Table 3 Mean differences (MD) in heart rate variability (HRV) between the different severities of neonatal hypoxic ischemic encephalopathy (HIE) by study

Number in the statistical analysis

Time of assessment

TH

HRV measures

Mean, 95% CI (severe)

Mean, 95% CI (mild)

MD, 95% CI

P-values

Goulding et al. 2015, Ireland [21]

Severe, n = 17

Mild, n = 40

12–48 h

No

SDNN (ms)

TINN (ms)

Mean VLF (ms²)

Mean LF (ms²)

Mean HF (ms²)

LF/HF ratio

8.5 (5.1, 14)

24.5 (14.8, 40.6)

27.5 (9.7, 78.2)

13.2 (4.1, 42.8)

4 (2.4, 5.8)

3.7 (2.4, 5.9)

18.6 (15.4, 22.4)

50 (40.6, 61.6)

138.8 (95.3, 202.1)

84.1 (54.4, 130.2)

16.8 (10, 28.2)

5.6 (4.4, 7.2)

−10.1 (− 15.8, − 4.4)

− 25.5 (− 42.2, − 8.8)

− 111.3 (− 175.6, − 47.0)

− 70.9 (− 113.4, − 28.4)

− 12.8 (− 24.1, − 1.6)

− 1.9 (− 4.1, 0.3)

< 0.01

< 0.01

< 0.01

< 0.01

0.03

0.09

Goulding et al.

2017,

Ireland [22]

Severe, n = 60

Mild, n = 110

6–72 h

Yes

SDNN (ms)

TINN (ms)

Mean VLF (ms²)

Mean LF (ms²)

Mean HF (ms²)

LF/HF ratio

10.1 (7.6, 13.4)

26.8 (20.5, 35)

40.1 (21.7, 74.3)

18.1 (9.3, 35.2)

5.8 (3.2, 10.7)

3.3 (2.3, 4.7)

20.4 (17.2, 24.2)

51.9 (43.9, 61.6)

162.1 (112.8, 232.5)

92.1 (61.9, 137)

17.5 (12, 25.4)

5.6 (4.5, 6.9)

−10.3 (− 14.8, − 5.8)

− 25.1 (− 36.6, − 13.6)

− 122.0 (− 187.4, − 56.6)

− 74.0 (− 113.7, − 34.3)

− 11.7 (− 19.4, − 4.0)

− 2.3 (− 4, − 0.6)

< 0.01

< 0.01

< 0.01

< 0.01

< 0.01

< 0.01

Number in the statistical analysis

Time of assessment

TH

HRV measures

Mean, 95% CI (moderate)

Mean, 95% CI

(mild)

MD, 95% CI

P-values

Goulding et al. 2015, Ireland [21]

Moderate, n = 16

Mild, n = 40

12–48 h

No

SDNN (ms)

TINN (ms)

Mean VLF (ms²)

Mean LF (ms²)

Mean HF (ms²)

LF/HF ratio

11.2 (7.8, 16.1)

28 (18.8, 41.6)

57 (28.7, 113)

29.4 (12.6, 68.5)

3.6 (1.3, 7.6)

9.4 (6.3, 13.9)

18.6 (15.4, 22.4)

50 (40.6, 61.6)

138.8 (95.3, 202.1)

84.1 (54.4, 130.2)

16.8 (10, 28.2)

5.6 (4.4, 7.2)

−7.4 (− 12.8, − 2.0)

− 22.0 (− 37.5, − 6.5)

− 81.8 (− 149.8, − 13.8)

− 54.7 (− 101.8, − 7.6)

− 13.2 (− 23.2, − 3.2)

3.7 (− 0.3, 7.9)

< 0.01

< 0.01

0.02

0.03

0.01

0.08

Goulding et al. 2017, Ireland [22]

Moderate, n = 48

Mild, n = 110

6–72 h

Yes

SDNN (ms)

TINN (ms)

Mean VLF (ms²)

Mean LF (ms²)

Mean HF (ms²)

LF/HF ratio

15.1 (11.2, 20.3)

42.5 (31.8, 56.8)

90.9 (48.5, 170.4)

52.8 (9.3, 107.7)

16.8 (8.7, 32.8)

3.5 (2.3, 5.1)

20.4 (17.2, 24.2)

51.9 (43.9, 61.6)

162.1 (112.8, 232.5)

92.1 (61.9, 137)

17.5 (12, 25.4)

5.6 (4.5, 6.9)

−5.3 (− 11, 0.4)

− 9.4 (− 24.7, 5.9)

− 71.2 (− 156.6, 14.2)

− 39.3 (− 101.2, 22.6)

− 0.7 (− 14.5, 13.1)

− 2.1 (− 3.9, − 0.3)

0.08

0.23

0.10

0.21

0.92

0.02

Number in the statistical analysis

Time of assessment

TH

HRV measures

Mean, 95% CI (severe)

Mean, 95% CI

(No HIE)

MD, 95% CI

P-values

Aliefendioglu et al. 2012, Turkey [19]

Severe, n = 10

No HIE, n = 24

End of first postnatal week

No

Mean LF (nu)

Mean HF (nu)

LF/HF ratio

27.8 (19.7, 35.9)

48.9 (44.5, 53.5)

0.6 (0.4, 0.9)

73.1 (70.3, 75.9)

20.3 (18.1, 22.5)

4 (3.3, 4.7)

−45.3 (− 53.8, − 36.8)

28.6 (23.7, 33.5)

− 3.4 (− 4.1, − 2.7)

< 0.01

< 0.01

< 0.01

Goulding et al. 2015, Ireland [21]

Severe, n = 17

No HIE, n = 17

12–48 h

No

SDNN (ms)

TINN (ms)

Mean VLF (ms²)

Mean LF (ms²)

Mean HF (ms²)

LF/HF ratio

8.5 (5.1, 14)

24.5 (14.8, 40.6)

27.5 (9.7, 78.2)

13.2 (4.1, 42.8)

4 (2.4, 5.8)

3.7 (2.4, 5.9)

32.9 (27.9, 38.8)

106.4 (93.5, 119.3)

422.1 (296.8, 598.2)

375.7 (263.5, 535.6)

93.6 (61.7, 142)

4.4 (3.3, 5.9)

−24.4 (−31.5, − 17.4)

− 81.9 (− 100.1, − 63.6)

− 394.6 (− 548.7, − 240.6)

− 362.4 (− 499.9, − 225.0)

− 89.7 (− 130.4, − 49.0)

− 0.7 (− 2.9, 1.5)

< 0.01

< 0.01

< 0.01

< 0.01

< 0.01

0.54

Number in the statistical analysis

Time of assessment

TH

HRV measures

Mean, 95% CI (moderate)

Mean, 95% CI

(No HIE)

MD, 95% CI

P-values

Aliefendioglu et al. 2012, Turkey [19]

Moderate, n = 12

No HIE, n = 24

End of first postnatal week

No

Mean LF (nu)

Mean HF (nu)

LF/HF ratio

57.8 (52.5, 63.1)

30.6 (26.6, 34.6)

1.9 (1.5, 2.4)

73.1 (70.3, 75.9)

20.3 (18.1, 22.5)

4 (3.3, 4.7)

−15.3 (− 21.3, − 9.3)

10.3 (5.8, 14.8)

− 2.1 (− 2.9, − 1.3)

< 0.01

< 0.01

< 0.01

Goulding et al. 2015, Ireland [21]

Moderate, n = 16

No HIE, n = 17

12–48 h

No

SDNN (ms)

TINN (ms)

Mean VLF (ms²)

Mean LF (ms²)

Mean HF (ms²)

LF/HF ratio

11.2 (7.8, 16.1)

28 (18.8, 41.6)

57 (28.7, 113)

29.4 (12.6, 68.5)

3.6 (1.3, 7.6)

9.4 (6.3, 13.9)

32.9 (27.9, 38.8)

106.4 (93.5, 119.3)

422.1 (296.8, 598.2)

375.7 (263.5, 535.6)

93.6 (61.7, 142)

4.4 (3.3, 5.9)

−21.7 (−28.6, − 14.8)

− 78.4 (− 95.6, − 61.2)

− 365.1 (− 521.1, − 209.1)

− 346.3 (− 485.2, − 207.4)

− 90.1 (− 130.4, − 49.7)

4.9 (0.9, 9.0)

< 0.01

< 0.01

< 0.01

< 0.01

< 0.01

0.02

Number in the statistical analysis

Time of assessment

TH

HRV measures

Mean, 95% CI (severe/moderate)

Mean, 95% CI (mild/no HIE)

MD, 95% Cl

P-values

Vergales et al. 2013, USA [20]

Severe/moderate, n = 25

Mild/no HIE, n = 11

Within first 24 h

Yes

SDRR (ms)

17.6 (13.8, 21.4)

26.8 (20.1, 33.5)

−9.2 (− 16.5, − 1.9)

0.02

NDA

1–7 days

Yes

SDRR (ms)

NDA

NDA

NDA

< 0.05 at day 1 and from day 3–7