Вариабельность сердечного ритма у детей 7 лет

Volume 8 Issue 6 2023

77

HEART RATE VARIABILITY IN 7 YEARS OLD CHILDREN

Akhmedova D.I.

1

, Popenkov A.V.

2

Republican Specialized Scientific and Practical Medical Center for Pediatrics of the

Ministry of Health of the Republic of Uzbekistan

1

,

Tashkent Pediatric Medical Institute

2

Abstract:

The article presents data on heart rate variability (HRV) in 7 years

old children. There are presented information of temporal, geometric, spectral

analysis of HRV as well as data of variation pulse oximetry. There is given a

comparative assessment of indicators depending on the gender and div mass index

of children. An analysis of the results of the study showed a strong direct and inverse

relationship between some of the indicators of HRV, as well as a difference in the

indicators of HRV in 7 years old children, depending on gender and div mass index.

Keywords:

7-year-old children, physical development, heart rate variability.

Heart rate variability (HRV) is the simplest and informative method of

assessing the status of the vegetative nervous system [5]. Also, HRV indicates the

adaptive capacity of the div and helps to identify the risk of unexpected death [1].

Most often, HRV is used in cardiology practice in determination of the adequacy of

therapy [4]. HRV is based on the determination of cardio intervals in the second

standard lead of electrocardiography. [2,3]. HRV assesses the physiological functions

of the div through the ratio of the activity of the different part of vegetative nervous

system [1], and allows to evaluate the functional capabilities of the div and carry

out preventive measures aimed at maintaining the health of the child [6]. For greater

reliability, the minimum recording should be at least 5 minutes. Also, orthostatic test,

Valsalva test are used for evaluation. To carry out these tests, it is necessary to adhere

to the stationarity condition. Studies should be conducted under the same conditions

and the length of the first and second records should be the same. Statistical data

processing methods are used to analyze heart rate variability. Statistical methods

based on the time difference between R-R intervals. These methods include HR

(heart rate), RRNN, mean RR interval duration, which evaluates the balance in the

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vegetative nervous system; SDNN is the square root of the cardio interval`s spread,

RMSSD and pNN50% are indicators that assess the state of the parasympathetic link

of the autonomic nervous system. Geometric methods are the least influenced by

artifacts, these include the triangular index and the St. George index, TINN reflect the

total HRV. In spectral analysis, the power is estimated depending on the oscillation

frequency. The frequency spectrum is usually divided into: high-frequency (0.2-0.4

Hz), low-frequency (0.04-0.15 Hz) and very low-frequency (0.003-0.04 Hz). Power

is measured in ms

2

. Measure the power contribution of the spectrum depending on

the frequency range. HF - high-frequency spectrum showing the activity of the

parasympathetic system, LF – indicates the activity of the sympathetic system, VLF –

reveals the activity of the suprasegmentally centers of the autonomic nervous system

[3].

Purpose of the study.

Determine the heart rate variability in 7 years old

children.

Materials and research methods.

The study involved 120 children. All

children underwent anthropometric measurements. There were selected only children

without acute and chronic diseases. The children were divided into 3 groups

depending on the div mass index. The first group consisted of 66 children with

BAZ (bmi for age) scores from -2 to +1 SDS; the second group included 29 children,

with a BAZ range of +1 to +2 SDS. The third group consisted of 25 children with

BAZ > +2 SDS. All children underwent ECG examination, cardiointervalography

with orthostatic test. The following indicators were used for analyses of HRV:

rrHRV, IQR, RRNN, HR, SDNN, RMSSD, pNN50%, TRI, ApEn, SD1, SD2,

SD1/SD2, VLF, LF, HF, IC, CV, Mo (the most common interval RR), SI (stress

index), RMI (respiratory modulation index), SAI (sympathoadrenal index), SWAI

(slow wave arrhythmia index), VPR (vegetative parasympathetic range), ARPI

(indicator of the adequacy of regulatory processes), VBI (vegetative balance index).

The statistical significance of the obtained measurements was determined by

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Student's t-test (t) with the calculation of the error probability (P). Significance level

p<0.05 was taken as statistically significant changes.

Results and discussions.

According to the results of the survey, correlations between

the indicators were revealed. An indicator >0.7 was taken as a strong correlation. A

strong direct correlation was found between: rrHRV - SDNN - RMSSD - pNN50% -

TRI - SD1/SD2 - CV - RMI. A strong inverse correlation was found between the

indicators: rrHRV and AMo (% of most common intervals RR), SI, SAI, SWAI,

ARPI, VPR. HR has a high inverse correlation with pNN50%, RMSSD, SDNN and a

high direct correlation with AMo, SI, SWI, ARPI. SI (stress index) and APRI (an

indicator of the activity of regulatory processes) have a strong inverse correlation

with rrHRV, SDNN, RMSSD, pNN50%, TRI. Correlation relationship between

statistical, spectral and geometric indicators with indicators of variation pulse

oximetry demonstrated in the table 1.

Table 1

Correlation relationship between statistical, spectral and geometric indicators

with indicators of variation pulse oximetry.

Indicators Mo

AMo SI

RMI SAI

SWAI ARPI VBI

rrHRV

0.50

-0.78 -0.75 0.71

-0.82 -0.65

-0.78

-0.74

RRNN

0.89

-0.59 -0.64 0.65

-0.63 -0.65

-0.73

-0.57

HR

-0.91 0.58

0.69

-0.61 0.65

0.64

0.75

0.61

SDNN

0.48

-0.73 -0.69 0.96

-0.77 -0.56

-0.7

-0.73

RMSSD

0.52

-0.68 -0.64 0.98

-0.75 -0.73

-0.67

pNN50

0.61

-0.75 -0.69 0.90

-0.81 -0.79

-0.75

-0.70

TRI

0.48

-0.89 -0.67 0.78

-0.76 -0.50

-0.84

-0.71

SD1

0.52

-0.68 -0.64 0.98

-0.75 -0.73

-0.67

SD2

0.43

-0.72 -0.71 0.90

-0.77 -0.42

-0.69

-0.75

SD1/SD2

0.53

-0.38 -0.42 0.73

-0.57 -0.99

-0.43

-0.4

LF%

-0.31 0.29

0.40

-0.58 0.52

0.70

0.32

0.41

HF%

0.31

-0.29 -0.40 0.58

-0.52 -0.70

-0.32

-0.41

LF/HF

-0.31 0.24

0.32

-0.47 0.44

0.63

0.29

0.32

VLF

-0.37 0.21

0.26

-0.54 0.35

0.64

0.26

LF

-0.17 0.18

0.24

-0.36 0.33

0.44

0.20

0.23

HF

0.25

-0.17 -0.23 0.40

-0.31 -0.36

-0.23

-0.24

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80

According to the indicators of anthropometric measurements, it was revealed

that the average height of boys is 131±7.4 сm., which corresponds to the 68th

percentile, and for girls - 128.34±6.4 cm (p<0.05), which corresponds to the 49th

percentile. The average weight of boys is 30.7±7.9 kg, and girls -29.10±6.5 kg

(p>0.05). The rrHRV indicator in boys was 7.66±2.7 c.u., and in girls it was 8.85±3.4

c.u. (p<0.05). The average heart rate in girls was slightly higher (89.13±12.1 bpm.)

than in boys (88.8±10 bpm), p>0.05. SDNN - an indicator reflecting the reserve

capacity of the div, was higher in girls (65.81±5.48 msec.) compared to boys

(54.88±3.51 msec.), p<0.05. Significant differences were also observed in RMSSD:

boys - 60.42±4.10 msec., girls - 76.61±7.48 msec. (p<0.05) and pNN50%: boys -

22.74±2.0%, girls - 29.24±3.56% (p<0.05). According to the indicators of the non-

linear evaluation method, a significant difference in the indicators was also

determined: TRI, ApEn, SD1, SD2. According to the spectral analysis data, the

power of the LF spectrum prevailed in boys, while the power of the HF spectrum

prevailed in girls (p<0.05).

Table 2

Anthropometric parameters and indicators of HRV in 7 years old children.

Index

Boys

Girls

Height, cm

131.13±0.82

128.34±1.02

Weight, kg

30.70±0.88

29.10±1.02

rrHRV* c.u.

7.66±0.31

8.85±0.55

IQR c.u.

6.56±0.27

7.14±0.36

RRNN, msec.

682.86±8.45

685.92±15.52

HR, bpm

88.80±1.10

89.13±1.91

SDNN, msec *

54.88±2.63

65.81±5.09

RMSSD, msec *

60.42±4.10

76.61±7.48

pNN50, % *

22.74±2.0

29.24±3.56

TRI c.u.*

2.97±0.11

3.37±0.21

ApEn c.u.*

0.83±0.01

0.78±0.02

SD1*

42.73±2.90

54.18±5.29

SD2*

63.64±2.057

74.28±5.19

SD1/SD2

0.65±0.02

0.69±0.03

LF, %

43.28±1.74

41.16±2.59

HF, %

56.72±1.74

58.84±2.59

LF/HF

0.94±0.08

0.85±0.11

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81

TP, ms2

1365.95

1302.23

VLF, ms2

531.71±22.52

476.25±33.53

LF, ms2 *

450.43±13.38

405.88±14.98

HF, ms2 *

383.82±10.89

420.10±18.0

IC

1.90±1.90

2.16±0.18

CV *

7.89±0.30

9.30±0.57

∆×

262.68±11.63

296.00±22.13

Mo, msec

669.76±8.0

664.00±11.71

Amo, msec

36.82±1.21

34.05±1.89

SI, c.u.

137.24±11.61

128.47±16.49

SAI, c.u.

1106.73±73.86

946.83±116.94

SWI, c.u. *

43.64±0.57

42.53±0.88

VPR, c.u.

6.86±0.57

6.61±0.57

ARPI, c.u.

56.35±2.34

53.30±3.61

Note * - p <0.05

According to the results of the temporal analysis of HRV, there were no

significant differences in heart rate in children both at rest and during the orthostatic

test. The lowest total indicator of HRV (SDNN - an indicator of restoration of div

reserves) both at rest and during the orthostatic test was observed in obese boys -

51.05±8.0 msec., and 41.69±5.46 msec., respectively. In girls, there were no

significant differences depending on the div mass index. This indicates a higher

reserve potential of the autonomic nervous system in girls compared to boys. In terms

of pNN50%, the 1st group had the highest rate: boys – 24.49±2.8%; girls - 32.32 ±

4.32%, while the lowest indicator was observed in children of the 3rd group: boys -

20.87 ± 5.2%, girls - 24.97 ± 7.8%, which indicates a high activity of the sympathetic

nervous system in obese children. In orthostatic test, the lowest indicators were

observed in children of the 2nd group: boys - 4.75 ± 1.52%, girls - 4.75 ± 1.11%.

Table 3

HRV indicators in 7 years old children at rest.

Index

1 group
(n=66)

2 group
(n=29)

3 group
(n=25)

Boys
(n=42)

Girls
(n=24)

Boys
(n=18)

Girls
(n=11)

Boys
(n=15)

Girls
(n=10)

HR,
bpm.

87.8±
1.3

88.2±
2.2

89.9±
1.5

89.1±
4.5

90.5±
3.98

90.8±
4.5

RRNN

688.9±

687.98±

670.14±

689.4±

679.62±

679.2±

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82

, msec. 10.3

17.4

11.57

35.11

29.5

38.2

SDNN,
msec.

56.6±
3.5

65.97±5.48 53.45±

3.49

67.74±
10.9

51.05±
8.07

63.78±
13.28

RMSS
D,
msec.

63.27±
5.63

77.29±8.23 55.4±

5.08

78.8±
16.95

57.66±
11.99

73.47±18.5
9

pNN50
, %

24.49±
2.80

32.32±
4.32

19.78±
2.78

28.08±8.
30

20.88±
5.3

24.98±
7.8

CV, % 7.9±

0.42

7.95±
0.48

8.55±
0.61

7.94±
0.89

6.89±
0.68

7.57±3216
0.94

Mo,
msec.

674.17±
9.67

667.37±15.
3

661.05±13.
11

668±
24.62

666.67±
26.95

654.54±
26.57

AMo,
%

35.14±
1.39*

33.89±
2.6

37.37±
1.91

31.5±
4.04

41.47±
4.19*

36.64±
4.02

VBI,
c.u.

173.29±
13.87*

146.48±27.
92

167.88±
19.78

155.03±
42.44

228.26±
48.32*

189.42±
34.03

ARPI,
c.u.

52.85±2.2
9*

52.41±4.87 57.06±

3.23

49.28±
7.63

66.63±
9.43*

58.49±
7.66

VPR,
c.u.

6.66±
0.45

6.07±
0.78

6.60±
0.59

6.57±
1.30

7.81±
1.20

7.58±
1.05

SI, c.u. 123.08±

10.34*

115.95±
24.39

129.11±
15.90

125.42±
37.03

192.81±49.
26*

152.87±28.
20

Note * - p <0.05

As can be seen from Table 3, the highest rates of AMo, VBI, ARPI are

observed in group 3 in children with obesity, and these rates are high in both boys

and girls. SI (an indicator reflecting the influence of the sympathetic department on

the autonomic nervous system): in boys of the 3rd group, with an orthostatic test, it

increases from 192.87 ± 49.2 c.u. up to 205.43±42.68 c.u., and for girls from

152.87±28.2 c.u. up to 208.98±48.3 c.u.

Table 4

HRV indicators in 7 years old children during orthostatic test.

Index

1 group
(n=66)

2 group
(n=29)

3 group
(n=25)

Boys
(n=42)

Girls
(n=24)

Boys
(n=18)

Girls
(n=11)

Boys
(n=15)

Girls
(n=10)

HR, bpm

103.0±
1.3

107.0±
2.6

105.0±
1.7

109.0±
4.65

104.0±
3.79

107.0±
4.66

RRNN, msec

582.87± 566.97± 571.98±

556.96±

584.72±

568.0±

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83

7.63

14.49

9.58

24.80

20.64

27.76

SDNN, msec

46.69±
2.82

45.82±
3.59

49.57±
4.04

44.22±
5.06

41.69±
5.46

44.7±
7.42

RMSSD, msec

32.11±
1.58

35.69±
3.47

32.62±
2.70

38.62±
7.53

31.95±
3.96

34.91±
6.17

pNN50, %

6.33±
1.01

8.08±
2.45

4.57±
1.11

4.75±
1.52

5.86±
2.10

8.54±
4.28

CV, %

7.90±
0.42

7.95±
0.48

8.55±
0.61

7.94±
0.89

6.89±
0.68

7.57±
0.94

Mo, msec

673.33±
14.32

648.42±
15.47

658.95±
14.46

644±
24.18

666.67±
26.67

654.55±
24.88

AMO, %

39.19±
1.18

36.32±
2.71

39.19±
1.18

39.90±
3.43

43.60±
3.24

41.18±
1.75

VBI, c.u.

173.29±
13.87*

168.41±
31.49

209.59±
48.99

165.11±
39.17

250.06±
43.99*

257.17±
55.97

ARPI, c.u.

44.51±
2.05*

46±
4.02

48.15±
2.57

42.90±
6.25

56.73±
7.17*

52.05±
6.61

VPR, c.u.

8.78±
0.63

8.43±
0.96

9.88±
2.11

9.46±
1.72

10.78±
1.60

11.34±
2.03

SI, c.u.

132.82±
11.50*

134.44±
27

166.78±
44.15

132.95±
33.67

205.43±
42.68*

208.98±
48.38

Note * - p <0.01

Conclusions.

According to the results of the study, it can be concluded that

there is a strong correlation between the indicators of heart rate variability, so there is

no need to apply all methods of assessment. There is a high significance of

differences between indicators in boys and girls. According to spectral analysis and

statistical analysis, the parasympathetic division of the nervous system predominates

in girls. However, when assessed according to the indicators proposed by R.M.

Baevsky [7,8], (stress index), hypersympathicotonia is noted in both girls and boys.

Based on this, it can be assumed that children aged 7 years are characterized by a

higher stress index than adolescents and adults. This period is critical for children,

and during the first year of education, children adapt to new environmental

conditions. There is a correlation between the excessive influence of the central and

sympathetic nervous systems on obese children, which is reflected in the indicators of

ARPI and SI during the orthostatic test.

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