HEART PERIOD VARIABILITY IN SLEEP

Analysis of heart period variability is a dynamic noninvasive techniqu e to quantify the autonomic control over the heart period. We recorded electroencephalographic, electro-oculographic, electromyographic and electrocardiographic data from 10 normal subjects during sleep using a n ambulatory polysomnographic monitor. R-R intervals were determined f or 10 min segments of electrocardiographic data from wakefulness, stag e 2 sleep, slow wave Sleep and REM sleep. Average heart period, instan taneous changes greater than 50 msec and fractal dimension were calcul ated and the time domain and phase plots were depicted. The R-R interv al time domain plots were subsequently analyzed using the discrete Fou rier transform. We found sleep stage specific, time domain and frequen cy domain changes in heart period variability, particularly using spec tral analysis of heart period. Increased power in the 0.2-0.4 Hz band was associated with stage 2 sleep when compared to awake and slow wave sleep states. Power in the 0.0-0.04 and 0.04-0.12 Hz bands was increa sed in association with REM sleep when compared to non-REM sleep, and slow wave sleep had diminished power in al! frequency bands. Our resul ts support other investigations demonstrating stage 2 sleep is associa ted with increased parasympathetic influences and REM sleep is associa ted with increased sympathetic and neurohumoral influences. We feel th at spectral analysis of heart period variability is an effective nonin vasive method to quantify changes in the autonomic influences over the heart during sleep.