Time and frequency domain measures of heart rate variability were stable over 3 to 65 days in normal subjects, with vagal tone-dependent variables being highly correlated (r > 0.8).
Observational (n=14)
Are time and frequency domain measures of heart rate variability stable over short periods of time in normal subjects?
Time and frequency domain measures of heart rate variability are highly reproducible and stable over short periods in normal subjects.
Effect estimate: r > 0.8
Both time and frequency domain measures of heart rate (HR) variability have been used to assess autonomic tone in a variety of clinical conditions. Few studies in normal subjects have been performed to determine the stability of HR variability over time, or the correlation between and within time and frequency domain measures of HR variability. Fourteen normal subjects aged 20 to 55 years were studied with baseline and placebo 24-hour ambulatory electrocardiograms performed 3 to 65 days apart to assess the reproducibility of the following time domain measures of cycle length variability: the standard deviation of all normal cycle intervals; mean normal cycle interval; mean day normal cycle interval; night/day difference in mean normal cycle interval; root-mean-square successive cycle interval difference; percentage of differences between adjacent normal cycle length intervals that are greater than 50 ms computed over the entire 24-hour electrocardiographic recording (proportion of adjacent intervals greater than 50 ms); and the frequency domain measures of high (0.15 to 40 Hz), low (0.003 to 0.15) and total (0.003 to 0.40) power. The mean and standard deviations of these measures were virtually identical between placebo and baseline measurements and within the studied time range. Variables strongly dependent on vagal tone (high-frequency, low-frequency and total power, root-mean-square successive difference, and percentage of differences between adjacent normal cycle intervals greater than 50 ms computed over the entire 24-hour electrocardiographic recording) were highly correlated (r greater than 0.8). It is concluded that measures of HR variability are stable over short periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)
Kleiger et al. (1991) conducted an observational in Normal subjects (n=14). Repeated 24-hour ambulatory electrocardiograms vs. Baseline was evaluated on Reproducibility of time and frequency domain measures of heart rate variability (r > 0.8). Time and frequency domain measures of heart rate variability were stable over 3 to 65 days in normal subjects, with vagal tone-dependent variables being highly correlated (r > 0.8).