Circadian rhythm of the signal averaged electrocardiogram and its relation to heart rate variability in healthy subjects
- aDepartment of Laboratory Medicine, Oita Medical University, Hasama-machi 1-1, Oita 879-55, Japan, bFirst Department of Internal Medicine, Oita Medical University
- Dr Nakagawa.
- Accepted 23 December 1997
Abstract
Objective To examine the circadian variation in the signal averaged electrocardiogram (saECG) and heart rate variability and investigate their relations in healthy subjects.
Methods 24 hour ECGs were obtained with a three channel recorder using bipolar X, Y, and Z leads in 20 healthy subjects. The following variables were determined hourly: heart rate, filtered QRS (f-QRS) duration, low and high frequency components of heart rate variability (LF and HF), and the LF/HF ratio.
Results Heart rate, f-QRS duration, HF, and the LF/HF ratio showed significant circadian rhythms, as determined by the single cosinor method. Heart rate and the LF/HF ratio increased during daytime, and f-QRS duration and HF increased at night. f-QRS duration was negatively correlated with heart rate (r = 0.95, p < 0.001) and the LF/HF ratio (r = 0.94, p < 0.001) and positively with HF (r = 0.93, p < 0.001).
Conclusions f-QRS duration has a significant circadian rhythm in healthy subjects and is closely related to the circadian rhythm of autonomic tone.
