Effect of Postural Changes on Complexity Measures of Heart Rhythm in Late Adolescents

摘要

Even trivial changing of body position from supine to sitting triggers complex cardiovascular adaptive response to prevent brain ischemiaThe study was performed to investigate heart rate asymmetry (HRA) and entropy-based heart rate variability (HRV) in stationary conditions in two body positions. Forty male students, aged 18-20 participated in this study. High resolution (4 kHz) ECG was recorded for 15 minutes; first in supine and after that in sitting position. 512 beat-to-beat interval (RRi) time-series were selected from each recording. Entropy-based parameters such as sample entropy (SampEn) and approximate entropy (ApEn) were computed. Heart cycles shorter (acceleration) or longer (deceleration) from the previous ones and sequential monotonic changes of RRi were also discriminated. Number of HR sequential runs significantly correlated with SampEn and ApEn both in sitting and supine position. Postural change from supine to sitting position resulted in a significant HR increase from 69 to 77 bpm. Both SampEn and ApEn were decreased after changing position (from 1.54 to 1.20 and from 1.23 to 1.08, respectively)Our data obtained from nonlinear HRV analysis indicate a reduction of cardiac control complexity following postural upright changing of body position.