Inhibition of the KCa2 potassium channel in atrial fibrillation: a randomized phase 2 trial

Existing antiarrhythmic drugs to treat atrial fibrillation (AF) have incomplete efficacy, contraindications and adverse effects, including proarrhythmia. AP30663, an inhibitor of the KCa2 channel, has demonstrated AF efficacy in animals; however, its efficacy in humans with AF is unknown. Here we conducted a phase 2 trial in which patients with a current episode of AF lasting for 7 days or less were randomized to receive an intravenous infusion of 3 or 5 mg kg-1 AP30663 or placebo. The trial was prematurely discontinued because of slow enrollment during the coronavirus disease 2019 pandemic. The primary endpoint of the trial was cardioversion from AF to sinus rhythm within 90 min from the start of the infusion, analyzed with Bayesian statistics. Among 59 patients randomized and included in the efficacy analyses, the primary endpoint occurred in 42% (5 of 12), 55% (12 of 22) and 0% (0 of 25) of patients treated with 3 mg kg-1 AP30663, 5 mg kg-1 AP30663 or placebo, respectively. Both doses demonstrated more than 99.9% probability of superiority over placebo, surpassing the prespecified 95% threshold. The mean time to cardioversion, a secondary endpoint, was 47 (s.d. = 23) and 41 (s.d. = 24) minutes for 3 mg kg-1 and 5 mg kg-1 AP30663, respectively. AP30663 caused a transient increase in the QTcF interval, with a maximum mean effect of 37.7 ms for the 5 mg kg-1 dose. For both dose groups, no ventricular arrhythmias occurred and adverse event rates were comparable to the placebo group. AP30663 demonstrated AF cardioversion efficacy in patients with recent-onset AF episodes. KCa2 channel inhibition may be an attractive mechanism for rhythm control of AF that should be studied further in randomized trials. ClinicalTrials.gov registration: NCT04571385 .

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 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.

Intravenous vernakalant in comparison with intravenous flecainide in the cardioversion of recent-onset atrial fibrillation

Background:

Pharmacological cardioversion of atrial fibrillation is a reasonable alternative for electrical cardioversion in acute atrial fibrillation. We compared the efficacy and safety of intravenous vernakalant and intravenous flecainide in patients with recent-onset (< 48 h) atrial fibrillation.

Methods:

A total of 200 consecutive patients, 100 patients undergoing cardioversion with intravenous vernakalant and 100 patients undergoing cardioversion with intravenous flecainide, were included in this single centre non-randomized retrospective study. The primary endpoint was conversion to sinus rhythm within 120 minutes from the drug administration.

Results:

Cardioversion was successful in 67% of patients treated with vernakalant and in 46% of patients treated with flecainide ( p=0.003). Vernakalant (odds ratio 1.99, 95% confidence interval 1.08–3.69, p=0.029) and female gender (odds ratio 2.48, 95% confidence interval 1.22–15.05, p=0.012) were significant predictors of successful cardioversion. The success rate of cardioversion was lowest among men treated with flecainide (36.9%). Patients treated with vernakalant were discharged earlier from the emergency department compared with those treated with flecainide (8.2 ± 4.7 h vs. 12.0 ± 6.0 h, p < 0.001). There was no difference in the complication rate between the groups. Vernakalant treated patients were older (59.3 ± 12.5 vs. 55.4 ± 13.0 years, p=0.03), had higher CHA2DS2-VASc score (1.4 ± 1.3 vs. 0.9 ± 1.2, p = 0.002) and were more often on beta-blocker medication (59% vs. 42%, p= 0.016) than flecainide treated patients.

Conclusion:

Vernakalant was safe, more effective and faster than flecainide in the cardioversion of recent-onset atrial fibrillation. The difference in efficacy was especially apparent among men.