Table 2 Heart rate variability indices in patients referred to spine surgery and controls during 5 minutes of supine and standing conditions

HR, bpm

69 ± 13

65 ± 10

3 (0 – 6 )

0.051

85 ± 14

78 ± 13

7 (3 – 10)

<0.0001

SDNN, ms

45 ± 28

48 ± 24

2 (−5 – 9)

0.598

51 ± 22

61 ± 27

−6 (−12 – 0)

0.065

HF power, ln ms²

5.6 ± 1.4

6.0 ± 1.3

−0.2 (−0.5 – 0.2)

0.356

4.5 ± 1.2

5.1 ± 1.2

−0.4 (−0.7 – -0.1)

0.011

LF power, ln ms²

6.0 ± 1.1

6.1 ± 1.0

−0.1 (−0.4 – 0.2)

0.404

6.3 ± 1.1

6.6 ± 0.9

−0.2 (−0.5 – 0.1)

0.074

LF-to-HF ratio

2.0 ± 1.7

1.9 ± 2.3

−0.3 (−0.8 – 0.2)

0.205

7.9 ± 6.4

5.8 ± 5.2

1.0 (−0.4 – 2.5)

0.159

SD1, ms

23 ± 15

28 ± 21

−2 (−6 – 3)

0.443

13 ± 7

18 ± 12

−4 (−6 – -1)

0.002

α₁

1.09 ± 0.23

1.01 ± 0.29

0.03 (−0.03 – 0.10)

0.304

1.58 ± 0.22

1.49 ± 0.24

0.73 (0.02 – 0.13)

0.012