Ivabradine is an effective antiarrhythmic therapy for congenital junctional ectopic tachycardia-induced cardiomyopathy during infancy: Case studies

HRAS-Mutant Cardiomyocyte Model of Multifocal Atrial Tachycardia

BACKGROUND

Germline HRAS gain-of-function pathogenic variants cause Costello syndrome (CS). During early childhood, 50% of patients develop multifocal atrial tachycardia, a treatment-resistant tachyarrhythmia of unknown pathogenesis. This study investigated how overactive HRAS activity triggers arrhythmogenesis in atrial-like cardiomyocytes (ACMs) derived from human-induced pluripotent stem cells bearing CS-associated HRAS variants.

METHODS

HRAS Gly12 mutations were introduced into a human-induced pluripotent stem cells-ACM reporter line. Human-induced pluripotent stem cells were generated from patients with CS exhibiting tachyarrhythmia. Calcium transients and action potentials were assessed in induced pluripotent stem cell-derived ACMs. Automated patch clamping assessed funny currents. HCN inhibitors targeted pacemaker-like activity in mutant ACMs. Transcriptomic data were analyzed via differential gene expression and gene ontology. Immunoblotting evaluated protein expression associated with calcium handling and pacemaker-nodal expression.

RESULTS

ACMs harboring HRAS variants displayed higher beating rates compared with healthy controls. The hyperpolarization activated cyclic nucleotide gated potassium channel inhibitor ivabradine and the Nav1.5 blocker flecainide significantly decreased beating rates in mutant ACMs, whereas voltage-gated calcium channel 1.2 blocker verapamil attenuated their irregularity. Electrophysiological assessment revealed an increased number of pacemaker-like cells with elevated funny current densities among mutant ACMs. Mutant ACMs demonstrated elevated gene expression (ie, ISL1, TBX3, TBX18) related to intracellular calcium homeostasis, heart rate, RAS signaling, and induction of pacemaker-nodal-like transcriptional programming. Immunoblotting confirmed increased protein levels for genes of interest and suppressed MAPK (mitogen-activated protein kinase) activity in mutant ACMs.

CONCLUSIONS

CS-associated gain-of-function HRASG12 mutations in induced pluripotent stem cells-derived ACMs trigger transcriptional changes associated with enhanced automaticity and arrhythmic activity consistent with multifocal atrial tachycardia. This is the first human-induced pluripotent stem cell model establishing the mechanistic basis for multifocal atrial tachycardia in CS.

Ivabradine for congenital ectopic tachycardia in newborn

INTRODUCTION

Congenital junctional ectopic tachycardia is a rare arrhythmia that occurs in patients without previous cardiac surgery. In this report, we wanted to present a 6-hour-old newborn with congenital junctional ectopic tachycardia resistant to conventional anti-arrhythmic medications, who was successfully treated with ivabradine and amiadarone combination.

CASE

A six-hour-old newborn girl was hospitalised in neonatal ICU because transient tachypnoea of the newborn. She was tachycardic, and supraventricular tachycardia was noticed. There was no answer to the adenosine esmolol treatment; even synchronised direct cardioversion intravenous amiodarone was started. Junctional ectopic tachycardia was diagnosed. We have added propranolol to the treatment and followed patient for 2 days. On the fourth day, junctional ectopic tachycardia rhythm still persisted; therefore, ivabradine treatment was added to the treatment. On the following day, the heart rhythm was slowed to 110/min, and propranolol was stopped; intravenous amiodarone treatment was changed to the oral form. The rhythm turned into sinus; two days after starting ivabradine and oral amiodarone.

CONCLUSION

Tachyarrhythmia originating in the atrioventricular node and atrioventricular junction including the bundle of His complex are junctional ectopic tachycardia. Congenital junctional ectopic tachycardia is rare, and it is mostly resistant to the conventional treatment.Ivabradine is a new anti-arrhythmic agent, used extensively to decrease sinus rate in the treatment of cardiac failure. Ivabradine may be an option for the resistant congenital ectopic tachycardia.

Successful treatment of the focal ectopic atrial tachycardia in an infant with a single dose of ivabradin

We report on a 12-month-old boy with an ectopic atrial tachycardia successfully treated with the ivabradine that acts on cardiac pacemaker cells by selectively inhibiting the If channel. The patient was diagnosed with supraventricular tachycardia in another centre, and multi-drug therapy was unsuccessful to restore sinus ryhthm, so he was sent to our hospital for catheter ablation. We stopped the medications the patient was taking and started using ivabradine. Sinus rhythm was restored 2 hours after ivabradine treatment was started.

Ivabradine in a 15-day-old male neonate with refractory focal atrial tachycardia

Ivabradine is used to reduce heart rate in children with chronic heart failure and dilated cardiomyopathy, it has recently been used off-label to treat tachyarrhythmias such as ectopic atrial tachycardia and junctional ectopic tachycardia (JET) in children. We report a successful ivabradine experience in a male neonate with refractory focal atrial tachycardia (FAT).

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.

Congenital junctional ectopic tachycardia in the paediatric emergency department

Congenital junctional ectopic tachycardia is a rare but serious cardiac arrhythmia seen in neonates and young infants. It is frequently resistant and refractory to first-line treatment options such as cardioversion with adenosine and direct current shock, and it carries a high morbidity and mortality rate. The aim of this article is to present the case of congenital junctional ectopic tachycardia observed in a 14-day-old neonate, highlighting the role of ivabradine in the management, followed by a discussion about current approaches to treatment.

Ivabradine-Flecainide as Breakthrough Drug Combination for Congenital Junctional Ectopic Tachycardia: A Case Report and Literature Review

Congenital junctional ectopic tachycardia (CJET) is a rare tachyarrhythmia that remains difficult to manage, with suboptimal control in most cases. Here, we report literature research on the use of ivabradine in the treatment of pediatric junctional ectopic tachycardia (JET), both congenital and postoperative, and describe the successful use of ivabradine-flecainide association for CJET therapy resistant to other antiarrhythmic agents. This new drug combination was effective in completely suppressing JET. Ivabradine-flecainide combination may be considered a new therapeutic strategy of CJET with a satisfactory efficacy/tolerability ratio in patients resistant to conventional drug combinations.

Tachycardia-induced cardiomyopathy secondary to incessant ectopic atrial tachycardia in two infants: Potential new indication for early initiation of enteral ivabradine

This report describes two cases of tachycardia-induced cardiomyopathy secondary to incessant ectopic atrial tachycardia (EAT) in an infant presenting with severe left ventricular dysfunction and hemodynamic instability. The two cases were managed differently. The first required mechanical ventilation and was resistant to conventional antiarrhythmic drugs. After the initiation of enteral ivabradine (0.15mg/kg) the heart rate slowed with significant improvement in hemodynamics, peripheral perfusion and sinus rhythm was restored after 12 hours. Ivabradine was continued and the patient was discharged home after 10 days of hospitalization. The second case was managed by early initiation of ivabradine and resulted in restoration of sinus rhythm within 4 hours, thus avoiding trials of conventional anti-arrhythmic drugs with unstable hemodynamic profile. The infant was discharged after 5 days of hospitalization on ivabradine..

Effect of Ivabradine on Cardiac Ventricular Arrhythmias: Friend or Foe?

Life-threatening ventricular arrhythmias, such as ventricular tachycardia and ventricular fibrillation remain an ongoing clinical problem and their prevention and treatment require optimization. Conventional antiarrhythmic drugs are associated with significant proarrhythmic effects that often outweigh their benefits. Another option, the implantable cardioverter defibrillator, though clearly the primary therapy for patients at high risk of ventricular arrhythmias, is costly, invasive, and requires regular monitoring. Thus there is a clear need for new antiarrhythmic treatment strategies. Ivabradine, a heartrate-reducing agent, an inhibitor of HCN channels, may be one of such options. In this review we discuss emerging data from experimental studies that indicate new mechanism of action of this drug and further areas of investigation and potential use of ivabradine as an antiarrhythmic agent. However, clinical evidence is limited, and the jury is still out on effects of ivabradine on cardiac ventricular arrhythmias in the clinical setting.

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.

Ivabradine Monotherapy for the Treatment of Congenital Junctional Ectopic Tachycardia in a Premature Neonate

Congenital junctional ectopic tachycardia is a rare and special type of supraventricular arrhythmia. Junctional ectopic tachycardia is characterized by persistently elevated heart rates that may cause an impairment in cardiac function. Junctional ectopic tachycardia is considered one of the most difficult-to-treat conditions even with a combination of antiarrhythmic medications. Ivabradine is a novel antiarrhythmic medication used to decrease the heart rate in adults with angina pectoris. We report a first case of a premature neonate with a normal heart structure who developed junctional ectopic tachycardia and was subsequently treated successfully with ivabradine.

Effect of ivabradine on cardiac arrhythmias: Antiarrhythmic or proarrhythmic?

Cardiac arrhythmias are a major source of mortality and morbidity. Unfortunately, their treatment remains suboptimal. Major classes of antiarrhythmic drugs pose a significant risk of proarrhythmia, and their side effects often outweigh their benefits. Therefore, implantable devices remain the only truly effective antiarrhythmic therapy, and new strategies of antiarrhythmic treatment are required. Ivabradine is a selective heart rate-reducing agent, an inhibitor of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, currently approved for treatment of coronary artery disease and chronic heart failure. In this review, we focus on the clinical and basic science evidence for the antiarrhythmic and proarrhythmic effects of ivabradine. We attempt to dissect the mechanisms behind the effects of ivabradine and indicate the focus of future studies.

The bradycardic agent ivabradine decreases conduction velocity in the AV node and in the ventricles in-vivo

Ivabradine blocks hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels, thereby lowering the heart rate, an action that is used clinically for the treatment of heart failure and angina pectoris. We and others have shown previously that ivabradine, in addition to its HCN channel blocking activity, also inhibits voltage-gated Na channels in vitro at concentrations that may be clinically relevant. Such action may reduce conduction velocity in cardiac atria and ventricles. Here, we explore the effect of administration of ivabradine on parameters of ventricular conduction and repolarization in the surface ECG of anesthetized mice. We found that 5 min after i.p. administration of 10 mg/kg ivabradine spontaneous heart rate had declined by ~13%, which is within the range observed in human clinical studies. At the same time a significant increase in QRS duration by ~18% was observed, suggesting a reduction in ventricular conduction velocity. During transesophageal pacing at heart rates between 100 and 220 beats/min there was no obvious rate-dependence of ivabradine-induced QRS prolongation. On the other hand, ivabradine produced substantial rate-dependent slowing of AV nodal conduction. We conclude that ivabradine prolongs conduction in the AV-node and in the ventricles in vivo.

Ivabradine as a stabilising anti-arrhythmic agent for multifocal atrial tachycardia

Multifocal atrial tachycardia has certain electrocardiographic similarities to atrial fibrillation. The mechanism of atrial fibrillation is heterogenous but in some cases may arise from a single ectopic driver with fibrillatory conduction to the rest of the atria. This has led to the speculation that multifocal atrial tachycardia may have a similar mechanistic unifocal site that disperses through the atrium in a fibrillatory pattern. Ivabradine has been reported to be efficacious in an adult with paroxysmal atrial fibrillation as well as in children with junctional or ectopic atrial tachycardias. This is the first report of successfully using ivabradine, a novel anti-arrhythmic If blocking agent, to convert multifocal atrial tachycardia in a 5-month-old critically ill infant to a pattern indicating a single ectopic atrial focus. This allowed the patient's single atrial focus to be ablated with return to sinus rhythm and decannulation from ventriculoarterial extracorporeal membrane oxygenation. This case suggests that multifocal atrial tachycardia may arise from a single automatic focus with downstream fibrillatory conduction to the atria.

Ectopic Atrial Tachycardia in a 12-Month-Old Girl Treated With Ivabradine and Beta-Blocker, a Case Report

We report on a 12-month-old girl with an ectopic atrial tachycardia successfully treated with the combination of a beta blocking agent and Ivabradine that acts on cardiac pacemaker cells by selectively inhibiting the I_f channel. Standard therapy had failed to control the tachycardia before. No side effects attributable to Ivabradine were noticed. Due to its mechanism of action Ivabradine is a promising novel agent for the therapy of tachycardia due to increased automaticity. Reports on the use of Ivabradine in young children or infants are rare, but show promising results for congenital junctional ectopic tachycardia. This report adds the second case of ectopic atrial tachycardia in this age group and novel treatment with Ivabradine to the literature.

Ivabradine for chronic heart rate control in persistent atrial fibrillation. Design of the BRAKE-AF project

INTRODUCTION AND OBJECTIVES

Ivabradine is an inhibitor of the If channel, the main determinant of the pacemaker function of the sinus node. The drug has been approved for the treatment of angina and heart failure. There is some evidence of its role as an inhibitor of atrial-ventricular node (AVN) conduction. The aim of the BRAKE-AF project is to assess ivabradine use for rate control in atrial fibrillation (AF).

METHODS

A multicenter, randomized, parallel, open-label, noninferiority phase III clinical trial will be conducted to compare ivabradine vs digoxin in 232 patients with uncontrolled permanent AF despite beta-blockers or calcium channel blockers. The primary efficacy endpoint is the reduction in daytime heart rate measured by 24-hour Holter monitoring at 3 months. This clinical trial will be supported by an electrophysiological study of the effect of ivabradine on the action potential of the human AVN. To do this, an experimental model will be used with Chinese hamster ovarium cells transfected with the DNA encoding the expression of the t channels involved in this action potential and recording of the ionic currents with patch clamp techniques.

RESULTS

New data will be obtained on the effect of ivabradine on the human AVN and its safety and efficacy in patients with permanent AF.

CONCLUSIONS

The results of the BRAKE-AF project might allow inclusion of ivabradine within the limited arsenal of drugs currently available for rate control in AF.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Identifier: NCT03718273.