The Mechanism of Atrial Antiarrhythmic Action of RSD1235

Efficacy and Safety of Intravenous Vernakalant in Rapid Cardioversion of Recent Onset Atrial Fibrillation: A Retrospective Single-Centre Study

BACKGROUND

We use vernakalant, an intravenous anti-arrhythmic, to cardiovert paroxysmal atrial fibrillation (AF) into sinus rhythm. It is a relatively atrium-selective, early-activating potassium and frequency-dependent sodium channel blocker with a half-life of 2 to 3 hours. Due to concerns regarding its safety profile, it is not Food and Drug Administration (FDA)-approved.

OBJECTIVE

This study aims to assess the efficacy of intravenous vernakalant in cardioversion of paroxysmal AF and the safety of its use.

METHODS

Patients with paroxysmal AF who presented to the American University of Beirut Medical Center (AUBMC) between 2015 and 2020 and received vernakalant for cardioversion were included. Patients did not receive vernakalant if they had any of the following: QTc > 440 ms, heart rate < 50 bpm, acute coronary syndrome within the last 30 days, second- and third-degree atrioventricular (AV) block in the absence of a pacemaker, severe aortic stenosis (AS), use of intravenous antiarrhythmics (class I and class III) within four hours of vernakalant infusion, systolic blood pressure <100 mmHg, and heart failure (New York Heart Association (NYHA) III or NYHA IV class). The primary endpoint is conversion to sinus rhythm for at least one minute within 90 minutes of the start of the vernakalant infusion. The secondary endpoint included the presence of these side effects: bradycardia, QTc prolongation, AV block, ventricular arrhythmias, hypotension, taste alteration/dysgeusia, sneezing, nausea, vomiting, paresthesia, cardiogenic shock, or death.

RESULTS

The study included 23 patients with paroxysmal AF (15 men, mean age 54 ± 14 years). Fourteen patients (61%) cardioverted to sinus rhythm within 90 minutes of the start of the Vernakalant infusion. Seven patients (30%) reverted to sinus rhythm within 15 minutes after the first infusion. After treatment with vernakalant, four patients (17%) developed sinus bradycardia, and four patients (17%) developed first-degree AV block. No patient had a QTc greater than 460 ms. None of the patients experienced sinus pauses, high-grade AV block, ventricular arrhythmias, hypotension, dysgeusia, sneezing, nausea, vomiting, paresthesia, cardiogenic shock, or death.

CONCLUSION

Vernakalant had 61% efficacy in the rapid cardioversion of paroxysmal AF to sinus rhythm, was well tolerated, and had a low rate of adverse events in our study population.

Tic-Tac: A Translational Approach in Mechanisms Associated with Irregular Heartbeat and Sinus Rhythm Restoration in Atrial Fibrillation Patients

Atrial fibrillation (AF) is a prevalent cardiac condition predominantly affecting older adults, characterized by irregular heartbeat rhythm. The condition often leads to significant disability and increased mortality rates. Traditionally, two therapeutic strategies have been employed for its treatment: heart rate control and rhythm control. Recent clinical studies have emphasized the critical role of early restoration of sinus rhythm in improving patient outcomes. The persistence of the irregular rhythm allows for the progression and structural remodeling of the atria, eventually leading to irreversible stages, as observed clinically when AF becomes permanent. Cardioversion to sinus rhythm alters this progression pattern through mechanisms that are still being studied. In this review, we provide an in-depth analysis of the pathophysiological mechanisms responsible for maintaining AF and how they are modified during sinus rhythm restoration using existing therapeutic strategies at different stages of clinical investigation. Moreover, we explore potential future therapeutic approaches, including the promising prospect of gene therapy.

Characterization of electropharmacological profile of an anti-atrial fibrillatory drug vernakalant along with potential risk toward torsade de pointes: Translational studies using isoflurane-anesthetized dogs and isolated rat aortic preparations

We simultaneously assessed electropharmacological effects of anti-atrial fibrillatory drug vernakalant and its potential risk toward torsade de pointes. Vernakalant hydrochloride in doses of 0.3 and 3 mg/kg/10 min was intravenously administered to isoflurane-anesthetized beagle dogs without (n = 5) and with (n = 4) α-adrenoceptor blockade. Its vascular effect was analyzed using the rat aortae (n = 12). Vernakalant increased total peripheral vascular resistance and preload to left ventricle, leading to transient elevation of mean blood pressure indirectly via non-adrenergic pathway. Vernakalant suppressed sinus automaticity, ventricular contractility and intra-atrial/atrioventricular nodal/intraventricular conductions, and decreased cardiac output. Moreover, vernakalant prolonged atrial/ventricular effective refractory period by 53/55 ms, respectively, whereas it delayed ventricular repolarization in a reverse frequency-dependent manner. The extent of prolongation in early/late ventricular repolarization and electrically vulnerable period was 26/32 and 9 ms, respectively when QT-interval prolongation was the greatest. We compared them with those of known anti-atrial fibrillatory drugs; ranolazine, amiodarone, dronedarone, dl-sotalol and bepridil. The magnitude of vernakalant to alter those variables was the greater among those drugs except that the atrial selectivity was the lesser of those. Thus, vernakalant is expected to be efficacious against atrial fibrillation, but caution should be excised on its use for patients having labile ventricular function and repolarization.

Discovery and Biomimetic Semisynthesis of Spirophyllines A-D from Uncaria rhynchophylla

Spirophyllines A-D (1-4), four new spirooxindole alkaloids all characterized by the spiro[pyrrolidin-3,3'-oxindole] core and a rare isoxazolidine ring, were isolated from Uncaria rhynchophylla. Their structures were determined by spectroscopic methods and confirmed by X-ray crystallography. Based on the biomimetic semisynthesis strategy, compounds 1-8 were synthesized in three steps via the key reactions of 1,3-dipolar cycloaddition and Krapcho decarboxylation from corynoxeine. Interestingly, compound 3 showed moderate inhibitory activity against the Kv1.5 potassium channel (IC50 = 9.1 μM).

Drug Interactions Affecting Antiarrhythmic Drug Use

Antiarrhythmic drugs (AAD) play an important role in the management of arrhythmias. Drug interactions involving AAD are common in clinical practice. As AADs have a narrow therapeutic window, both pharmacokinetic as well as pharmacodynamic interactions involving AAD can result in serious adverse drug reactions ranging from arrhythmia recurrence, failure of device-based therapy, and heart failure, to death. Pharmacokinetic drug interactions frequently involve the inhibition of key metabolic pathways, resulting in accumulation of a substrate drug. Additionally, over the past 2 decades, the P-gp (permeability glycoprotein) has been increasingly cited as a significant source of drug interactions. Pharmacodynamic drug interactions involving AADs commonly involve additive QT prolongation. Amiodarone, quinidine, and dofetilide are AADs with numerous and clinically significant drug interactions. Recent studies have also demonstrated increased morbidity and mortality with the use of digoxin and other AAD which interact with P-gp. QT prolongation is an important pharmacodynamic interaction involving mainly Vaughan-Williams class III AAD as many commonly used drug classes, such as macrolide antibiotics, fluoroquinolone antibiotics, antipsychotics, and antiemetics prolong the QT interval. Whenever possible, serious drug-drug interactions involving AAD should be avoided. If unavoidable, patients will require closer monitoring and the concomitant use of interacting agents should be minimized. Increasing awareness of drug interactions among clinicians will significantly improve patient safety for patients with arrhythmias.

Antiarrhythmic Effects of Vernakalant in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes from a Patient with Short QT Syndrome Type 1

(1) Background: Short QT syndrome (SQTS) may result in sudden cardiac death. So far, no drugs, except quinidine, have been demonstrated to be effective in some patients with SQTS type 1 (SQTS1). This study was designed to examine the potential effectiveness of vernakalant for treating SQTS1 patients, using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with SQTS1. (2) Methods: Patch clamp and calcium imaging techniques were used to examine the drug effects. (3) Results: Vernakalant prolonged the action potential duration (APD) in hiPSC-CMs from a SQTS1-patient (SQTS1-hiPSC-CMs). In spontaneously beating SQTS1-hiPSC-CMs, vernakalant reduced the arrhythmia-like events induced by carbachol plus epinephrine. Vernakalant failed to suppress the hERG channel currents but reduced the outward small-conductance calcium-activated potassium channel current. In addition, it enhanced Na/Ca exchanger currents and late sodium currents, in agreement with its APD-prolonging effect. (4) Conclusions: The results demonstrated that vernakalant can prolong APD and reduce arrhythmia-like events in SQTS1-hiPSC-CMs and may be a candidate drug for treating arrhythmias in SQTS1-patients.

Design, synthesis, and biological evaluation of arylmethylpiperidines as Kv1.5 potassium channel inhibitors

Kv1.5 potassium channel, encoded by KCNA5, is a promising target for the treatment of atrial fibrillation, one of the common arrhythmia. A new series of arylmethylpiperidines derivatives based on DDO-02001 were synthesised and evaluated for their ability to inhibit Kv1.5 channel. Among them, compound DDO-02005 showed good inhibitory activity (IC₅₀ = 0.72 μM), preferable anti-arrhythmic effects and favoured safety. These results indicate that DDO-02005 can be a promising Kv1.5 inhibitor for further studies.

Peptide Inhibitors of Kv1.5: An Option for the Treatment of Atrial Fibrillation

The human voltage gated potassium channel Kv1.5 that conducts the IKur current is a key determinant of the atrial action potential. Its mutations have been linked to hereditary forms of atrial fibrillation (AF), and the channel is an attractive target for the management of AF. The development of IKur blockers to treat AF resulted in small molecule Kv1.5 inhibitors. The selectivity of the blocker for the target channel plays an important role in the potential therapeutic application of the drug candidate: the higher the selectivity, the lower the risk of side effects. In this respect, small molecule inhibitors of Kv1.5 are compromised due to their limited selectivity. A wide range of peptide toxins from venomous animals are targeting ion channels, including mammalian channels. These peptides usually have a much larger interacting surface with the ion channel compared to small molecule inhibitors and thus, generally confer higher selectivity to the peptide blockers. We found two peptides in the literature, which inhibited IKur: Ts6 and Osu1. Their affinity and selectivity for Kv1.5 can be improved by rational drug design in which their amino acid sequences could be modified in a targeted way guided by in silico docking experiments.

Cardioversion of recent-onset atrial fibrillation using intravenous antiarrhythmics: A European perspective

Pharmacological cardioversion using intravenous antiarrhythmic agents is commonly indicated in symptomatic patients with recent-onset atrial fibrillation (AF). Except in hemodynamically unstable patients who require emergency direct current electrical cardioversion, for the majority of hemodynamically stable patients, pharmacological cardioversion represents a valid option and requires the clinician to be familiar with the properties and use of antiarrhythmic agents. The main characteristics of selected intravenous antiarrhythmic agents for conversion of recent-onset AF, the reported success rates, and possible adverse events are discussed. Among intravenous antiarrhythmics, flecainide, propafenone, amiodarone, sotalol, dofetilide, ibutilide, and vernakalant are commonly used. Antazoline, an old antihistaminic agent with antiarrhythmic properties was also reported to give encouraging results in Poland. Intravenous flecainide and propafenone are the only Class I agents still recommended by recent guidelines. Intravenous new Class III agents as dofetilide and ibutilide have high and rapid efficacy in converting AF to sinus rhythm but require strict surveillance with electrocardiogram (ECG) monitoring during and after intravenous administration because of the potential risk of QT prolongation and Torsades de Pointes, which can be prevented and properly managed. Vernakalant, a partial atrial selective was shown to have a high success rate and to be safe in real-life use.

New Strategies for the Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the clinical practice. It significantly contributes to the morbidity and mortality of the elderly population. Over the past 25-30 years intense effort in basic research has advanced the understanding of the relationship between the pathophysiology of AF and atrial remodelling. Nowadays it is clear that the various forms of atrial remodelling (electrical, contractile and structural) play crucial role in initiating and maintaining the persistent and permanent types of AF. Unlike in ventricular fibrillation, in AF rapid ectopic firing originating from pulmonary veins and re-entry mechanism may induce and maintain (due to atrial remodelling) this complex cardiac arrhythmia. The present review presents and discusses in detail the latest knowledge on the role of remodelling in AF. Special attention is paid to novel concepts and pharmacological targets presumably relevant to the drug treatment of atrial fibrillation.

Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option

Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.

Anti-arrhythmic investigations in large animal models of atrial fibrillation

Atrial fibrillation (AF) constitutes an increasing health problem in the aging population. Animal models reflecting human phenotypes are needed to understand the mechanisms of AF, as well as to test new pharmacological interventions. In recent years, a number of large animal models, primarily pigs, goats, dog and horses have been used in AF research. These animals can to a certain extent recapitulate the human pathophysiological characteristics and serve as valuable tools in investigating new pharmacological interventions for treating AF. This review focuses on anti-arrhythmic investigations in large animals. Initially, spontaneous AF in small and large mammals is discussed. This is followed by a short presentation of frequently used methods for inducing short- and long-term AF. The major focus of the review is on anti-arrhythmic compounds either frequently used in the human clinic (ranolazine, flecainide, vernakalant and amiodarone) or being promising new AF medicine candidates (I_K,Ach , I_SK,Ca and I_K2P blockers).

The Acetylcholine-Activated Potassium Current Inhibitor XAF-1407 Terminates Persistent Atrial Fibrillation in Goats

Aims: The acetylcholine-activated inward rectifier potassium current (IKACh) has been proposed as an atrial-selective target for the treatment of atrial fibrillation (AF). Using a novel selective IKACh inhibitor XAF-1407, the study investigates the effect of IKACh inhibition in goats with pacing-induced, short-term AF. Methods: Ten goats (57 ± 5 kg) were instrumented with pericardial electrodes. Electrophysiological parameters were assessed at baseline and during intravenous infusion of XAF-1407 (0.3, 3.0 mg/kg) in conscious animals before and after 2 days of electrically induced AF. Following a further 2 weeks of sustained AF, cardioversion was attempted with either XAF-1407 (0.3 followed by 3 mg/kg) or with vernakalant (3.7 followed by 4.5 mg/kg), an antiarrhythmic drug that inhibits the fast sodium current and several potassium currents. During a final open chest experiment, 249 unipolar electrograms were recorded on each atrium to construct activation patterns and AF cardioversion was attempted with XAF-1407. Results: XAF-1407 prolonged atrial effective refractory period by 36 ms (45%) and 71 ms (87%) (0.3 and 3.0 mg/kg, respectively; pacing cycle length 400 ms, 2 days of AF-induced remodeling) and showed higher cardioversion efficacy than vernakalant (8/9 vs. 5/9). XAF-1407 caused a minor decrease in the number of waves per AF cycle in the last seconds prior to cardioversion. Administration of XAF-1407 was associated with a modest increase in QTc (<10%). No ventricular proarrhythmic events were observed. Conclusion: XAF-1407 showed an antiarrhythmic effect in a goat model of AF. The study indicates that IKACh represents an interesting therapeutic target for treatment of AF. To assess the efficacy of XAF-1407 in later time points of AF-induced remodeling, follow-up studies with longer period of AF maintenance would be necessary.

Vernakalant for cardioversion of recent-onset atrial fibrillation: a systematic review and meta-analysis

AIMS

To evaluate the efficacy and safety of vernakalant for the cardioversion of atrial fibrillation (AF).

METHODS AND RESULTS

We reviewed the literature for randomized trials that compared vernakalant to another drug or placebo in patients with AF of onset ≤7 days. We used a random-effects model to combine quantitative data and rated the quality of evidence using the GRADE (Grades of Recommendation, Assessment, Development and Evaluation). From 441 total citations in MEDLINE, EMBASE, and CENTRAL (December 2018), we identified nine trials evaluating 1358 participants. Six trials compared vernakalant to placebo, two trials compared vernakalant to ibutilide, and one trial compared vernakalant to amiodarone. We found significant methodological bias in four trials. For conversion within 90 min, vernakalant was superior to placebo [50% conversion, risk ratio (RR) 5.15; 95% confidence interval (CI); 2.24-11.84, I2 = 91%], whereas we found no significant difference in conversion when vernakalant was compared with an active drug (56% vs. 24% conversion, RR 2.40; 95% CI 0.76-7.58, I2 = 94). Sinus rhythm was maintained at 24 h in 85% (95% CI 80-88%) of patients who converted acutely with vernakalant. Overall, we judged the quality of evidence for efficacy to be low based on inconsistency and suspected publication bias. There was no significant difference in the risk of significant adverse events between vernakalant and comparator (RR 0.95; 95% CI 0.70-1.28, I2 = 0, moderate quality evidence). Vernakalant is safe and effective for rapid and durable restoration of sinus rhythm in patients with recent-onset AF.

CONCLUSION

Vernakalant should be a first line option for the pharmacological cardioversion of patients with haemodynamically stable recent-onset AF without severe structural heart disease.

Vernakalant for Rapid Cardioversion of Recent-Onset Atrial Fibrillation: Results from the SPECTRUM Study

Aims

Rapid restoration of sinus rhythm using pharmacological cardioversion is commonly indicated in patients with symptomatic recent-onset atrial fibrillation (AF). The objectives of this large, international, multicenter observational study were to determine the safety and effectiveness of intravenous (IV) vernakalant for conversion of AF to sinus rhythm in daily practice.

Methods and Results

Consenting patients with symptomatic recent-onset AF (< 7 days) treated with IV vernakalant were enrolled and followed up to 24 h after the last infusion or until discharge, in order to determine the incidence of predefined serious adverse events (SAEs) and other observed SAEs and evaluate the conversion rate within the first 90 min. Overall, 2009 treatment episodes in 1778 patients were analyzed. The age of patients was 62.3 ± 13.0 years (mean ± standard deviation). Median AF duration before treatment was 11.1 h (IQR 5.4–27.0 h). A total of 28 SAEs occurred in 26 patients including 19 predefined SAEs, i.e., sinus arrest (n = 4, 0.2%), significant bradycardia (n = 11, 0.5%), significant hypotension (n = 2, 0.1%), and atrial flutter with 1:1 conduction (n = 2, 0.1%). There were no cases of sustained ventricular arrhythmias or deaths. All patients who experienced SAEs recovered fully (n = 25) or with sequelae (n = 1). Conversion rate to sinus rhythm was 70.2%, within a median of 12 min (IQR 8.0–28.0 min).

Conclusions

This large multicenter, international observational study confirms the good safety profile and the high effectiveness of vernakalant for the rapid cardioversion of recent-onset AF in daily hospital practice.

Revisiting Antiarrhythmic Drug Therapy for Atrial Fibrillation: Reviewing Lessons Learned and Redefining Therapeutic Paradigms

Since the clinical use of digitalis as the first pharmacological therapy for atrial fibrillation (AF) 235 years ago in 1785, antiarrhythmic drug therapy has advanced considerably and become a cornerstone of AF clinical management. Yet, a preventive or curative panacea for sustained AF does not exist despite the rise of AF global prevalence to epidemiological proportions. While multiple elevated risk factors for AF have been established, the natural history and etiology of AF remain incompletely understood. In the present article, the first section selectively highlights some disappointing shortcomings and current efforts in antiarrhythmic drug therapy to uncover reasons why AF is such a clinical challenge. The second section discusses some modern takes on the natural history of AF as a relentless, progressive fibro-inflammatory "atriomyopathy." The final section emphasizes the need to redefine therapeutic strategies on par with new insights of AF pathophysiology.

Pharmacological management of atrial fibrillation in patients with heart failure with reduced ejection fraction: review of current knowledge and future directions

Introduction: Both heart failure with reduced ejection fraction (HFrEF) and atrial fibrillation (AF) independently cause significant morbidity and mortality. The two conditions commonly coexist and AF in the setting of HFrEF is associated with worse mortality, hospitalizations, and quality of life compared to HFrEF without AF. Despite the large burden of these conditions, there is no clear optimal management strategy for when they occur together.Areas covered: This review focuses on the pharmacological management of AF in HFrEF. Studies were identified through PubMed search of relevant keywords. The authors review key clinical trials that have influenced management strategies and guidelines. The authors focus on the classes of drugs used to treat AF for both rate and rhythm control strategies including beta-blockers, digoxin, amiodarone, and dofetilide. Additionally, the authors discuss select non-antiarrhythmic medications that affect AF in HFrEF. The authors highlight the strengths and weakness of the data supporting the use of these medications and suggest future directions.Expert opinion: The pharmacological treatment of AF in HFrEF will need further refinement alongside the emerging role of catheter ablation. Novel HF medications and antiarrhythmics offer new tools to prevent the development of AF, as well as for rate and rhythm control strategies.

Postoperative Atrial Fibrillation Following Cardiac Surgery: From Pathogenesis to Potential Therapies

Postoperative atrial fibrillation (POAF) is a major complication after cardiac surgery which can lead to high rates of morbidity and mortality, an enhanced length of hospital stay, and an increased cost of care. POAF is postulated to be a multifactorial phenomenon; however, some major pathogeneses have been proposed, including inflammatory pathways, oxidative stress, and autonomic dysfunction. Genetic studies also showed that inflammatory pathways, beta-1 adrenoreceptor variants, G protein-coupled receptor kinase 5 gene variants, and non-coding single-nucleotide polymorphisms in the 4q25 chromosomal locus are involved in this phenomenon. Moreover, several predisposing factors lead to the development of POAF, consisting of pre-, intra-, and postoperative contributors. The main predisposing factors comprise age, prior history of major cardiovascular risk factors, and ischemia-reperfusion injury during surgery. The management of POAF is based on the usual therapies used for non-surgical AF, including medications for either rate control or rhythm control in hemodynamically unstable patients. The perioperative administration of β-blockers and some antiarrhythmic agents has been recommended in major international guidelines. In addition, upstream therapies consisting of colchicine, magnesium, statins, and antioxidants have attenuated the incidence of POAF; however, some uncomfortable side effects developed in large randomized trials. The use of anticoagulation has also resulted in less mortality in patients with POAF at higher risk of thromboembolic events. Despite these recommendations, the actual regimen for the prevention of POAF remains controversial. In this review, we highlight the pathogenesis, predisposing factors, and potential therapeutic options for the management of patients at risk for or with POAF following cardiac surgery.

Atria-selective antiarrhythmic drugs in need of alliance partners

Atria-selective antiarrhythmic drugs in need of alliance partners. Guideline-based treatment of atrial fibrillation (AF) comprises prevention of thromboembolism and stroke, as well as antiarrhythmic therapy by drugs, electrical rhythm conversion, ablation and surgical procedures. Conventional antiarrhythmic drugs are burdened with unwanted side effects including a propensity of triggering life-threatening ventricular fibrillation. In order to solve this therapeutic dilemma, 'atria-selective' antiarrhythmic drugs have been developed for the treatment of supraventricular arrhythmias. These drugs are designed to aim at atrial targets, taking advantage of differences in atrial and ventricular ion channel expression and function. However it is not clear, whether such drugs are sufficiently antiarrhythmic or whether they are in need of an alliance partner for clinical efficacy. Atria-selective Na⁺ channel blockers display fast dissociation kinetics and high binding affinity to inactivated channels. Compounds targeting atria-selective K⁺ channels include blockers of ultra rapid delayed rectifier (Kv1.5) or acetylcholine-activated inward rectifier K⁺ channels (Kir3.x), inward rectifying K⁺ channels (Kir2.x), Ca²⁺-activated K⁺ channels of small conductance (SK), weakly rectifying two-pore domain K⁺ channels (K_2P), and transient receptor potential channels (TRP). Despite good antiarrhythmic data from in-vitro and animal model experiments, clinical efficacy of atria-selective antiarrhythmic drugs remains to be demonstrated. In the present review we will briefly summarize the novel compounds and their proposed antiarrhythmic action. In addition, we will discuss the evidence for putative improvement of antiarrhythmic efficacy and potency by addressing multiple pathophysiologically relevant targets as possible alliance partners.

Introducing Vernakalant into Clinical Practice

Vernakalant is an antiarrhythmic drug licensed for the pharmacological cardioversion of recent onset AF. Randomised clinical trials, backed up by real-world experience, have confirmed its efficacy at restoring sinus rhythm. Vernakalant can be administered simply with a short time to action, facilitating early discharge from hospital in selected patients in place of electrical cardioversion. The authors explore the data behind vernakalant and discuss how it can be introduced into clinical practice.

Implementing vernakalant: a novel approach to cardioversion

Atrial fibrillation (AF) is the most common arrhythmia, and there is a one in four lifetime risk of developing the condition for people who are over the age of 40. Vernakalant, a new addition to intravenous antiarrhythmic drugs for cardioversion of AF, is the first atrial-specific antiarrhythmic drug for pharmacological cardioversion of recent onset AF and is more effective than placebo and amiodarone. The drug offers patients an alternative to other pharmacological agents for chemical cardioversion and avoids the risks associated with electrical cardioversion. Its main advantage is rapid conversion of AF, which potentially reduces atrial remodelling and it can be used in patients with little or no underlying cardiovascular disease and in those with moderate disease such as stable coronary and hypertensive heart disease. Post-marketing and clinical trials suggest a favourable rate of conversion to sinus rhythm. Jersey General Hospital was the first in the UK to obtain and introduce the drug in practice. This article describes the evidence and guidelines for its use and the local implementation process.

Cardiovascular pharmacology of K2P17.1 (TASK-4, TALK-2) two-pore-domain K+ channels

K_2P17.1 (TASK-4, TALK-2) potassium channels are expressed in the heart and represent potential targets for pharmacological management of atrial and ventricular arrhythmias. Reduced K_2P17.1 expression was found in atria and ventricles of heart failure (HF) patients. Modulation of K_2P17.1 currents by antiarrhythmic compounds has not been comprehensively studied to date. The objective of this study was to investigate acute effects of clinically relevant antiarrhythmic drugs on human K_2P17.1 channels to provide a more complete picture of K_2P17.1 electropharmacology. Whole-cell patch clamp and two-electrode voltage clamp electrophysiology was employed to study human K_2P17.1 channel pharmacology. K_2P17.1 channels expressed in Xenopus laevis oocytes were screened for sensitivity to antiarrhythmic drugs, revealing significant activation by propafenone (+ 296%; 100 μM), quinidine (+ 58%; 100 μM), mexiletine (+ 21%; 100 μM), propranolol (+ 139%; 100 μM), and metoprolol (+ 17%; 100 μM) within 60 min. In addition, the currents were inhibited by amiodarone (- 13%; 100 μM), sotalol (- 10%; 100 μM), verapamil (- 21%; 100 μM), and ranolazine (- 8%; 100 μM). K_2P17.1 channels were not significantly affected by ajmaline and carvedilol. Concentration-dependent K_2P17.1 activation by propafenone was characterized in more detail. The onset of activation was fast, and current-voltage relationships were not modulated by propafenone. K_2P17.1 activation was confirmed in mammalian Chinese hamster ovary cells, revealing 7.8-fold current increase by 100 μM propafenone. Human K_2P17.1 channels were sensitive to multiple antiarrhythmic drugs. Differential pharmacological regulation of repolarizing K_2P17.1 background K⁺ channels may be employed for personalized antiarrhythmic therapy.

Efficacy and safety of intravenous vernakalant for the rapid conversion of recent-onset atrial fibrillation: A meta-analysis

BACKGROUND

Atrial fibrillation is a common cardiac arrhythmia with increasing prevalence in the aging population. It is a major cause of emergency department visits worldwide. Vernakalant, a relatively new antiarrhythmic drug with selectively preferential effects on the atrial tissue is currently used in many European countries for the termination of recent-onset atrial fibrillation. Presently, the drug is still not approved by the United States Food and Drug Administration due to safety concerns. We evaluate the efficacy and safety of vernakalant for the conversion of recent-onset atrial fibrillation or atrial flutter into normal sinus rhythm (NSR).

METHODS

PubMed/MEDLINE (1993-2017), the Cochrane Central Register of Controlled Trials (2000-2017), and reference lists of relevant articles were searched for randomized controlled trials (RCTs) comparing vernakalant to a control drug and extracted subsequently.

RESULTS

Nine RCTs were identified and included in the meta-analysis. Pooled analysis of events extracted for a total of 1421 patients with recent-onset atrial fibrillation showed a statistically significant increase in cardioversion within 90 minutes from drug infusion (Relative Risk [RR], 6.61; 95% Confidence Interval [CI], 2.78 - 15.71; p < .00001). In terms of adverse events, vernakalant was considered safe in comparison to control drugs (RR, 0.80; 95% CI, 0.61-1.05; p = .11).

CONCLUSION

Vernakalant is effective for rapid conversion of recent-onset atrial fibrillation into NSR. However, although it showed a safe profile in terms of side effects in this analysis, we are still hesitant about this conclusion and few safety issues should be addressed within specific patients' subgroups.

A double-blind, randomised, placebo-controlled, cross-over study assessing the use of XEN-D0103 in patients with paroxysmal atrial fibrillation and implanted pacemakers allowing continuous beat-to-beat monitoring of drug efficacy

PURPOSE

The ultrarapid delayed rectifier current (I_Kur) carried by Kv1.5 channels, which are solely expressed in the atrium, is a potential target for safer treatment of paroxysmal atrial fibrillation (PAF). XEN-D0103 is a nanomolar ion channel blocker that selectively inhibits potassium ion flux through the Kv1.5 ion channel. The efficacy of XEN-D0103 in reducing AF burden was assessed in patients with DDDRp permanent pacemakers (PPMs) and PAF.

METHODS

A double-blind, placebo-controlled, cross-over study was performed in patients with PAF and DDDRp PPMs with advanced atrial and ventricular Holters allowing beat-to-beat arrhythmia follow-up. All anti-arrhythmic drugs were withdrawn before randomised treatment. After baseline assessment, patients were randomly assigned to two treatment periods of placebo then XEN-D0103 50 mg bd, or XEN-D0103 50 mg bd then placebo.

RESULTS

Fifty-four patients were screened and 21 patients were eligible and included in the randomised trial. All 21 patients completed both treatment periods. The primary endpoint was change in AF burden assessed by PPM. There was no significant difference in AF burden on treatment with XEN-D0103 versus placebo. There was a reduction in the mean frequency of AF episodes (relative reduction 0.72, 95% CI 0.66 to 0.77; p < 0.0001). XEN-D0103 was safe and well tolerated, and there were no serious adverse events. XEN-D0103 did not have any apparent effect on heart rate compared to placebo.

CONCLUSIONS

XEN-D0103 did not reduce AF burden in patients with PAF and dual chamber pacemakers providing beat-to-beat monitoring. XEN-D0103 was well tolerated and did not have any apparent effect on heart rate. Although single-ion channel blockade with XEN-D0103 did not affect AF in this study, there might be a potential for this agent to be used in combination with other atrially specific drugs in the treatment of AF.

EUDRACT TRIAL REGISTRATION NUMBER

2013-004456-38.

Cardiac Potassium Channels: Physiological Insights for Targeted Therapy

The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and refractoriness would contribute to an optimized approach to antiarrhythmic therapy that minimizes potential cardiac and extracardiac toxicity. Of these, K⁺ channels contribute numerous and diverse currents with specific actions on different phases in the time course of AP repolarization. These features and their site-specific distribution make particular K⁺ channel types attractive therapeutic targets for the development of pharmacological agents attempting antiarrhythmic therapy in conditions such as atrial fibrillation. However, progress in the development of such temporally and spatially selective antiarrhythmic drugs against particular ion channels has been relatively limited, particularly in view of our incomplete understanding of the complex physiological roles and interactions of the various ionic currents. This review summarizes the physiological properties of the main cardiac potassium channels and the way in which they modulate cardiac electrical activity and then critiques a number of available potential antiarrhythmic drugs directed at them.

Rate-Dependent Role of IKur in Human Atrial Repolarization and Atrial Fibrillation Maintenance

The atrial-specific ultrarapid delayed rectifier K⁺ current (I_Kur) inactivates slowly but completely at depolarized voltages. The consequences for I_Kur rate-dependence have not been analyzed in detail and currently available mathematical action-potential (AP) models do not take into account experimentally observed I_Kur inactivation dynamics. Here, we developed an updated formulation of I_Kur inactivation that accurately reproduces time-, voltage-, and frequency-dependent inactivation. We then modified the human atrial cardiomyocyte Courtemanche AP model to incorporate realistic I_Kur inactivation properties. Despite markedly different inactivation dynamics, there was no difference in AP parameters across a wide range of stimulation frequencies between the original and updated models. Using the updated model, we showed that, under physiological stimulation conditions, I_Kur does not inactivate significantly even at high atrial rates because the transmembrane potential spends little time at voltages associated with inactivation. Thus, channel dynamics are determined principally by activation kinetics. I_Kur magnitude decreases at higher rates because of AP changes that reduce I_Kur activation. Nevertheless, the relative contribution of I_Kur to AP repolarization increases at higher frequencies because of reduced activation of the rapid delayed-rectifier current I_Kr. Consequently, I_Kur block produces dose-dependent termination of simulated atrial fibrillation (AF) in the absence of AF-induced electrical remodeling. The inclusion of AF-related ionic remodeling stabilizes simulated AF and greatly reduces the predicted antiarrhythmic efficacy of I_Kur block. Our results explain a range of experimental observations, including recently reported positive rate-dependent I_Kur-blocking effects on human atrial APs, and provide insights relevant to the potential value of I_Kur as an antiarrhythmic target for the treatment of AF.

Chemical cardioversion of recent-onset atrial fibrillation in the emergency department using vernakalant hydrochloride achieves safe and rapid restoration of sinus rhythm and facilitates same day discharge

BACKGROUND

Vernakalant hydrochloride is a rapid-acting antiarrhythmic drug licensed in the EU since 2010 for the conversion of recent-onset atrial fibrillation with proven efficacy and safety when compared with placebo and amiodarone in randomized clinical trials.

AIMS

The aim of our study was to determine the feasibility of same day discharge (following 2 h monitoring) from the emergency department after successful cardioversion using vernakalant hydrochloride.

METHODS

Patients with recent-onset atrial fibrillation treated in the emergency department of a large Dublin academic teaching hospital. Patients received a maximum of two weight based 10 min infusions of vernakalant. Hypotensive events (>30% initial blood pressure), arrhythmias, conversion rates, and time to conversion were recorded.

RESULTS

Sinus rhythm was restored in 35 out of 42 patients (83%) in an average of 8.8 min (median 8 min), average CHA2DS2-VASc of 0.92, HAS-BLED of 0.21 and average symptoms duration of 12 h. There were no hypotensive or arrhythmogenic events. 41 out of 42 patients were discharged after 2 h of monitoring.

CONCLUSIONS

Vernakalant hydrochloride has provided a quick, safe, and practical means of achieving rapid restoration of sinus rhythm in our ED population with stable recent-onset AF who would otherwise not have undergone routine electrically cardioversion and same day discharge.

Vernakalant is superior to ibutilide for achieving sinus rhythm in patients with recent-onset atrial fibrillation: a randomized controlled trial at the emergency department

Aims

Ibutilide is a rapid-acting antiarrhythmic drug with worldwide use for conversion of recent-onset atrial fibrillation. Vernakalant, approved in the EU in 2010, is likewise used intravenously, with proven efficacy and safety compared with placebo and amiodarone in randomized clinical trials. The aim of our study was to compare the time to conversion and the conversion rate within 90 min in patients with recent-onset atrial fibrillation treated with vernakalant or ibutilide.

Methods and Results

A randomized controlled trial registered at clinicaltrials.gov (NCT01447862) was performed in 100 patients with recent-onset atrial fibrillation treated at the emergency department of a tertiary care hospital. Patients received up to two short infusions of vernakalant (n = 49; 3 mg/kg followed by 2 mg/kg if necessary) or ibutilide (n = 51; 1 mg followed by another 1 mg if necessary) according to the manufacturer's instructions. Clinical and laboratory variables, adverse events, conversion rates, and time to conversion were recorded. Time to conversion of AF to sinus rhythm was significantly shorter in the vernakalant group compared with the ibutilide group (median time: 10 vs. 26 min, P = 0.01), and likewise the conversion success within 90 min was significantly higher in the vernakalant group (69 vs. 43%, log-rank P = 0.002). No serious adverse events occurred.

Conclusion

Vernakalant was superior to ibutilide in converting recent-onset atrial fibrillation to sinus rhythm in the emergency department setting.

Potassium Channel Remodeling in Heart Disease

Heart disease produces substantial remodeling of K(+) channels that in general promotes arrhythmia occurrence. In the case of ventricular arrhythmias, K(+) channel remodeling contributes to the arrhythmic risk and increases vulnerability to torsades de pointes with K(+) channel inhibiting drugs. Atrial K(+) channel remodeling caused by atrial fibrillation promotes arrhythmia stability and presents opportunities for the development of new drugs targeting atrial inward rectifier K(+) currents. A better understanding of K(+) channel remodeling will help clinicians to appreciate arrhythmia mechanisms and determinants in a variety of clinical situations and to better manage arrhythmia therapy in patients with heart disease.

Mechanism of Proarrhythmic Effects of Potassium Channel Blockers

Any disturbance of electrical impulse formation in the heart and of impulse conduction or action potential (AP) repolarization can lead to rhythm disorders. Potassium (K(+)) channels play a prominent role in the AP repolarization process. In this review we describe the causes and mechanisms of proarrhythmic effects that arise as a response to blockers of cardiac K(+) channels. The largest and chemically most diverse groups of compound targets are Kv11.1 (hERG) and Kv7.1 (KvLQT1) channels. Finally, the proarrhythmic propensity of atrial-selective K(+) blockers inhibiting Kv1.5, Kir3.1/3.4, SK, and K2P channels is discussed.

Antiarrhythmic effect of vernakalant in electrically remodeled goat atria is caused by slowing of conduction and prolongation of postrepolarization refractoriness

BACKGROUND

Vernakalant inhibits several potassium currents and causes a rate- and voltage-dependent inhibition of the sodium current.

OBJECTIVE

The aim of this study was to evaluate the antiarrhythmic mechanism of vernakalant in normal and electrically remodeled atria.

METHODS

Fourteen goats were instrumented with electrodes on both atria. Drug effects on refractory period (ERP), conduction velocity (CV), and atrial fibrillation cycle length (AFCL) were determined in normal goats (control) and after 2 (2dAF) or 11 (11dAF) days of pacing-induced atrial fibrillation (AF) in awake goats. To evaluate the contribution of changes in conduction and ERP, the same experiments were performed with flecainide and AVE0118. In a subset of goats, monophasic action potentials were recorded during anesthesia.

RESULTS

Vernakalant dose-dependently prolonged ERP and decreased CV in CTL experiments. Both effects were maintained after 2dAF and 11dAF. After 11dAF, conduction slowed down by 8.2 ± 1.5 cm/s and AFCL increased by 55 ± 3 ms, leading to AF termination in 5 out of 9 goats. Monophasic action potential measurements revealed that ERP prolongation was due to enhanced postrepolarization refractoriness. During pacing, vernakalant had comparable effects on CV as flecainide, while effect on ERP was comparable to AVE0118. During AF, all compounds had comparable effects on median AFCL and ERP despite differences in their effects on CV during pacing.

CONCLUSION

The antiarrhythmic effect of vernakalant in the goat, at clinically relevant plasma concentrations, is based on both conduction slowing and ERP prolongation due to postrepolarization refractoriness. These electrophysiological effects were not affected by long-term electrical remodeling of the atria.

Understanding the cellular mode of action of vernakalant using a computational model: answers and new questions

Vernakalant is a new antiarrhythmic agent for the treatment of atrial fibrillation. While it has proven to be effective in a large share of patients in clinical studies, its underlying mode of action is not fully understood. In this work, we aim to link experimental data from the subcellular, tissue, and system level using an in-silico approach. A Hill’s equation-based drug model was extended to cover the frequency dependence of sodium channel block. Two model variants were investigated: M1 based on subcellular data and M2 based on tissue level data. 6 action potential (AP) markers were evaluated regarding their dose, frequency and substrate dependence. M1 comprising potassium, sodium, and calcium channel block reproduced the reported prolongation of the refractory period. M2 not including the effects on potassium channels reproduced reported AP morphology changes on the other hand. The experimentally observed increase of ERP accompanied by a shortening of APD90 was not reproduced. Thus, explanations for the drug-induced changes are provided while none of the models can explain the effects in their entirety. These results foster the understanding of vernakalant’s cellular mode of action and point out relevant gaps in our current knowledge to be addressed in future in-silico and experimental research on this aspiring antiarrhythmic agent.

[Rate and rhythm control in atrial fibrillation : pharmacological approaches]

Atrial fibrillation is the most common form of cardiac arrhythmia, occurring in 1-2 % of the population and due to an increased life expectancy the prevalence will increase further. Pharmacological treatment of atrial fibrillation is an important component of basic initial therapeutic options for patients with atrial fibrillation. Independent of an individually adjusted prevention of thromboembolism, rate and rhythm management can also be carried out. While rate control mainly applies to all patients, rhythm control is only indicated in patients who remain clinically symptomatic despite sufficient rate control. Profound knowledge about antiarrhythmic drugs including specific interactions is necessary due to the variable individual effects and sometimes severe side effects.

Inhibition of IKr potentiates development of atrial-selective INa block leading to effective suppression of atrial fibrillation

BACKGROUND

The availability of safe and effective drugs for the management of atrial fibrillation (AF) remains an unmet medical need.

OBJECTIVES

The purpose of this study was to test the hypothesis that the inhibition of the rapidly activating delayed rectifier potassium current (IKr) greatly potentiates the development of atrial-selective sodium channel current (INa) block, leading to more effective suppression of AF.

METHODS

Electrophysiological and anti-AF effects of highly selective INa and IKr blockers (lidocaine and E-4031) individually and in combination were determined in canine coronary-perfused atrial and ventricular preparations. Acetylcholine (1 µM) was used to induce persistent AF.

RESULTS

Lidocaine (10 µM) caused a relatively small abbreviation of the action potential duration measured at 90% repolarization in both atria and ventricles, but caused atrial-selective prolongation of the effective refractory period owing to the induction of post-repolarization refractoriness. Lidocaine also caused modest atrial-selective depression of other INa-mediated parameters including excitability, maximum rate of rise of the action potential upstroke, and conduction time. E-4031 (1 µM) prolonged the action potential duration measured at 90% repolarization and effective refractory period in an atrial-predominant manner. A combination of lidocaine and E-4031 caused a greater atrial-selective depression of INa-mediated parameters. Persistent acetylcholine-mediated AF developed in 100% of atria under control conditions, in 80% (4 of 5) after pretreatment with lidocaine (10 µM), in 100% (4 of 4) after E-4031 (1 µM), and in only 14% (1 of 7) after the combination of lidocaine and E-4031.

CONCLUSION

Our results provide a proof of concept that IKr block greatly potentiates the effects of rapidly dissociating INa blockers to depress sodium channel-dependent parameters in the canine atria but not in the ventricles, thus contributing significantly to suppression of AF.

Intravenous vernakalant for the rapid conversion of recent onset atrial fibrillation: systematic review and meta-analysis

Atrial fibrillation is the most common cardiac arrhythmia and is associated with increased mortality and morbidity. Conversion to sinus rhythm is usually appropriate in patients with acute, symptomatic atrial fibrillation in order to reduce symptoms and prevent complications. Electrical cardioversion is the most used and widespread technique, but requires deep sedation and a fasting state. Pharmacological alternatives are burdened by a delayed onset of action and potential proarrhythmic effects. Therefore, new therapeutic options are being sought. Among those, vernakalant, showed a good efficacy profile and a short onset of action, but with conflicting evidence regarding potential serious adverse events. This drug profile will summarize the pharmacology behind this new drug and review recent evidence in terms of safety and efficacy.

Predictors of successful cardioversion with vernakalant in patients with recent-onset atrial fibrillation

BACKGROUND

Vernakalant is a novel atrial-selective antiarrhythmic drug able to convert recent-onset atrial fibrillation (AF) with reportedly low proarrhythmic risk. Successful cardioversion predictors are largely unknown. We sought to evaluate clinical and electrocardiographic predictors of cardioversion of recent-onset AF with vernakalant.

METHODS

Consecutive patients with AF ≤48 hours admitted for cardioversion with vernakalant (n = 113, median age 62 years, 69 male) were included. Sinus rhythm (SR) within 90 minutes after infusion start was considered to be successful cardioversion. Predictive values of demographics, concomitant therapy, comorbidities, and electrocardiographic parameters were assessed. Atrial fibrillatory rate (AFR), exponential decay, and mean fibrillatory wave amplitude were measured from surface ECG using QRST cancellation and time-frequency analysis.

RESULTS

Cardioversion was achieved in 66% of patients. Conversion rate was higher in women than in men (80% vs 58%, P = 0.02) while none of other clinical characteristics, including index AF episode duration, could predict SR restoration. Female gender was predictive of vernakalant's effect in logistic regression analysis (OR = 2.82 95%CI 1.18-6.76, P = 0.020). There was no difference in AFR (350 ± 60 vs 348 ± 62 fibrillations per minute [fpm], P = 0.893), mean fibrillatory wave amplitude (86 ± 33 vs 88 ± 67 μV, P = 0.852), or exponential decay (1.30 ± 0.42 vs 1.35 ± 0.42, P = 0.376) between responders and nonresponders.

CONCLUSIONS

Female gender is associated with a higher rate of SR restoration using intravenous (i.v.) vernakalant for recent-onset AF. ECG-derived indices of AF organization, which previous studies associated with effect of rhythm control interventions, did not predict vernakalant's effect.

Clinical update on the management of atrial fibrillation

Atrial fibrillation (AF) is a cardiac arrhythmia associated with significant morbidity and mortality, affecting more than 3 million people in the United States and 1-2% of the population worldwide. Its estimated prevalence is expected to double within the next 50 years. During the past decade, there have been significant advances in the treatment of AF. Studies have demonstrated that a rate control strategy, with a target resting heart rate between 80 and 100 beats/minute, is recommended over rhythm control in the vast majority of patients. The CHA2 DS2 ≥ (congestive heart failure, hypertension, age ≥ 65 yrs, diabetes mellitus, stroke or transient ischemic attack, vascular disease, female gender) scoring system is a potentially useful stroke risk stratification tool that incorporates additional risk factors to the commonly used CHADS2 (congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, stroke transient ischemic attack) scoring tool. Similarly, a convenient scheme, termed HAS-BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly, drugs/alcohol concomitantly), to assess bleeding risk has emerged that may be useful in select patients. Furthermore, new antithrombotic strategies have been developed as potential alternatives to warfarin, including dual-antiplatelet therapy with clopidogrel plus aspirin and the development of new oral anticoagulants such as dabigatran, rivaroxaban, and apixaban. Vernakalant has emerged as another potential option for pharmacologic conversion of AF, whereas recent trials have better defined the role of dronedarone in the maintenance of sinus rhythm. Finally, catheter ablation represents another alternative to manage AF, whereas upstream therapy with inhibitors of the renin-angiotensin-aldosterone system, statins, and polyunsaturated fatty acids could potentially prevent the occurrence of AF. Despite substantial progress in the management of AF, significant uncertainty surrounds the optimal treatment of this condition.

A new antiarrhythmic drug in the treatment of recent-onset atrial fibrillation: vernakalant

Vernakalant is a new antiarrhythmic agent recently approved in Europe for the rapid cardioversion of recent-onset atrial fibrillation. It works by blocking early-activating K+ atrial channels and frequency-dependent atrial Na+ channels, prolonging atrial refractory periods and rate-dependent slowing atrial conduction, without promoting ventricular arrhythmia. Preclinical and clinical trials showed good toleration of this drug. The main purpose of our review is to describe all the trials that led to the incorporation of vernakalant into the current European atrial fibrillation guidelines.

Suitability, efficacy, and safety of vernakalant for new onset atrial fibrillation in critically ill patients

Objectives. This study investigates the suitability, safety, and efficacy of vernakalant in critically ill patients with new onset atrial fibrillation (AF) after cardiac surgery. Methods. Patients were screened for inclusion and exclusion criteria according to the manufacturers' recommendations. Included patients were treated with 3 mg/kg of vernakalant over 10 min and, if unsuccessful, a second dose of 2 mg/kg. Blood pressure was measured continuously for 2 hours after treatment. Results. Of the 191 patients screened, 159 (83%) were excluded, most importantly due to hemodynamic instability (59%). Vernakalant was administered to 32 (17% of the screened) patients. Within 6 hours, 17 (53%) patients converted to sinus rhythm. Blood pressure did not decrease significantly 10, 30, 60, and 120 minutes after the vernakalant infusion. However, 11 patients (34%) experienced a transient decrease in mean arterial blood pressure <60 mmHg. Other adverse events included nausea (n = 1) and bradycardia (n = 2). Conclusions. Applying the strict inclusion and exclusion criteria provided by the manufacturer, only a minority of postoperative ICU patients with new onset AF qualified for vernakalant. Half of the treated patients converted to sinus rhythm. The drug was well tolerated, but close heart rate and blood pressure monitoring remains recommended.

Vernakalant for the conversion of atrial fibrillation: the new kid on the block?

Conversion of recent onset atrial fibrillation (AF) to sinus rhythm with antiarrhythmic drugs reduces the risk of hemodynamic instability, hospitalizations, and atrial remodeling seen with persistent AF. This is the main reason for pharmacological or electrical cardioversion to be considered first line of treatment for recent onset AF. Is there a role for new antiarrhythmic drugs in the conversion of AF as the first approach to a rhythm-control strategy? Vernakalant is a novel and relativity atrial selective drug which inhibits atrial-selective K(+) currents, with only a small inhibitory effect on the rapidly activating delayed rectifier K(+) current (IKr) in the ventricle. In this brief Review, we tell the journey of vernakalant to become an attractive alternative to achieve pharmacological cardioversion of AF.

Electrophysiological profile of vernakalant in an experimental whole-heart model: the absence of proarrhythmia despite significant effect on myocardial repolarization

AIM

The most recent European Society of Cardiology (ESC) update on atrial fibrillation has introduced vernakalant (VER) for pharmacological cardioversion of atrial fibrillation. The aim of the present study was to investigate the safety profile of VER in a sensitive model of proarrhythmia.

METHODS AND RESULTS

In 36 Langendorff-perfused rabbit hearts, VER (10, 30 µM, n = 12); ranolazine (RAN, 10, 30 µM, n = 12), or sotalol (SOT, 50; 100 µM, n = 12) were infused after obtaining baseline data. Monophasic action potentials and a 12-lead electrocardiogram showed a significant QT prolongation after application of VER as compared with baseline (10 µM: +25 ms, 30 µM: +50 ms, P < 0.05) accompanied by an increase of action potential duration (APD). The increase in APD90 was accompanied by a more marked increase in effective refractory period (ERP) leading to a significant increase in post-repolarization refractoriness (PRR, 10 µM: +30 ms, 30 µM: +36 ms, P < 0.05). Vernakalant did not affect the dispersion of repolarization. Lowered potassium concentration in bradycardic hearts did not provoke early afterdepolarizations (EADs) or polymorphic ventricular tachycardia (pVT). Comparable results were obtained with RAN. Hundred micromolars of SOT led to an increase in QT interval (+49 ms) and APD90 combined with an increased ERP and PRR (+23 ms). In contrast to VER, 100 µM SOT led to a significant increase in dispersion of repolarization and to the occurrence of EAD in 10 of 12 and pVT in 8 of 12 hearts.

CONCLUSION

In the present study, application of VER and SOT led to a comparable prolongation of myocardial repolarization. Both drugs increased the PRR. However, VER neither affect the dispersion of repolarization nor induce EAD and therefore did not cause proarrhythmia.

[New developments in the antiarrhythmic therapy of atrial fibrillation]

Atrial fibrillation often affects elderly people with cardiovascular disease and takes a progressive course with increasing resistance to treatment. For the latter, electrical and structural changes (remodelling) seem to be responsible that are directly related to the high excitatory rate in the atria. Therapeutic strategies for atrial fibrillation consist of (i) treating the underlying cardiovascular disease, (ii) re-establishing sinus rhythm and (iii) reducing ventricular rate. Rapid pharmacological or electrical cardioversion is expected to prevent remodelling. Classical antiarrhythmic drugs are notoriously ineffective and burdened with serious cardiac and extracardiac side effects so that there is an urgent need for effective and safe novel compounds. In this review the three recently introduced drugs dronedarone, vernakalant and ranolazine are discussed with respect to the use in atrial fibrillation. Other new antiarrhythmic agents are still in the developmental phase and aim at atria-selective mechanisms thereby excluding ventricular proarrhythmic effects. The mechanisms of action will be discussed in the context of the present understanding of the pathophysiology of onset and maintenance of atrial fibrillation.