Heart Rate Variability in the Evaluation of Functional Status

1
Heart Rate Variability in the Evaluation of
Functional Status

• Giedrius Varoneckas
• Institute Psychophysiology and RehabilitationVydu
  no Str. 4, Palanga, Lithuaniae-mail
  giedvar_at_ktl.mii.lt

2
Background

• Autonomic heart rate (HR) control, measured by
  means of HR variability, might be seen as
  characteristic of cardiovascular function,
  responsible for energetic supply of any
  activities, physical, mental, or emotional
• There is generally agreed, that all activities
  followed by increased sympathetic influence
  involves an increase of HR frequency and a
  decrease of HR variability (HRV)
• Such model is appropriate for the main
  population, although not for all an exception
  might be well-trained sportsmen with high quality
  achievements

3
Hypothesis

• HR frequency and HRV might be used for evaluation
  of quality of work of operators mental or
  physical work loads
• HR frequency and HRV responses are not uniform
  for all subjects
• The level of HR and HRV responses and direction
  of HRV changes are dependent on their baseline
  level related to the subjects functional status

4
Autonomic HR control goes through three main
mechanisms

• balance between of sympathetic-parasympathetic
  branches of autonomic nervous system (HR
  frequency and oscillatory structure)
• tonic control (HR variability)
• reflex control (mainly baroreflex)

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Methods

• HR variability at rest in stationary situation

Power spectrum of RR interval sequence (Fast
Fourier analysis or autoregression analysis)

• HR response - to active orthostatic test (AOT)
  - to exercise (bicycle ergometry - BE)
• HR analysis using Poincare plot of RR intervals,
  collected during complex of tests (sleep,
  wakefulness, AOT, and BE), as a measure of
  overall ability to adapt to environmental
  changes internal or external

6
HR analysis using power spectrum
Three main frequency components were measured
very low frequency component (VLFC),
low frequency component (LFC), high frequency
component (HFC) in absolute (ms) and relative
(percent) values for evaluation of autonomic
humoral,sympathetic-parasympathetic and
parasympathetic control, correspondingly.
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Heart rate analysis during active orthostatic
test
RR, ms
RR
?RRB
RRB
Supine Standing-up
Up-right
?RRB, s RR, s - RRB, s Maximal HR response to
active orthostatic test (AOT)
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HR response to standard physical load
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Heart rate analysis using Poincare plot
?RRr, difference on plot diagonal between
minimal (RRmin) and maximal (RRmax) RR
values ?RRt, maximal HR variability, or tonic
control level, as maximal width-difference
between of two points at parallel tangential
lines determining plot RRmin, maximal HR
frequency RRmax, HR frequency at its minimal level
?RRrt
?RRr
RRmin
RRmax
 P, square of the plot, representing overall HR
variability
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Baseline level of autonomic control at rest (in
supine) makes possible to evaluate

• balance between of P/S activation
• tonic control level, depending of P/S
  interaction
• reflex control level might be drawn from HR
  maximal response to AOT

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Patterns of time and frequency domain HR
characteristics
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Rhythmogram patterns during quiet supine

• Well-trained
• sportsman
• Trained
• sportsman
• Sportsman
• Non-trained
• healthy subject

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HR and respiration patterns according
prevalence of vagal control
maximal influence high input normal vagal
control
14
Range of the HRV patterns of healthy Ss and the
differences ofHR responses to deep
breathingenables to suspect different HR
responses to AOT, exercise, other activities,
involving changes of interplay between of P/S
control
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Rhythmogram patterns during quiet supine

• Well-trained
• sportsman
• Trained
• sportsman
• Sportsman
• Non-trained
• healthy subject

• strongly reduced HRV pattern - V ??? S ?0
• slightly increased HFC V ?? S ?inspiration
• maximal domination of HFC with dispersed
  periodicity - V ?? S ?
• lowering again HRV with dominating HFC
• of
  strong periodicity V ? S ??

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Patterns of HR periodical structure in healthy
subject

• strongly reduced HRV pattern - V ??? S ?0
• slightly increased HFC V ?? S ? inspiration
• maximal domination of HFC with dispersed
  periodicity - V ?? S ?
• lowering again HRV with dominating HFC
• of
  strong periodicity V ? S ??

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Patterns of HR responses to active orthostatic
test

• Well-trained sportsman
• Trained sportsman
• Sportsman
• Non-trained healthy subject

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Patterns of HR responses to standard physical load

• Well-trained sportsman
• Trained sportsman
• Sportsman
• Non-trained healthy subject

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Correlation of HR and respiratory arrhythmia to
maximal oxygen consumption in well-trained
sportsmen
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Oxygen consumption and HR parameters in relation
to HR variability and fitness level
Vo2, maximal oxygen consumption RR1, RR
interval in supine RR2, RR interval during
standing RRB, maximal HR response to AOT
RRW1, HR during 1st load of PWC170 test RRW2,
HR during 2nd load of PWC170 test
21
HR parameters at morning-time, day-time just
after training, and evening-time in sportsmen
with prevailing aerobic or anaerobic processes
22
HR patterns during AOT of the same sportsman at
excellent state and overtraining
t, s
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Concluding the presented results

• HRV might be very useful for evaluation of
  physical training process, however
• the range and a direction of HR and its
  variability are dependent on functional status
  (e.g. fitness) of particular person and could be
  evaluated in relation to its baseline level

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Sleep, being non-uniform state, due to shifts of
sleep stages, followed by the changes in
autonomic HR control, might be seen as a specific
testing condition of the latter without an use of
work load
Non-REM sleep is characterized by an increase of
parasympathetic control and a slight decrease of
sympathetic one, while REM sleep is followed by
withdrawal of parasympathetic and an increase of
sympathetic one
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Looking from the point of presented
classification of HR variability pattern at
wakefulness might be expected similar dependence
of a responses to shifts of sleep stages on
initial HR frequency and HR variability before
sleep
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RR interval, HR variability, and respiratory
arrhythmia as functions of sleep stages in
trained sportsmen and non-trained healthy
subjects
RR, s
RA, s
?RR, s
W 1 2 3 4 REM
W 1 2 3 4 REM
W 1 2 3 4 REM
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Poincare plots and power spectra of all-night HR
recording
Sportsman
Healthy subject
CAD patient
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Absolute (ms2) relative characteristics () of
power spectra of all-night HR recording
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Heart rate, stroke volume, and cardiac output as
a functions of sleep stages
RR, s
SV, ml
CO, l/min
RR,
SV,
CO,
W 1 2 3 4 REM
W 1 2 3 4 REM
W 1 2 3 4 REM
Healthy Ss
CAD Pts
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An example of HR power spectra during individual
sleep stages in a healthy Ss
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Changes of HR power spectrum components impact
during shifts of sleep stages
Healthy Ss
CAD pts - typical
CAD pts - reduced
W Stage 1
Stage 2 Stage 3 Stage 4
REM
VLFC,
LFC,
HFC,
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The restorative function of sleep towards the
cardiovascular system in trained sportsmen and
non-trained healthy Ss
Trained sportsmen
Healthy Ss
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The restorative function of sleep towards the
cardiovascular system in healthy SS and CAD pts
Healthy Ss
CAD pts
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HR variability during different testing
conditions in healthy subject and CAD pts
 
Healthy subjects
CAD pts
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HR variability in well-trained sportsman and
non-trained subject
well-trained sportsman non-trained subject
Sleep AOT evening-time AOT morning-time
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HR variability in CAD patient with and without
HR restoration
with HR restoration inability to restore
Sleep AOT evening-time AOT morning-time
37
Total sleep time
Healthy Subjects Pts with HR
restoration CAD
Patients Pts showing Inability to
restore
min
min

38

Sleep structure in CAD patients with
Restoration of HR control Inability
to restore HR
min
plt.05



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Sleep structure in subjects distributed
according to the HR reflex control changes
during sleep
1 group 2 group 3 group
TST, min 326.1 319.5 310.51
Sleep Efficiency, 87.8 85.91 84.11
REM latency, min 95.2 94.5 90.1
WASO, 12.2 14.11 15.91
BM, 2.6 2.7 2.9
Stage 1, 8.8 9.7 10.61
Stage 2, 52.1 53.3 53.5
Stages 3, 8.6 6.81 5.61,2
Stages 4, 2.6 1.21,2 .941
REM Sleep, 13.1 12.2 10.61,2
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Concluding the last session
restoration of both P and S control of HR, as
well as hemodynamics was dependent on a level of
autonomic HR control, e.g. on the subjects
functional status at baseline level
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Conclusions

• Autonomic HR control measured by means of HR
  variability at baseline level is dependent on the
  subjects functional status
• The responses of functional testing (physical,
  mental, or sleep) depends on the baseline level
  of autonomic control, i.e. HR variability pattern
• Both of them, baseline autonomic control and its
  modifications during individual testing
  conditions might, be used for training or work
  (physical or mental) process control
• This is true for responses to physical work load,
  reflex testing, or shifts of sleep stages, as
  well as to ability to recover cardiovascular
  system during sleep