Variability of ventricular periods during paroxysmal atrial fibrillation: digoxin vs. placebo

This study investigated whether the irregularity of ventricular cycle length during atrial fibrillation (AF) is affected by Digoxin. 41 patients with paroxysmal AF in a randomised crossover comparison of Digoxin and Placebo underwent 24-hour ambulatory monitoring on each treatment. Tapes containing AF episodes of at least 2 minutes were selected (24 recordings on Placebo and 17 on Digoxin). The mean (mRR) and standard deviation (SDRR) of RR intervals was calculated for each 30 s segment of AF. The resulting SDRR values were clustered according to bins of mRR values ranging from 350 to 650 ms in 25 ms steps. In each bin, the SDRR values of all Placebo and all Digoxin recordings were statistically compared for the top 5, 10, and 15 percentiles of each bin which represented the extremes of ventricular cycle length irregularity during AF. There were no significant differences between the total data of SDRR values in individual bins of mRR. However, the top 5, 10, and 15 percentiles of SDRR values corresponding to mRR values from 350 to 550 ms were significantly reduced by Digoxin (p<0.0001).