Characterization of hERG K+ channel inhibition by the new class III antiarrhythmic drug cavutilide

Cavutilide (niferidil, refralon) is a new class III antiarrhythmic drug which effectively terminates persistent atrial fibrillation (AF; 84.6% of patients, mean AF duration 3 months) and demonstrates low risk of torsade de pointes (1.7%). ERG channels of rapid delayed rectifier current(IKr) are the primary target of cavutilide, but the particular reasons of higher effectiveness and lower proarrhythmic risk in comparison with other class III IKr blockers are unclear. The inhibition of hERG channels expressed in CHO-K1 cells by cavutilide was studied using whole-cell patch-clamp. The present study demonstrates high sensitivity of IhERG expressed in CHO-K1 cells to cavutilide (IC50 = 12.8 nM). Similarly to methanesulfonanilide class III agents, but unlike amiodarone and related drugs, cavutilide does not bind to hERG channels in their resting state. However, in contrast to dofetilide, cavutilide binds not only to opened, but also to inactivated channels. Moreover, at positive constantly set membrane potential (+ 60 mV) inhibition of IhERG by 100 nM cavutilide develops faster than at 0 mV and, especially, - 30 mV (τ of inhibition was 78.8, 103, and 153 ms, respectively). Thereby, cavutilide produces IhERG inhibition only when the cell is depolarized. During the same period of time, cavutilide produces greater block of IhERG when the cell is depolarized with 2 Hz frequency, if compared to 0.2 Hz. We suggest that, during the limited time after injection, cavutilide produces stronger inhibition of IKr in fibrillating atrium than in non-fibrillating ventricle. This leads to beneficial combination of antiarrhythmic effectiveness and low proarrhythmicity of cavutilide.

Relief of persistent atypical atrial flutter: experience with the use of niferidil

An increase in life expectancy contributes to a steady growth  of diseases of the cardiovascular system. In recent years, there has been a stable increase in the prevalence  of rhythm  disturbances  in the population.  Fibrillation and atrial flutter are among  the most common  causes  of a decrease  in the quality of life and an increase in mortality. However, the effectiveness  of various methods of treatment is not absolute,  and therefore the development and introduction  of new antiarrhythmic drugs  is particularly  relevant. Thus,  the use of a class III antiarrhythmic drug  (niferidil) is of unconditional interest, and literature data describing the effectiveness  of its use for the relief of atypical atrial flutter are extremely few. The article presents a case of successful  relief of a persistent form of atypical atrial flutter in a 79-year-old patient using three consecutive intravenous injections of niferidil at a dose of 10 mcg/kg with a 15-minute interval in 19 hours after the start of therapy. The presented clinical case confirms the effectiveness of drug cardioversion with the use of niferidil and makes it possible to consider it as an alternative to electrical cardioversion  in patients with atypical atrial flutter.

Safety and Effectiveness of Pharmacologic Conversion of Atrial Fibrillation and Flutter: Results of Multicenter Trial. Part II: Assessment of Safety

Aim. We aimed to assess safety and effectiveness of class III antiarrhythmic drug Refralon for conversion of atrial fibrillation (AFib) and flutter (AFl) in post-registration trial and to compare data of primary center (National medical research center in cardiology) with data of other hospitals.

Material and Methods. We performed retrospective cohort study in 727 patients (451 enrolled in primary center and 276 enrolled in other hospitals) admitted between June 24, 2014 and June 24, 2019. Refralon was administered for conversion of AFib and AFl in intense care units in escalating doses (10-30 micrograms/kg) intravenously.

Results. Conversion of AFib and AFl into sinus rhythm was achieved in 53,6% after administration of 10 mcg/kg dose, in 73% after administration of 20 mcg/kg dose and in 91,6% after administration of Refralon in dose up to 30 mcg/kg. No mortality and no major adverse cardiac events registered in our study. Asystole >3.0 sec observed in 5% (35 of 727) of patients): in 5% (24 of 451) of patients enrolled in primary center and in 4% (11 of 276) of patients enrolled in other hospitals; 95% confidence interval (CI) [-0.09; 0.113]. Asystole> 5.0 s observed in 1.7% of patients who further required non-urgent implantation of a permanent pacemaker due to manifestations of sinus node dysfunction. Cardiac conduction disturbances (exclusively sinus bradycardia) were registered in 7% (53 of 727) patients: in 8% (37 of 451) of patients enrolled in primary center and in 6% (17 of 276) of patients enrolled in other hospitals; 95% CI: [-0.1; 0.15]. Only 0.14% of patients had symptomatic sinus bradycardia that resolved after atropine injection. Ventricular arrhythmias (exclusively Torsade de pointes tachycardia in excessive QT interval prolongation) were registered in 1.7% (12 of 727) patients: in 2% (9 of 451) of patients in primary center and in 1% (3 of 276) of patients of other hospitals; 95% CI: [-0.06; 0.08]. QTc interval prolongation to values >500 ms documented in 19% (138 of 727) of patients: in 21% (95 of 451) of patients in primary center and in 16% (43 of 276) of patients in other hospitals; 95% CI: [-0.13; 0.24].

Conclusion: In post-registration multicenter trial Refralon demonstrated good safety profile in conversion of AFib and AFl. Potential risk of TdP tachycardia mandates precautions with the use of the drug. In other hospitals Refralon did not demonstrate lower safety than in primary medical center.

Safety and Effectiveness of Pharmacologic Conversion of Atrial Fibrillation and Flutter: Results of Multicenter Trial. Part I: Study Rationale, Design and Assessment of Effectiveness

Aim. We aimed to assess safety and effectiveness of class III antiarrhythmic drug Refralon for conversion of atrial fibrillation (AFib) and flutter (AFl) in post-registration trial and to compare data of primary center (National medical research center in cardiology) with data of other hospitals.

Material and Methods. We performed retrospective cohort study in 727 patients (451 enrolled in primary center and 276 enrolled in other hospitals) admitted between June 24, 2014 and June 24, 2019. Refralon was administered for conversion of AFib and AFl in intense care units in escalating doses (10-30 mcg/kg) intravenously. Primary endpoints: restoration of sinus rhythm (SR) within 24 hours after the start of infusion of the study drug in a total dose of up to 30 pg / kg; registration of SR on an electrocardiogram (ECG) 24 hours after the start of the study drug infusion. Secondary endpoints: restoration of SR after infusion of the study drug at a dose of 10 pg / kg; restoration of SR after infusion of the studied drug in a total dose of up to 20 pg / kg; no recurrence of AFib/AFl after restoration of AFl within 24 hours of observation after the start of the study drug infusion.

Results. Conversion to SR was achieved in 53,6% (391 of 727) after administration of 10 mcg/kg dose, in 73% (531 of 727) after administration of 20 mcg/kg dose and in 91,6% (666 of 727) after administration in dose up to 30 mcg/kg. SR was restored in 89% (402 of 451) of patients in primary center, and in 96% (264 of 276) of patients in other hospitals; 95% confidence interval (CI): (-0,1;-0,03). SR preserved 24 hours after conversion in 98% (650 of 666) successfully converted patients. In primary center SR preserved in 97% (390 of 402) successfully converted patients. In other hospitals - in 98,5% (260 of 264) successfully converted patients. 95 CI: (-0,09;0,06).

Conclusion: In post-registration multicenter trial Refralon demonstrated high effectiveness in conversion of AFib and AFl to SR. In other hospitals Refralon did not demonstrate lower effectiveness than in primary medical center.

Recent advances in diagnosis and management of atrial fibrillation

Alterations of heart rhythm are a common clinical event. They can be caused by almost any kind of heart disorder. Atrial fibrillation (AF) is the most common type of abnormal heart rhythm. Prevalence of AF in the general population is 1-2%, and given that AF incidence rate continues to increase it can be predicted that the number of patients will be doubled within the next 50 years. This review provides the most recent diagnostic and treatment methods, including both unique domestic antiarrhythmic drugs and non - drug methods for AF treatment which were developed and implemented in clinical practice at NMRC of Cardiology of the Ministry of Health of the Russian Federation.