title: Correlations Between Cardiovascular Autonomic Control Indices During the Two-hour Immobilization Test in Healthy Subjects.
abstract: OBJECTIVE
  The aim of the present study was to assess the features of dynamics of cardiovascular autonomic indices and correlations between them during the two-hour immobilization test in healthy subjects.
  
  
  METHODS
  Photoplethysmogram (PPG) and electrocardiogram were recorded simultaneously during the two-hour immobilization test in 14 healthy subjects (5 men and 9 women) aged 29±5 years (mean±SD). Dynamics of heart rate variability (HRV) power spectrum in high-frequency and low-frequency ranges (in ms2 and percents of total spectral power), mean heart rate (HR), and index S of synchronization between 0.1-Hz rhythms in PPG and HR were analyzed.
  
  
  RESULTS
  Individual dynamics of all studied cardiovascular autonomic indices during the two-hour immobilization test was unique in each healthy subject. Two groups of healthy subjects were identified basing on individual features of autonomic control. The group with initial low level of index S maintained the low level of S during the two-hour immobilization test. The group with initial high index S maintained the high level of S only during the first 100 minutes of test. During the last 20 minutes of test, index S was similar in both groups. Many cardiovascular autonomic indices correlate between themselves for an individual subject, but they do not correlate between the subjects. Multiple regression analysis in each subject has shown a high correlation between mean HR and all other studied autonomic parameters in 57% of subjects (multiple R>0.9, P<0.05). For 204 records analyzed without taking into account the individual features of subjects, the above mentioned correlation was smaller (multiple R=0.45, P<0.001). Index S was found out to be the most independent one among the autonomic indices.
  
  
  CONCLUSIONS
  Cardiovascular autonomic control is characterized by a pronounced variability among healthy subjects and stability in time in each subject. We have not found any regularity in variation of cardiovascular autonomic indices, which is common for the entire group of healthy subjects during the two-hour immobilization test. Mean HR is a summary index of efficiency of heart autonomic control. Index S is the most independent cardiovascular autonomic parameter.
authors.affiliation: Centre of New Cardiological Informational Technologies, Research Institute of Cardiology, Saratov State Medical University, Saratov, Russia; Department of Surgical Treatment for Interactive Pathology, Bakulev Scientific Center for Cardiovascular Surgery, Moscow, Russia; Department of Nano- and Biomedical Technologies, Saratov State University, Saratov, Russia.
authors.forename: A R
authors.initials: AR
authors.lastname: Kiselev
authors.affiliation: Department of Surgical Treatment for Interactive Pathology, Bakulev Scientific Center for Cardiovascular Surgery, Moscow, Russia.
authors.forename: V A
authors.initials: VA
authors.lastname: Shvartz
authors.affiliation: Department of Nano- and Biomedical Technologies, Saratov State University, Saratov, Russia.
authors.forename: A S
authors.initials: AS
authors.lastname: Karavaev
authors.affiliation: 2 Department of Cardiology, Central Clinical Military Hospital, Moscow, Russia.
authors.forename: S A
authors.initials: SA
authors.lastname: Mironov
authors.affiliation: Saratov Branch of the Institute of Radio Engineering and Electronics, Saratov, Russia.
authors.forename: V I
authors.initials: VI
authors.lastname: Ponomarenko
authors.affiliation: Centre of New Cardiological Informational Technologies, Research Institute of Cardiology, Saratov State Medical University, Saratov, Russia; Department of Nano- and Biomedical Technologies, Saratov State University, Saratov, Russia.
authors.forename: V I
authors.initials: VI
authors.lastname: Gridnev
authors.affiliation: Saratov Branch of the Institute of Radio Engineering and Electronics, Saratov, Russia.
authors.forename: M D
authors.initials: MD
authors.lastname: Prokhorov
keywords: 0.1-Hz oscillations; autonomic control; cardiovascular system; healthy subjects; heart rate variability; immobilization test; photoplethysmogram; synchronization