Key result
Standing during an active orthostatic test increased heart rate variability irreversibility and decreased blood pressure variability irreversibility compared to the supine position.
Why the study?
Does the active orthostatic test alter the time irreversibility of heart rate and blood pressure variability in healthy young subjects?
Observational (n=28)
Does the active orthostatic test alter the time irreversibility of heart rate and blood pressure variability in healthy young subjects?
Time irreversibility of beat-to-beat HRV and BPV is significantly altered during orthostasis, implicating the involvement of the autonomic nervous system.
Highlights autonomic modulation during orthostasis in healthy youth; extends observational HRV/BPV data but leaves clinical utility open.
Time irreversibility is a characteristic feature of non-equilibrium, complex systems such as the cardiovascular control mediated by the autonomic nervous system (ANS). Time irreversibility analysis of heart rate variability (HRV) and blood pressure variability (BPV) represents a new approach to assess cardiovascular regulatory mechanisms. The aim of this paper was to assess the changes in HRV and BPV irreversibility during the active orthostatic test (a balance of ANS shifted towards sympathetic predominance) in 28 healthy young subjects. We used three different time irreversibility indices-Porta's, Guzik's and Ehler's indices (P%, G% and E, respectively) derived from data segments containing 1000 beat-to-beat intervals on four timescales. We observed an increase in the HRV and a decrease in the BPV irreversibility during standing compared to the supine position. The postural change in irreversibility was confirmed by surrogate data analysis. The differences were more evident in G% and E than P% and for higher scale factors. Statistical analysis showed a close relationship between G% and E. Contrary to this, the association between P% and G% and P% and E was not proven. We conclude that time irreversibility of beat-to-beat HRV and BPV is significantly altered during orthostasis, implicating involvement of the autonomous nervous system in its generation.
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Chládeková et al. (2012) conducted an observational in Healthy (n=28). Active orthostatic test (standing) vs. Supine position was evaluated on Changes in HRV and BPV irreversibility (Porta's, Guzik's and Ehler's indices). Standing during an active orthostatic test increased heart rate variability irreversibility and decreased blood pressure variability irreversibility compared to the supine position.
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