Heart Rate Variability

in the Evaluation of Functional Status

Giedrius Varoneckas

Institute Psychophysiology and RehabilitationVyduno Str. 4, Palanga, Lithuania

e-mail: giedvar@ktl.mii.lt

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

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

subject’s functional status

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)

Methods

• 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

Power spectrum of RR interval sequence

(Fast Fourier analysis or autoregression analysis)

• HR variability at rest in stationary situation

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.

HR analysis using power spectrum

Heart rate analysis during active orthostatic test

RRRRBB, s = RR, s - RR, s = RR, s - RRBB, s, s

Maximal HR response to active orthostatic test (AOT)Maximal HR response to active orthostatic test (AOT)

Supine Standing-up Up-right

RR, ms

RR

RRB

RRB

%100,

,,%

sRR

sRRRR B

B

HR response to standard physical load

Heart rate analysis using Poincare plot

RR r

RRmin RRmax

RRrt

 P, square of the plot, representing

overall HR variability

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

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

Patterns of time and frequency domain HR characteristics

Rhythmogram patterns during quiet supine

Well-trained sportsman

Trainedsportsman

Sportsman

Non-trained healthy subject

HR and respiration patterns according prevalence of vagal control

maximal influence

high input

normal vagal control

Range of the HRV patterns of healthy Ss and the differences of

HR responses to deep breathing

enables to suspect

different HR responses to AOT, exercise, other activities,

involving changes of interplay between of P/S control

Rhythmogram patterns during quiet supine

Well-trained sportsman

Trainedsportsman

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

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

Patterns of HR responses to active orthostatic test

Well-trained sportsman

Trained sportsman

Sportsman

Non-trained healthy subject

Patterns of HR responses to standard physical load

Well-trained sportsman

Trained sportsman

Sportsman

Non-trained healthy subject

Correlation of HR and respiratory arrhythmia to maximal oxygen consumption in well-trained sportsmen

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

HR parameters at morning-time, day-time just after training, and evening-time in sportsmen with prevailing aerobic or anaerobic processes

0

0.5

1

1.5

0

0.02

0.04

0.06

0

0.2

0.4

0.6RR, s

RR, s

RRB, s

0

0.05

0.1

0.15

0.2RA, s

Morning Day (after Eveningtraining)

Morning Day (after Eveningtraining)

HR patterns during AOT of the same sportsman at excellent state and overtraining

t, s

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

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

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

RR interval, HR variability, and respiratory arrhythmia as functions of sleep stages in trained sportsmen and non-trained healthy subjects

0,04

0,08

0,12

Non-trained healthysubjects

Trained sportsmen

0.75

0.95

1.15

1.35

0,04

0,08

0,12RR, s RA, s

W 1 2 3 4 REM W 1 2 3 4 REM W 1 2 3 4 REM

RR, s

Poincare plots and power spectra of all-night HR recording

Sportsman Healthy subject CAD patient

Absolute (ms2) & relative characteristics (%) of power spectra of all-night HR recording

0

1000

2000

3000

4000

5000

6000

ULFC VLFC LFC HFC

S(f), ms2

0

10

20

30

40

50

ULFC VLFC LFC HFC

S(f),%

Sportsmen

Normals

CAD pts

50

70

90

110

3

5

7

Heart rate, stroke volume, and cardiac output as a functions of sleep stages

1

1

1RR, s SV, ml CO, l/min

90

100

110

120

70

90

110

130

70

90

110

130

W 1 2 3 4 REM

RR, % SV, % CO, %

W 1 2 3 4 REM W 1 2 3 4 REM

Healthy Ss CAD Pts

An example of HR power spectra during individual sleep stages in a healthy Ss

Sveikieji

0

25

50

75

100

Tipinës

0

25

50

75

100

Redukuotosios

0

25

50

75

100

B LM1 LM2 LM3 LM4 GM

NLLDK, % NLDK, % NADK, %

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, %

The restorative function of sleep towards the cardiovascular system in trained sportsmen and non-trained healthy Ss

RR, ms

0,8

0,9

1

1,1

1,2

1,3

W 1 2 3 4

SV ml

40

80

120

W 1 2 3 4

CO, l/min

3

4

5

6

7

W 1 2 3 4

RR, ms

0,8

0,9

1

1,1

1,2

W 1 2 3 4Sleep cycles

I II III IV REMSleep stages:

SV, ml

30

70

110

W 1 2 3 4

Sleep cycles

CO, l/min.

2

3

4

5

6

7

W 1 2 3 4

Sleep cycles

RRB

20

30

40

50

RRB

20

30

40

50

Day Evening Morning

TPR

800

1200

1600

2000

2400

TPR

800

1400

2000

2600

Tra

ined

sp

ort

smen

Hea

lth

y S

s

The restorative function of sleep towards the cardiovascular system in healthy SS and CAD pts

RR, ms

0,8

0,9

1

1,1

1,2

1,3

W 1 2 3 4

SV, ml

40

80

120

W 1 2 3 4

CO, l/min

3

4

5

6

7

W 1 2 3 4

RR, ms

0,8

0,9

1

1,1

1,2

W 1 2 3 4Sleep cycles

I II III IV REMSleep stages:

SV, ml

40

80

120

W 1 2 3 4

Sleep cycles

CO, l/min.

3

5

7

W 1 2 3 4

Sleep cycles

RRB

20

30

40

50

RRB

20

30

40

50

Day-time Evening Morning

TPR

800

1200

1600

2000

TPR

800

1400

2000

2600

3200

CA

D p

tsH

ealt

hy

Ss

HR variability during different testing conditions in healthy subject and CAD pts

Sleep AOT evening-time AOT morning-time AOT day-time + Exercise test

 

CA

D p

tsH

ealt

hy

sub

jec

ts

HR variability in well-trained sportsman and non-trained subject

Sleep AOT evening-time

AOT morning-time

well-trained sportsman

non-trained subject

HR variability in CAD patient with and without HR restoration

with HR

restoration

inability to restore

Sleep AOT evening-time

AOT morning-time

Total sleep time

0

100

200

300

400

TST0

100

200

300

400

TST

min min

Healthy Subjects Pts with HR restoration

CAD Patients Pts showing Inability to restore

*

0

50

100

150

200

WASO Stage 1 Stage 2 Stage 3 Stage 4 REM

min

*

*

Restoration of HR control Inability to restore HR

*

Sleep structure in CAD patients with

* p<.05

Sleep structure in subjects distributed according to the HR reflex control changes during sleep

1 group 2 group 3 group

TST, min 326.1 319.5 310.5*1

Sleep Efficiency, % 87.8 85.9*1 84.1*1

REM latency, min 95.2 94.5 90.1

WASO, % 12.2 14.1*1 15.9*1

BM, % 2.6 2.7 2.9

Stage 1, % 8.8 9.7 10.6*1

Stage 2, % 52.1 53.3 53.5

Stages 3, % 8.6 6.8*1 5.6*1,2

Stages 4, % 2.6 1.2*1,2 .94*1

REM Sleep, % 13.1 12.2 10.6*1,2

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

Conclusions

• Autonomic HR control measured by means of HR variability at baseline level is dependent on the subject’s 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