Comparative hemodynamic and neurohormonal effects of intravenous captopril and digoxin and their combinations in patients with severe heart failure

Mechanisms of current therapeutic strategies for heart failure: more questions than answers?

Heart failure (HF) is a complex, multifactorial and heterogeneous syndrome with substantial mortality and morbidity. Over the last few decades, numerous attempts have been made to develop targeted therapies that may attenuate the known pathophysiological pathways responsible for causing the progression of HF. However, therapies developed with this objective have sometimes failed to show benefit. The pathophysiological construct of HF with numerous aetiologies suggests that interventions with broad mechanisms of action which simultaneously target more than one pathway maybe more effective in improving the outcomes of patients with HF. Indeed, current therapeutics with clinical benefits in HF have targeted a wider range of intermediate phenotypes. Despite extensive scientific breakthroughs in HF research recently, questions persist regarding the ideal therapeutic targets which may help achieve maximum benefit. In this review, we evaluate the mechanism of action of current therapeutic strategies, the pathophysiological pathways they target and highlight remaining knowledge gaps regarding the mode of action of these interventions.

Regulation of the microvasculature during small muscle mass exercise in chronic obstructive pulmonary disease vs. chronic heart failure

Aim: Skeletal muscle convective and diffusive oxygen (O2) transport are peripheral determinants of exercise capacity in both patients with chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF). We hypothesised that differences in these peripheral determinants of performance between COPD and CHF patients are revealed during small muscle mass exercise, where the cardiorespiratory limitations to exercise are diminished. Methods: Eight patients with moderate to severe COPD, eight patients with CHF (NYHA II), and eight age- and sex-matched controls were studied. We measured leg blood flow (Q̇leg) by Doppler ultrasound during submaximal one-legged knee-extensor exercise (KEE), while sampling arterio-venous variables across the leg. The capillary oxyhaemoglobin dissociation curve was reconstructed from paired femoral arterial-venous oxygen tensions and saturations, which enabled the estimation of O2 parameters at the microvascular level within skeletal muscle, so that skeletal muscle oxygen conductance (DSMO2) could be calculated and adjusted for flow (DSMO2/Q̇leg) to distinguish convective from diffusive oxygen transport. Results: During KEE, Q̇leg increased to a similar extent in CHF (2.0 (0.4) L/min) and controls (2.3 (0.3) L/min), but less in COPD patients (1.8 (0.3) L/min) (p <0.03). There was no difference in resting DSMO2 between COPD and CHF and when adjusting for flow, the DSMO2 was higher in both groups compared to controls (COPD: 0.97 (0.23) vs. controls 0.63 (0.24) mM/kPa, p= 0.02; CHF 0.98 (0.11) mM/kPa vs. controls, p= 0.001). The Q̇-adjusted DSMO2 was not different in COPD and CHF during KEE (COPD: 1.19 (0.11) vs. CHF: 1.00 (0.18) mM/kPa; p= 0.24) but higher in COPD vs. controls: 0.87 (0.28) mM/kPa (p= 0.02), and only CHF did not increase Q̇-adjusted DSMO2 from rest (p= 0.2). Conclusion: Disease-specific factors may play a role in peripheral exercise limitation in patients with COPD compared with CHF. Thus, low convective O2 transport to contracting muscle seemed to predominate in COPD, whereas muscle diffusive O2 transport was unresponsive in CHF.

Digoxin Initiation and Outcomes in Patients with Heart Failure with Preserved Ejection Fraction

BACKGROUND

Digoxin reduces the risk of heart failure hospitalization in patients with heart failure with reduced ejection fraction. Less is known about this association in patients with heart failure with preserved ejection fraction (HFpEF), the examination of which was the objective of the current study.

METHODS

In the Medicare-linked OPTIMIZE-HF registry, 7374 patients hospitalized for HF had ejection fraction ≥50% and were not receiving digoxin prior to admission. Of these, 5675 had a heart rate ≥50 beats per minute, an estimated glomerular filtration rate ≥30 mL/min/1.73 m2 or did not receive inpatient dialysis, and digoxin was initiated in 524 of these patients. Using propensity scores for digoxin initiation, calculated for each of the 5675 patients, we assembled a matched cohort of 513 pairs of patients initiated and not initiated on digoxin, balanced on 58 baseline characteristics (mean age, 80 years; 66% women; 8% African American). Hazard ratios (HRs) and 95% confidence intervals (CIs) for outcomes associated with digoxin initiation were estimated in the matched cohort.

RESULTS

Among the 1026 matched patients with HFpEF, 30-day heart failure readmission occurred in 6% and 9% of patients initiated and not initiated on digoxin, respectively (HR 0.70; 95% CI, 0.45-1.10; P = .124). HRs (95% CIs) for 30-day all-cause readmission and all-cause mortality associated with digoxin initiation were 0.95 (0.73-1.23; P = .689) and 0.93 (0.55-1.56; P = .773), respectively. Digoxin initiation had no association with 6-year outcomes.

CONCLUSION

Digoxin initiation prior to hospital discharge was not associated with 30-day or 6-year outcomes in older hospitalized patients with HFpEF.

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.

Safety and Prognostic Impact of Early Treatment with Angiotensin-Converting Enzyme Inhibitors or Angiotensin Receptor Blockers in Patients with Acute Heart Failure

BACKGROUND

Although angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) have been recommended for patients with heart failure, their clinical and prognostic impact in the very acute phase of acute heart failure (AHF) is unclear, mainly because data on their safety and efficacy are lacking.

METHODS

This study was a post hoc analysis of the REALITY-AHF trial. Patients with AHF who did not take an ACEI or ARB at admission were enrolled. Patients who received these medications within 48 h of admission were categorized as the ACEI/ARB group, and all other patients were categorized as the no ACEI/ARB group. The primary endpoint was a composite of all-cause death and heart failure readmission within 1 year of admission.

RESULTS

Of the 1682 patients in the REALITY-AHF cohort, 900 were enrolled in this study, and 288 (32%) were included in the ACEI/ARB group. After propensity score matching, 152 pairs were evaluated, and no significant difference was found for in-hospital mortality, worsening renal function, or length of hospital stay. The ACEI/ARB group had significantly higher event-free survival (hazard ratio 0.51; 95% confidence interval 0.32-0.82; p = 0.006).

CONCLUSIONS

Early initiation of ACEIs/ARBs within 48 h of admission for hospitalized patients with AHF was not associated with adverse events and correlated with improved outcomes at 1 year from admission.

Questionable utility of digoxin in left-ventricular assist device recipients: A multicenter, retrospective analysis

Background

While clinical experience with left ventricular assist devices (LVAD) continues to grow and evolve, little is known regarding the ongoing use of certain medications in this population. We sought to evaluate the utility of digoxin in LVAD recipients and its association with outcomes.

Methods

A total of 505 patients who underwent continuous-flow LVAD implantation at 5 centers from 2007–2015 were included. Patients were divided into 4 groups: not on digoxin at any time (ND; n = 257), received digoxin pre implant (PreD; n = 144), received digoxin pre and post implant (ContD; n = 55), and received digoxin only post implant (PostD; n = 49). Survival and all-cause readmission were compared between the 4 groups.

Results

There was no difference in survival at 1 year nor at 3 years between groups (ND = 88%, 66%, respectively; PreD = 85%, 66%; ContD = 86%, 57%; PostD = 90%, 51%; p = 0.7). Readmission per 100 days also was not different between groups (ND = 0.5, PreD = 0.6, ContD = 0.5, PostD = 0.7; p = 0.1).

Conclusions

In this large, multicenter cohort, use of digoxin was not associated with any significant benefit in regard to mortality or hospitalization in patients supported with a continuous-flow LVAD. Importantly, its discontinuation post implant did not worsen all-cause hospitalization or survival.

Digoxin Discontinuation and Outcomes in Patients With Heart Failure With Reduced Ejection Fraction

BACKGROUND

The deleterious effects of discontinuation of digoxin on outcomes in ambulatory patients with chronic heart failure (HF) with reduced ejection fraction (HFrEF) receiving angiotensin-converting enzyme inhibitors are well-documented.

OBJECTIVES

The authors sought to determine the relationship between digoxin discontinuation and outcomes in hospitalized patients with HFrEF receiving more contemporary guideline-directed medical therapies including beta-blockers and mineralocorticoid receptor antagonists.

METHODS

Of the 11,900 hospitalized patients with HFrEF (EF ≤45%) in the Medicare-linked OPTIMIZE-HF (Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure) registry, 3,499 received pre-admission digoxin, which was discontinued in 721 patients. Using propensity scores for digoxin discontinuation, estimated for each of the 3,499 patients, a matched cohort of 698 pairs of patients, balanced on 50 baseline characteristics (mean age 76 years; mean EF 28%; 41% women; 13% African American; 65% on beta-blockers) was assembled.

RESULTS

Four-year post-discharge, digoxin discontinuation was associated with significantly higher risks of HF readmission (hazard ratio [HR]: 1.21; 95% confidence interval [CI]: 1.05 to 1.39; p = 0.007), all-cause readmission (HR: 1.16; 95% CI: 1.04 to 1.31; p = 0.010), and the combined endpoint of HF readmission or all-cause mortality (HR: 1.20; 95% CI: 1.07 to 1.34; p = 0.002), but not all-cause mortality (HR: 1.09; 95% CI: 0.97 to 1.24; p = 0.163). Discontinuation of digoxin was associated with a significantly higher risk of all 4 outcomes at 6 months and 1 year post-discharge. At 30 days, digoxin discontinuation was associated with higher risks of all-cause mortality (HR: 1.80; 95% CI: 1.26 to 2.57; p = 0.001) and the combined endpoint (HR: 1.36; 95% CI: 1.09 to 1.71; p = 0.007), but not of HF readmission (HR: 1.19; 95% CI: 0.90 to 1.59; p = 0.226) or all-cause readmission (HR: 1.03; 95% CI: 0.84 to 1.26; p = 0.778).

CONCLUSIONS

Among hospitalized older patients with HFrEF on more contemporary guideline-directed medical therapies, discontinuation of pre-admission digoxin therapy was associated with poor outcomes.

The effects of heart rate control in chronic heart failure with reduced ejection fraction

Elevated heart rate has been associated with worse prognosis both in the general population and in patients with heart failure. Heart rate is finely modulated by neurohormonal signals and it reflects the balance between the sympathetic and the parasympathetic limbs of the autonomic nervous system. For this reason, elevated heart rate in heart failure has been considered an epiphenomenon of the sympathetic hyperactivation during heart failure. However, experimental and clinical evidence suggests that high heart rate could have a direct pathogenetic role. Consequently, heart rate might act as a pathophysiological mediator of heart failure as well as a marker of adverse outcome. This hypothesis has been supported by the observation that the positive effect of beta-blockade could be linked to the degree of heart rate reduction. In addition, the selective heart rate control with ivabradine has recently been demonstrated to be beneficial in patients with heart failure and left ventricular systolic dysfunction. The objective of this review is to examine the pathophysiological implications of elevated heart rate in chronic heart failure and explore the mechanisms underlying the effects of pharmacological heart rate control.

Prevalent digoxin use and subsequent risk of death or hospitalization in ambulatory heart failure patients with a reduced ejection fraction-Findings from the Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) randomized controlled trial

BACKGROUND

Despite more than 200 years of clinical experience and a pivotal trial, recently published research has called into question the safety and efficacy of digoxin therapy in heart failure (HF).

METHODS

HF-ACTION (ClinicalTrials.gov Number: NCT00047437) enrolled 2331 outpatients with HF and an EF ≤35% between April 2003 and February 2007 and randomized them to aerobic exercise training versus usual care. Patients were grouped according to prevalent digoxin status at baseline. The association between digoxin therapy and outcomes was assessed using Cox proportional hazard and inverse-probability weighted (IPW) regression models adjusted for demographics, medical history, medications, laboratory values, quality of life, and exercise parameters.

RESULTS

The prevalence of digoxin therapy decreased from 52% during the first 6 months of enrollment to 35% at the end of the HF-ACTION trial (P <0.0001). Study participants were 59± 13 years of age, 72% were male, and approximately half had an ischemic etiology of HF. Patients receiving digoxin at baseline tended to be younger and were more likely to report New York Heart Association functional class III/IV symptoms (rather than class II) compared to those not receiving digoxin. Patients taking digoxin had worse baseline exercise capacity as measured by peak VO₂ and 6-min walk test and greater impairments in health status as reflected by the Kansas City Cardiomyopathy Questionnaire. The association between digoxin and the risk of death or hospitalization differed depending on whether Cox proportional hazard (Hazard Ratio 1.03, 95% Confidence Interval 0.92-1.16; P = .62) or IPW regression models (HR 1.08, 95% CI 1.00-1.17; P = .057) were used to adjust for potential confounders.

CONCLUSION

Although digoxin use was associated with high-risk clinical features, the association between digoxin therapy and outcomes was dependent on the statistical methods used for multivariable adjustment. Clinical equipoise exists and additional prospective research is required to clarify the role of digoxin in contemporary clinical practice including its effects on functional capacity, quality of life, and long-term outcomes.

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.

Is Heart Rate a Norepiphenomenon in Heart Failure?

There has been an increased focus on heart rate as a target in the management of cardiovascular disease and more specifically in heart failure with preserved ejection fraction in recent years with several studies showing the benefit of a lower resting heart rate on outcomes. This review paper examines the pathophysiology behind the benefits of lowering heart rate in heart failure and also the evidence for and against the pharmacological agents available to achieve this.

Digoxin in Heart Failure with a Reduced Ejection Fraction: A Risk Factor or a Risk Marker?

Digoxin is one of the oldest compounds used in cardiovascular medicine. Nevertheless, its mechanism of action and most importantly its clinical utility have been the subject of an endless dispute. Positive inotropic and neurohormonal modulation properties are attributed to digoxin, and it was the mainstay of heart failure therapeutics for decades. However, since the institution of β-blockers and aldosterone antagonists as part of modern heart failure medical therapy, digoxin prescription rates have been in free fall. The fact that digoxin is still listed as a valid therapeutic option in both American and European heart failure guidelines has not altered clinicians' attitude towards the drug. Since the publication of original Digitalis Investigation Group trial data, a series of reports based predominately on observational studies and post hoc analyses have raised concerns about the clinical efficacy and long-term safety of digoxin. In the present review, we will attempt a critical appraisal of the available clinical evidence regarding the efficacy and safety of digoxin in heart failure patients with a reduced ejection fraction. The methodological issues, strengths, and limitations of individual studies will be highlighted.

Hemodynamic responses to small muscle mass exercise in heart failure patients with reduced ejection fraction

To better understand the mechanisms responsible for exercise intolerance in heart failure with reduced ejection fraction (HFrEF), the present study sought to evaluate the hemodynamic responses to small muscle mass exercise in this cohort. In 25 HFrEF patients (64 ± 2 yr) and 17 healthy, age-matched control subjects (64 ± 2 yr), mean arterial pressure (MAP), cardiac output (CO), and limb blood flow were examined during graded static-intermittent handgrip (HG) and dynamic single-leg knee-extensor (KE) exercise. During HG exercise, MAP increased similarly between groups. CO increased significantly (+1.3 ± 0.3 l/min) in the control group, but it remained unchanged across workloads in HFrEF patients. At 15% maximum voluntary contraction (MVC), forearm blood flow was similar between groups, while HFrEF patients exhibited an attenuated increase at the two highest intensities compared with controls, with the greatest difference at the highest workload (352 ± 22 vs. 492 ± 48 ml/min, HFrEF vs. control, 45% MVC). During KE exercise, MAP and CO increased similarly across work rates between groups. However, HFrEF patients exhibited a diminished leg hyperemic response across all work rates, with the most substantial decrement at the highest intensity (1,842 ± 64 vs. 2,675 ± 81 ml/min; HFrEF vs. control, 15 W). Together, these findings indicate a marked attenuation in exercising limb perfusion attributable to impairments in peripheral vasodilatory capacity during both arm and leg exercise in patients with HFrEF, which likely plays a role in limiting exercise capacity in this patient population.

The use of digoxin in patients with worsening chronic heart failure: reconsidering an old drug to reduce hospital admissions

Digoxin is the oldest cardiac drug still in contemporary use, yet its role in the management of patients with heart failure (HF) remains controversial. A purified cardiac glycoside derived from the foxglove plant, digoxin increases ejection fraction, augments cardiac output, and reduces pulmonary capillary wedge pressure without causing deleterious increases in heart rate or decreases in blood pressure. Moreover, it is also a neurohormonal modulator at low doses. In the pivotal DIG (Digitalis Investigation Group) trial, digoxin therapy was shown to reduce all-cause and HF-specific hospitalizations but had no effect on survival. With the discovery of neurohormonal blockers capable of reducing mortality in HF with reduced ejection fraction, the results of the DIG trial were viewed as neutral, and the use of digoxin declined precipitously. Although modern drug and device-based therapies have dramatically improved the survival of ambulatory patients with HF, outcomes for patients with worsening chronic HF, defined as deteriorating signs and symptoms on standard therapy often leading to unscheduled clinic or emergency department visits or hospitalization, have largely remained unchanged over the past 2 decades. The available data suggest that a therapeutic trial of digoxin may be appropriate in patients with worsening chronic heart failure who remain symptomatic.

Digoxin use and lower 30-day all-cause readmission for Medicare beneficiaries hospitalized for heart failure

BACKGROUND

Heart failure is the leading cause for hospital readmission, the reduction of which is a priority under the Affordable Care Act. Digoxin reduces 30-day all-cause hospital admission in chronic systolic heart failure. Whether digoxin is effective in reducing readmission after hospitalization for acute decompensation remains unknown.

METHODS

Of the 5153 Medicare beneficiaries hospitalized for acute heart failure and not receiving digoxin, 1054 (20%) received new discharge prescriptions for digoxin. Propensity scores for digoxin use, estimated for each of the 5153 patients, were used to assemble a matched cohort of 1842 (921 pairs) patients (mean age, 76 years; 56% women; 25% African American) receiving and not receiving digoxin, who were balanced on 55 baseline characteristics.

RESULTS

Thirty-day all-cause readmission occurred in 17% and 22% of matched patients receiving and not receiving digoxin, respectively (hazard ratio [HR] for digoxin, 0.77; 95% confidence interval [CI], 0.63-0.95). This beneficial association was observed only in those with ejection fraction <45% (HR 0.63; 95% CI, 0.47-0.83), but not in those with ejection fraction ≥ 45% (HR 0.91; 95% CI, 0.60-1.37; P for interaction, .145), a difference that persisted throughout the first 12 months postdischarge (P for interaction, .019). HRs (95% CIs) for 12-month heart failure readmission and all-cause mortality were 0.72 (0.61-0.86) and 0.83 (0.70-0.98), respectively.

CONCLUSIONS

In Medicare beneficiaries with systolic heart failure, a discharge prescription of digoxin was associated with lower 30-day all-cause hospital readmission, which was maintained at 12 months, and was not at the expense of higher mortality. Future randomized controlled trials are needed to confirm these findings.

Standard nonspecific therapies in the management of pulmonary arterial hypertension

Recent advances in pulmonary arterial hypertension (PAH) research have created a new era of PAH-specific therapies. Although these therapeutics have revolutionized PAH therapy, their innovation was predated by supportive but nonspecific medical therapies adapted from their use in more common cardiopulmonary diseases. These therapies include oxygen therapy, diuretics, digoxin, anticoagulation, and high-dose calcium channel blockers. Expert opinion continues to support the use of adjunct therapies based on current pathologic understandings of PAH combined with some evidence extrapolated from small studies. This article discusses why these therapies continue to play an important role in the treatment of patients with PAH.

[Digitalis and theophylline: old and superfluous?]

Digitalis and theophylline are some of the oldest drugs used to treat cardiopulmonary diseases. Despite a long history, the evidence for both drugs is still inconsistent, in parts negative. In this context, geriatric medicine represents a special area of conflict. On the one hand, both drugs may play a role in the treatment of advanced heart failure and chronic obstructive pulmonary disease, particularly in the treatment of symptoms. On the other hand, both drugs are often listed as potentially inappropriate medications for the elderly. This paper discusses the evidence for both drugs based on the current literature.

Effect of oral digoxin in high-risk heart failure patients: a pre-specified subgroup analysis of the DIG trial

AIMS

In the Digitalis Investigation Group (DIG) trial, digoxin reduced mortality or hospitalization due to heart failure (HF) in several pre-specified high-risk subgroups of HF patients, but data on protocol-specified 2-year outcomes were not presented. In the current study, we examined the effect of digoxin on HF death or HF hospitalization and all-cause death or all-cause hospitalization in high-risk subgroups during the protocol-specified 2 years of post-randomization follow-up.

METHODS AND RESULTS

In the DIG trial, 6800 ambulatory patients with chronic HF, normal sinus rhythm, and LVEF ≤45% (mean age 64 years, 26% women, 17% non-whites) were randomized to receive digoxin or placebo. The three high-risk groups were defined as NYHA class III-IV symptoms (n = 2223), LVEF <25% (n = 2256), and cardiothoracic ratio (CTR) >55% (n = 2345). In all three high-risk subgroups, compared with patients in the placebo group, those in the digoxin group had a significant reduction in the risk of the 2-year composite endpoint of HF mortality or HF hospitalization: NYHA III-IV [hazard ratio (HR) 0.65; 95% confidence interval (CI) 0.57-0.75; P < 0.001], LVEF <25% (HR 0.61; 95% CI 0.53-0.71; P < 0.001), and CTR >55% (HR 0.65; 95% CI 0.57-0.75; P < 0.001). Digoxin-associated HRs (95% CI) for 2-year all-cause mortality or all-cause hospitalization for subgroups with NYHA III-IV, LVEF <25%, and CTR >55% were 0.88 (0.80-0.97; P = 0.012), 0.84 (0.76-0.93; P = 0.001), and 0.85 (0.77-0.94; P = 0.002), respectively.

CONCLUSIONS

Digoxin improves outcomes in chronic HF patients with NYHA class III-IV, LVEF <25%, or CTR >55%, and should be considered in these patients.

Haemodynamic effects, safety, and pharmacokinetics of human stresscopin in heart failure with reduced ejection fraction

AIMS

Human stresscopin is a corticotropin-releasing factor (CRF) type 2 receptor (CRFR2) selective agonist and a member of the CRF peptide family. Stimulation of CRFR2 improves cardiac output and left ventricular ejection fraction (LVEF) in patients with stable heart failure (HF) with reduced LVEF. We examined the safety, pharmacokinetics, and effects on haemodynamics and serum biomarkers of intravenous human stresscopin acetate (JNJ-39588146) in patients with stable HF with LVEF ≤ 35% and cardiac index (CI) ≤ 2.5 L/min/m(2).

METHODS AND RESULTS

Sixty-two patients with HF and LVEF ≤ 35% were instrumented with a pulmonary artery catheter and randomly assigned (ratio 3:1) to receive an intravenous infusion of JNJ-39588146 or placebo. The main study was an ascending dose study of three doses (5, 15, and 30 ng/kg/min) of study drug or placebo administered in sequential 1 h intervals (3 h total). Statistically significant increases in CI and reduction in systemic vascular resistance (SVR) were observed with both the 15 ng/kg/min (2 h time point) and 30 ng/kg/min (3 h time point) doses of JNJ-39588146 without significant changes in heart rate (HR) or systolic blood pressure (SBP). No statistically significant reductions in pulmonary capillary wedge pressure (PCWP) were seen with any dose tested in the primary analysis, although a trend towards reduction was seen.

CONCLUSION

In HF patients with reduced LVEF and CI, ascending doses of JNJ-39588146 were associated with progressive increases in CI and reductions in SVR without significant effects on PCWP, HR, or SBP.

TRIAL REGISTRATION

NCT01120210.

Pharmacologic therapy for New York Heart Association class IV heart failure

As the incidence of heart failure increases, the number of patients with advanced heart failure is anticipated to grow. Substantial progress in the treatment of heart failure has been achieved over the past few decades. Several classes of medications have been studied and found effective, including beta-blockers, angiotensin converting enzyme inhibitors or angiotensin receptor blockers, aldosterone antagonists, vasodilators, digoxin, and inotropes. The evidence base for the use of these medications in the treatment of patients with New York Heart Association (NYHA) class IV heart failure is reviewed.

Agents with inotropic properties for the management of acute heart failure syndromes. Traditional agents and beyond

Treatment with inotropic agents is one of the most controversial topics in heart failure. Initial enthusiasm, based on strong pathophysiological rationale and apparent empirical efficacy, has been progressively limited by results of controlled trials and registries showing poorer outcomes of the patients on inotropic therapy. The use of these agents remains, however, potentially indicated in a significant proportion of patients with low cardiac output, peripheral hypoperfusion and end-organ dysfunction caused by heart failure. Limitations of inotropic therapy seem to be mainly related to their mechanisms of action entailing arrhythmogenesis, peripheral vasodilation, myocardial ischemia and damage, and possibly due to their use in patients without a clear indication, rather than to the general principle of inotropic therapy itself. This review will discuss the characteristics of the patients with a potential indication for inotropic therapy, the main data from registries and controlled trials, the mechanism of the untoward effects of these agents on outcomes and, lastly, perspectives with new agents with novel mechanisms of action.

Effects of digoxin on muscle reflexes in normal humans

Blockade of the skeletal muscle Na(+)-K(+)-ATPase pump by digoxin could result in a more marked hyperkaliema during a forearm exercise, which in turn could stimulate the mechano- and metaboreceptors. In a randomized, double-blinded, placebo-controlled, and cross-over-design study, we measured mean blood pressure (MBP), heart rate (HR), ventilation (V(E)), oxygen saturation (SpO(2)), muscle sympathetic nerve activity (MSNA), venous plasma potassium and lactic acid during dynamic handgrip exercises, and local circulatory arrest in 11 healthy subjects. Digoxin enhanced MBP during exercise but not during the post-handgrip ischemia and had no effect on HR, V(E), SpO(2), and MSNA. Venous plasma potassium and lactic acid were also not affected by digoxin-induced skeletal muscle Na(+)-K(+)-ATPase blockade. We conclude that digoxin increased MBP during dynamic exercise in healthy humans, independently of changes in potassium and lactic acid. A modest direct sensitization of the muscle mechanoreceptors is unlikely and other mechanisms, independent of muscle reflexes and related to the inotropic effects of digoxin, might be implicated.

Early pharmacological treatment of acute heart failure syndromes: A systematic review of clinical trials

CONTEXT

Acute Heart Failure Syndromes (AHFS) is a common admission diagnosis associated with high mortality and hospital readmissions. Given the mixed results of recent clinical trials, the early management of AHFS remains controversial.

OBJECTIVE

To review the recent evidence regarding current and investigational therapies for the early management of AHFS.

DATA SOURCES

A systematic search of peer-reviewed publications was performed on MEDLINE and EMBASE from January 1990 to August 2006. The results of unpublished or ongoing trials were obtained from presentations at national and international meetings and pharmaceutical industry releases. Bibliographies from these references were also reviewed, as were additional articles identified by content experts.

STUDY SELECTION AND DATA EXTRACTION

Criteria used for study selection were controlled study design, relevance to clinicians and validity based on venue of publication and power analysis.

DATA SYNTHESIS

Although all current intravenous therapies for the early management of AHFS appear to improve hemodynamics, this may not always translate into short-term clinical benefit.

CONCLUSION

The results of the trials conducted to date in AHFS have generally been disappointing. There is, therefore, an unmet need for new therapeutic approaches for the early management of AHFS that may improve the short-term and long-term outcomes.

Management of acute decompensated heart failure

Acute decompensated heart failure is the most common cause for hospitalization among patients over 65 years of age. It may result from new onset of ventricular dysfunction or, more typically, exacerbation of chronic heart failure symptoms. In-hospital mortality remains high for both systolic and diastolic forms of the disease. Therapy is largely empirical as few randomized, controlled trials have focused on this population and consensus practice guidelines are just beginning to be formulated. Treatment should be focused upon correction of volume overload, identifying potential precipitating causes, and optimizing vasodilator and beta-adrenergic blocker therapy. The majority of patients (>90%) will improve without the use of positive inotropic agents, which should be reserved for patients with refractory hypotension, cardiogenic shock, end-organ dysfunction, or failure to respond to conventional oral and/or intravenous diuretics and vasodilators. The role of aldosterone antagonists, biventricular pacing, and novel pharmacological agents including vasopressin antagonists, endothelin blockers, and calcium-sensitizing agents is also reviewed.

Review of current and investigational pharmacologic agents for acute heart failure syndromes

Acute heart failure syndromes (AHFS) are a major public health problem and present a therapeutic challenge to clinicians. Commonly used agents in the treatment of AHFS include diuretics, vasodilators (eg, nitroglycerin, nitroprusside, nesiritide), and inotropes (eg, dobutamine, dopamine, milrinone). Patients admitted to hospital with AHFS and low cardiac output state (AHFS/LO) represent a subgroup with very high inhospital and postdischarge mortality rates. Most of these patients require intravenous inotropic therapy. However, the use of current intravenous inotropes has been associated with risk for hypotension, atrial and ventricular arrhythmias, and possibly increased postdischarge mortality, particularly in those with coronary artery disease. Consequently, there is an unmet need for new agents to safely improve cardiac performance (contractility and/or active relaxation) in this patient population. This article reviews a selection of current and investigational agents for the treatment of AHFS, with a main focus on the high-risk patient population with AHFS/LO.

Digitalis in heart failure! Still applicable?

In patients with heart failure and atrial fibrillation cardiac glycosides, generally in combination with beta-blockers, are indicated to control ventricular rate. In systolic heart failure and sinus rhythm, however, the use of digitalis continues to be debated. There are special concerns that cardiac glycosides might lead to an increased mortality rate in women. Retrospective analyses, however, do not indicate any sex-based differences in the effectiveness of cardiac glycosides. Beneficial effects of cardiac glycosides in heart failure seem to be related to the attenuation of sympathetic activation and neurohumoral alterations, which is already obtained at low digoxin serum concentrations, while high serum levels are associated with increased mortality. Therefore, in patients with sinus rhythm who remain symptomatic under an optimized therapy with ACE inhibitors, beta-blockers and diuretics in addition to digitalis should be considered regardless of the gender. However, target serum digoxin concentrations should be low in a range of 0.5 to 0.8 ng/ml.

Overview of current noninodilator therapies for acute heart failure syndromes

Several treatment strategies exist for patients hospitalized with acute heart failure syndromes (AHFS). These therapies traditionally focus on improving hemodynamics and relieving congestion. This review focuses on noninodilator therapies, including diuretics, nitrovasodilators (nitroprusside and nitroglycerin), vasodilators (nesiritide), digoxin, and intravenous angiotensin-converting enzyme inhibitors. These agents are used based on their associated symptomatic improvements alone. In the hospitalized setting, none of these agents have demonstrated benefits on long-term outcomes. Future work in AHFS should strive to understand the influence of conventional and new pharmacologic therapies on the underlying pathophysiology of AHFS, the processes that lead to myocardial injury and progressive heart failure, and measurable clinical outcomes.

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.

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.

Effects of chronic clonidine administration on sympathetic nerve traffic and baroreflex function in heart failure

Congestive heart failure is characterized by a sympathetic activation that is coupled with a baroreflex impairment. Whether these alterations are affected by clonidine is unknown. In 26 normotensive patients age 58.0+/-1.1 years (mean+/-SEM) affected by congestive heart failure (New York Heart Association functional class II or III) and treated with furosemide and enalapril, we measured mean arterial pressure, heart rate, venous plasma norepinephrine, and muscle sympathetic nerve traffic (microneurography) at rest and during baroreceptor stimulation and deactivation caused by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively. Measurements were repeated after a 2-month administration of transdermal clonidine patch (14 patients) or placebo (12 patients) according to a double-blind, randomized sequence. Clonidine caused a slight, nonsignificant reduction in mean arterial pressure and heart rate without affecting exercise capacity and echocardiographically determined left ventricular ejection fraction. In contrast, both plasma norepinephrine and sympathetic nerve traffic were significantly reduced (-46.8% and -26.7%, respectively; P<0.01 for both). This reduction was coupled with no change in cardiac and sympathetic baroreflex responses. Transdermal placebo administration for a 2-month period did not affect any of the above-mentioned variables. Thus, in congestive heart failure patients who are undergoing conventional drug treatment, chronic clonidine administration exerts marked sympathoinhibitory effects without adversely affecting cardiac functions and clinical state. Whether this leads to further therapeutic benefits remains to be tested.

Sudden death in heart failure patients: effects of optimized medical therapy

Although medical therapy, particularly with angiotensin-converting enzyme (ACE) inhibitors, has been demonstrated to prolong life in patients with chronic heart failure, the effect of standard medical therapy on sudden unexpected death in patients with heart failure is less well understood. Recent clinical trials have provided new insights into this growing problem. The impact of modern medical therapy for heart failure, including ACE inhibitors, beta-adrenergic antagonists, digoxin, calcium channel antagonists, and antiarrhythmic interventions will be discussed.

Angiotensin II blunts, while an angiotensin-converting enzyme inhibitor augments, reflex sympathetic inhibition in humans

1. The role of angiotensin (Ang)II in and the effects of angiotensin-converting enzyme (ACE) inhibitors on the regulation of sympathetic neural activity were examined in humans. 2. We measured baseline values of muscle sympathetic nerve activity (MSNA) and its reflex inhibition in 28 patients with essential hypertension with elevated plasma renin activity (PRA; > 1.0 ng/mL per h = 0.28 ng/L per s) before and after either acute or chronic oral administration of an ACE inhibitor or placebo and in 20 normotensive subjects before and after infusion of either AngII (5 ng/kg per min = 4.8 pmol/kg per min) or vehicle (5% dextrose). Muscle sympathetic nerve activity was recorded from the tibial nerve and its reflex inhibition was evaluated during pressor responses to bolus injection of phenylephrine (2 micrograms/kg, i.v.). 3. Blood pressure was significantly decreased (P < 0.01) after the acute oral administration of captopril (25 mg), accompanied by a slight increase in MSNA in patients with essential hypertension compared with control patients who received placebo administration. Reflex changes in MSNA were significantly augmented after oral administration of captopril (-4.1 +/- 0.5 vs -6.2 +/- 0.6%/mmHg, respectively; P < 0.01), with a significant reduction of plasma AngII, while they were not affected by placebo administration. 4. In contrast, acute AngII infusion was accompanied by decreases in both PRA and MSNA in normotensive subjects. Reflex changes in MSNA were significantly reduced after AngII infusion (-11.0 +/- 0.8 vs -7.4 +/- 1.0%/mmHg, respectively; P < 0.01) but not after vehicle alone. 5. Chronic ACE inhibition by 12 week oral imidapril administration (5-10 mg/day) significantly (P < 0.05) decreased baseline values of MSNA, which were accompanied by a significant (P < 0.05) increase in the reflex inhibition of MSNA, while plasma concentrations of noradrenaline were unaffected. 6. These results indicate that AngII blunts reflex inhibition of sympathetic neural activity and that inhibition of the renin-angiotensin system by an ACE inhibitor augments reflex regulation of sympathetic neural activity and reduces baseline values in patients with essential hypertension.

The effect of chronic mechanical circulatory support on neuroendocrine activation in patients with end-stage heart failure

OBJECTIVE

To evaluate if the improvement of patients supported with a Novacor was associated with a normalization in neuroendocrine activity.

METHODS

Six patients had a Novacor implanted for end-stage heart failure. Four patients were transplanted after a mean of 4.5 months (range 3-6). One patient was weaned after 5 months and one died of a cerebral haemorrhage 5 weeks after implantation. Analysis of neuroendocrine activity was made prior to implantation and after 14, 30, 60 and 90 days. Levels of aldosterone, renin, cortisol, testosterone and T3 were measured using radio-immunoassays. Twenty-four hour urinary collections were made for assessment of adrenaline and noradrenaline excretion.

RESULTS

Renin activity fell to normal after 14 days (16 +/- 3.0 ng/ml per h to 4.28 +/- 2.1 ng/ml per h, P < 0.05) and was maintained at 90 days. A similar picture was seen with aldosterone (1.5 +/- 0.4 nM to 0.12 +/- 0.07 nM, P < 0.05). Norepinephrine (67.46 +/- 14.1 microg/24 h) and epinephrine 12.9 +/- 2.5 microg/24 h) fell to normal physiological levels during the same time period. Cortisol levels were above normal pre-implantation but fell by day 30 (665.25 +/- 80.0 nM to 461.8 +/- 43.0 nM, P < 0.01). T3 and testosterone were lower than normal pre-implantation (T3 50 +/- 9.5 ng/dl vs. 90-200 ng/dl, testosterone 6.83 +/- 1.7 nM vs. 13-35 nM). T3 normalized after 90 days (81 +/- 11.7 ng/dl) and testosterone after 60 days (16.3 +/- 1.7 nM).

CONCLUSION

Neuroendocrine function is abnormal in patients with cardiac failure who require circulatory support. The Novacor improved this, but metabolic recovery was delayed. The positive effect on the neuroendocrine axis, in the absence of activation of other endocrine systems, suggests that prolonged support may be well tolerated.

Angiotensin II and sympathoactivation in heart failure

Excessive activity of the sympathetic nervous system (SNS) contributes to the development and progression of the syndrome of congestive heart failure (CHF) in patients with decreased left ventricular function. The factors underlying chronic sympathoactivation are poorly understood, particularly in stable patients. This review summarizes both clinical and experimental data regarding the effects of angiotensin II (A-II) on the activity of the SNS. The focus is on both the direct effects of A-II on the SNS and an indirect effect medicated through alteration in function of the baroreflex. Available evidence is consistent with a potentially important effect of A-II on SNS activity, perhaps most likely via the baroreflex. Important issues regarding the direct effect of A-II on regional SNS activity, and on the physiological relevance of effects seen only at high plasma concentration of A-II remain to be fully elucidated.

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?

Effect of Digoxin on Ventricular Remodeling and Responsiveness of beta-Adrenoceptors in Chronic Volume Overload

BACKGROUND: Digoxin improves baroreflex function and reduces neurohumoral activation in severe heart failure, but it is uncertain how digoxin affects ventricular remodeling and progression to left ventricular dysfunction. In addition, the effect of digoxin in in vitro beta-adrenoceptor density and function, and contractile reserve in vivo is not well understood. METHODS AND RESULTS: To study this, we compared digoxin with placebo treatment in rats with chronic volume overload induced by aortocaval fistula and in sham-operated control animals. Left ventricular end-diastolic cavity dimensions (LVDd) and wall thickness were measured weekly by in vivo transthoracic echocardiography, and left ventricular mass (LVM) and percent fractional shortening (%FS) were calculated. Six weeks after fistula creation, simultaneous echocardiographic and invasive hemodynamic evaluation at rest and in response to incremental dobutamine (1-10 µg/kg/min intravenously) were measured. Myocardial plasma membrane beta-adrenoceptor density and maximal adenylate cyclase responses (V(max)) to isoproterenol, 5'-guanylylimi dodiphosphate, and forskolin were measured in vitro. Volume overload induced progressive increases in LVDd and LVM over the 6-week study period. Percent fractional shortening at rest, and the change in %FS in response to dobutamine stress were dramatically reduced 6 weeks after fistula creation. Although 6-week fistula animals had unchanged beta-adrenoceptor density (B(max)) and binding affinity (K(d)) as compared with controls, maximal adenylate cyclase responses to stimulation in vitro (V(max)) were markedly reduced. Digoxin treatment prevented this loss of responsiveness of adenylate cyclase but did not affect beta-adrenoceptor density or affinity in vitro. Digoxin had no effect on LVDd, LVM, %FS, or the response to dobutamine infusion in vivo. CONCLUSIONS: Although digoxin prevented beta-adrenoceptor desensitization and improved in vitro myocardial adenylate cyclase response, the cardiac response to adrenergic stimulation in vivo was not significantly improved. These results suggest that the role of beta-adrenoceptor desensitization in the progression from volume overload hypertrophy to left ventricular dysfunction and heart failure may be less important than previously thought. Furthermore, although digoxin treatment did produce modest hemodynamic benefits, it did not prevent progressive remodeling in this model.