Circadian variations in atrial fibrillatory frequency in persistent human atrial fibrillation

Atrial fibrillatory frequency reflects the atrial refractory period during AF. This study was conducted to investigate noninvasively the diurnal fluct uations of fibrillatory frequency in persistent human atrial fibrillation a nd to determine the relationship between changes in ventricular rate and fi brillatory frequency. Ambulatory ECGs were recorded in 30 patients (18 men, 12 women, mean age 60 +/- 11 years) with persistent AF (> 24 hours). AF fr equency was measured in 1-minute ECG segments by subtracting averaged QRST complexes and applying Fourier analysis to the resulting signals at 4 PM, 1 0 PM, 4 AM, and 10 AM. Peak frequency was determined in the 3-12 Hz frequen cy band. Mean fibrillatory frequency measured 6.6 +/- 0.6 Hz (range 5.0-7.8 Hz). Two different frequency patterns were distinguished comparing maximal diurnal versus nocturnal fibrillatory frequency. In six (20%) patients an increase (P = 0.045) in nocturnal fibrillatory frequency (type I) was found . In the remaining 24 (80%) patients a decrease ( P < 0.001) in fibrillator y frequency occurred (type II). Type I AF showed a strong inverse correlati on between relative changes (percent) in ventricular rate and fibrillatory frequency obtained from two consecutive measurement points (r = -0.88 to -. 97, P < 0.01), whereas in type II AF a moderate positive correlation (r = 0 .36 to 0.41, P < 0.05) was detected. These data indicate a circadian patter n in AF frequency that concurs with ventricular rate changes suggesting a m odulating influence of the autonomic nervous system on atrial electrophysio logy in persistent human AF.