Pharmacological Cardioversion With Antazoline in Atrial Fibrillation: The Results of the CANT Study

BACKGROUND: Antazoline mesylate represents an antihistamine capable of rapid and safe cardioversion of atrial fibrillation, yet evidence concerning its efficacy in comparison to other medications is insufficient. The study aimed to evaluate the success rate and safety of pharmacological cardioversion of atrial fibrillation with intravenous antazoline (CANT [Cardioversion With Antazoline Mesylate] study) in the setting of the emergency department. METHODS AND RESULTS: After reviewing 1984 medical records, 450 eligible patients (22.7%) with short‐duration atrial fibrillation subject to pharmacological cardioversion were enrolled in a retrospective observational analysis. The choice of antiarrhythmic drug was left to the discretion of the attending physician. The primary end point was successful cardioversion in the emergency department. The safety end point comprised bradycardia <45 bpm, hypotension, syncope, or death. The study population (mean age, 65.5±11.9 years; 52.9% females) was characterized by a median atrial fibrillation episode duration of 10 hours. Antazoline, alone or in combination, was administered in 24.2% (n=109) and 40% (n=180), respectively; amiodarone was administered in 46.7% and propafenone in 9.3%, while ≥2 antiarrhythmic drugs were administered in 19.8% of patients. Antazoline had the highest success rate of pharmacological cardioversion among all drugs (85.3%), which was comparable with propafenone (78.6%; relative risk, 1.09, 95% confidence interval, 0.91–1.30; P=0.317) and higher than amiodarone treatment (66.7%; relative risk, 1.28, 95% confidence interval, 1.13–1.45; P<0.001; number needed to treat, 5.4). The rate of cardioversion with antazoline alone was higher than combined amiodarone and/or propafenone (68.1%; relative risk, 1.25; 95% confidence interval, 1.12–1.40, P=0.0001). No safety end points were reported in the antazoline group, while 5 incidents occurred in the non‐antazoline cohort (P=0.075). CONCLUSIONS: Antazoline represents an efficacious and safe method of pharmacological cardioversion in a real‐life setting.