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.

Vernakalant for Cardioversion of Recent-Onset Atrial Fibrillation in the Emergency Department: The SPECTRUM Study

INTRODUCTION

Intravenous vernakalant is a therapeutic option for symptomatic, recent-onset atrial fibrillation (AF). This secondary analysis from the large SPECTRUM study assessed the safety and effectiveness of vernakalant when used in the emergency department setting (ED group) or in an inpatient hospital setting (non-ED group).

METHODS

This post hoc analysis of the international, observational, post-authorization SPECTRUM study included 1,289 and 720 recent-onset AF episodes in adults in the ED and non-ED groups, respectively. Safety endpoints included the evaluation of pre-defined health outcomes of interest (HOIs) and other serious adverse events (SAEs) during vernakalant treatment and during the first 24 h after the last infusion. Effectiveness endpoints comprised the rate of successful vernakalant cardioversion, the time from the start of the vernakalant infusion to cardioversion, and the length of hospital stay. Data were analysed using descriptive statistics.

RESULTS

The safety profile of vernakalant was similar in the ED and non-ED groups. In the ED group, 12 pre-defined HOIs were reported in 11 patients (0.9%); all but one occurred within 2 h after start of the first infusion. These events comprised nine significant bradycardia cases, of which one was associated with transient hypotension and three with sinus arrest, and 2 cases of atrial flutter with 1:1 conduction. Five other SAEs were reported. All patients with vernakalant-related events recovered without sequelae. No Torsade de Pointes, ventricular fibrillation, or deaths occurred. Successful cardioversion was reported in 67.8% (95% confidence interval: 65.2-70.4) and 66.4% (62.5-70.1) of episodes, with a median time to conversion of 11.0 and 10.0 min in the ED and non-ED groups, respectively. Patients had a median length of hospital stay of 7.4 h and 17.1 h in the ED and non-ED groups, respectively.

CONCLUSION

Intravenous vernakalant was well tolerated with similar cardioversion rates in patients treated in the ED or non-ED setting and does not require admission to a coronary care unit or intensive care unit. First-line treatment with vernakalant could allow an early discharge in patients with recent-onset AF treated in the ED.

Bi-atrial high-density mapping reveals inhibition of wavefront turning and reduction of complex propagation patterns as main antiarrhythmic mechanisms of vernakalant

Aims

Complex propagation patterns are observed in patients and models with stable atrial fibrillation (AF). The degree of this complexity is associated with AF stability. Experimental work suggests reduced wavefront turning as an important mechanism for widening of the excitable gap. The aim of this study was to investigate how sodium channel inhibition by vernakalant affects turning behaviour and propagation patterns during AF.

Methods and results

Two groups of 8 goats were instrumented with electrodes on the left atrium, and AF was maintained by burst pacing for 3 or 22 weeks. Measurements were performed at baseline and two dosages of vernakalant. Unipolar electrograms were mapped (249 electrodes/array) on the left and right atrium in an open-chest experiment. Local activation times and conduction vectors, flow lines, the number of fibrillation waves, and local re-entries were determined. At baseline, fibrillation patterns contained numerous individual fibrillation waves conducting in random directions. Vernakalant induced conduction slowing and cycle length prolongation and terminated AF in 13/15 goats. Local re-entries were strongly reduced. Local conduction vectors showed increased preferential directions and less beat-to-beat variability. Breakthroughs and waves were significantly reduced in number. Flow line curvature reduced and waves conducted more homogenously in one direction. Overall, complex propagation patterns were strongly reduced. No substantial differences in drug effects between right and left atria or between goats with different AF durations were observed.

Conclusions

Destabilization of AF by vernakalant is associated with a lowering of fibrillation frequency and inhibition of complex propagation patterns, wave turning, local re-entries, and breakthroughs.

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.

Vernakalant and electrical cardioversion for AF - Safe and effective

Aims

Rapid restoration of sinus rhythm is an integral part of the management of recent-onset atrial fibrillation. We aimed to assess safety and efficacy of vernakalant, a multi-channel blocking agent, in combination with external electrical cardioversion.

Methods

This prospective cohort study comprised 230 patients (female 35%; median age 50 IQR 42-55) with recent-onset AF presenting to a university tertiary care center during a 6-year period. Management included intravenous vernakalant followed by electrical cardioversion in case of pharmacological failure.

Results

Within 11 min (IQR 8-29), sinus rhythm could be restored by sole pharmacological management in 167 patients (73%). A left ventricular function lower than 55% (OR 3.51 (1.45-8.52)) and prior atrial fibrillation episodes being classified as persistent (OR 2.33 (1.13-4.80)) were significant predictors for non-response to vernakalant. Electrical cardioversion was successful in all patients but one within 196 min (IQR 149-300) of administration of first dosage of vernakalant. No serious adverse events could be observed. 3 patients needed further in-patient care.

Conclusion

Management of recent-onset atrial fibrillation consisting of intravenous vernakalant followed by electrical cardioversion in case of failure appears safe and efficacious. Achieving a rapid conversion, this approach could potentially save resources and costs.

Vernakalant in Atrial Fibrillation: A Relatively New Weapon in the Armamentarium Against an Old Enemy

Atrial fibrillation is the most common sustained cardiac arrhythmia, and its prevalence is increasing with age; also it is associated with significant morbidity and mortality. Rhythm control is advised in recent-onset atrial fibrillation, and in highly symptomatic patients, also in young and active individuals. Moreover, rhythm control is associated with lower incidence of progression to permanent atrial fibrillation. Vernakalant is a relatively new anti-arrhythmic drug that showed efficacy and safety in recent-onset atrial fibrillation. Vernakalant is indicated in atrial fibrillation (⩽7 days) in patients with no heart disease (class I, level A) or in patients with mild or moderate structural heart disease (class IIb, level B). Moreover, Vernakalant may be considered for recent-onset atrial fibrillation (⩽3 days) post cardiac surgery (class IIb, level B). Although it is mainly indicated in patients with recent-onset atrial fibrillation and with no structural heart disease, it can be given in moderate stable cardiac disease as alternative to Amiodarone. Similarly to electrical cardioversion, pharmacological cardioversion requires a minimal evaluation and cardioversion should be included in a comprehensive management strategy for better outcome.

[Vernakalant in hospital emergency practice: safety and effectiveness]

OBJECTIVES

To study the effectiveness and safety of vernakalant for restoration of sinus rhythm in patients with atrial fibrillation (AF) in routine hospital emergency department care, and to evaluate factors associated with a more effective response.

MATERIAL AND METHODS

Prospective multicenter cohort study enrolling consecutive patients who were administered vernakalant for medical cardioversion of AF between September 2014 through March 2016 in 5 hospitals in the Spanish autonomous community of Valencia.

RESULTS

We studied 165 cases. The median (interquartile range) was 68 years (56-77) years. Cardioversion with vernakalant was effective in 77.6% (95% CI, 71.1%-84%). The median time to conversion was 8 ( 6-12) minutes after a first dose and 34 (22-62) minutes after a second dose. A prior history of cardiac insufficiency was nonsignificantly less common in patients who converted with vernakalant (6.3%) than in those who did not (18.9%) (adjusted odds ratio [OR], 0.45 [95% CI, 0.13-1.56]; P=.208). Having no prior history of AF was nonsignificantly related to greater effectiveness (in 54.7% vs in 35.1% with prior AF). Duration less than 12 hours was significantly associated with greater effectiveness (83.6% vs 59.5%; adjusted OR, 2.76 [95% CI, 1.12-6.80]; P=.028). Adverse events were reported for 30 patients. None of the events had clinically important consequences, and in only 2 cases (1.2%) was it necessary to suspend treatment.

CONCLUSION

Vernakalant is effective and safe for restoring sinus rhythm in the hospital emergency department.

Safety and efficacy of vernakalant for the conversion of atrial fibrillation to sinus rhythm; a phase 3b randomized controlled trial

BACKGROUND

Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with significant health risks. One strategy to mitigate the risks associated with long-term AF is to convert AF to sinus rhythm (SR). This study assessed the efficacy and safety of vernakalant hydrochloride for the pharmacological conversion of AF to SR.

METHODS

Patients with recent-onset (duration >3 h- ≤ 7 days) symptomatic AF and no evidence or history of congestive heart failure were randomized in a 2:1 ratio to receive vernakalant or placebo. Patients received an infusion of vernakalant (3 mg/kg) or placebo over 10 min, followed by a second infusion of vernakalant (2 mg/kg) or placebo 15 min later if AF had not been terminated. The primary efficacy endpoint was conversion of AF to SR for at least 1 min within 90 min of the start of drug infusion. The primary safety endpoint was a composite of: occurrence of clinically significant hypotension, clinically significant ventricular arrhythmia (including torsades de pointes, ventricular tachycardia or ventricular fibrillation) or death within 2 h of starting the drug infusion.

RESULTS

A total of 217 patients were randomized to receive vernakalant (n = 145) or placebo (n = 72). Of the 129 individuals who received vernakalant, 59 (45.7 %) converted to SR compared with one of the 68 patients (1.5 %) who received placebo (p < 0.0001). Conversion to SR was significantly faster with vernakalant than with placebo (p < 0.0001), and a greater proportion of patients who received vernakalant than those who received placebo reported no AF-related symptoms at 90 min (p = 0.0264). The primary composite safety endpoint was observed in one patient receiving vernakalant and in no patients receiving placebo. In the vernakalant arm, dysgeusia, paraesthesia and sneezing were the most common treatment-emergent adverse events, and three serious adverse events occurred that were considered to be related to study drug.

CONCLUSIONS

Vernakalant resulted in rapid cardioversion of recent-onset AF in almost half of the study population and was generally well tolerated. The safety outcomes affirmed the need for careful selection and management of haemodynamically stable candidates for cardioversion.

TRIAL REGISTRATION

NCT00989001 .

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.

Vernakalant-facilitated electrical cardioversion: comparison of intravenous vernakalant and amiodarone for drug-enhanced electrical cardioversion of atrial fibrillation after failed electrical cardioversion

AIMS

Electrical cardioversion is one cornerstone for the rhythm control strategy of atrial fibrillation (AF), which is, however, hampered by immediate AF recurrence (IRAF) or failed electrical cardioversion (FECV). We aimed to investigate the potential role of vernakalant for facilitated electrical cardioversion in cardioversion-resistant AF.

METHODS AND RESULTS

The subjects of this study were 63 patients referred to the Heart Centre Leipzig between November 2011 and May 2014 for transthoracic electrical cardioversion of AF. All patients experienced after antiarrhythmic-naïve electrical cardioversion either IRAF (n = 44; 70%) or FECV (n = 19; 30%). After drug infusion, electrical cardioversion was successful in 66.7% of vernakalant-treated as opposed to 46.7% of amiodarone-treated patients (P = 0.109). Multivariate analysis revealed treatment with vernakalant (OR 0.057, 95% CI 0.006-0.540, P = 0.013), treatment with ACEI or ARB (OR 0.101, 95% CI 0.015-0.691 P = 0.019), and IRAF after initial CV (OR 0.047, 95% CI 0.004-0.498, P = 0.011) as predictors for successful, drug-facilitated electrical cardioversion. Subgroup analysis of 18 patients with previous AF ablation revealed a significantly higher success rate of electrical cardioversion after infusion of vernakalant than after infusion of amiodarone (66.7 vs. 11.1%, P = 0.016).

CONCLUSION

Vernakalant may therefore be considered as a useful agent for facilitated electrical cardioversion in cardioversion-resistant AF.

[Treatment of atrial fibrillation in intensive care units and emergency departments]

BACKGROUND

Atrial fibrillation is the most common arrhythmia in patients hospitalized in intensive care units and emergency departments and is associated with an increased morbidity and mortality. In critically ill patients, atrial fibrillation can cause hemodynamic instability and cardiogenic shock. The mechanisms and the management of atrial fibrillation are significantly different in critically ill patients compared to outpatients.

DIAGNOSIS AND TREATMENT

The initial management includes the evaluation of the hemodynamic consequences of new-onset atrial fibrillation and the optimization of reversible causes. In patients with hemodynamic instability the rapid restoration of an adequate perfusion pressure is the initial goal. Often, a rapid conversion in sinus rhythm is required to achieve hemodynamic stabilization. Electrical cardioversion, if possible performed after pretreatment with an antiarrhythmic drug to increase the success rate, frequently plays a central role in the conversion to sinus rhythm of hemodynamically unstable patients. Stable patients are initially treated with a short-acting intravenous β-blocker to achieve heart rate control. A conversion to sinus rhythm may be achieved pharmacologically with vernakalant, an atrial-specific multichannel blocker.

EVALUATION

All patients with atrial fibrillation lasting more than 48 h should be evaluated for anticoagulation in order to reduce cardio-embolic complications. After recovering from the acute illness, atrial fibrillation persists only in a minority of patients.

Vernakalant activates human cardiac K(2P)17.1 background K(+) channels

Atrial fibrillation (AF) contributes significantly to cardiovascular morbidity and mortality. The growing epidemic is associated with cardiac repolarization abnormalities and requires the development of more effective antiarrhythmic strategies. Two-pore-domain K(+) channels stabilize the resting membrane potential and repolarize action potentials. Recently discovered K2P17.1 channels are expressed in human atrium and represent potential targets for AF therapy. However, cardiac electropharmacology of K2P17.1 channels remains to be investigated. This study was designed to elucidate human K2P17.1 regulation by antiarrhythmic drugs. Two-electrode voltage clamp and whole-cell patch clamp electrophysiology was used to record K2P currents from Xenopus oocytes and Chinese hamster ovary (CHO) cells. The class III antiarrhythmic compound vernakalant activated K2P17.1 currents in oocytes an in mammalian cells (EC50,CHO=40 μM) in frequency-dependent manner. K2P17.1 channel activation by vernakalant was specific among K2P channel family members. By contrast, vernakalant reduced K2P4.1 and K2P10.1 currents, in line with K2P2.1 blockade reported earlier. K2P17.1 open rectification characteristics and current-voltage relationships were not affected by vernakalant. The class I drug flecainide did not significantly modulate K2P currents. In conclusion, vernakalant activates K2P17.1 background potassium channels. Pharmacologic K2P channel activation by cardiovascular drugs has not been reported previously and may be employed for personalized rhythm control in patients with AF-associated reduction of K(+) channel function.

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.

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.

Inhibition of cardiac two-pore-domain K+ (K2P) channels by the antiarrhythmic drug vernakalant--comparison with flecainide

The mixed ion channel blocker, vernakalant (RSD1235), is effective in rapid conversion of atrial fibrillation (AF) to sinus rhythm (SR). Suppression of cardiac two-pore-domain potassium (K2P) channels causes action potential prolongation and has recently been proposed as a novel antiarrhythmic strategy. The objective of this study was to investigate acute effects of vernakalant on human K2P2.1 (TREK-1) and K2P3.1 (TASK-1) channels to provide a more complete picture of its antiarrhythmic mechanism of action. The class IC antiarrhythmic drug flecainide was studied as a comparator agent. Two-electrode voltage clamp and whole-cell patch clamp electrophysiology was used to record K2P currents from Xenopus oocytes and Chinese hamster ovary (CHO) cells. Vernakalant inhibited cardiac K2P2.1 channels expressed in Xenopus oocytes and in CHO cells. The IC50 value obtained from mammalian cells (13.3 µM) was close to the range of vernakalant levels reported in patients (2-8 µM), indicating potential clinical significance of K2P2.1 blockade. Open rectification characteristics and current-voltage relationships of K2P2.1 currents were not affected by vernakalant. Vernakalant did not significantly reduce K2P3.1 currents. Finally, the class I antiarrhythmic drug flecainide had no effect on K2P2.1 or K2P3.1 channels. In conclusion, the recently developed antiarrhythmic drug vernakalant targets human K2P2.1 K(+) background channels. This previously unrecognized inhibitory property adds to the multichannel blocking profile of vernakalant and extends the mechanistic basis for its anti-fibrillatory effect.

Vernakalant is devoid of proarrhythmic effects in the complete AV block dog model

The anesthetized chronic AV-blocked dog (cAVB) and methoxamine-sensitized rabbit model are widely used to determine pro-arrhythmic properties of drugs. In general, both models show similar results. However, conflicting data have also been reported; K201 and AZD1305 induced Torsade de Pointes (TdP) exclusively in cAVB dogs. Vernakalant, an antiarrhythmic drug that blocks several ion channels has been approved only in Europe. Its propensity to induce repolarization-dependent TdP arrhythmias has been evaluated solely in the methoxamine-sensitized rabbits. We therefore assessed the proarrhythmic potential of vernakalant in the cAVB dog model. Vernakalant was evaluated in 10 mongrel dogs (sinus rhythm (SR) 2mg/kg; chronic AV block (cAVB) 2+3mg/kg). The same dogs were challenged with dofetilide (25 μg/kg) to evaluate TdP inducibility. During the serial experiments the animals were paced from the right ventricular apex (60 beats/min). Short-term variability of repolarization (STV) was quantified for proarrhythmic risk. In SR (n=8) vernakalant prolonged QT (265 ± 11 to 311 ± 18 ms P<0.01(**)) but not PQ or QRS. In cAVB (n=8), 2mg/kg vernakalant prolonged QT (391 ± 43 to 519 ± 73 ms(**)) and QRS (103 ± 24 to 108 ± 23 ms(**)). After a 30 min lag-time, 3mg/kg vernakalant (n=4) increased QT to a lesser extent (413 ± 34 to 454 ± 27 ms(**)) while maintaining QRS prolongation (114 ± 18 to 122 ± 20 ms(**)). Neither dose increased STV or caused arrhythmias. Dofetilide prolonged QT (398 ± 51 to 615 ± 71 ms(**)), increased STV (1.0 ± 0.4 to 2.2 ± 1.0 ms P<0.05(⁎)) and induced TdP arrhythmias in 6/8(⁎) cAVB dogs. Vernakalant did not induce arrhythmias in the cAVB dog model. Higher dosages (3mg/kg) did not prolong repolarization further whereas negative inotropic effects were starting to become apparent precluding further increases in dose.

Conversion of Recent-Onset Atrial Fibrillation: Which Drug is the Best?

Introduction: Vernakalant is a new, safe and effective drug used intravenously. It has proven to be more rapid in converting recent onset atrial fibrillation (AF) to sinus rhythm compared to placebo, amiodarone, propafenone and flecainide in clinical studies with few patients. At present no study has been conducted comparing these three drugs with a more substantial number of patients. The aim of our study is to compare the time to conversion to sinus rhythm, hospital stay and adverse events between vernakalant versus flecainide and propafenone in patients with a recent-onset AF. Materials and Methods: 150 hemodynamically stable patients with recent onset AF without structural heart disease were prospectively included. A single oral dose of propafenone 600 mg was administered to 50 patients; 50 patients received intravenous vernakalant; and 50 patients received a single oral dose of flecainide 300 mg. Clinical and laboratory variables were recorded. Results: Baseline characteristics were similar in the three groups.Time to conversion to sinus rhythm was 12 minutes in the vernakalant group versus 151 minutes in the propafenone group and 162 minutes in flecainide group (p< 0.01) The hospital stay was 243 minutes in the vernakalant group versus 422 minutes in the propafenone group and 410 minutes in flecainide group (p<0.01) (Figure 2). No adverse events were reported. Conclusion: The time to conversion to sinus rhythm and hospital stay were statistically shorter in vernakalant group compared to flecainide and to propafenone. There were no adverse events in the three groups.