Abstract 3698: Acute Oral Loading of 1C Antiarrhythmic Drugs On-Top of Chronic Antiarrhythmic Therapy in Recent Onset Atrial Fibrillation
Background. Data about the use of oral loading of 1C antiarrhythmic drugs (1C-AAD) on-top of chronic antiarrhythmic therapy to convert atrial fibrillation (AF) relapses to sinus rhythm (SR), are lacking in current literature.
Methods. The study group consists of 241 patients (pts), mean age 58±12 ys, with history of paroxysmal AF without or with only minimal structural heart disease, chronically treated with class 1C-AAD as prophylaxis. In case of recent onset (<48 hours) AF relapse they randomly received 1C-AAD (Gr.1C) propafenone 600 mg or flecainide 300 mg, in a single loading oral dose at the time scheduled for the next chronic drug administration or adding placebo (PLA) (Gr.PL) to the usually administered chronic drug. Conversion to SR after 2, 4, 6 hours, was considered as criterion of efficacy.
Results. The 2 groups were comparable in terms of gender, age, etiology, duration of AF, mean ventricular rate at baseline and left atrial dimension. Mean time to treatment was 3±2 hs in Gr.1C vs 3±2 hs in Gr.PL. Twenty pts (8,3%) (11 in Gr.1C, 9 in Gr.PL) spontaneusly reverted to SR before drug administration. Conversion rate to SR was higher in Gr.1C compared to Gr.PL, at each considered time-frame: 50/109(46%) pts vs 24/112(21%) pts after 2hs, 80/109(73%) pts vs 40/112(36%) pts after 4hs, 87/109(80%) pts vs 58/112(52%) pts after 6hs (all P < 0.0001). No serious adverse events were detected in each group, 1 case of regular tachycardia (RT) with 1:1 AV conduction was noted in each group. Minor side effects ensued in 18 (17%) pts Gr.1C (12 RT, 6 bradycardia), and in 11 (10%) (RT only) in Gr.PLA, p=NS. Mean time to conversion was lower in Gr.1C (135±100′) compared to Gr.PL (198±105′), p<0.001.
Conclusions. Single loading oral dose with 1C drugs is safe and efficaciuos in converting recent onset atrial fibrillation to sinus rhythm in patients chronically treated with the same drug for prophylaxys.