalis in the management of heart failure has been controversial, but ironically the drug has now been proved to favorably affect the neurohormonal disorders and its reevaluation is now being intensively investigated. More recently, attention has been focused on other inotropic agents that have a complex and diversified mechanism. Recent clinical studies have demonstrated that they are potentially useful in the long-term treatment of heart failure patients. These agents have some phosphodiesterase-inhibitory action but also possess additional effects, including acting as cytokine inhibitors, immunomodulators, or calcium sensitizers. However, their therapeutic ratio is narrow and further studies are warranted to establish their optimal doses and their eventual status in the treatment of heart failure.

Prolongation of the life span of cardiomyopathic hamster by the adrenergic beta 1-selective partial agonist denopamine

Influence of cardiotonic agents on the prognosis of heart failure depends on the individual therapeutic agents, and favorable and unfavorable effects of these agents have been reported in clinical trials. We studied the effect of the cardiotonic agent denopamine on the life span of cardiomyopathic hamsters (BIO 14.6 strain) in the heart failure period. Non-treated hamsters started to die at 40 weeks of age, and their survival rate decreased to 23.8% at the age of 65 weeks. Hamsters treated with denopamine (400 ppm in diet) from 36 weeks of age did not die until the age of 52 weeks, except in cases of accidental death. The survival rate of this group at 65 weeks of age was about 40%. Survival rates of these 2 groups were significantly different (P < 0.05) when animals with accidental death were excluded. To elucidate the mechanism of the effect of denopamine, we performed several experiments after dietary treatment with denopamine for 4 to 6 weeks from 37 weeks of age. Denopamine treatment lowered plasma levels of noradrenaline and dopamine (P < 0.05), but affected neither the cardiac contractility nor the beta-adrenoceptor density. In summary, denopamine significantly decreases the mortality of cardiomyopathic hamsters. Its effect to lower the plasma catecholamine levels may be responsible for the beneficial effect of denopamine.

Double-blind, placebo-controlled study of the effects of carvedilol in patients with moderate to severe heart failure. The PRECISE Trial. Prospective Randomized Evaluation of Carvedilol on Symptoms and Exercise

BACKGROUND

Carvedilol has improved the symptomatic status of patients with moderate to severe heart failure in single-center studies, but its clinical effects have not been evaluated in large, multicenter trials.

METHODS AND RESULTS

We enrolled 278 patients with moderate to severe heart failure (6-minute walk distance, 150 to 450 m) and a left ventricular ejection fraction < or = 0.35 at 31 centers. After an open-label, run-in period, each patient was randomly assigned (double-blind) to either placebo (n = 145) or carvedilol (n = 133; target dose, 25 to 50 mg BID) for 6 months, while background therapy with digoxin, diuretics, and an ACE inhibitor remained constant. Compared with placebo, patients in the carvedilol group had a greater frequency of symptomatic improvement and lower risk of clinical deterioration, as evaluated by changes in the NYHA functional class (P = .014) or by a global assessment of progress judged either by the patient (P = .002) or by the physician (P < .001). In addition, treatment with carvedilol was associated with a significant increase in ejection fraction (P < .001) and a significant decrease in the combined risk of morbidity and mortality (P = .029). In contrast, carvedilol therapy had little effect on indirect measures of patient benefit, including changes in exercise tolerance or quality-of-life scores. The effects of the drug were similar in patients with ischemic heart disease or idiopathic dilated cardiomyopathy as the cause of heart failure.

CONCLUSIONS

These findings indicate that, in addition to its favorable effects on survival, carvedilol produces important clinical benefits in patients with moderate to severe heart failure treated with digoxin, diuretics, and an ACE inhibitor.

Digitalis in the treatment of heart failure in the elderly. The GIFA study results

Digitalis glycosides have played an important role in the treatment of patients with heart failure (HF) for more than two centuries. Despite the introduction of new therapeutic strategies in the treatment of HF, and controversies regarding the role of digitalis in HF in sinus rhythm and its effect on mortality, digoxin is one of the most commonly prescribed drugs in the community and in hospital settings, particularly in the elderly. The Italian Group of Pharmacosurveillance in the Elderly (GIFA) monitored 20,047 hospitalized patients in 1988, 1991 and 1993, and found that digoxin was the most frequently prescribed drug in the management of HF. Inappropriate prescriptions of digitalis, defined with standardized criteria, were uncommon, and the mean daily dosage was low. Compared to earlier studies the incidence rate of adverse drug reactions (ADRs) to digoxin, was also low. The reduction in ADRs incidence was probably due to a better understanding of digoxin pharmacokinetics and to a lower daily dosage in the elderly. Nevertheless, digoxin toxicity was significantly more frequent in patients aged >or= 80 years than in those aged < 65 and and 65-79 years. In a multidrug approach to the treatment of chronic HF, digoxin exerts clinical benefits also in patients with sinus rhythm, it is not costly, it is easy to administer, and toxic effects are not common.

Medical therapy can improve the biological properties of the chronically failing heart. A new era in the treatment of heart failure

Myocardial failure has been considered to be an irreversible and progressive process characterized by ventricular enlargement, chamber geometric alterations, and diminished pump performance. However, more recent evidence has suggested that certain types of medical therapy may lead to retardation and even reversal of the cardiomyopathic process. In the failing heart, long-term neurohormonal/autocrine-paracrine activation results in abnormalities in myocyte growth, energy production and utilization, calcium flux, and receptor regulation that produce a progressively dysfunctional, mechanically inefficient heart. Interventions such as ACE inhibition and beta-blockade result in a reduction in the harmful long-term consequences of neurohormonal/autocrine-paracrine effects and retard the progression of left ventricular dysfunction or ventricular remodeling. Furthermore, in subjects with idiopathic dilated or ischemic cardiomyopathy, antiadrenergic therapy with beta-blocking agents appears to be able to partially reverse systolic dysfunction and ventricular remodeling. Although the precise mechanisms underlying this latter effect have not yet been elucidated, the general mechanism appears to be via improvement in the biological function of the cardiac myocyte. Such an improvement in the intrinsic defect(s) responsible for myocardial failure will likely translate into important clinical benefits.

Value of digoxin in heart failure and sinus rhythm: new features of an old drug?

Digoxin has been a controversial drug since its introduction >200 years ago. Although its efficacy in patients with heart failure and atrial fibrillation is clear, its value in patients with heart failure and sinus rhythm has often been questioned. In the 1980s, reports of some large-scale trials indicated that digoxin, with or without vasodilators or angiotensin-converting enzyme inhibitors, reduced signs and symptoms of congestive heart failure and improved exercise tolerance. This beneficial influence was mainly found in patients with more advanced heart failure and dilated ventricles, whereas the effect in those with mild disease appeared to be less pronounced. In the last few years, new data have shown that digoxin may also have clinical value in mild heart failure, either when used in combination with other drugs or when administered alone. As neurohumoral activation has increasingly been recognized to be a contributing factor in the disease progression of chronic heart failure, the modulating effects of digoxin on neurohumoral and autonomic status have received more attention. Also, there is evidence that relatively low doses of digoxin may be at least as effective as higher doses and have a lower incidence of side effects. Further, the recognition that the use of digoxin too early after myocardial infarction may be harmful and the development of other drugs, in particular angiotensin-converting enzyme inhibitors, have obviously changed the place of digoxin in the treatment of chronic heart failure. The large-scale survival trial by the Digitalis Investigators Group (DIG), whose preliminary results have recently been presented, has shown that although digoxin has a neutral effect on total mortality during long-term treatment, it reduces the number of hospital admissions and deaths due to worsening heart failure. The potentially new features of the old drug digoxin are discussed in this review.

Cellular basis for improved left ventricular pump function after digoxin therapy in experimental left ventricular failure

OBJECTIVES

The present study examined left ventricular (LV) and myocyte contractile performance and electrophysiologic variables after long-term digoxin treatment in a model of LV failure.

BACKGROUND

A fundamental therapeutic agent for patients with chronic LV dysfunction is the cardiac glycoside digoxin. However, whether digoxin has direct effects on myocyte contractile function and electrophysiologic properties in the setting of chronic LV dysfunction remains unexplored.

METHODS

Left ventricular and isolated myocyte function and electrophysiologic variables were examined in five control dogs, five dogs after the development of long-term rapid pacing (rapid pacing, 220 beats/min, 4 weeks) and five dogs with rapid pacing given digoxin (0.25 mg/day) during the pacing period (rapid pacing and digoxin).

RESULTS

Left ventricular ejection fraction decreased in the dogs with rapid pacing compared with that in control dogs (30 +/- 2% vs. 68 +/- 3%, p < 0.05) and was higher with digoxin than that in the rapid pacing group (38 +/- 3%, p = 0.038). Left ventricular end-diastolic volume increased in the rapid pacing group compared with the control group (84 +/- 6 ml vs. 59 +/- 7 ml, p < 0.05) and remained increased with digoxin (79 +/- 6 ml). Isolated myocyte shortening velocity decreased in the rapid pacing group compared with the control group (37 +/- 1 microns/s vs. 59 +/- 1 microns/s, p < 0.05) and increased with digoxin compared with rapid pacing (46 +/- 1 microns/s, p < 0.05). Action potential maximal upstroke velocity was diminished in the rapid pacing group compared with the control group (135 +/- 6 V/s vs. 163 +/- 9 V/s, p < 0.05) and increased with digoxin compared with rapid pacing (155 +/- 12 V/s, p < 0.05). Action potential duration increased in the rapid pacing group compared with the control group (247 +/- 10 vs. 216 +/- 6 ms, p < 0.05) and decreased with digoxin compared with rapid pacing (219 +/- 12 ms, p < 0.05).

CONCLUSIONS

In this model of rapid pacing-induced LV failure, digoxin treatment improved LV pump function, enhanced isolated myocyte contractile performance and normalized myocyte action potential characteristics. This study provides unique evidence to suggest that the cellular basis for improved LV pump function with digoxin treatment in the setting of LV failure has a direct and beneficial effect on myocyte contractile function and electrophysiologic measures.

Metoprolol in dilated cardiomyopathy: is it possible to identify factors predictive of improvement? The Heart Muscle Disease Study Group

BACKGROUND

Some controlled clinical trials showed a beneficial effect of beta-blockers on symptoms, exercise tolerance, and left ventricular function in dilated cardiomyopathy. The purpose of this study was to investigate if there are clinical variables at baseline that could predict a favorable response to long-term metoprolol therapy.

METHODS AND RESULTS

Since November 1987, 94 consecutive patients with dilated cardiomyopathy and left ventricular ejection fraction less than 0.40 were treated with metoprolol (mean final dosage, 136 +/- 32 mg) associated with tailored medical therapy with digitalis, diuretics, and angiotensin-converting enzyme inhibitors. Eighty-four surviving patients had a complete 2-year noninvasive follow-up period. Ten patients died or were transplanted before the final assessment. Improvement was defined according to a clinical score based on left ventricular ejection fraction (increase > or = 10 U), left ventricular end-diastolic diameter (decrease > or = 10%), regression of restrictive filling pattern, New York Heart Association functional class, exercise tolerance (increase > or = 2 minutes), and cardiothoracic ratio (decrease > or = 10%). According to these criteria, 48 patients (51.1%) were classified as improved. Multivariate analysis identified a group of patients with a history of mild hypertension (blood pressure between 140/90 and 170/100 mmHg) and significantly higher probability of improvement with longterm metoprolol (odds ratio [OR], 2.22; 95% confidence interval, 1.25-3.94; P = .007). Among the 71 patients with normal blood pressure (< 140/90 mmHg), heart rate in upright position (100 vs 75 beats/min: OR, 2; 95% confidence interval, 1.38-4.94; P = .003), left ventricular ejection fraction 0.20-0.33 versus less than 0.20 (OR, 4.72; 95% confidence interval, 1.06-21.04; P = .042), and New York Heart Association class I-II versus III-IV (OR, 2.74; 95% confidence interval, 0.97-7.75; P = .05) were significantly associated with a positive response to metoprolol. At baseline, both supine and upright heart rate were significantly higher in patients who improved, but heart rate in the upright position was the most significant predictor of improvement in patients with normal blood pressure at multivariate analysis.

CONCLUSIONS

According to the authors' logit model, patients with a history of mild hypertension or with a higher resting heart rate, associated with controlled symptoms of heart failure (New York Heart Association class I-II) or moderate to severe left ventricular ejection fraction (range, 0.20-0.33) showed a remarkable probability of long-term (2-year) improvement on metoprolol.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Effect of a new beta-blocker, nipradilol, on cardiac function and neurohumoral factors in idiopathic dilated cardiomyopathy

This study investigated the therapeutic efficacy of a new beta-blocker, nipradilol, a non-selective agent with vasodilating activity, for the treatment of idiopathic dilated cardiomyopathy (DCM). The New York Heart Association functional class improved in the nipradilol group (n = 9, p < 0.01), but not in the control group who received conventional therapy (n = 9). The observation period was 19 +/- 7 months in the nipradilol group, and 20 +/- 9 months in the control group. Before therapy there was no difference in heart rate between the 2 groups (76 +/- 12 vs 79 +/- 15 beats/min). The end-diastolic and end-systolic left ventricular dimensions decreased in the nipradilol group (p < 0.05), but not in the control group. Radionuclide ventriculography revealed that the left ventricular ejection fraction increased in the nipradilol group (27 +/- 8 to 41 +/- 18%, p < 0.05), but not in the control group (27 +/- 11 to 27 +/- 8%). Plasma norepinephrine tended to be lowered, although not significantly, whereas plasma alpha atrial natriuretic peptide significantly decreased after the therapy (p < 0.01) in the treatment group. Lymphocyte beta-adrenoceptors were up-regulated in the nipradilol group (p < 0.05). None of these parameters changed during the observation period in the control group. Thus, nipradilol improved symptoms and cardiac function with a favorable effect on neurohumoral factors in patients with DCM.

Inotropic agents in older patients with chronic heart failure--current perspectives

Until recently, inotropic therapy has been regarded as the most direct remedy for the left ventricular systolic dysfunction that often underlies the development of heart failure. Nevertheless, all the agents with significant inotropic properties that have been evaluated to date (such as beta adrenergic stimulants, phosphodiesterase inhibitors, and high-dose vesnarinone) showed significant increases in mortality with long-term administration. However, it is noteworthy that the participants in trials to evaluate inotropic therapy were not representative of geriatric heart failure patients for age, gender, and comorbidity. Thus, results from these studies must be interpreted cautiously when treatment for chronic heart failure must be applied to elderly subjects. At present, digitalis is the only inotropic agent recommended for long-term treatment, because it improves symptoms and prevents disease progression through neurohormonal and baroreceptor mechanisms; nevertheless, its long-term safety is still undetermined. The role of low-dose vesnarinone, pimobendan and ibopamine, which share neurohormonal, rather than inotropic, mechanisms of action, is still under investigation. Pending the definition of these issues, ACE-inhibitors and diuretics remain the mainstay of therapy for chromic heart failure.

Influence of digitalis on left ventricular functional response to exercise in congestive heart failure

This was a double-blind, placebo-controlled, crossover study designed to determine the influence of digitalis treatment on left ventricular (LV) response to physical exercise in patients with congestive heart failure (CHF). In 10 patients with CHF (ejection fraction 29 +/- 2%), LV function was assessed during upright bicycle exercise using an ambulatory radionuclide detector for continuous noninvasive monitoring of cardiac function. Exercise was performed during control conditions and after a 3-week treatment with digoxin (0.25 mg/day orally) or placebo. Ten normal volunteers matched for sex and age constituted the control group. In normals, exercise ejection fraction and end-diastolic volume increased (both p <0.001), while end-systolic volume decreased progressively (p <0.001). In control conditions, patients with CHF had a sharp increase in heart rate during exercise, while ejection fraction did not change; both end-diastolic and end-systolic volumes increased significantly (both p <0.001) during exercise. During digoxin treatment, heart rate response to exercise recorded in patients with CHF was comparable to that recorded in normal subjects. In addition, a significant increase in ejection fraction during exercise was detected (P <0.001), and the increase in end-systolic volume was significantly smaller than that observed in control conditions (p <0.05). When patients received placebo, the responses of LV function to exercise were comparable to those observed in control conditions. These findings demonstrate that digitalis has a favorable influence on LV functional adaptation to exercise in CHF.

[Current status of treatment of chronic cardiac insufficiency]

When there is no correctable cause, cardiac failure continues to progress and outcome is poor. However several controlled clinical trials have shown that several therapeutic agents relieve symptoms, improve exercise tolerance and, for some, reduce mortality. Patients in NYHA functional class II, III and IV, whose systolic function is impaired should be treated by digitalis, diuretics and angiotensin-converting-enzyme inhibitors. These therapeutic agents are complementary and each of them are required. Moreover a study has shown that the impairment of patients in NYHA functional class I (who are still asymptomatic but with a ventricular ejection fraction < 35%) could be slowed by angiotensin-converting-enzyme inhibitors. In each case, it is of paramount importance to exclude treatable causes of heart failure because the best the symptomatic treatment can do is slow the inevitable worsening of the disease.

Energetically optimal left ventricular pressure for the failing human heart

BACKGROUND

An energy-starved failing heart would benefit from more effective transfer of the mechanical energy of ventricular contraction to blood propulsion. However, the energetically optimal loading conditions for the failing heart are difficult to establish. In the present study, we analyzed the optimal left ventricular pressure to achieve maximal mechanical efficiency of the failing heart in humans.

METHODS AND RESULTS

We determined the relation between left ventricular pressure-volume area and myocardial oxygen consumption per beat (VO2), stoke work, and mechanical efficiency (stroke work/VO2) in 13 patients with different contractile states. We also calculated the optimal end-systolic pressure that would theoretically maximize mechanical efficiency for a given end-diastolic volume and contractility. Left ventricular pressure-volume loops were constructed by plotting the instantaneous left ventricular pressure against the left ventricular volume at baseline and during pressure loading. The contractile properties of the ventricle were defined by the slope of the end-systolic pressure-volume relation. In patients with less compromised ventricular function, the operating end-systolic pressure was close to the optimal pressure, achieving nearly maximal mechanical efficiency. As the heart deteriorated, however, the optimal end-systolic pressure became significantly lower than normal, whereas the actual pressure remained within the normal range. This discrepancy resulted in worsening of ventriculoarterial coupling and decreased mechanical efficiency compared with theoretically maximal efficiency.

CONCLUSIONS

Homeostatic mechanisms to maintain arterial blood pressure within the normal range cause the failing heart to deviate from energetically optimal conditions.

Effects of increasing maintenance dose of digoxin on left ventricular function and neurohormones in patients with chronic heart failure treated with diuretics and angiotensin-converting enzyme inhibitors

BACKGROUND

Despite almost three centuries of use, the appropriate dosage of digitalis in patients with chronic heart failure and normal sinus rhythm has not been well studied.

METHODS AND RESULTS

We studied 22 patients with heart failure who were receiving constant daily doses of digoxin, diuretics, and angiotensin-converting enzyme (ACE) inhibitors. In 18 patients, the oral daily dose of digoxin was increased from a mean of 0.20 +/- 0.07 to 0.39 +/- 0.11 mg/day corresponding to an increase in the serum digoxin concentration from 0.67 +/- 0.22 to 1.22 +/- 0.35 ng/mL. Radionuclide and echocardiographic left ventricular ejection fraction; maximal treadmill time; heart failure score; serum concentrations of norepinephrine, aldosterone, atrial natriuretic factor, and antidiuretic hormone; and plasma renin activity were obtained before and after the increase in digoxin dose. Subsequently, 9 patients were randomized to receive digoxin and 9 to receive placebo and radionuclide ejection fraction measured after 12 weeks. With the higher dose of digoxin compared with the lower dose, there was a significant increase in radionuclide ejection fraction from 23.7 +/- 9.6% to 27.1 +/- 11.8% (P = .007). No significant changes were noted in heart failure score; exercise tolerance; serum concentrations of norepinephrine, atrial natriuretic factor, and antidiuretic hormone; and plasma renin activity. There was, however, an increase in serum aldosterone concentration. Twelve weeks after the patients were randomized to receive digoxin or placebo, there was a significant decrease in ejection fraction (from 29.4 +/- 10.4% to 23.7 +/- 8.9%) in the placebo group but not in patients who continued to receive digoxin (P = .002).

CONCLUSIONS

The increase in maintenance digoxin dose, while maintaining serum concentrations within therapeutic range, resulted in a significant increase in left ventricular ejection fraction that was not associated with significant changes in heart failure score, exercise tolerance, and neurohumoral profile.

EMD 53998 acts as Ca(2+)-sensitizer and phosphodiesterase III-inhibitor in human myocardium

The effect of EMD 53998 (EMD) (0.1-100 mumol/l), chemically a racemic thiadiazinone derivative, suggested to be a potent Ca(2+)-sensitizer, was studied in human failing and nonfailing left ventricular myocardium. For comparison, the effects of the pyridazinone derivative pimobendan (0.1-300 mumol/l), isoprenaline (Iso) (0.001-3 mumol/l) as well as CaCl2 (1.8-15 mmol/l Ca2+) were investigated. The positive inotropic responses were examined in electrically driven (1 Hz, 37 degrees C) human left ventricular papillary muscle strips from terminally failing hearts (NYHAIV, n = 24) and nonfailing donor hearts (NF, n = 9). The effect of EMD on the Ca(2+)-sensitivity of skinned fiber preparations from the very same human failing hearts were studied as well. EMD and pimobendan increased force of contraction (FOC) in a concentration-dependent manner. As judged from the EC50-values, EMD increased FOC more potently than pimobendan. EMD was significantly more effective than pimobendan to increase FOC in papillary muscle strips from NYHA IV (EMD: +2.5 +/- 0.1 mN; pimobendan: +0.8 +/- 0.2 mN) as well as from nonfailing hearts (EMD: +3.1 +/- 0.5 mN; pimobendan: +1.2 +/- 0.2 mN). Only in terminally failing myocardium, EMD increased FOC as effectively as Iso. After inotropic stimulation with EMD, pimobendan, or Iso, carbachol (1000 mumol/l) reduced FOC in left ventricular papillary muscle strips, indicating a cAMP-dependent mode of action. In skinned fiber experiments, EMD increased Ca(2+)-sensitivity significantly more (p < 0.01) than pimobendan.

IN CONCLUSION

EMD increases FOC in human myocardium via sensitizing of the contractile proteins towards Ca2+ and by inhibition of phosphodiesterase III-isoenzymes. EMD is a potent calcium sensitizing agent in human myocardium. Thiadiazinone derivatives could be one step in the evolution to more potent and selective calcium-sensitizers.