Clinical Efficacy and Safety of Antazoline in Comparison to Propafenone in Conversion of Paroxysmal Atrial Fibrillation to Sinus Rhythm - a Single Center, Randomized, Double-blinded Study (the AnProAF Study).

Background

Atrial fibrillation (AF) is the most common type of arrhythmia, and occurs in approximately 3% of the population over 20 years of age and 9% of those over 80 years of age [1]. Restoration of sinus rhythm (SR) remains an integral part of the treatment for this type of arrhythmia. Early pharmacological (PCV) or electrical cardioversion (ECV) is necessary to improve symptoms, prevent the side effects of the prolonged crisis of arrhythmia, and avoid hospitalization. ECV requires general sedation and does not prevent from immediate AF recurrence. Therefore, the majority of patients are qualified for pharmacological attempts to terminate the arrhythmia. The early PCV of AF to SR may be achieved by administration of Class (Vaughan-Williams) IA, IC, and III antiarrhythmic drugs (AADs): flecainide, ibutilide, dofetilide, propafenone, amiodarone, or novel agent vernakalant. These AADs have limitations such as proarrhythmic side effects in patients with structural heart disease (IC), delayed onset of action (amiodarone), high cost, and low availability (vernakalant) [1].

An efficacious, well-tolerated, less expensive antiarrhythmic drug with rapid onset of action is necessary. Antazoline meslate is an antihistaminic agent with antiarrhythmic quinidine-like properties, which have been documented in 1960s [2,3]. Electrophysiologically, antazoline prolongs action potential duration and lowers its amplitude, prolongs phase-0 duration, reduces phase-4 of resting potential, and reduces excitability of cardiac tissue. Anticholinergic action of this drug leads to transient increase of heart rate, improving atrioventricular conduction and increasing the corrected QT-interval, left atrial refractory period, and inter-atrial conduction time [4-6]. In human healthy volunteers, the terminal elimination half-life of antazoline was 2.29 hours with a mean residence time of 3.45 hours [7]. In clinical practice, the drug can be administered intravenously in boluses of 50-100 mg every 3-5 minutes until successful cardioversion or up to a cumulative dose of 250-350 mg [8].

In Poland, it was registered for intravenous termination of supraventricular arrhythmias. Unfortunately, antazoline is not listed in any of the formal guidelines due to the lack of large randomized trials comparing this drug with other AADs in SR restoration. To the best of our knowledge, only one randomized clinical trial has been published that evaluated the antiarrhythmic effect of antazoline in comparison to placebo [9]. In antazoline group (38 patients), successful conversion of AF to SR was achieved in 72.2%, with a median duration of 16 minutes. Other published observational studies have shown high efficacy of antazoline, ranging between 50% and 80% and a rapid onset of action with cardioversion duration between 7 and 20 minutes [3,8,10-14]. The aim of this randomized, double blind, placebo-controlled, non-inferiority clinical trial is to assess clinical efficacy of antazoline in rapid conversion of atrial fibrillation to sinus rhythm in patients with paroxysmal atrial fibrillation without significant valvular disease or advanced heart failure.

Methods Study objectives The purpose of the study is to assess clinical efficacy of antazoline in rapid conversion of AF to SR in comparison to propafenone in patients with paroxysmal atrial fibrillation without significant valvular disease or advanced heart failure. Due to a presumed lack of statistical power, secondary end points and safety analysis will be considered exploratory.