A New Method for the Estimation of Coefficient of Variation of R-R Intervals by Means of Holter ECG : First Report. An Application for the Circadian Rhythm of Coefficient of Variation of R-R Intervals.

We developed a new system for the estimation of coefficient of variation of R-R intervals (CV), using Holter ECG and personal computer. As an application of this system, circadian rhythm of CV was studied in 25 normal subjects with mean age of 36 years and 5 hyperthyroid patients with mean age of 41 years. When calculated with any basic heart pulses from 50 to 1000, CV was hardly changed in all position of standing, sitting, and lying in the daytime and sleeping at night. Then, according to previous reports, CV was calculated with the basic pulse of 100 through 24 hours. In the daytime, CV decreased when the mean heart rate increased in all subjects. In contrast with the daytime, two types of CV was shown during sleep at night ; In 18 normal subjects and 3 hypeythyroid patients, CV was prominently lower during sleep than in the daytime for the same mean heart rate (A type). And, in 7 normal subjects and 2 hyperthyroid patients, CV showed negative correlation with mean heart rate during sleep, as shown in the daytime (B type). It may be suggested that A type shows the suppressed activity of both sympathetic and parasympathetic nerve systems during the deep sleep, although sympathetic nerve activity was so sustained even during the deep sleep that parasympathetic nerve activity was also not suppressed in B type. These results suggest that this new system using Holter ECG is useful for detection of autonomic nerve function