Effects of a high dose intravenous bolus amiodarone in patients with atrial fibrillation and a rapid ventricular rate

Background Amiodarone, given as intravenous bolus has not yet been studied in patients with atrial fibrillation and a high ventricular rate. Methods One hundred consecutive patients with atrial fibrillation and a ventricular rate above 135 bpm were randomized to receive either 450 mg amiodarone or 0.6 mg digoxin given as a single bolus through a peripheral venous access. If the ventricular rate exceeded 100 bpm after 30 min, another 300 mg amiodarone or 0.4 mg digoxin were added. Primary endpoints of the study were the ventricular rate and the occurrence of sinus rhythm after 30 and 60 min. Secondary endpoints were blood pressure during the first hour after drug administration, and safety regarding drug induced hypotension, and phlebitis at the infusion site. Results Baseline heart rate was 144 ± 19 in the amiodarone group and 145 ± 15 in the digoxin group (p = 0.72). Following amiodarone, heart rate was 104 ± 25 after 30 min compared to 116 ± 23 in the digoxin group (p = 0.02) and 94 ± 22 versus 105 ± 22 after 60 min (p = 0.03). After 30 min, sinus rhythm was documented in 14 (28%) patients following amiodarone compared to 3 (6%) patients in the digoxin group (p = 0.003), and after 60 min in 21 (42%) versus 9 (18%) patients (p = 0.012). Asymptomatic hypotension was observed in 4 amiodarone treated patients, and superficial phlebitis in 1 patient. Conclusions Amiodarone, given as an intravenous bolus is relatively safe and more effective than digoxin for heart rate control and conversion to sinus rhythm in patients with atrial fibrillation and a rapid ventricular rate.