[Spectrum analysis of heart rate. A method of studying the role of the autonomic nervous system in the regulation of blood circulation].

Spectral analysis of heart rate variability has recently been shown to be a reliable noninvasive test for quantitative assessment of cardiovascular automatic regulatory responses. In 12 ambulant normotensive healthy young males (mean age 23 +/- 1 years) after a period of 10 min. for stabilisation, a continuous ecg recording (lead CM-5) for 8 min. was obtained in the supine and standing position, with a controlled respiration rate 15/min. Power spectrum of 512 point time series (R-R intervals) in both positions was calculated using a fast Fourier transform-based window periodogram method. Based upon results from the literature the power spectrum analysis was performed on two components: low frequency LF (0.05-0.15 Hz) and high frequency HF (0.15-0.50 Hz). Mean R-R interval decreased on standing position from 0.79 +/- 0.10 s to 0.59 +/- 0.11 s (p less than 0.001). The ratio HF/LF in supine was 0.63 +/- 0.70 and on standing position 2.54 +/- 0.73 (p less than 0.001). The relative LF component of the total HR power spectrum increased from 22.8% +/- 12.1% to 42.9 +/- 14.4% (p less than 0.001) after changing the position from supine to standing, and the relative HF component decreased from 56.3 +/- 22.4% to 25.5 +/- 16.2 (p less than 0.001). The total power was significantly lower when standing in comparison to supine position (681 +/- 519 s2, 1188 +/- 963 s2 respectively, p less than 0.05). Our results suggest that heart rate fluctuations in supine position in normal men are mainly vagally determined (HF power spectrum component).(ABSTRACT TRUNCATED AT 250 WORDS)