Twenty-four-hour pattern of ventricular excitation rhythm in resting normal human subjects.

Abstract

Using a biotelemetry system, the electrocardiogram (ECG) was continuously measured over 24 hr in a given environmental condition in 8 normal human subjects. The frequency of ventricular excitation rhythm (VER) was obtained from inverse of R-R interval of ECG. This study was undertaken to be informed of the variation of VER over 24 hr in resting normal subjects with different ages. The averaged frequency of VER per day (VERB) and its relative coefficient of variation (CV) ranged from 1.44 to 1.01 Hz (mean : 1.24 Hz) and 26 to 10% (mean : 20%) with age of 10 to 73 years (mean : 42 years). VERd and CV showed a tendency to decrease with age. The VERd histogram showed not a normal distribution but a multimodal distribution. Two or three large positive deviations, denoted as L, N, and H modal components, from the normal distribution curve were detected. The mode of L and H modal components was 1.01 and 1.37 Hz, respectively. The frequency distribution of L and H modal components changed with relation to a circadian rhythm and sleepwakefulness cycles. An hourly histogram of ventricular excitation rhythm (VERh) frequently showed an unimodal distribution and the relative coefficient of variation of VERh ranged from 7.9 to 13.3 % which was smaller than that of CV. The mode of VERh histogram changed in association with the circadian rhythm, the sleep-wakefulness cycles and a fluctuation period of 2 to 3 hr.

Predominantβ-adrenoceptor blocking effect of xamoterol averaged over the day in patients with mild to moderate heart failure: insight into the mechanism of its long-term clinical efficacy

“…The mean and SD of the R-R intervals of individual histograms were calculated from the digitised data. Each histogram showed a bi-modat profile, consisting of a peak with short R-R intervals and a peak with long R-R invervals, as previously reported [16,17]. In all subjects the peaks of the short and long R-R intervals were distributed in the daytime and night-time, respectively, as previously reported [17].…”

“…Each histogram showed a bi-modat profile, consisting of a peak with short R-R intervals and a peak with long R-R invervals, as previously reported [16,17]. In all subjects the peaks of the short and long R-R intervals were distributed in the daytime and night-time, respectively, as previously reported [17]. To evaluate the daytime and night-time effects of xamoterol independently, each peak was approximated to the normal distribution by the least squares method.…”

“…However, Cai et al reported in patients with atrial fibrillation that R-R interval histograms obtained from the same subject but on different days were almost identical [26]. Second, the approximation of the daytime and night-time peaks to a normal distribution may not be appropriate for description of the contour of the histogram [17]. In the present study, however, as the attempt was made to assess the direction of the peak shift, a more mathematically strict approximation might not provide further information.…”