title: Estimation of fast vagal response by time-dependent analysis of heart rate variability in normal subjects.
abstract: In this study, the selective windowed discrete Fourier transform algorithm (SDA) for time-frequency analysis was applied on non-stationary heart rate signals, recorded during vagal perturbations. These perturbations were achieved in healthy subjects (aged 6-42 years) by inducing the oculocardiac reflex and the diving response. The results showed that the SDA can detect and quantify the expected, although brief, increase in vagal tone, by displaying a marked transient increase in the respiratory peak of the time-dependent spectrum. It allowed us to demonstrate an age-dependent reduction of the vagal response, obtained from the respiratory peak of the heart rate time-dependent spectrum. The SDA approach is thus an adequate tool for the evaluation of an instantaneous change in vagal activity, as well as steady-state vagal activity, including the detection of a malfunction or an exaggerated response of the parasympathetic tone. Since changes in heart rate control are expressed by a transient response, they would not have been detected by a standard, steady-state spectral analysis of heart rate variability, which requires the consideration of long and steady trace lengths and would therefore cause smearing of such fast changes. Time-dependent, or transient changes in autonomic control can thus be detected and quantified by SDA time-frequency analysis.
authors.affiliation: Abramson Institute of Medical Physics, Sackler Faculty of Exact Sciences, Tel Aviv University, Israel.
authors.forename: L
authors.initials: L
authors.lastname: Keselbrener
authors.forename: A
authors.initials: A
authors.lastname: Baharav
authors.forename: S
authors.initials: S
authors.lastname: Akselrod
mesh_terms: D000328:Adult; D000465:Algorithms; D002648:Child; D003080:Cold Temperature; D005260:Female; D005583:Fourier Analysis; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D012016:Reference Values; D012024:Reflex, Oculocardiac / Q000502:physiology*; D013997:Time Factors; D014276:Trigeminal Nerve / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*