Double-Blind Placebo-Controlled Trial of Digoxin in Symptomatic Paroxysmal Atrial Fibrillation

Background —Digoxin is commonly prescribed in symptomatic paroxysmal atrial fibrillation (AF) but has never been evaluated in this condition. Methods and Results —From a multicenter registry, 43 representative patients with frequent symptomatic AF episodes were recruited into a randomized, double-blind crossover comparison of digoxin (serum concentration, 1.29±0.35 nmol/L) and placebo. The study end point was the occurrence of 2 AF episodes (documented by patient-activated monitors), censored at 61 days. The median time to 2 episodes was 13.5 days on placebo and 18.7 days on digoxin ( P <0.05). The relative risk (95% CI) of 2 episodes (placebo:digoxin) was 2.19 (1.07 to 4.50). A similar effect was seen on the median time to 1 episode: increased from 3.5 to 5.4 days ( P <0.05), relative risk 1.69 (0.88 to 3.24). The mean±SD ventricular rates during AF recordings during placebo and digoxin treatment were 138±32 and 125±35 bpm, respectively ( P <0.01). Twenty-four–hour ambulatory ECG recordings did not show significant differences in the frequency or duration of AF or in ventricular rate. Conclusions —Digoxin reduces the frequency of symptomatic AF episodes. However, the estimated effect is small and may be due to a reduction in the ventricular rate or irregularity rather than an antiarrhythmic action.