Open AccessThis section edited by Marek Malik, M. D. Heart rate variability during repeated incremental head‐up tilt discloses time dependence of individual autonomic dynamics
Author(s) -
Bootsma Marianne,
Swenne Cees A.,
Bruschke Albert V. G.
Publication year - 1996
Publication title -
clinical cardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.263
H-Index - 72
eISSN - 1932-8737
pISSN - 0160-9289
DOI - 10.1002/clc.4960190112
Subject(s) - supine position , medicine , reproducibility , heart rate variability , heart rate , cardiology , autonomic nervous system , linear regression , tilt (camera) , blood pressure , statistics , mathematics , geometry
According to the Rosenblueth‐Simeone model, the heart rate (HR) is proportional to the sympathovagal balance. The individual proportionality constant is the intrinsic HR, which can be determined only invasively. The percentage low‐frequency spectral HR variability power, relative to the low‐ plus high‐frequency spectral power (%LF) has been raised as a noninvasive alternative. We previously studied young healthy male subjects, in whom gradual autonomic changes were induced by incremental head‐up tilt (0–10–20–30–40–45–50–55–60–65–70–75–80° ). At each tilt angle we computed HR and %LF. Linear regressions of %LF on HR, characterizing individual autonomic dynamics, confirmed that, within a subject, changes in %LF were proportional to changes in HR. For the current study, we made repeated measurements in 19 subjects after 1 to 8 months. in six subjects, the session 1 and session 2 regression lines differed significantly ( t ‐test, p < 0.05), demonstrating the time dependence of the autonomic dynamics. in such cases, similar HR values on different days are to be associated with different %LF values. We also determined the reproducibility of the supine HR and %LF values. For all 19 subjects, the coefficients of variation were 7 and 22%, respectively: HR reproduces better than %LF. Hence, time‐dependent autonomic dynamics contribute systematically to the inferior reproducibility of %LF.