Diurnal variations of the dominant cycle length of chronic atrial fibrillation.
High-resolution digital Holter recording was carried out in 21 patients (15 men, 64 +/- 12 yr) with chronic atrial fibrillation. Dominating atrial cycle length (DACL) was derived by frequency domain analysis of QRST-reduced electrocardiograms. Daytime mean DACL was 150 +/- 17 ms, and nighttime mean was 157 +/- 22 ms (P = 0. 0002). Diurnal fluctuation in DACL differed among patients: it tended to be virtually absent in those with a short mean DACL, but in those with longer DACL the night-day difference was as much as 23 ms (R = 0.72, P < 0.001, correlation of mean DACL to night-day difference). Mean DACL also correlated with ventricular cycle length (R = 0.40, P < 0.001), particularly at night (r = 0.49). The shorter cycle lengths found in this study during the day are consistent with sympathetic and/or other physiological modulation, but since increased vagal tone shortens atrial refractoriness in most models, parasympathetic influences are not likely to play a major role. Alternatively, atrial effective refractory period may not be the sole determinant of atrial cycle length during atrial fibrillation.
Meurling
C J
CJ
Department of Cardiology, Lund University Hospital, Lund, Sweden.
Waktare
J E
JE
Holmqvist
F
F
Hedman
A
A
Camm
A J
AJ
Olsson
S B
SB
Malik
M
M
D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D002908:Chronic Disease; D002940:Circadian Rhythm; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted