If Inhibition with Ivabradine

Pacemaker Channels and the Chronotropic Response in Health and Disease

Loss or dysregulation of the normally precise control of heart rate via the autonomic nervous system plays a critical role during the development and progression of cardiovascular disease-including ischemic heart disease, heart failure, and arrhythmias. While the clinical significance of regulating changes in heart rate, known as the chronotropic effect, is undeniable, the mechanisms controlling these changes remain not fully understood. Heart rate acceleration and deceleration are mediated by increasing or decreasing the spontaneous firing rate of pacemaker cells in the sinoatrial node. During the transition from rest to activity, sympathetic neurons stimulate these cells by activating β-adrenergic receptors and increasing intracellular cyclic adenosine monophosphate. The same signal transduction pathway is targeted by positive chronotropic drugs such as norepinephrine and dobutamine, which are used in the treatment of cardiogenic shock and severe heart failure. The cyclic adenosine monophosphate-sensitive hyperpolarization-activated current (If) in pacemaker cells is passed by hyperpolarization-activated cyclic nucleotide-gated cation channels and is critical for generating the autonomous heartbeat. In addition, this current has been suggested to play a central role in the chronotropic effect. Recent studies demonstrate that cyclic adenosine monophosphate-dependent regulation of HCN4 (hyperpolarization-activated cyclic nucleotide-gated cation channel isoform 4) acts to stabilize the heart rate, particularly during rapid rate transitions induced by the autonomic nervous system. The mechanism is based on creating a balance between firing and recently discovered nonfiring pacemaker cells in the sinoatrial node. In this way, hyperpolarization-activated cyclic nucleotide-gated cation channels may protect the heart from sinoatrial node dysfunction, secondary arrhythmia of the atria, and potentially fatal tachyarrhythmia of the ventricles. Here, we review the latest findings on sinoatrial node automaticity and discuss the physiological and pathophysiological role of HCN pacemaker channels in the chronotropic response and beyond.

Detection of retinal dysfunction induced by HCN channel inhibitors using multistep light stimulus and long-duration light stimulus ERG in rats

Ivabradine, a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel inhibitor, has been reported to induce photosensitivity-related visual disturbances such as phosphene in humans. Ivabradine-induced visual disturbances are caused by inhibition of HCN channels in the retina, and the mechanisms have been verified using HCN channel knockout mice and electroretinography (ERG). However, in rats, classical ERG using single flash light stimulus with standard analyses of waveform amplitude and latency has not revealed abnormal retinal function after administration of ivabradine. To verify whether retinal dysfunction after ivabradine administration was detectable in rats, we performed ERG using multistep flash light stimulation at the time when plasma concentration of ivabradine was high. Furthermore, the mechanism of the change in the waveform that appeared after the b-wave was investigated. Ivabradine and cilobradine, a selective HCN channel inhibitor, were administered subcutaneously to rats at 4-40 mg/kg as a single dose, and flash or long-duration ERG recordings at each light stimulus luminance were conducted 1.5 h after administration. Plasma and retinal concentrations of both compounds were measured immediately after the ERG recordings. In the flash ERG, prolongation of a- and/or b-wave latencies were detected at each light stimulus, and dose-dependent waveform changes after the b-wave were recorded at the specific light stimulus luminance for both compounds. These ERG changes increased in response to increasing plasma and retinal concentrations for both ivabradine and cilobradine. In the long-duration light stimulus ERG, a change in the waveform of the b-wave trough and attenuation of the c-wave were recorded, suggesting that the feedback control in the photoreceptor cells may be inhibited. This study revealed that the retinal dysfunction by HCN channel inhibitors in rats can be detected by multistep light stimulus ERG. Additionally, we identified that the inhibition of feedback current and the sustained responses in the photoreceptor cells cause the retinal dysfunction of HCN channel inhibitors in rats.

Screening effects of HCN channel blockers on sleep/wake behavior in zebrafish

Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels generate electrical rhythmicity in various tissues although primarily heart, retina and brain. The HCN channel blocker compound, Ivabradine (Corlanor), is approved by the US Food and Drug Administration (FDA) as a medication to lower heart rate by blocking hyperpolarization activated inward current in the sinoatrial node. In addition, a growing body of evidence suggests a role for HCN channels in regulation of sleep/wake behavior. Zebrafish larvae are ideal model organisms for high throughput drug screening, drug repurposing and behavioral phenotyping studies. We leveraged this model system to investigate effects of three HCN channel blockers (Ivabradine, Zatebradine Hydrochloride and ZD7288) at multiple doses on sleep/wake behavior in wild type zebrafish. Results of interest included shorter latency to daytime sleep at 0.1 μM dose of Ivabradine (ANOVA, p: 0.02), moderate reduction in average activity at 30 μM dose of Zatebradine Hydrochloride (ANOVA, p: 0.024) in daytime, and increased nighttime sleep at 4.5 μM dose of ZD7288 (ANOVA, p: 0.036). Taken together, shorter latency to daytime sleep, decrease in daytime activity and increased nighttime sleep indicate that different HCN channel antagonists affected different parameters of sleep and activity.

cAMP-mediated upregulation of HCN channels in VTA dopamine neurons promotes cocaine reinforcement

Chronic cocaine exposure induces enduring neuroadaptations that facilitate motivated drug taking. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are known to modulate neuronal firing and pacemaker activity in ventral tegmental area (VTA) dopamine neurons. However, it remained unknown whether cocaine self-administration affects HCN channel function and whether HCN channel activity modulates motivated drug taking. We report that rat VTA dopamine neurons predominantly express Hcn3-4 mRNA, while VTA GABA neurons express Hcn1-4 mRNA. Both neuronal types display similar hyperpolarization-activated currents (Ih), which are facilitated by acute increases in cAMP. Acute cocaine application decreases voltage-dependent activation of Ih in VTA dopamine neurons, but not in GABA neurons. Unexpectedly, chronic cocaine self-administration results in enhanced Ih selectively in VTA dopamine neurons. This differential modulation of Ih currents is likely mediated by a D2 autoreceptor-induced decrease in cAMP as D2 (Drd2) mRNA is predominantly expressed in dopamine neurons, whereas D1 (Drd1) mRNA is barely detectable in the VTA. Moreover, chronically decreased cAMP via Gi-DREADD stimulation leads to an increase in Ih in VTA dopamine neurons and enhanced binding of HCN3/HCN4 with tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b), an auxiliary subunit that is known to facilitate HCN channel surface trafficking. Finally, we show that systemic injection and intra-VTA infusion of the HCN blocker ivabradine reduces cocaine self-administration under a progressive ratio schedule and produces a downward shift of the cocaine dose-response curve. Our results suggest that cocaine self-administration induces an upregulation of Ih in VTA dopamine neurons, while HCN inhibition reduces the motivation for cocaine intake.

Comparative Efficacy of Different Drugs for the Treatment of Dilated Cardiomyopathy: A Systematic Review and Network Meta-analysis

BACKGROUND AND OBJECTIVE

At present, the therapies of dilated cardiomyopathy concentrated on the symptoms of heart failure and related complications. The study is to evaluate the clinical efficacy of a combination of various conventional and adjuvant drugs in treating dilated cardiomyopathy via network meta-analysis.

METHODS

The study was reported according to the PRISMA 2020 statement. From inception through 27 June 2022, the PubMed, Embase, Cochrane library, and Web of Science databases were searched for randomized controlled trials on medicines for treating dilated cardiomyopathy. The quality of the included studies was evaluated according to the Cochrane risk of bias assessment. R4.1.3 and Revman5.3 software were used for analysis.

RESULTS

There were 52 randomized controlled trials in this study, with a total of 25 medications and a sample size of 3048 cases. The network meta-analysis found that carvedilol, verapamil, and trimetazidine were the top three medicines for improving left ventricular ejection fraction (LVEF). Ivabradine, bucindolol, and verapamil were the top 3 drugs for improving left ventricular end-diastolic dimension (LVEDD). Ivabradine, L-thyroxine, and atorvastatin were the top 3 drugs for improving left ventricular end-systolic dimension (LVESD). Trimetazidine, pentoxifylline, and bucindolol were the top 3 drugs for improving the New York Heart Association classification (NYHA) cardiac function score. Ivabradine, carvedilol, and bucindolol were the top 3 drugs for reducing heart rate (HR).

CONCLUSION

A combination of different medications and conventional therapy may increase the clinical effectiveness of treating dilated cardiomyopathy. Beta-blockers, especially carvedilol, can improve ventricular remodeling, cardiac function, and clinical efficacy in patients with dilated cardiomyopathy (DCM). Hence, they can be used if patients tolerate them. If LVEF and HR do not meet the standard, ivabradine can also be used in combination with other treatments. However, since the quality and number of studies in our research were limited, large sample size, multi-center, and high-quality randomized controlled trials are required to corroborate our findings.

Management of Heart Failure With Reduced Ejection Fraction

Heart failure with reduced ejection fraction (HFrEF) is a complex and progressive clinical condition characterized by dyspnea and functional impairment. HFrEF has a high burden of mortality and readmission rate making it one of the most significant public health challenges. Basic treatment strategies include diuretics for symptom relief and use of quadruple therapy (Angiotensin receptor blocker/neprilysin inhibitors, evidence-based beta-blockers, mineralocorticoid receptor antagonists, and sodium-glucose co-transporter 2 inhibitors) for reduction in hospitalizations, all-cause mortality, and cardiovascular mortality. Despite compelling evidence of clinical benefit, guideline directed medical therapy is vastly underutilized in the real-world clinical practice. Other medications such as intravenous iron, ivabradine, hydralazine/nitrates and vericiguat may also have a role in certain subgroup of HFrEF patients. Specific groups of patients with HFrEF may also be candidates for various device therapies such as implanted cardioverter defibrillators, cardiac resynchronization therapy and trans catheter mitral valve repair. This review provides a comprehensive overview of drug and device management approaches for patients with HFrEF, recommendations for initiation and titrations of therapies, and challenges associated with guideline directed medical therapy in the management of patients with HFrEF (Graphical abstract).

The Impact of Altered HCN1 Expression on Brain Function and Its Relationship with Epileptogenesis

Hyperpolarization-activated cyclic nucleotide-gated cation channel 1 (HCN1) is predominantly expressed in neurons from the neocortex and hippocampus, two important regions related to epilepsy. Both animal models for epilepsy and epileptic patients show decreased HCN1 expression and HCN1-mediated Ih current. It has been shown in neuroelectrophysiological experiments that a decreased Ih current can increase neuronal excitability. However, some studies have shown that blocking the Ih current in vivo can exert antiepileptic effects. This paradox raises an important question regarding the causal relationship between HCN1 alteration and epileptogenesis, which to date has not been elucidated. In this review, we summarize the literature related to HCN1 and epilepsy, aiming to find a possible explanation for this paradox, and explore the correlation between HCN1 and the mechanism of epileptogenesis. We analyze the alterations in the expression and distribution of HCN1 and the corresponding impact on brain function in epilepsy. In addition, we also discuss the effect of blocking Ih on epilepsy symptoms. Addressing these issues will help to inspire new strategies to explore the relationship between HCN1 and epileptogenesis, and ultimately promote the development of new targets for epilepsy therapy.

Short-Term Results of Ivabradine versus Metoprolol: The Effects on Atrial Fibrillation in Patients Undergoing Off-Pump Coronary Artery Bypass Grafting

INTRODUCTION

Classic coronary artery bypass grafting (CABG) surgery involves diastolic cardiac arrest under cardiopulmonary bypass, while off-pump CABG (OPCABG) has become widespread in recent years.

METHODS

174 patients who underwent OPCABG were included in the study. Patients were divided into two groups. Group I (n=90) received ivabradine and Group M (n=84) received metoprolol before surgery until postoperative day 10. Intraoperative arrhythmias and hypotension were recorded. Postoperative atrial fibrillation (AF) and arrhythmia, mortality and morbidity rates were assessed based on the 30-day postoperative follow-up.

RESULTS

There were no significant differences in the intraoperative amount of inotropic support and red blood cell transfusion between groups (P=0.87 and P=0.31). However, the rates of intraoperative arrhythmias and hypotension were not significantly higher in Group M (P=0.317 and P=0.47). Ventricular tachycardia/ventricular fibrillation (VT/VF) was observed in 2 patients in both groups. Postoperative AF occurred in 7 patients (7.7%) in Group I and in 10 patients (11.9%) in Group M. Although there was a trend towards a higher prevalence of AF in Group M patients, this did not reach statistical significance. In addition, mortality and morbidity rates were comparable between groups.

Effects of ivabradine and atenolol on heart rate and heart rate variability in healthy cats over a 24 h period: A pilot study

BACKGROUND

Ivabradine is used to treat tachycardia; unlike atenolol, it does not affect blood pressure or myocardial contractility. This study compared the impact of ivabradine and atenolol on heart rate (HR) and HR variability (HRV) during a 24 h period, feeding and sleeping times, via a Holter electrocardiogram in healthy cats. We hypothesised that ivabradine and atenolol would lower the HRs equally well, even at times of excitement and rest, such as during feeding and sleep; that ivabradine, unlike atenolol, would have an effect on HRV.

METHODS

Five clinically healthy cats were used in the prospective blinded crossover study receiving 3 days of ivabradine (0.30 mg/kg per os twice daily) followed by atenolol (6.25 mg/cat per os twice daily, range 1.3-2.0 mg/kg) or receiving atenolol followed by ivabradine. A placebo period was initiated before the start of the crossover test, data obtained during that period were used as a baseline (BL). Evaluation parameters included HR and HRV, for the whole 24 h period and for feeding and sleeping times, comparing the effect of ivabradine and atenolol with BL.

RESULTS

The HR for the whole 24 h, feeding and sleeping times, were significantly lower with ivabradine and atenolol, compared to BL (p < 0.05). The HRV for the whole 24 h and sleeping time were significantly higher after ivabradine compared with BL and after atenolol.

CONCLUSIONS

In healthy cats, ivabradine and atenolol significantly reduced the HR regardless of excitement and rest; their effects were comparable. Ivabradine significantly increased HRV in comparison to BL whereas atenolol did not.

Ivabradine toxicity: a case report

BACKGROUND

We describe a case of symptomatic bradycardia resulting from ivabradine toxicity by measurement of ivabradine levels, of which there are limited reports in the literature.

CASE PRESENTATION

A 43-year-old White female presented with several days of near syncope and dizziness accompanied by a drop in her heart rate to 50 beats per minute. She was taking ivabradine for inappropriate sinus tachycardia. After excluding several other causes of bradycardia, we made the diagnosis of ivabradine toxicity by measurement of serum ivabradine levels, an approach that is currently not clinically available.

CONCLUSIONS

Measurement of serum ivabradine levels and knowledge of the pharmacokinetic properties of the drug can be utilized to confirm the diagnosis of ivabradine toxicity.

Calcitonin gene-related peptide predicts therapeutic response to midodrine hydrochloride in children with vasovagal syncope

The vasoconstriction agent midodrine hydrochloride is a vital treatment for pediatric patients diagnosed with vasovagal syncope (VVS), although the efficacy is variable. This study was designed to explore the value of calcitonin gene-related peptide (CGRP) in predicting the effect of midodrine hydrochloride treatment upon VVS patients. In total, 55 children diagnosed with VVS were treated with midodrine hydrochloride for 3 months. Therapeutic response was evaluated using a symptom score system. CGRP levels were significantly higher in VVS patients (68.700 ± 6.460) than in control subjects (43.400 ± 5.810; t = 18.207, P < 0.001) and symptom scores correlated positively with CGRP concentrations (r = 0.779, P < 0.001). Patients treated with midodrine hydrochloride showed a significant reduction in symptom scores [4 (0, 6.5) vs. 1 (1, 2); z = -6.481; P < 0.001]. However, the value of plasma CGRP were potently elevated in the positive-response subjects than in the negative-response subjects (70.080 ± 5.040) vs. (61.150 ± 3.090); t = 5.817; P < 0.001). The area under the ROC curve showed that the value of CGRP for predicting the therapeutic response to midodrine hydrochloride was 0.946 (95% CI: 0.879-0.997, P < 0.001). With high sensitivity (97.7%) and specificity (83.3%), CGRP predicted the therapeutic response to midodrine hydrochloride (cut-off value, 62.56 pg/ml). In conclusion, CGRP can be used to predict the effect of midodrine hydrochloride administration in VVS patients.

The Bradycardic Agent Ivabradine Acts as an Atypical Inhibitor of Voltage-Gated Sodium Channels

Background and purpose: Ivabradine is clinically administered to lower the heart rate, proposedly by inhibiting hyperpolarization-activated cyclic nucleotide-gated cation channels in the sinoatrial node. Recent evidence suggests that voltage-gated sodium channels (VGSC) are inhibited within the same concentration range. VGSCs are expressed within the sinoatrial node and throughout the conduction system of the heart. A block of these channels thus likely contributes to the established and newly raised clinical indications of ivabradine. We, therefore, investigated the pharmacological action of ivabradine on VGSCs in sufficient detail in order to gain a better understanding of the pro- and anti-arrhythmic effects associated with the administration of this drug.

Experimental Approach: Ivabradine was tested on VGSCs in native cardiomyocytes isolated from mouse ventricles and the His-Purkinje system and on human Na_v1.5 in a heterologous expression system. We investigated the mechanism of channel inhibition by determining its voltage-, frequency-, state-, and temperature-dependence, complemented by a molecular drug docking to the recent Na_v1.5 cryoEM structure. Automated patch-clamp experiments were used to investigate ivabradine-mediated changes in Na_v1.5 inactivation parameters and inhibition of different VGSC isoforms.

Key results: Ivabradine inhibited VGSCs in a voltage- and frequency-dependent manner, but did not alter voltage-dependence of activation and fast inactivation, nor recovery from fast inactivation. Cardiac (Na_v1.5), neuronal (Na_v1.2), and skeletal muscle (Na_v1.4) VGSC isoforms were inhibited by ivabradine within the same concentration range, as were sodium currents in native cardiomyocytes isolated from the ventricles and the His-Purkinje system. Molecular drug docking suggested an interaction of ivabradine with the classical local anesthetic binding site.

Conclusion and Implications: Ivabradine acts as an atypical inhibitor of VGSCs. Inhibition of VGSCs likely contributes to the heart rate lowering effect of ivabradine, in particular at higher stimulation frequencies and depolarized membrane potentials, and to the observed slowing of intra-cardiac conduction. Inhibition of VGSCs in native cardiomyocytes and across channel isoforms may provide a potential basis for the anti-arrhythmic potential as observed upon administration of ivabradine.

Ivabradine: A Potential Therapeutic for Children With Refractory SVT

Background: In April 2015, ivabradine was approved by the Food and Drug Administration for the treatment of patients with coronary artery disease and heart failure (HF). The use of this medication has been linked with improved clinical outcomes and reduced rates of hospitalization in patients with symptomatic HF and a baseline heart rate of 70 bpm and above. Nonetheless, little is known about the use of ivabradine in pediatric patients with supraventricular tachycardia (SVT). This use is not well-studied and is only endorsed by a few case reports and case series.

Aim: This study discusses the off-label utilization of ivabradine in pediatric patients with SVT, and highlights its efficacy in treating treatment-resistant (refractory) SVT.

Methods: We conducted a retrospective single-center observational study involving pediatric patients with SVT treated at our center between January 2016 and October 2020. We identified the total number of patients with SVT, and the number of patients with refractory SVT treated with Ivabradine. Similarly, we performed a thorough review of the databases of PubMed, Medline and Google Scholar to compare the clinical course of our patients to those described in the literature.

Results: Between January 2016 and October 2020, 79 pediatric patients with SVT were seen and treated at our center. A treatment-resistant SVT was noted only in three patients (4%). Ivabradine was used in these patients as a single or combined therapy. The rest (96%) were successfully treated with conventional anti-arrhythmics such as β-blockers, flecainide, and other approved medications. In the ivabradine group, successful reversal to sinus rhythm was achieved in two of the three patients (66%), one patient was treated with a combination therapy of amiodarone and ivabradine, and the other patient was treated only with ivabradine.

Conclusion: Overall, promissory results are associated with the use of ivabradine in pediatric patients with refractory SVT. Ivabradine appears to be a safe and well-tolerated medication that can induce adequate suppression of SVT, complete reversal to sinus rhythm, and effective enhancement of left ventricular function.

The Effect of Ivabradine on Hospitalization of Heart Failure Patients: A Retrospective Cohort Study

BACKGROUND

Ivabradine is recommended in heart failure (HF) patients to reduce cardiovascular death and hospitalization due to worsening of HF symptoms.

AIMS AND OBJECTIVES

To study the effect of Ivabradine in addition to guideline-directed medical therapy (GDMT) in a group of HF patients with HR more than 70 bpm, HF with reduced ejection fraction (HFrEF) left ventricular ejection fraction (LVEF ≤ 40%), and New York Heart Association class II-IV.

METHODS

The study was conducted at Heart Hospital, Hamad Medical Corporation, Qatar. HF patients with age > 18 years, LVEF ≤40%, on GDMT, and HR of ≥70 bpm were included. The study population was divided into two groups: ivabradine group and non-ivabradine group. The primary outcomes were risk, number and length of hospitalizations due to worsening HF, and cardiovascular mortality. The secondary outcome was all-cause mortality. Baseline characteristics were collected at enrollment. Study outcomes were compared in the two groups by applying Chi-square and Fisher's exact tests. Logistic regression model was applied to assess both hospitalizations and cardiovascular mortality.

RESULTS

A total of 111 patients were studied, 37 (33.94%) ivabradine group and 74 (66.67%) non-ivabradine group. Risk of hospitalization was lower in Ivabradine group compared to non-Ivabradine group (odds ratio: 0.43, 95% confidence interval [CI]: 0.16-1.015, P = 0.094). Average length of hospitalization in ivabradine and non-ivabradine groups was 12.54 and 8.91 days, respectively (incidence rate ratio [IRR]: 1.63, 95% CI: 0.79-3.38, P = 0.187). Compared to non-ivabradine, ivabradine patients had lower number of hospitalizations (IRR: 1.13, 95% CI: 0.61-2.11, P = 0.694). Death rate in both ivabradine and non-ivabradine groups was 3.

CONCLUSIONS

Ivabradine along with GDMT reduces the risk of hospitalization due to worsening HF symptoms. Ivabradine had no significant effect on cardiovascular mortality and all-cause mortality. HFrEF non-Arabs patients have lower risk, number and length of hospitalization, and mortality compared to Arabs.

Effect of early use of ivabradine on left ventricular remodeling after primary percutaneous coronary intervention in patients with acute ST-segment elevation myocardial infarction: A pilot test

OBJECTIVE

To investigate the effect of early use of ivabradine on left ventricular remodeling after primary percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI).

METHODS

A total of 66 STEMI patients with sinus rhythm and the resting heart rate ≥80 bpm after successful emergency PCI were included. The patients in the test group were treated with ivabradine combined with metoprolol at 12 hr after PCI, while the control group was given only metoprolol orally. Their resting heart rate was controlled to <70 bpm at discharge and followed for 180 days. Heart rate and blood pressure were measured regularly. Echocardiogram was performed. N-terminal pro-B-type natriuretic peptide (NT-proBNP), high sensitivity troponin T, high sensitivity troponin I, and high sensitivity C-reactive protein were measured. The major adverse cardiovascular events during hospitalization and follow-up period were recorded.

RESULTS

Compared with the control group, the heart rate of the test group decreased significantly (p < .05). Compared with the control group, the left ventricular end-diastolic volume and left ventricular end-systolic volume were significantly decreased while left ventricular ejection fraction was significantly increased in the test group at 90 days after operation. NT-proBNP of the test group was significantly lower than that of the control group at 7 days after operation (p < .05).

CONCLUSION

For STEMI patients, early use of ivabradine combined with standard therapy such as β-blocker after successful reperfusion can achieve effective heart rate control, with great safety and tolerance. But the effect of ivabradine on left ventricular remodeling is uncertain.

Effect of ivabradine on left ventricular diastolic function of patients with heart failure with preserved ejection fraction -IVA-PEF study

BACKGROUND

High resting heart rate (HR) is a known marker of cardiovascular outcomes for heart failure (HF) patients. Ivabradine is a new class of HR lowering drug and a specific inhibitor of the I_f current in the sinoatrial node. Ivabradine substantially and significantly reduces major risks associated with HF when added to guideline-based treatment for left ventricular (LV) ejection fraction ≤35% and HR ≥70 bpm in sinus rhythm. On the other hand, HF with preserved ejection fraction (HFpEF) currently accounts for roughly half of all HF cases and usually presents as LV diastolic dysfunction. However, the association between HR reduction and LV diastolic function for HFpEF patients remains uncertain.

METHODS/DESIGN

This investigation into the effect of IVAbradine on left ventricular diastolic function of patients with heart failure with Preserved Ejection Fraction (IVA-PEF) is a multicenter, prospective, uncontrolled, open-label, single assignment, and an interventional single-arm study to investigate the effect of ivabradine on LV diastolic function of HFpEF patients. The key inclusion criterion is HFpEF with resting HR ≥75bpm in sinus rhythm. After completed informed consent forms are obtained, patients will be given 5 mg/day of ivabradine during the study. LV diastolic function is assessed in terms of mitral inflow E and mitral e' annular velocities (E/e'). The primary endpoint will be defined as a change in E/e' between baseline and 3 months after the start of administration of ivabradine.

CONCLUSION

The findings of our trial may provide a new perspective on ivabradine for the treatment of HFpEF.

Pacemaking Activity in the Peripheral Nervous System: Physiology and Roles of Hyperpolarization Activated and Cyclic Nucleotide-Gated Channels in Neuropathic Pain

The most famous pacemaking activity found in the human body is in the cardiac system. However, pacemaking is also widely present in the nervous system. The ion channels responsible for the pacemaking activity are called hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels. HCN channels are activated during hyperpolarization and create an inward current named I_h containing mixed sodium and potassium ions. The molecular mechanism of these unique features remains mysterious. In the peripheral nervous system (PNS), pacemaking is unique because it is only present in pathologic states when nerve damage occurs and leads to neuropathic pain. For this reason, pacemaking in neuropathic pain is also known as ectopic discharge. In our literature review, the HCN channel physiology is one of the research interests. We will present studies exploring the molecular mechanisms involved in HCN gating and ion permeability. The second research question is, what makes the pacemaking activity unique in the PNS? Thus, our paper will include studies that discuss the role of HCN channels in neuropathic pain. Given the fundamental role of HCN channels in regulating neuronal cells' discharge activity, the modulation of their function for therapeutic purposes could be useful in various pathological conditions. Here we review the present knowledge of the efficacy of HCN blocker treating neuropathic pain in humans.

A Phase 4, Open-Label, Single-Arm Study Assessing the Efficacy and Safety of Ivabradine in African American Patients with Heart Failure and Reduced Ejection Fraction

Introduction

There are limited data on ivabradine therapy in black patients and none in African Americans. We performed an open-label, prospective study at two centers in the United States. African American patients with heart failure (HF) (N = 30), left ventricular ejection fraction ≤ 35%, and in sinus rhythm with resting heart rate (HR) ≥ 70 bpm received ivabradine 2.5–7.5 mg twice daily for 57 days.

Methods

The primary endpoint was change in HR from baseline to day 57, compared with the −5 bpm change observed in the absence of ivabradine in the placebo group of the SHIFT study. The safety endpoint was treatment-emergent adverse events (TEAEs). Exploratory endpoints were change from baseline to day 57 in 6-minute walk test (6MWT) distance, HR difference during a 6MWT (i.e. HR at minute 6 − resting HR), and physical activity counts.

Results

At day 57, the estimated least squares mean change from baseline in HR was −9.5 bpm (95% CI −13.0, −6.0). The estimated mean treatment difference with ivabradine versus a presumed −5 bpm change from baseline HR, as seen in the placebo group of the SHIFT study, was −4.5 bpm (95% CI −8.0, −1.0; p = 0.013). The mean (SE) changes in 6MWT distance and HR difference during the 6MWT were 16.3 (10.8) meters and 2.3 (3.7) bpm, respectively. Ivabradine therapy did not result in greater physical activity. TEAEs were reported in 11 (36.7%) patients.

Conclusion

These data support ivabradine use in African American patients with HF with reduced ejection fraction who meet typical treatment criteria.

Trial Registration

ClinicalTrials.gov identifier, NCT03456856

Electronic supplementary material

The online version of this article (10.1007/s40119-020-00196-1) contains supplementary material, which is available to authorized users.

Heart Failure With Reduced Ejection Fraction: A Review

IMPORTANCE

Worldwide, the burden of heart failure has increased to an estimated 23 million people, and approximately 50% of cases are HF with reduced ejection fraction (HFrEF).

OBSERVATIONS

Heart failure is a clinical syndrome characterized by dyspnea or exertional limitation due to impairment of ventricular filling or ejection of blood or both. HFrEF occurs when the left ventricular ejection fraction (LVEF) is 40% or less and is accompanied by progressive left ventricular dilatation and adverse cardiac remodeling. Assessment for heart failure begins with obtaining a medical history and physical examination. Also central to diagnosis are elevated natriuretic peptides above age- and context-specific thresholds and identification of left ventricular systolic dysfunction with LVEF of 40% or less as measured by echocardiography. Treatment strategies include the use of diuretics to relieve symptoms and application of an expanding armamentarium of disease-modifying drug and device therapies. Unless there are specific contraindications, patients with HFrEF should be treated with a β-blocker and one of an angiotensin receptor-neprilysin inhibitor, angiotensin-converting enzyme inhibitor, or angiotensin receptor blocker as foundational therapy, with addition of a mineralocorticoid receptor antagonist in patients with persistent symptoms. Ivabradine and hydralazine/isosorbide dinitrate also have a role in the care of certain patients with HFrEF. More recently, sodium-glucose cotransporter 2 (SGLT2) inhibitors have further improved disease outcomes, significantly reducing cardiovascular and all-cause mortality irrespective of diabetes status, and vericiguat, a soluble guanylate cyclase stimulator, reduces heart failure hospitalization in high-risk patients with HFrEF. Device therapies may be beneficial in specific subpopulations, such as cardiac resynchronization therapy in patients with interventricular dyssynchrony, transcatheter mitral valve repair in patients with severe secondary mitral regurgitation, and implantable cardiac defibrillators in patients with more severe left ventricular dysfunction particularly of ischemic etiology.

CONCLUSIONS AND RELEVANCE

HFrEF is a major public health concern with substantial morbidity and mortality. The management of HFrEF has seen significant scientific breakthrough in recent decades, and the ability to alter the natural history of the disease has never been better. Recent developments include SGLT2 inhibitors, vericiguat, and transcatheter mitral valve repair, all of which incrementally improve prognosis beyond foundational neurohormonal therapies. Disease morbidity and mortality remain high, with a 5-year survival rate of 25% after hospitalization for HFrEF.

The hyperpolarization-activated cyclic nucleotide-gated 4 channel as a potential anti-seizure drug target

BACKGROUND AND PURPOSE

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are encoded by four genes (HCN1-4) with distinct biophysical properties and functions within the brain. HCN4 channels activate slowly at robust hyperpolarizing potentials, making them more likely to be engaged during hyperexcitable neuronal network activity seen during seizures. HCN4 channels are also highly expressed in thalamic nuclei, a brain region implicated in seizure generalization. Here, we assessed the utility of targeting the HCN4 channel as an anti-seizure strategy using pharmacological and genetic approaches.

EXPERIMENTAL APPROACH

The impact of reducing HCN4 channel function on seizure susceptibility and neuronal network excitability was studied using an HCN4 channel preferring blocker (EC18) and a conditional brain specific HCN4 knockout mouse model.

KEY RESULTS

EC18 (10 mg·kg^-1 ) and brain-specific HCN4 channel knockout reduced seizure susceptibility and proconvulsant-mediated cortical spiking recorded using electrocorticography, with minimal effects on other mouse behaviours. EC18 (10 μM) decreased neuronal network bursting in mouse cortical cultures. Importantly, EC18 was not protective against proconvulsant-mediated seizures in the conditional HCN4 channel knockout mouse and did not reduce bursting behaviour in AAV-HCN4 shRNA infected mouse cortical cultures.

CONCLUSIONS AND IMPLICATIONS

These data suggest the HCN4 channel as a potential pharmacologically relevant target for anti-seizure drugs that is likely to have a low side-effect liability in the CNS.

Ivabradine Improves Cardiac Function and Increases Exercise Capacity in Patients with Chronic Heart Failure

To systematically review and conduct a meta-analysis of the ivabradine-induced improvement in cardiopulmonary function, exercise capacity, and primary composite endpoints in patients with chronic heart failure (CHF).This study was a systematic review and meta-analysis.Databases, including PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Clinical Trials and European Union Clinical Trials, were searched for randomized placebo-controlled trials. The efficacy and safety of ivabradine treatment in patients with CHF were assessed and compared to those of the standard anti-heart failure treatment. Review Manager 5.3 software was used to analyze the relative risk (RR) for dichotomous data and the mean difference (MD) for continuous data.In total, 22 studies with 24,562 patients were included. Cardiopulmonary function analysis showed that treatment with added ivabradine reduced the heart rate (MD = -17.30, 95% confidence interval (CI): 19.52--15.08, P < 0.00001), significantly increased the left ventricular ejection fraction (LVEF) (MD = 3.90, 95% CI: 0.40-7.40, P < 0.0001), and led to a better New York Heart Association (NYHA) classification. Ivabradine significantly reduced the minute ventilation/carbon dioxide production (VE/VCO₂) (MD = -2.68, 95% CI: -4.81--0.55, P = 0.01) and improved the peak VO₂ (MD = 2.80, 95% CI: 1.05-4.55, P = 0.002) and the exercise capacity, including the exercise duration with a submaximal load (MD = 7.82, 95% CI: -2.57--18.21, P < 0.00001) and the 6-minute walk distance. The RR of cardiovascular death or worsening heart failure was significantly decreased (RR = 0.93, 95% CI: 0.87--0.98, P = 0.01) in the patients treated with ivabradine. Additionally, the RRs of heart failure and hospitalization also decreased (RR = 0.91, 95% CI: 0.85--0.97, P = 0.006; RR = 0.86, 95% CI: 0.79--0.93, P = 0.0002). Safety analysis showed no significant difference in the RR of severe adverse events between the ivabradine group and the standard anti-heart failure treatment group (P = 0.40). However, ivabradine significantly increased the RR of visual symptoms in CHF patients (RR = 3.82, 95% CI: 1.80--8.13, P = 0.0005).Existing evidence showed that adding ivabradine treatment significantly improved the cardiopulmonary function and increased the exercise capacity of patients with CHF. Adding ivabradine to the standard anti-heart failure treatment reduced the mortality and hospitalization risk and improved the quality of life. Finally, ivabradine significantly increased the RR of visual symptoms in CHF patients.This is the first systematic review and meta-analysis to focus on the efficacy of ivabradine, which improved the cardiac function and increased the exercise capacity in patients with chronic heart failure (CHF). Therefore, this study will help evaluate the quality of life after adding ivabradine to the treatment of patients with CHF, even though there are differences in the standard for resting heart rate, left ventricular ejection fraction (LVEF), and New York Heart Association (NYHA) class in the included studies. This hybrid effect might be smaller when analyzed separately but might have a higher heterogeneity when analyzed in multiple studies.

Postoperative Management in Patients with Pheochromocytoma and Paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are rare catecholamine-secreting neuroendocrine tumors of the adrenal medulla and sympathetic/parasympathetic ganglion cells, respectively. Excessive release of catecholamines leads to episodic symptoms and signs of PPGL, which include hypertension, headache, palpitations, and diaphoresis. Intraoperatively, large amounts of catecholamines are released into the bloodstream through handling and manipulation of the tumor(s). In contrast, there could also be an abrupt decline in catecholamine levels after tumor resection. Because of such binary manifestations of PPGL, patients may develop perplexing and substantially devastating cardiovascular complications during the perioperative period. These complications include hypertension, hypotension, arrhythmias, myocardial infarction, heart failure, and cerebrovascular accident. Other complications seen in the postoperative period include fever, hypoglycemia, cortisol deficiency, urinary retention, etc. In the interest of safe patient care, such emergencies require precise diagnosis and treatment. Surgeons, anesthesiologists, and intensivists must be aware of the clinical manifestations and complications associated with a sudden increase or decrease in catecholamine levels and should work closely together to be able to provide appropriate management to minimize morbidity and mortality associated with PPGLs.

Ivabradine in Cancer Treatment-Related Left Ventricular Dysfunction

BACKGROUND

Patients developing cancer treatment-related left ventricular dysfunction (CTrLVD) require a prompt therapy. Hypotension, dizziness, and fatigue often limit the use of angiotensin-converting enzyme inhibitors (ACEi), angiotensin receptor blockers (ARB), and β-blockers (BB) in cancer patients who may already be afflicted by these symptoms. Ivabradine is a heart rate-lowering drug that does not cause hypotension and may be used in heart failure with reduced left ventricular ejection fraction (LVEF).

OBJECTIVE

The aim of this paper was to investigate the role of ivabradine to treat CTrLVD.

METHODS

A retrospective analysis in a cohort of 30 patients with CTrLVD (LVEF < 50%) receiving ivabradine on top of the maximal tolerated dose of ACEi/ARB and BB was performed. We evaluated cardiovascular treatment, oncologic treatment, LVEF, functional class (New York Heart Association [NYHA]), and fatigue during the study period.

RESULTS

Ivabradine was initially started at the dose of 2.5 mg/b.i.d. in most patients and then carefully titrated. Hypotension (70%) and fatigue (77%) were the main causes limiting the treatment with ACEi/ARB and BB. After a mean follow-up of 6.5 months, LVEF increased from 45.1% (SD = 6.4) to 53.2% (SD = 3.9; p < 0.001). When patients were analyzed according to the type of cancer therapy, no difference in LVEF changes across the groups was found. NYHA class ameliorated in 11 patients, while fatigue improved in 8 patients. No serious cardiovascular side effects were reported.

CONCLUSIONS

The ability to improve symptoms and LVEF in unfit cancer patients makes ivabradine a reasonable pharmacological tool for treating CTrLVD.

Acute effect of ivabradine on heart rate and myocardial oxygen consumption in dogs with asymptomatic mitral valve degeneration

Degenerative mitral valve disease (DMVD) is a common cardiac disease in geriatric dogs characterized by the degeneration of the mitral valve, leading to decreased cardiac output and activation of the sympathetic and renin-angiotensin-aldosterone system. This disease results in an increased resting heart rate (HR) and myocardial oxygen consumption (MVO2). A recent publication demonstrated that dogs with asymptomatic DMVD had a significantly higher HR and systemic blood pressure (BP) than age-matched control dogs. This higher HR will eventually contribute to increased MVO2. This study aimed to determine the effects of a single oral dose of ivabradine on the HR, MVO2 as assessed by the rate-pressure product, and BP in dogs with asymptomatic DMVD. Seven beagles with naturally occurring DMVD were instrumented by the Holter recorder and an oscillometric device to measure electrocardiogram and BP for 24 and 12 h, respectively. Each dog was randomly subjected to receive either placebo or ivabradine (0.5, 1.0 and 2.0 mg/kg). The results revealed that oral administration of ivabradine significantly decreased the HR and rate-pressure product in a dose-dependent manner without adverse effects. The highest dose of 2.0 mg/kg significantly reduced systolic and mean BP. Therefore, the findings imply that a single oral ivabradine administration at a dose of 1.0 mg/kg is suitable for dogs with asymptomatic DMVD to reduce the HR and MVO2 without marked effects on BP. This may potentially make ivabradine promising for management of an elevated HR in DMVD dogs.

Role of ivabradine in management of stable angina in patients with different clinical profiles

In chronic stable angina, elevated heart rate contributes to the development of symptoms and signs of myocardial ischaemia by increasing myocardial oxygen demand and reducing diastolic perfusion time. Accordingly, heart rate reduction is a well-known strategy for improving both symptoms of myocardial ischaemia and quality of life (QOL). The heart rate-reducing agent ivabradine, a direct and selective inhibitor of the I_f current, decreases myocardial oxygen consumption while increasing diastolic time, without affecting myocardial contractility or coronary vasomotor tone. Ivabradine is indicated for treatment of stable angina and chronic heart failure (HF). This review examines available evidence regarding the efficacy and safety of ivabradine in stable angina, when used as monotherapy or in combination with beta-blockers, in particular angina subgroups and in patients with stable angina with left ventricular systolic dysfunction (LVSD) or HF. Trials involving more than 45 000 patients receiving treatment with ivabradine have shown that this agent has antianginal and anti-ischaemic effects, regardless of age, sex, severity of angina, revascularisation status or comorbidities. This heart rate-lowering agent might also improve prognosis, reduce hospitalisation rates and improve QOL in angina patients with chronic HF and LVSD.

Ivabradine in Postural Orthostatic Tachycardia Syndrome: Preliminary Experience in Children

OBJECTIVE

Ivabradine is a selective and specific inhibitor of the I(f) current in the sinoatrial and atrioventricular nodes. It decreases heart rate and myocardial oxygen consumption at rest and during exercise. It is used in adults for management of heart failure and angina, but promising results have been obtained in postural orthostatic tachycardia syndrome (POTS). There is little experience of ivabradine in childhood, although it is used on a compassionate basis. Our aim was to review our experience of ivabradine in a retrospective evaluation of pediatric patients with POTS.

METHODS

We evaluated all patients younger than 18 years for whom ivabradine had been prescribed for this indication, from February 2008 to June 2014.

RESULTS

Twenty-two patients were identified (15 female). Median age was 14.5 years (11-17 years). The ivabradine dosage after up-titration was 0.1 mg/kg per dose twice daily. In 15 (68%) symptoms improved. Ivabradine was suspended in five, but only in one for worsening of symptoms. There was a reduction in heart rate on resting electrocardiogram (EKG) from a mean (standard deviation) of 82.5 (13.6) bpm to a mean of 71 (16.5) bpm (p = 0.007). No patient had increased duration of QTc (p = 0.44). One (4.5%) experienced phosphenes.

CONCLUSIONS

From this initial experience, ivabradine is safe in patients younger than 18 years with POTS. We observed improvement of symptoms in 68% and phosphenes in less than 5%. Further studies are needed to assess the safety in a randomized control setting.

Gabapentin Modulates HCN4 Channel Voltage-Dependence

Gabapentin (GBP) is widely used to treat epilepsy and neuropathic pain. There is evidence that GBP can act on hyperpolarization-activated cation (HCN) channel-mediated I_h in brain slice experiments. However, evidence showing that GBP directly modulates HCN channels is lacking. The effect of GBP was tested using two-electrode voltage clamp recordings from human HCN1, HCN2, and HCN4 channels expressed in Xenopus oocytes. Whole-cell recordings were also made from mouse spinal cord slices targeting either parvalbumin positive (PV⁺) or calretinin positive (CR⁺) inhibitory neurons. The effect of GBP on I_h was measured in each inhibitory neuron population. HCN4 expression was assessed in the spinal cord using immunohistochemistry. When applied to HCN4 channels, GBP (100 μM) caused a hyperpolarizing shift in the voltage of half activation (V_1/2) thereby reducing the currents. Gabapentin had no impact on the V_1/2 of HCN1 or HCN2 channels. There was a robust increase in the time to half activation for HCN4 channels with only a small increase noted for HCN1 channels. Gabapentin also caused a hyperpolarizing shift in the V_1/2 of I_h measured from HCN4-expressing PV⁺ inhibitory neurons in the spinal dorsal horn. Gabapentin had minimal effect on I_h recorded from CR⁺ neurons. Consistent with this, immunohistochemical analysis revealed that the majority of CR⁺ inhibitory neurons do not express somatic HCN4 channels. In conclusion, GBP reduces HCN4 channel-mediated currents through a hyperpolarized shift in the V_1/2. The HCN channel subtype selectivity of GBP provides a unique tool for investigating HCN4 channel function in the central nervous system. The HCN4 channel is a candidate molecular target for the acute analgesic and anticonvulsant actions of GBP.

HCN Channel Targets for Novel Antidepressant Treatment

Major depressive disorder (MDD) is a chronic and potentially life threatening illness that carries a staggering global burden. Characterized by depressed mood, MDD is often difficult to diagnose and treat owing to heterogeneity of syndrome and complex etiology. Contemporary antidepressant treatments are based on improved monoamine-based formulations from serendipitous discoveries made > 60 years ago. Novel antidepressant treatments are necessary, as roughly half of patients using available antidepressants do not see long-term remission of depressive symptoms. Current development of treatment options focuses on generating efficacious antidepressants, identifying depression-related neural substrates, and better understanding the pathophysiological mechanisms of depression. Recent insight into the brain's mesocorticolimbic circuitry from animal models of depression underscores the importance of ionic mechanisms in neuronal homeostasis and dysregulation, and substantial evidence highlights a potential role for ion channels in mediating depression-related excitability changes. In particular, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are essential regulators of neuronal excitability. In this review, we describe seminal research on HCN channels in the prefrontal cortex and hippocampus in stress and depression-related behaviors, and highlight substantial evidence within the ventral tegmental area supporting the development of novel therapeutics targeting HCN channels in MDD. We argue that methods targeting the activity of reward-related brain areas have significant potential as superior treatments for depression.

Application of optical action potentials in human induced pluripotent stem cells-derived cardiomyocytes to predict drug-induced cardiac arrhythmias

INTRODUCTION

Human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) are emerging as new and human-relevant source in vitro model for cardiac safety assessment that allow us to investigate a set of 20 reference drugs for predicting cardiac arrhythmogenic liability using optical action potential (oAP) assay.

METHODS

Here, we describe our examination of the oAP measurement using a voltage sensitive dye (Di-4-ANEPPS) to predict adverse compound effects using hiPS-CMs and 20 cardioactive reference compounds. Fluorescence signals were digitized at 10kHz and the records subsequently analyzed off-line. Cells were exposed to 30min incubation to vehicle or compound (n=5/dose, 4 doses/compound) that were blinded to the investigating laboratory. Action potential parameters were measured, including rise time (T_rise) of the optical action potential duration (oAPD).

RESULTS

Significant effects on oAPD were sensitively detected with 11 QT-prolonging drugs, while oAPD shortening was observed with I_Ca-antagonists, I_Kr-activator or ATP-sensitive K⁺ channel (K_ATP)-opener. Additionally, the assay detected varied effects induced by 6 different sodium channel blockers. The detection threshold for these drug effects was at or below the published values of free effective therapeutic plasma levels or effective concentrations by other studies.

DISCUSSION

The results of this blinded study indicate that OAP is a sensitive method to accurately detect drug-induced effects (i.e., duration/QT-prolongation, shortening, beat rate, and incidence of early after depolarizations) in hiPS-CMs; therefore, this technique will potentially be useful in predicting drug-induced arrhythmogenic liabilities in early de-risking within the drug discovery phase.

The Role of Ivabradine in the Management of Angina Pectoris

Stable angina pectoris affects 2–4 % of the population in Western countries and entails an annual risk of death and nonfatal myocardial infarction of 1–2 % and 3 %, respectively. Heart rate (HR) is linearly related to myocardial oxygen consumption and coronary blood flow, both at rest and during stress. HR reduction is a key target for the prevention of ischemia/angina and is an important mechanism of action of drugs which are recommended as first line therapy for the treatment of angina in clinical guidelines. However, many patients are often unable to tolerate the doses of beta blocker or non-dihydropyridine calcium antagonists required to achieve the desired symptom control. The selective pacemaker current inhibitor ivabradine was developed as a drug for the management of patients with angina pectoris, through its ability to reduce HR specifically. The available data suggest that ivabradine is a well-tolerated and effective anti-anginal agent and it is recommended as a second-line agent for relief of angina in guidelines. However, recent clinical trials of ivabradine have failed to show prognostic benefit and have raised potential concerns about safety. This article will review the available evidence base for the current role of ivabradine in the management of patients with symptomatic angina pectoris in the context of stable coronary artery disease.

Experimental and early investigational drugs for angina pectoris

INTRODUCTION

Ischemic heart disease (IHD) is a major cause of death and disability among Western countries and angina pectoris is the most prevalent symptomatic manifestation. Strategies to improve management of chronic stable angina are a priority. Areas covered: A comprehensive review was conducted using the Medline and Cochrane databases as well as the clinical trial databases in the United States and Europe. Traditional therapies for angina will be discussed. This review particularly emphasizes investigational therapies for angina (including pharmacological agents, cell and gene based therapies, and herbal medications). Expert opinion: There has been renewed interest in older anti-angina agents (e.g., perhexiline, amiodarone, and phosphodiestrase-5 inhibitors). Other anti-inflammatory agents (e.g., allopurinol and febuxostat) are currently undergoing evaluation for angina therapy. Therapeutic angiogenesis continues to face some challenges. Future trials should evaluate the optimum patient population that would benefit from this form of therapy.

An evidence-based review of recent advances in therapy for heart failure with reduced ejection fraction (HFrEF)

An estimated 5.1 million Americans have chronic heart failure and this is expected to increase 25% by 2030. Heart failure is a clinical syndrome that evolves from either functional or structural changes to the ventricles that lead to filling or ejection abnormalities. Thus far, pharmacotherapy has been show to be beneficial in patients only with reduced ejection fraction; however, new therapies have been developed in hopes of reducing the burden of heart failure. In this review, we will discuss current pharmacotherapies recommended in American College of Cardiology/American Heart Association guidelines, the evidence behind these recommendations as well as new and emerging therapies that have been developed.

Effect of early treatment with ivabradine combined with beta-blockers versus beta-blockers alone in patients hospitalised with heart failure and reduced left ventricular ejection fraction (ETHIC-AHF): A randomised study

OBJECTIVES

To analyse the effect of the early coadministration of ivabradine and beta-blockers (intervention group) versus beta-blockers alone (control group) in patients hospitalised with heart failure and reduced left ventricular ejection fraction (HFrEF).

METHODS

A comparative, randomised study was performed to compare the treatment strategies of beta-blockers alone versus ivabradine and beta-blockers starting 24hours after hospital admission, for acute HF in patients with an left ventricular ejection fraction (EF)<40%, sinus rhythm, and a heart rate (HR)>70bpm.

RESULTS

A total of 71 patients were examined, 33 in the intervention group and 38 in the control group. No differences were observed with respect to their baseline characteristics or standard treatment at discharge. HR at 28days (64.3±7.5 vs. 70.3±9.3bpm, p=0.01) and at 4months (60.6±7.5 vs. 67.8±8bpm, p=0.004) after discharge were significantly lower in the intervention group. Significant differences were found with respect to the EF and brain natriuretic peptide levels at 4months. No differences in clinical events (rehospitalisation/death) were reported at 4months. No severe side effects attributable to the early administration of ivabradine were observed.

CONCLUSIONS

The early coadministration of ivabradine and beta-blockers during hospital admission for acute HFrEF is feasible and safe, and it produces a significant decrease in HR at 28days and at 4months after hospital discharge. It also seemed to improve systolic function and functional and clinical parameters of HF patients at short-term.

Update on ivabradine for heart failure

Despite dramatic advances in therapy for heart failure (HF) during the past 3 decades, hospitalization and mortality rates remain relatively high. In recent decades, it has become apparent that HF is divisible into two equally lethal but pathophysiologically different sub-classes, the first comprising patients with LV systolic dysfunction [heart failure with reduced ejection fraction (HFrEF)] and the other, approximately equal in size, involving patients with "preserved" systolic function [heart failure with preserved ejection fraction (HFpEF)]. Evidence-based event reducing therapy currently is available only for HFrEF. With the completion of seminal trials of beta blockers, now part of standard therapy for HFrEF, it was apparent that heart rate slowing is an underlying basis of clinical effectiveness of HFrEF therapy. With the discovery of the "f current" that modulates the slope of spontaneous diastolic depolarization of the sino-atrial node, a non-beta blockade approach to heart rate slowing became available. Ivabradine, the first FDA-approved f-current blocker for HFrEF, markedly reduces hospitalizations for worsening heart failure, while also progressively reducing mortality as pre-therapy heart rate increases, and also promotes beneficial left ventricular remodeling, improves health-related quality of life and is effective despite a wide range of comorbidities. The drug is well tolerated and adverse effects are relatively few. Ivabradine represents an important addition to the armamentarium for mitigation of HFrEF.

Impact of Ivabradine on Central Aortic Blood Pressure and Myocardial Perfusion in Patients With Stable Coronary Artery Disease

Treatment of hypertensive patients with β-blockers reduces heart rate and decreases central blood pressure less than other antihypertensive drugs, implying that reducing heart rate without altering brachial blood pressure could increase central blood pressure, explaining the increased cardiovascular risk reported with β-blocker. We describe a randomized, double-blind study to explore whether heart rate reduction with the If inhibitor ivabradine had an impact on central blood pressure. We included 12 normotensive patients with stable coronary artery disease, heart rate ≥70 bpm (sinus rhythm), and stable background β-blocker therapy. Patients received ivabradine 7.5 mg BID or matched placebo for two 3-week periods with a crossover design and evaluation by aplanation tonometry. Treatment with ivabradine was associated with a significant reduction in resting heart rate after 3 weeks versus no change with placebo (-15.8±7.7 versus +0.3±5.8 bpm; P=0.0010). There was no relevant between-group difference in change in central aortic systolic blood pressure (-4.0±9.6 versus +2.4±12.0 mm Hg; P=0.13) or augmentation index (-0.8±10.0% versus +0.3±7.6%; P=0.87). Treatment with ivabradine was associated with a modest increase in left ventricular ejection time (+18.5±17.8 versus +2.8±19.3 ms; P=0.074) and a prolongation of diastolic perfusion time (+215.6±105.3 versus -3.0±55.8 ms with placebo; P=0.0005). Consequently, ivabradine induced a pronounced increase in Buckberg index, an index of myocardial viability (+39.3±27.6% versus -2.5±13.5% with placebo; P=0.0015). In conclusion, heart rate reduction with ivabradine does not increase central aortic blood pressure and is associated with a marked prolongation of diastolic perfusion time and an improvement in myocardial perfusion index.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrialsregister.eu. Unique identifier: 2011-004779-35.

Addition of ivabradine to β-blocker improves exercise capacity in systolic heart failure patients in a prospective, open-label study

INTRODUCTION

Difficulties initiating and uptitrating β-blockers due to tolerability can complicate management of heart failure. Among other actions, β-blockers reduce heart rate, which is an important cardiovascular risk factor in heart failure. A new therapeutic strategy is ivabradine, which reduces resting heart rate and is associated with improved outcomes.

METHODS

A 5-month, prospective, open-label, nonrandomized single-center study was performed in 69 patients. All patients had chronic heart failure with left ventricular systolic dysfunction in sinus rhythm, each were initiated on 3.125 mg twice daily (bid) carvedilol alone (n = 36) or 3.125 mg bid carvedilol/5 mg bid ivabradine (n = 33), on top of background therapy including angiotensin-converting enzyme inhibitor (88%), diuretics (86%), antiplatelet agents (91%), and statins (90%). Dosages were uptitrated every 2 weeks to 25 mg bid carvedilol in both groups and 7.5 mg bid ivabradine maximum in the carvedilol/ivabradine group. Uptitration of carvedilol lasted 1.9 ± 0.4 months with carvedilol/ivabradine and 2.8 ± 0.6 months with carvedilol alone (P < 0.05).

RESULTS

The patients receiving ivabradine had lower resting heart rate at 5 months (61.6 ± 3.1 versus 70.2 ± 4.4 bpm, P < 0.05). Adding ivabradine to carvedilol in patients with heart failure was associated with increases in the 6-min walk test and ejection fraction (all P < 0.05). Treatment tolerability was satisfactory. Patients receiving ivabradine and carvedilol had lower heart rates and better exercise capacity than those on carvedilol alone.

CONCLUSION

Adding ivabradine to carvedilol in patients with chronic heart failure improves the uptitration of β-blocker. The results merit further verification in a prospective double-blind study.