New System for the Assessment of Autonomic Nervous Activity during 24-Hour Period by Spectral Analysis of the Heart Rate

Abstract

We developed a new system for the evaluation of autonomic nervous tone by heart rate spectral analysis during twenty-four-hour ambulatory electrocardiographic (ECG) monitoring. Automatic detection of prominent respiratory peak in power spectra could be done by applying the threshold value of eight of the S/N ratio with sensitivity of 80.8% and specificity of 97.1%. The prominent respiratory peak is observed predominantly during sleep. The confidence interval and confidence arc of the amplitude at maximal S/N ratio during ECG monitoring in nine normal subjects are between 5.99 bpm and ll.45 bpm, and between 0 : 16AM and 4 : 48 AM respectively. This method may provide a way of monitoring cardiac parasympathetic activity over 24 hours.