Randomized, crossover, controlled comparison of oral loading versus intravenous infusion of propafenone in recent-onset atrial fibrillation.

A population of 123 patients with recent-onset (< 72 hours) atrial fibrillation (AF) without heart failure was randomly treated with propafenone (PFN) intravenously (i.v.) (2 mg/kg bolus followed by 0.0078 mg/kg/min infusion) or in a single oral dose (o.s.) (600 mg), or with placebo (PLA) (phase 1). If AF persisted 8 hours later, patients on active drugs received the alternative formulation (crossover), and patients receiving PLA remained on PLA (phase 2). A 24-hour Holter monitoring was performed and conversion to sinus rhythm (SR) at 1, 4, and 8 hours of each phase was used as the criterion of efficacy. Conversion to SR occurred within 1 hour in 48% of patients with i.v.-PFN, 15% with o.s.-PFN, and in 17% with PLA (both P < 0.05 vs i.v.-PFN). Oral PFN was superior to PLA at 4 hours (71% vs 33%, P = 0.001) and 8 hours (78% vs 48%, P < 0.01), and 1 at 8 hours also superior to i.v.-PFN (53%, P < 0.03). The mean conversion time within 4 hours was shorter with i.v.-PFN (25 +/- 15') than with o.s.-PFN (167 +/- 166', P < 0.001) or with PLA (156 +/- 107', P < 0.001). The rates of conversion to SR with i.v.-PFN after o.s.-PFN failure were comparable to PLA at any observation time, whereas nonresponders to i.v.-PFN who received o.s.-PFN had significantly higher conversion rates than with placebo at both 4 hours (65% vs 19%) and 8 hours (76% vs 24%; both P < 0.045). Neither serious adverse effects nor episodes of regular tachycardia with 1:1 AV conduction were noted. PFN administered intravenously or in a single oral loading dose was safe and efficacious in converting recent-onset AF to SR. The rates of conversion were different with different routes of administration: i.v.-PFN was superior to o.s.-PFN over a short observation period, while the overall efficacy of o.s.-PFN was superior at 8 hours.

Regular ventricular rhythms before conversion of recent onset atrial fibrillation to sinus rhythm.

The incidence of fast atrial tachycardias with regular ventricular rhythm was assessed in a population of 243 patients with recent onset (< 72 hours) atrial fibrillation (AF), without heart failure, randomly treated with single loading oral dose of propafenone (600 mg), flecainide (300 mg), digoxin (1 mg), or placebo for acute conversion to sinus rhythm (SR). Fast atrial arrhythmias developed in 14 (6%) patients: 6/92 treated with propafenone, 3/34 treated with flecainide, 1/25 treated with digoxin, and 4/92 who received placebo (P = NS). Heart rate > 175 beats/min with 1:1 AV conduction ensued in 4 cases: 2 treated with flecainide and 2 treated with placebo; in the other cases 2:1 AV conduction was observed. Widening of QRS during regular tachycardia was observed in 4 patients; 3 who received propafenone and 1 who received flecainide. Conversion to SR within 4 hours was achieved in 55/92 (60%) patients treated with propafenone, 20/34 (59%) patients treated with flecainide, 7/25 (28%) patients treated with digoxin, and 19/92 (20%) treated with placebo (P < 0.001 propafenone vs placebo and flecainide vs placebo; P < 0.05 propafenone vs digoxin and flecainide vs digoxin). Periods of regular tachycardia are expected in recent onset AF and may not necessarily represent a proarrhythmic effect of Class 1C drugs, rather than mark the transition from AF to SR. Class 1C agents are probably responsible for widening of the QRS complex seen during these tachycardias. Propafenone and flecainide appear equally effective in converting recent onset AF.