Acute effects of digoxin on total systemic vascular resistance in congestive heart failure due to dilated cardiomyopathy: a hemodynamic-hormonal study

Acausal Modelling of Advanced-Stage Heart Failure and the Istanbul Heart Ventricular Assist Device Support with Patient Data

BACKGROUND

In object-oriented or acausal modelling, components of the model can be connected topologically, following the inherent structure of the physical system, and system equations can be formulated automatically. This technique allows individuals without a mathematics background to develop knowledge-based models and facilitates collaboration in multidisciplinary fields like biomedical engineering. This study conducts a preclinical evaluation of a ventricular assist device (VAD) in assisting advanced-stage heart failure patients in an acausal modelling environment.

METHODS

A comprehensive object-oriented model of the cardiovascular system with a VAD is developed in MATLAB/SIMSCAPE, and its hemodynamic behaviour is studied. An analytically derived pump model is calibrated for the experimental prototype of the Istanbul Heart VAD. Hemodynamics are produced under healthy, diseased, and assisted conditions. The study features a comprehensive collection of advanced-stage heart failure patients' data from the literature to identify parameters for disease modelling and to validate the resulting hemodynamics.

RESULTS

Regurgitation, suction, and optimal speeds are identified, and trends in different hemodynamic parameters are observed for the simulated pathophysiological conditions. Using pertinent parameters in disease modelling allows for more accurate results compared to the traditional approach of arbitrary reduction in left ventricular contractility to model dilated cardiomyopathy.

CONCLUSION

The current research provides a comprehensive and validated framework for the preclinical evaluation of cardiac assist devices. Due to its object-oriented nature, the featured model is readily modifiable for other cardiovascular diseases for studying the effect of pump operating conditions on hemodynamics and vice versa in silico and hybrid mock circulatory loops. The work also provides a potential teaching tool for understanding the pathophysiology of heart failure, diagnosis rationale, and degree of assist requirements.

Digoxin Combined with Aerobic Interval Training Improved Cardiomyocyte Contractility

Digoxin is a cardiotonic that increases the cardiac output without causing deleterious effects on heart, as well as improves the left ventricular performance during physical exercise. We tested whether the association between chronic digoxin administration and aerobic interval training (AIT) promotes beneficial cardiovascular adaptations by improving the myocardial contractility and calcium (Ca²⁺⁾ handling. Male Wistar rats were randomly assigned to sedentary control (C), interval training (T), sedentary digoxin (DIGO) and T associated to digoxin (TDIGO). AIT was performed on a treadmill (1h/day, 5 days/week) for 60 days, consisting of successive 8-min periods at 80% and 20% of VO₂máx for 2 min. Digoxin was administered by orogastric gavage for 60 days. Left ventricle samples were collected to analysis of Ca²⁺ handling proteins; contractility and Ca²⁺ handling were performed on isolated cardiomyocytes. TDIGO group had a greater elevation in fractional shortening (44%) than DIGO, suggesting a cardiomyocyte contractile improvement. In addition, T or TDIGO groups showed no change in cardiomyocytes properties after Fura2-acetoxymethyl ester, as well as in sarcoplasmic reticulum Ca^2+-ATPase (SERCA2a), phospholamban and calcineurin expressions. The main findings indicate that association of digoxin and aerobic interval training improved the cardiomyocyte contractile function, but these effects seem to be unrelated to Ca²⁺ handling.

The Role of Digoxin in the Treatment of Chronic Congestive Heart Failure

It is now well established that digoxin is an effective drug for the treatment of heart failure. Since treatment with angiotensin-converting enzyme (ACE) inhibitors reduces mortality in congestive heart failure, digoxin should be added to ACE inhibitors in patients with moderate or severe heart failure. The beneficial effects of digoxin may be due, in part, to its well-documented sympathoinhibitory effects that can avert the adverse effects of long-term excessive sympathetic adrenergic stimulation in heart failure.

Deleterious cardiovascular effect of exosome in digitalis-treated decompensated congestive heart failure

Heart failure (HF) is a medical condition inability of the heart to pump sufficient blood to meet the metabolic demand of the body to take place. The number of hospitalized patients with cardiovascular diseases is estimated to be more than 1 million each year, of which 80% to 90% of patients ultimately progress to decompensated HF. Digitalis glycosides exert modest inotropic actions when administered to patients with decompensated HF. Although its efficacy in patients with HF and atrial fibrillation is clear, its value in patients with HF and sinus rhythm has often been questioned. A series of recent studies have cast serious doubt on the benefit of digoxin when added to contemporary HF treatment. We are hypothesizing the role and mechanism of exosome and its biological constituents responsible for worsening the disease state and mortality in decompensated HF patients on digitalis.

Effect of digitalis level on readmission and mortality rate among heart failure reduced ejection fraction patients

INTRODUCTION

Digitalis has been used for over 200 years to treat patients with heart failure, and evidence supports its use to improve clinical symptoms and quality of life, but not survival. The objective of this retrospective study was to evaluate the effects of digitalis on readmission and mortality in patients with heart failure with reduced ejection fraction (HFrEF) who were receiving current guideline recommended medical therapy.

METHODS

We reviewed medical record data from a retrospective cohort study of 1047 patients admitted to the hospital from 2005 to 2014 with decompensated HFrEF. 244 received digitalis, at some point during patient trajectory, and 803 never received digitalis. The primary outcomes of interest were the length of stay in hospital, readmission rates after discharge at 1, 6, 12, and 24 months and the overall mortality rate, at the same time points.

RESULTS

We studied the effects of digitalis after adjusting for age, sex, race, potentially confounding comorbidities, and prescription medications. Digitalis treatment is associated with decreases in EF in patients with HFrEF (OR = -2.83, P < 0.001) and was associated with an increased readmission rate for any reason after discharge from the hospital at 6, 12, and 24 months, 53%, 34%, and 35%, respectively. No statistically significant difference was found between patients who received digitalis and those who did not (referent group) for the length of hospital stay and overall mortality rate.

CONCLUSION

Digitalis use is associated with increased re-admission rates for any reason following discharge from the hospital at 6, 12, and 24 months.

Contemporary Controversies in Digoxin Use in Systolic Heart Failure

Digoxin remains one of the oldest therapies for heart failure; however, its safety and efficacy have been controversial since its initial use. Questions that remain include the clinical efficacy of digoxin when added to contemporary medical therapy, when and if it should be added, and how to minimize adverse effects. In this review, we will summarize recent data on the use of digoxin in systolic heart failure and address some of the controversies regarding the role of digoxin in the modern era of heart failure treatment.

Pharmacologic Management of Chronic Heart Failure: A Review

Standard drug therapy of systolic heart failure has been evaluated in large-scale randomized clinical trials and includes angiotensin-converting enzyme (ACE) inhibi tors, which should be used as first-line therapy, diuret ics for the management of extracellular fluid volume excess, and digoxin. In combination with ACE inhibitors and diuretics, with or without digoxin, some β-adrener gic receptor blockers attenuate disease progression and improve outcome in mild-to-moderate systolic heart failure. The pharmacologic management of chronic dia stolic heart failure is largely empirical and directed at reducing symptoms. Symptoms caused by increased ventricular filling pressures may be diminished by diuret ics and nitrovasodilators. Some calcium channel antago nists and most β-blockers prolong diastolic filling time by slowing heart rate, thereby improving the symptoms of diastolic heart failure.

Time and technology will tell: the pathophysiologic basis of neurohormonal modulation in heart failure

The central roles of neurohormonal abnormalities in the pathobiology of heart failure have been defined in recent decades. Experiments have revealed both systemic involvement and intricate subcellular regulation by circulating effectors of the sympathetic nervous system, the renin-angiotensin-aldosterone system, and others. Randomized clinical trials substantiated these findings, establishing neurohormonal antagonists as cornerstones of heart failure pharmacotherapy, and occasionally offering further insight on mode of benefit. This review discusses the use of β-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone receptor antagonists in the treatment of heart failure, with particular attention to the pathophysiologic basis and mechanisms of action.

Role of mitochondrial dysfunction in cardiac glycoside toxicity

Cardiac glycosides, which inhibit the plasma membrane Na(+) pump, are one of the four categories of drug recommended for routine use to treat heart failure, yet their therapeutic window is limited by toxic effects. Elevated cytoplasmic Na(+) ([Na(+)](i)) compromises mitochondrial energetics and redox balance by blunting mitochondrial Ca(2+) ([Ca(2+)](m)) accumulation, and this impairment can be prevented by enhancing [Ca(2+)](m). Here, we investigate whether this effect underlies the toxicity and arrhythmogenic effects of cardiac glycosides and if these effects can be prevented by suppressing mitochondrial Ca(2+) efflux, via inhibition of the mitochondrial Na(+)/Ca(2+) exchanger (mNCE). In isolated cardiomyocytes, ouabain elevated [Na(+)](i) in a dose-dependent way, blunted [Ca(2+)](m) accumulation, decreased the NADH/NAD+redox potential, and increased reactive oxygen species (ROS). Concomitant treatment with the mNCE inhibitor CGP-37157 ameliorated these effects. CGP-37157 also attenuated ouabain-induced cellular Ca(2+) overload and prevented delayed afterdepolarizations (DADs). In isolated perfused hearts, ouabain's positive effects on contractility and respiration were markedly potentiated by CGP-37157, as were those mediated by β-adrenergic stimulation. Furthermore, CGP-37157 inhibited the arrhythmogenic effects of ouabain in both isolated perfused hearts and in vivo. The findings reveal the mechanism behind cardiac glycoside toxicity and show that improving mitochondrial Ca(2+) retention by mNCE inhibition can mitigate these effects, particularly with respect to the suppression of Ca(2+)-triggered arrhythmias, while enhancing positive inotropic actions. These results suggest a novel strategy for the treatment of heart failure.

The control of adrenergic function in heart failure: therapeutic intervention

Chronic heart failure is characterised by excess adrenergic activity that augurs a poor prognosis. The reasons for increased adrenergic activity are complex and incompletely understood. The circumstantial evidence relating increased activity to adverse outcome is powerful, but not yet conclusive. In normal subjects, autonomic control of the circulation is predominantly under the control of sympatho-inhibitory inputs from the arterial and cardiopulmonary baroreceptors, with a small input from the excitatory ergo- and chemo-receptors. In heart failure, the situation is reversed, with loss of the restraining input from the baroreceptors and an increase in the excitatory inputs, resulting in excessive adrenergic activity. The circumstantial evidence linking neuroendocrine activation with poor outcome coupled with the clinical success of inhibition of the renin-angiotensin-aldosterone system has long suggested that inhibition of adrenergic activity might be beneficial in heart failure. There is a number of potential ways of achieving this. Improved treatment of heart failure itself may reduce sympathetic drive. There is an interplay between angiotensin II, aldosterone and the sympathetic nervous system, and thus RAAS antagonists, such as angiotensin converting enzyme inhibitors and spironolactone could directly reduce sympathetic activation. Exercise rehabilitation may similarly reduce sympathetic activity.Recently, beta-adrenergic receptor antagonists have been conclusively shown to improve symptoms, reduce hospitalisations and increase survival. However, the demonstration that central reduction of sympathetic activity with agents such as moxonidine increases morbidity and mortality suggests that we do not properly understand the role of sympathetic activation in the pathophysiology of heart failure.

Digoxin remains useful in the management of chronic heart failure

Despite the introduction of a variety of new classes of drugs for the management of heart failure, digoxin continues to have an important role in long-term outpatient management. A wide variety of placebo-controlled clinical trials have unequivocally shown that treatment with digoxin can improve symptoms, quality of life, and exercise tolerance in patients with mild, moderate, or severe heart failure. These benefits are evident regardless of the underlying rhythm (normal sinus rhythm or atrial fibrillation), etiology of the heart failure, or concomitant therapy (eg. ACE inhibitors). Unlike other agents with positive inotropic properties, digoxin does not increase all-cause mortality and has a substantial benefit in reducing heart failure hospitalizations. Consensus guidelines have recently been published by the Heart Failure Society of America and the American College of Cardiology/American Heart Association, and they contain the following recommendations for digoxin treatment: 1. Digoxin should be considered for the outpatient treatment of all patients who have persistent symptoms of heart failure (NYHA class II-IV) despite conventional pharmacologic therapy with diuretics, ACE inhibitors, and a beta-blocker when the heart failure is caused by systolic dysfunction (the strength of evidence = A for NYHA class II and III; strength of evidence = C for NYHA class IV). 2. Digoxin is not indicated as primary treatment for the stabilization of patients with acutely decompensated heart failure. (Strength of evidence = B). Digoxin may be initiated after emergent treatment of heart failure has been completed in an effort to establish a long-term treatment strategy. 3. Digoxin should not be administered to patients who have significant sinus or atrioventricular block, unless the block has been treated with a permanent pacemaker (strength of evidence = B). The drug should be used cautiously in patients who receive other agents known to depress sinus or atrioventricular nodal function (such as amiodarone or a beta-blocker) (strength of evidence = B). 4. The dosage of digoxin should be 0.125-0.25 mg daily in the majority of patients (strength of evidence = C). The lower dose should be used in patients over 70 years of age, those with impaired renal function, or those with a low lean body mass. Higher doses (eg, digoxin 0.375-0.50 mg daily) are rarely needed. Loading doses of digoxin are not necessary during initiation of therapy for patients with chronic heart failure. 5. Serial assessment of serum digoxin levels is unnecessary in most patients. The radioimmunoassay was developed to assist in the evaluation of toxicity, not the efficacy of the drug. There appears to be little relationship between serum digoxin concentration and the drug's therapeutic effects. 6. Digoxin toxicity is commonly associated with serum levels >2 ng/mL but may occur with lower digoxin levels if hypokalemia, hypomagnesemia, or hypothyroidism coexist. Likewise, the concomitant use of agents such as quinidine, verapamil, spironolactone, flecainide, and amiodarone can increase serum digoxin levels and increase the likelihood of digoxin toxicity. 7. For patients with heart failure and atrial fibrillation with a rapid ventricular response, the administration of high doses of digoxin (>0.25 mg daily) for the purpose of rate control is not recommended. When necessary, additional rate control should be achieved by the addition of beta-blocker therapy or amiodarone (strength of evidence = C). If amiodarone is added, the dose of digoxin should be reduced. Digitalis preparations are now entering their fourth century of clinical use for the treatment of chronic heart failure symptoms. Its clinical efficacy can no longer be doubted and its safety has been verified by the multicenter DIG trial. Future advances in pharmacogenetics should facilitate identification of those patients most likely to benefit from its pharmacologic effects.

Digoxin

After 200 years of use, digitalis still appears to have a place in our armamentarium for heart failure and atrial fibrillation despite the proven survival benefits with ACE inhibitors and beta-blockers. Digoxin therapy is inexpensive and well tolerated and may result in considerable savings. Digoxin is the only oral inotrope that does not increase mortality in heart failure patients, particularly if low doses are being used. Digoxin therapy should be used in patients with systolic heart failure who continue to have signs and symptoms despite therapeutic doses of ACE inhibitors or diuretics or in patients with atrial fibrillation with or without heart failure for rate control.

Hemodynamic and plasma atrial natriuretic peptide responses to acute digitalis therapy in patients with normal and impaired left ventricular function

BACKGROUND

Digitalis has a long history in the treatment of heart failure but its effects on cardiac hemodynamics and neurohormonal modulation are not well characterized.

AIMS

The purpose of this study was to evaluate the relationship between atrial natriuretic peptide (ANP) and the hemodynamic responses to acute digitalis administration in patients with normal and impaired left ventricular function (LVD).

METHODS AND RESULTS

Thirty patients were enrolled in the study, 20 with LVD (LVEF=22+/-8%) and 10 control subjects (LVEF=77+/-10%). Hemodynamics and plasma ANP concentrations were measured supine and with leg elevation before and after digitalis. In patients with normal ventricular function, the hemodynamic stress of leg elevation in the pre-digitalis state resulted in significant (P<0.05) increases in PAWP and MPAP. Digitalis administration in the supine position produced reductions in heart rate, PAWP, MPAP and CI; SVR was increased. In LVD patients leg elevation further increased PAWP, RAP and MPAP. Digitalis in the supine position, however, reduced RAP, MPAP and PAWP and increased CI. These improved hemodynamics were preserved during the stress of leg elevation. Leg elevation following digitalis resulted in increased ANP concentrations despite decreased cardiac filling pressures.

CONCLUSIONS

Acute digitalis administration results in hemodynamic improvement in LVD patients which may in part result from digitalis stimulated release of myocardial ANP under conditions of hemodynamic stress.

The effect of chronic digitalization on pump function in systolic heart failure

BACKGROUND

Short- and intermediate-term use of cardiac glycosides promotes inotropy and improves the ejection fraction in systolic heart failure.

AIM

To determine whether chronic digitalization alters left ventricular function and performance.

METHODS

Eighty patients with mild-to-moderate systolic heart failure (baseline ejection fraction < or =45%) participated from our institution in a multi-center, chronic, randomized, double-blind study of digitalis vs. placebo. Of the 40 survivors, 38 (20 allocated to the digitalis arm and 18 to the placebo arm) were evaluated at the end of follow-up (mean, 48.4 months). Left ventricular systolic function was assessed by both nuclear ventriculography and echocardiography. The ejection fraction was measured scintigraphically, while the ventricular volumes were computed echocardiographically.

RESULTS

The groups did not differ, at baseline or end-of-study, with respect to the ejection fraction and the loading conditions (arterial pressure, ventricular volumes and heart rate) by either intention-to-treat or actual-treatment-received analysis. Over the course of the trial, the digitalis arm exhibited no significant increase in the use of diuretics (18%, P=0.33), in distinction from the placebo group (78%, P=0.004), and a longer stay on study drug among those patients who withdrew from double-blind treatment (28.6 vs. 11.4 months, P=0.01).

CONCLUSION

Following chronic use of digitalis for mild-to-moderate heart failure, cross-sectional comparison with a control group from the same inception cohort showed no appreciable difference in systolic function or performance. Thus, the suggested clinical benefit cannot be explained by an inotropic effect.

Medical management of mild-to-moderate heart failure before the advent of beta blockers

Clinical trials of beta blockers in heart failure have generally required that patients be receiving optimal drug therapy before randomization to the study medication. Therefore, because beta blockers are used in addition to conventional drug therapy, review of the standard drug therapy of mild-to-moderate heart failure before the advent of beta blockade is essential to understanding the role of beta blockers in the treatment of heart failure. The conventional medical management of systolic heart failure includes angiotensin-converting enzyme (ACE) inhibitors, which should be used as first-line therapy; diuretics, for the management of body fluid-volume excess; digoxin; and some other vasodilators. These therapies have been evaluated in large-scale, randomized, controlled trials. ACE inhibitors have been shown to significantly attenuate disease progression and improve outcome (ie, morbidity and mortality) in patients with mild-to-moderate systolic heart failure. Controversial or unproven therapies include nonglycoside inotropic agents, angiotensin II receptor antagonists, antiarrhythmic agents, anticoagulants, and calcium channel blockers. The pharmacologic management of diastolic heart failure is largely empirical and is directed at reducing symptoms. Symptoms caused by increased ventricular filling pressures may be treated with diuretics and long-acting nitrates. Some calcium channel blockers and most beta blockers prolong diastolic filling time by slowing heart rate, thereby potentially improving the symptoms of diastolic heart failure. Calcium antagonists, beta blockers, diuretics, and ACE inhibitors may also promote regression of left ventricular hypertrophy and thus improve ventricular compliance, possibly preventing the development of diastolic dysfunction. Because randomized controlled trials of diastolic heart failure are lacking, this review focuses on the conventional management of mild-to-moderate systolic heart failure before the advent of beta blockade.

The role of neurohormonal antagonists in hibernating myocardium

Hibernating myocardium is characterized by chronic reduction of myocardial blood flow due to obstructive coronary artery disease, causing reversible left ventricular dysfunction and flow-metabolism mismatch. The condition is unstable and increasing demand may lead to further left ventricular dysfunction or necrosis causing death or worsening heart failure. Recognition of the condition is difficult and requires complex cardiac imaging protocols. Treatment protocols are also poorly defined. This review addresses both the diagnostic and therapeutic aspects of hibernating myocardium.

Cardiac glycosides in the next millennium

Despite the documented efficacy of cardiac glycosides in improving symptoms in patients with heart failure caused by systolic ventricular dysfunction, considerable debate continues as to whether the use of this class of drugs should continue into the next millennium. In this review, the authors briefly examine the basic pharmacology of these drugs relevant to the treatment of heart failure, emphasizing their role in reducing sympathetic nervous system activity in patients with advanced heart failure. Next, withdrawal trials and the Digoxin Investigation Group dataset are reviewed in some detail. Despite these important additional data on the safety and efficacy of digitalis use in heart failure that became available in the 1990s, considerable controversy remains. Perhaps most importantly, if the mechanism by which these drugs improve symptoms in patients with heart failure is principally mediated by sympatholytic activity, do they remain relevant as beta-adrenergic antagonists become standard therapy for this disease?

The short-term effects of digoxin in patients with right ventricular dysfunction from pulmonary hypertension

OBJECTIVE

Studies on the effects of digoxin in patients with right ventricular failure and normal left ventricular function have not been performed. We evaluated the short-term effects of digoxin administration in patients with primary pulmonary hypertension on hemodynamics, neurohormones, and baroreceptor responsiveness.

DESIGN

This was a prospective study with patients serving as their own controls.

SETTING

University Hospital Intensive Care Unit with central monitoring.

PATIENTS

Seventeen patients with primary pulmonary hypertension and symptomatic heart failure were enrolled.

INTERVENTIONS

Following baseline hemodynamics, neurohormonal samples were drawn and the heart rate response to change in blood pressure following a challenge of phenylephrine and nitroprusside were recorded. One mg of intravenous digoxin was given and the measurements repeated after 2 hours.

RESULTS

Following digoxin there was a significant increase in cardiac output (3.49+/-1.2 to 3.81+/-1.2 L/min., p=0.028), a significant fall in norepinephrine (680+/-89 to 580+/-85 pg/ml, p=.013), and a significant increase in atrial natriuretic peptide (311+/-44 to 421+/-9 pg/ml, p=0.01). All of the patients had changes in heart rate and blood pressure following phenylephrine and nitroprusside challenge, but there was no significant difference in the change in heart rate response to change in blood pressure when rechallenged after digoxin treatment.

CONCLUSION

Digoxin produces a modest increase in cardiac output in patients with pulmonary hypertension and right ventricular failure, as well as a significant reduction in circulating norepinephrine. No detectable effects of digoxin on baroreceptor responsiveness were apparent. The use of digoxin in pulmonary hypertension is warranted.

Use of angiotensin-converting enzyme inhibitors as monotherapy and in combination with diuretics and calcium channel blockers

Angiotensin-converting enzyme (ACE) inhibitors have earned an important place in medical therapy since their discovery about two decades ago. This family of drug has grown tremendously since the introduction of captopril in 1981. There are currently more than 14 ACE inhibitors in the world and 9 are available in the United States. Although these agents share many similarities, they differ in their pharmacokinetic properties, approved indications, and cost. This paper provides guidance for selection of ACE inhibitors by examining the pharmacokinetics, pharmacodynamics, drug interactions, adverse effects, and cost of these agents. Combination products of ACE inhibitors with either diuretics or calcium channel blockers also are reviewed.

Heart failure in patients with preserved left ventricular systolic function: do digitalis glycosides have a role?

It is being increasingly appreciated that a substantial number of patients with congestive heart failure (CHF) have relatively preserved systolic function. Although these individuals appear to have a somewhat better prognosis than those with low ejection fractions, they experience significant symptoms and frequently require hospitalization. In these patients, CHF is often attributed to left ventricular diastolic dysfunction, but this represents a potentially misleading over-simplification. In contrast to CHF associated with left ventricular systolic dysfunction, little is known about how to treat patients with preserved systolic function. Perhaps the major point of consensus has been that the use of digitalis glycosides is inappropriate in this group. Unexpectedly, however, in the recently completed Digitalis Investigators Group trial, a subgroup of nearly 1,000 patients with radionuclide ejection fractions > or = 45% experienced a similar reduction in heart failure endpoints with digoxin therapy as patients with 25% to 44% ejection fractions. The purpose of this article is to review the diverse causes of CHF with preserved systolic function and to examine the potential mechanisms by which digoxin may be producing beneficial effect in this setting.

Digitalis increases brain natriuretic peptide in patients with severe congestive heart failure

Ouabain can cause increased secretion of atrial natriuretic peptide (ANP) from atrial cardiocyte culture, but the effects of digitalis in a therapeutic range on the secretion of cardiac natriuretic peptide including ANP and brain natriuretic peptide (BNP), mainly from the ventricle, in patients with congestive heart failure remain to be investigated. Therefore we studied the acute effects of intravenous infusion of a relatively low dose of digitalis or placebo on hemodynamics and neurohumoral factors including the plasma levels of ANP and BNP and cyclic guanosine monophosphate, a second messenger of cardiac natriuretic peptide, in 13 patients with severe congestive heart failure. No significant change in the hemodynamic parameters or neurohumoral factors was observed with placebo. After 1 hour of intravenous administration of deslanoside (0.01 mg/kg), there was a significant decrease of plasma renin activity and angiotensin II, aldosterone, and norepinephrine levels but no significant change of plasma levels of vasopressin and a significant decrease of the pulmonary capillary wedge pressure but no significant change in cardiac index. In addition, plasma levels of ANP (217 +/- 47 vs 281 +/- 70 pg/ml, p < 0.05), BNP (628 +/- 116 vs 689 +/- 132 pg/ml, p < 0.05), and cyclic guanosine monophosphate (9.7 +/- 1.1 vs 10.9 +/- 1.5 pmol/ml, p < 0.05) increased despite the decrease of pulmonary capillary wedge pressure (19.7 +/- 2.3 vs 16.8 +/- 2.3 mm Hg, p < 0.05). These results indicate the acute intravenous low dose of digitalis resulted in a significant increase in plasma levels of ANP, BNP, and cyclic guanosine monophosphate concomitant with the significant decrease of pulmonary capillary wedge pressure, suggesting the acute direct action of digitalis on the cardiac natriuretic peptides released from the heart in patients with severe congestive heart failure.

[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.

Influence of hemodynamic changes on neuroendocrine response in acute heart failure

We studied 15 patients with acute deterioration of chronic left ventricular heart failure. We compared the influence of reduction of ventricular filling pressures with glyceryl trinitrate versus reduction of ventricular filling pressures with diuretics on plasma concentration of epinephrine, norepinephrine, aldosterone and renin activity. Reduction of ventricular filling pressures with glyceryl trinitrate had no influence on plasma concentrations of epinephrine, norepinephrine, aldosterone and renin activity. After reduction of ventricular filling pressures with diuretics plasma concentrations of epinephrine, norepinephrine and aldosterone decreased, while plasma renin activity did not change. We conclude that there is a difference in the influence of reduction of ventricular filling pressures with glyceryl trinitrate versus reduction of ventricular filling pressures with diuretics, on neuroendocrine response in patients with acute deterioration of left ventricular heart failure. Thus some of the neuroendocrine effects of glyceryl trinitrate are likely to be different from those of diuretics, though that they both produce a reduction in left ventricular filling pressure.

Is there an expanded role for digoxin in patients with heart failure and sinus rhythm? A protagonist viewpoint

The evidence supporting the efficacy of digoxin in patients with heart failure who are in sinus rhythm is substantial. Digoxin improves hemodynamics, exercise capacity, symptoms, and quality of life and reduces hospitalizations. All of this is accomplished with a drug that is very inexpensive and can be given once daily. Its safety has been established through the DIG trial. Although digoxin does not decrease mortality beyond that of diuretics and ACE inhibitors, it does not increase mortality, unlike many positive inotropes. Furthermore, digoxin, in addition to ACE inhibitors and a diuretic, decreases the hospitalization rate due to worsening of heart failure. From a managed care perspective, as well as that of the patient, this is of enormous benefit. A pharmacoeconomic analysis estimated that continuation of digoxin in patients with stable congestive heart failure could save the healthcare system an estimated $ 400 million, based on costs from one hospital. The issue is not whether to use digoxin in these patients, but rather, how early to initiate therapy. From some of the recent data in patients with systolic dysfunction and mild heart failure, as well as knowledge of the neurohormonal activation that occurs early in these patients, it could be suggested that early use of neurohormonal modulators, including digoxin, would decrease the progression of heart failure. Thus, rather than waiting for symptoms despite optimal doses of an ACE inhibitor and diuretic, as suggested by the AHCPR practice guideline for heart failure, initiation of digoxin therapy in patients as early as NYHA class II at a dosage that will achieve a serum concentration of 1.0 ng/mL or less should occur. With the understanding of digoxin's effect on the neurohormonal systems, its role in patients with preserved systolic function needs to be reexplored. The debate can now focus on asymptomatic patients or those with preserved systolic function. Could these patients benefit from therapy with digoxin as well?

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.

Digoxin reduces cardiac sympathetic activity in severe congestive heart failure

OBJECTIVES

This study evaluated the effect of digoxin on cardiac sympathetic activity in patients with congestive heart failure.

BACKGROUND

Digoxin favorably alters autonomic tone in heart failure. Whether it reduces cardiac sympathetic drive in the setting of heart failure is unknown.

METHODS

Digoxin (0.25 mg intravenously) was administered to 12 patients with severe heart failure and elevated left ventricular end-diastolic pressure (> 14 mm Hg, Group A), 5 patients with less severe heart failure who had normal left ventricular end-diastolic pressure (> 14 mm Hg, Group B) and 6 patients with normal ventricular function. Seven additional patients with heart failure were studied as a time control group. Cardiac and total body norepinephrine spillover, systemic arterial pressure, left ventricular filling pressure and peak positive first derivative of left ventricular pressure were all assessed before and 30 min after administration of digoxin.

RESULTS

In Group A there were no changes in hemodynamic variables or total body norepinephrine spillover after digoxin administration; however, there was a significant reduction in cardiac norepinephrine spillover (263 +/- 70 to 218 +/- 62 pmol/min, mean +/- SEM, p < 0.001). In contrast, in Group B, digoxin caused a significant increase in cardiac norepinephrine spillover that was not associated with any hemodynamic changes or a change in total body spillover. There were no hemodynamic changes or a change in total body spillover. There were no hemodynamic or spillover changes in the time control or normal ventricular function group.

CONCLUSIONS

Digoxin, in the absence of detectable inotropic or hemodynamic effects, caused a reduction in cardiac norepinephrine spillover in patients with heart failure who had elevated filling pressures. This finding suggests a potentially beneficial primary autonomic action of digoxin in patients with severe heart failure.

Effect of the implantable left ventricular assist device on neuroendocrine activation in heart failure

BACKGROUND

The HeartMate left ventricular assist device has been successfully used as a bridge to cardiac transplantation. Because many patients exhibit marked clinical improvement in their heart failure after HeartMate implantation, we studied the physiological effect of this device on the neurohormonal axis.

METHODS AND RESULTS

In 13 patients awaiting transplant (mean cardiac index, 1.7 +/- 0.3 L.min-1.m-2) who underwent HeartMate implantation, venous atrial natriuretic peptide, epinephrine, norepinephrine, plasma renin activity, angiotensin, and arginine vasopressin were measured immediately before insertion and at explant/transplantation. Mean time to explant was 86 +/- 40 days. All patients were taken off inotropic medications within 1 month. Mean cardiac index on support before explant was 3.1 +/- 0.9 L.min-1.m-2. Plasma renin activity decreased from 57 +/- 56 ng.mL-1.h-1 at baseline (before insertion) to 3 +/- 3 ng.mL-1.h-1 at explant (mean percent change, 92%; P < .001). Angiotensin II level decreased from 237 +/- 398 U/L at baseline to 14 +/- 14 U/L at explant (mean percent change, 73%; P < .001). Plasma epinephrine level fell from 6800 +/- 1323 pg/mL at baseline to 46 +/- 46 pg/mL at explant (mean percent change, 86%; P < .001). Norepinephrine level decreased from 2953 +/- 1457 pg/mL at baseline to 518 +/- 290 pg/mL at explant (mean percent change, 79%; P < .001). Atrial natriuretic peptide fell from baseline values of 227 +/- 196 to 168 +/- 40 pg/mL at explant (mean percent change, -49%; P = 519); and arginine vasopressin level decreased from 6 +/- 6 pg/mL at baseline to 0.8 +/- 0.5 pg/mL (mean percent change, 69%; P = .002).

CONCLUSIONS

We provide data supporting that the neurohormonal axis markedly improves after HeartMate implantation, providing biochemical confirmation of the improvement in hemodynamic status.

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.

Effects of intravenous digoxin on pulmonary venous and transmitral flows in patients with chronic heart failure of different degrees

Acute effects of digoxin on diastole were evaluated noninvasively by combining data simultaneously obtained by Doppler echocardiograms (echo-Doppler) of transmitral and pulmonary venous flow curves in 38 patients with dilated and failing hearts, who had been stable for at least 7 days before the study. According to the resting ejection fraction (EF), patients were subdivided into Group 1 (EF < 30%: n = 20, mean EF values 23 +/- 8%) and Group 2 (EF > or = 30%: n = 18, mean EF values 40 +/- 3%). Significant differences were observed at rest between the two groups in both transmitral (shorter deceleration time and isovolumic relaxation time and increased peak E and E/A ratio in Group 1 vs. Group 2) and transpulmonary (reduced systolic forward component and systolic fraction of the flow curves in Group 1 compared with Group 2 and control subjects) parameters. Digoxin (1 mg subdivided into two doses, each infused over a 15-min period with 2 h between the doses) significantly modified the diastolic profile in Group 1 patients in the absence of statistically relevant changes in EF: a significant decrease of transmitral peak E (from 76 +/- 17 to 60 +/- 15 cm/s, p < 0.05) and E/A ratio (from 2.5 +/- 1 to 1.6 +/- 0.6; p < 0.05) and a significant lengthening of deceleration time (from 115 +/- 20 to 160 +/- 18 ms; p < 0.05) were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Reassessment of digoxin and other low-dose positive inotropes in the treatment of chronic heart failure

Digoxin and other low doses of drugs that have inotropic properties may have an important role to play in the therapy of patients with chronic heart failure. There is convincing evidence that digoxin is effective in relieving the signs and symptoms of heart failure due to systolic dysfunction. While earlier results with some of the other agents have been disappointing, recent data suggest that a reevaluation of these agents is necessary. There is now compelling evidence that lower doses of these agents may be clinically useful without necessarily having any significant hemodynamic effects. The recent experience with vesnarinone is especially promising in showing that therapy with these agents may improve survival in addition to improving clinical status. It is becoming recognized that hemodynamic activity should not necessarily be a prerequisite for clinical utility for those agents. The neuroendocrine and electrophysiologic effects of many of these agents, including digitalis, remain incompletely characterized and may play an important role in their therapeutic benefit. It appears that certain drugs that have inotropic properties may be effective only when their inotropic effects are not readily demonstrated. Further research into the appropriate mechanisms of action and proper dosing of these drugs may lead to a renewed interest in the use of positive inotropes for chronic heart failure.

Medical advances in the treatment of congestive heart failure

The increased incidence and prevalence of congestive heart failure place a high priority on novel treatment strategies. Left ventricular ejection fraction remains the single most valuable measurement providing both diagnostic and prognostic insights. The most systematic approach to heart failure involves an objective assessment of functional disability, to include exercise tests such as a 6-minute walk under standardized conditions. Left ventricular dysfunction incites a host of neurohumoral compensations that are of fundamental importance in the heart failure syndrome expression. Both vasoconstrictor and vasodilator neurohormones are stimulated and provide new therapeutic opportunities. The therapeutic approach to heart failure begins with a strong emphasis on prevention, patient education, and self-participation in therapy with respect to both its monitoring and adjustment. Diuretics remain a mainstay of therapy but, in the face of severe heart failure, may become ineffectual, requiring constant infusion of loop-active diuretics, combination diuretics, or diuretics in association with concomitant low-dose dopamine infusion. Vasodilator therapy has been an important advance: combination hydralazine and nitrate therapy was initially shown to be efficacious in improving survival, and more recently, angiotensin-converting enzyme (ACE) inhibitors, in the form of enalapril, have shown incremental benefit on survival over this combination. Interestingly, there is now evidence from both SOLVD and SAVE to demonstrate an unexpected and, as yet, unexplained reduction in the frequency of both unstable angina and myocardial infarction. Although, on balance, the weight of evidence concerning the long-term efficacy of inotropic agents has been disappointing, especially as it relates to their unfavorable effects on survival, recent information on vesnarinone, an agent with a complex and diversified mechanism of action, suggests that with appropriate doses, improved symptoms and survival are possible. A substantial amount of new information from randomized placebo-controlled trials attests to the symptomatic relief, hemodynamic improvement, and gain in exercise performance achieved by digoxin. A long-term survival study is ongoing to assess its effects on mortality. beta-Blockers, especially metoprolol, appear beneficial in some patients with heart failure, possibly related to their reduction in sympathetic nervous activity and restoration of beta-receptor population, with resultant improved contractile performance, enhanced myocardial relaxation, and overall increase in cardiac efficiency. Based on available evidence, the best contemporary approach to treatment involves the use of ACE inhibitors coupled with diuretic therapy, either continuous or intermittent, to relieve central or peripheral congestion. The addition of digoxin or a hydralazine nitrate combination is a logical next step, with commencement of low-dose beta-blocker a reasonable option.(ABSTRACT TRUNCATED AT 400 WORDS)

Withdrawal of digoxin from patients with chronic heart failure treated with angiotensin-converting-enzyme inhibitors. RADIANCE Study

BACKGROUND

Although digoxin is effective in the treatment of patients with chronic heart failure who are receiving diuretic agents, it is not clear whether the drug has a role when patients are receiving angiotensin-converting-enzyme inhibitors, as is often the case in current practice.

METHODS

We studied 178 patients with New York Heart Association class II or III heart failure and left ventricular ejection fractions of 35 percent or less in normal sinus rhythm who were clinically stable while receiving digoxin, diuretics, and an angiotensin-converting-enzyme inhibitor (captopril or enalapril). The patients were randomly assigned in a double-blind fashion either to continue receiving digoxin (85 patients) or to be switched to placebo (93 patients) for 12 weeks. Otherwise, their medical therapy for heart failure was not changed.

RESULTS

Worsening heart failure necessitating withdrawal from the study developed in 23 patients switched to placebo, but in only 4 patients who continued to receive digoxin (P < 0.001). The relative risk of worsening heart failure in the placebo group as compared with the digoxin group was 5.9 (95 percent confidence interval, 2.1 to 17.2). All measures of functional capacity deteriorated in the patients receiving placebo as compared with those continuing to receive digoxin (P = 0.033 for maximal exercise tolerance, P = 0.01 for submaximal exercise endurance, and P = 0.019 for New York Heart Association class). In addition, the patients switched from digoxin to placebo had lower quality-of-life scores (P = 0.04), decreased ejection fractions (P = 0.001), and increases in heart rate (P = 0.001) and body weight (P < 0.001).

CONCLUSIONS

These findings indicate that the withdrawal of digoxin carries considerable risks for patients with chronic heart failure and impaired systolic function who have remained clinically stable while receiving digoxin and angiotensin-converting-enzyme inhibitors.

Hemodynamic response of a canine model of chronic heart failure to intravenous dobutamine, nitroprusside, enalaprilat, and digoxin

The hemodynamic effects of acute intravenous administration of nitroprusside, dobutamine, enalaprilat, and digoxin was investigated in a canine model of chronic heart failure (CHF) produced by multiple sequential intracoronary microembolizations. Dobutamine (4 micrograms/kg/min) increased cardiac output (2.4 +/- 0.1 vs. 4.0 +/- 0.4 l/min; p < .001) and LV ejection fraction (LVEF; 26 +/- 1 vs. 30 +/- 4%; p < .01), and decreased systemic vascular resistance (SVR; 3620 +/- 170 vs. 2470 +/- 190 dynes sec cm-5; p < .001). Nitroprusside (3 micrograms/kg/min) acted as a venodilator; it decreased pulmonary artery wedge pressure (16 +/- 1 vs. 13 +/- 1 mmHg; p < .01) and SVR (3730 +/- 440 vs. 3210 +/- 280 dynes sec cm-5; NS) but had no effect on cardiac output. Enalaprilat (1.875 mg) produced a significant increase of cardiac output (3.0 +/- 0.5 vs. 3.8 +/- 0.5 l/min; p < .001) and LVEF (22 +/- 1 vs. 30 +/- 1%; p < .01), and decreased SVR (3280 +/- 400 vs. 2450 +/- 250 dynes sec cm-5; p < .01). Intravenous digoxin at a cumulative dose of 0.75 mg increased LVEF (23 +/- 2 vs. 31 +/- 2%; p < .01) but had no effect on SVR. These data indicate that this canine model of CHF responds to acute pharmacologic intervention in a manner comparable to that seen in patients with CHF. Accordingly, this model may be a useful tool for the preclinical evaluation of new drugs targeted toward the treatment of CHF and for investigating the mechanisms of action of drugs currently used for the treatment of this disease state.

Recognition and management of asymptomatic patients with left ventricular dysfunction

In recent years there have been encouraging developments in the therapy for congestive heart failure. Vasodilator therapy, as an adjunct to digitalis and diuretics, has made a major impact. Vasodilator therapy results in improved left ventricular (LV) ejection fraction, improved functional capacity, and enhanced quality of life. When an angiotensin-converting enzyme (ACE) inhibitor is used, several studies published since 1988 show that these improvements are accompanied by improved survival. Yet many questions remain. Principal among these is how to approach the patient who has significantly depressed LV function, but is asymptomatic or has only minimal symptoms. In these patients the prognosis cannot be based on New York Heart Association (NYHA) functional class, but must reflect objective measurements of ventricular function. Any intervention should be specifically designed to improve survival, since functional capacity and quality of life are apparently unimpaired. On the other hand, there are no data at present to suggest that intervention in these patients will improve survival. This article considers the evaluation of such asymptomatic patients and potential therapeutic approaches. These are the use of cardiac glycosides, the use of ACE inhibitors, or their combination. Circumstantial evidence supporting their use in this select patient population is considered. It is stressed that any decision to intervene therapeutically in the asymptomatic patient must be made by the physician on an individual basis.

Acute hemodynamic effects of digoxin alone or in combination with other vasoactive agents in patients with congestive heart failure

Although digitalis preparations have been in use for greater than 200 years, it is only within the last 2 decades that the central hemodynamic and neurohumoral effects occurring over several hours following intravenous administration of digoxin have been investigated in patients with congestive heart failure (CHF). Although digoxin has been shown to stimulate myocardial contractility in tissue preparations, its positive inotropic activity does not consistently translate into improvements in hemodynamic measurements in humans. Digoxin given intravenously results in increased cardiac index and decreased heart rate, left ventricular filling pressure, and right atrial pressure, as well as in acute attenuation of neurohumoral abnormalities, in patients with chronic CHF who have abnormal baseline hemodynamic measurements. Unlike other drugs with positive inotropic activity, however, digoxin does not influence hemodynamics in normal volunteers or in CHF patients in whom hemodynamics have been normalized with other therapies. These differing effects may be related to the drug's diverse peripheral vascular effects in CHF patients in whom vasodilation may occur in comparison with those that occur in normal subjects in whom the peripheral vasoconstrictor effects may prevent the inotropic effects of the drug from being translated into an increase in cardiac output. The hemodynamic effects of digoxin in patients with chronic CHF due primarily to diastolic dysfunction have not been fully investigated. Intravenous digoxin produces hemodynamic effects in patients with CHF associated with acute myocardial infarction, but these changes are small compared with those resulting from the administration of dobutamine. Digoxin does not appear to influence hemodynamic measurements in patients with right ventricular dysfunction unless concomitant left ventricular failure is present. In patients with chronic left ventricular dysfunction, the hemodynamic effects of intravenous digoxin and vasodilators are enhanced when these agents are given in combination.

Changes in circulating norepinephrine with hemofiltration in advanced congestive heart failure

In congestive heart failure (CHF), hemofiltration is associated with an obvious decrease in circulating norepinephrine. This method was used for investigating the mechanisms whereby plasma norepinephrine is increased in chronic CHF. In 23 cases of advanced CHF, hemofiltration (2,983 +/- 1,228 ml) lowered plasma norepinephrine by 515 +/- 444 pg/ml. This effect was prompt, persisted or became greater in the next 24 hours. It was not associated with significant changes in cardiac output, aortic pressure or systemic vascular resistance. It did not appear to depend on variations in parameters related to the sympathetic activity, such as plasma renin, right atrial, wedge pulmonary artery and renal perfusion pressures, and was independent of duration and amount of hemofiltration. These observations did not support the concept that the norepinephrine decrease was the main consequence of a neural sympathetic inhibition. Hemofiltration increased diuresis by 606 +/- 415 ml; changes were prompt and correlated inversely (r = -0.7; p less than 0.01) with those in plasma norepinephrine. The same unknown mechanism of the increased urinary output might potentiate the norepinephrine removal from the blood by the kidney, or hemofiltration and the augmented diuresis might result in a regression of congestion of lungs and kidneys, leading to an improved extraction of norepinephrine. In CHF, a relation may exist between fluid retention and norepinephrine and in advanced stages, circulating norepinephrine, although strikingly increased, is devoid of important cardiovascular effects. At these stages, plasma norepinephrine is probably unreliable as an index of the sympathetic neural activity.