Altered heart rate variability and pulse-wave velocity after spinal cord injury

Table 3 Comparison of heart rate variability parameters between patients with and without spinal cord injury

	SCI (n = 60)	Non-SCI (n = 60)	P value
Continuous variables
HRT	79.93 ± 13.19	77.03 ± 9.90	0.18b
SDNN	27.11 ± 18.45	34.30 ± 11.18	< 0.001a,c
RMSSD	21.54 ± 17.65	25.19 ± 9.51	< 0.001a,c
PSI	125.42 ± 126.02	58.68 ± 63.64	< 0.001a,c
TP	813.78 ± 2211.10	989.19 ± 671.65	< 0.001a,c
LF/HF ratio	1.80 ± 2.52	1.98 ± 2.68	0.20c
VLF	519.54 ± 1903.98	443.89 ± 372.20	0.001a,c
LF	179.09 ± 319.20	299.85 ± 292.49	< 0.001a,c
HF	115.16 ± 133.82	245.45 ± 276.53	< 0.001a,c
LF norm	51.33 ± 20.21	55.78 ± 18.33	0.21a
HF norm	48.67 ± 20.21	44.22 ± 18.33	0.21a
Categorical variables
HRT
Low (≤ 60)	1 (1.7%)	2 (3.3%)	0.51d
Normal (60–90)	45 (75.0%)	49 (81.7%)
High (> 90)	14 (23.3%)	9 (15.0%)
SDNN
Low (≤ 30)	45 (75.0%)	20 (33.3%)	< 0.001a,d
Normal (> 30)	15 (25.0%)	40 (66.7%)
RMSSD
Low (≤ 20)	41 (68.3%)	21 (35.0%)	< 0.001a,d
Normal (> 20)	19 (31.7%)	39 (65.0%)
PSI
Normal (≤ 50)	18 (30.0%)	39 (65.0%)	< 0.001a,d
High (> 50)	42 (70.0%)	21 (35.0%)
TP
Low (≤ 1000)	52 (86.7%)	32 (53.3%)	< 0.001a,d
Normal (> 1000)	8 (13.3%)	28 (46.7%)
LF/HF ratio
Low (≤ 0.5)	15 (25.0%)	9 (15.0%)	0.42d
Normal (0.5-2.0)	30 (50.0%)	33 (55.0%)
High (> 2.0)	15 (25.0%)	18 (30.0%)

HRT: Heart rate over a given period of time; SDNN: Standard deviation of all normal-to-normal intervals; RMSSD: Square root of the mean of the sum of the squares of differences between adjacent normal-to-normal intervals; PSI: Physical stress index; TP: Total power; LF/HF: The ratio or low frequency to high frequency; VLF: Very low frequency; LF: Low frequency; HF: High frequency.

^aStatistically significant (P < 0.05).

^bT-test.

^cMann–Whitney U test.

^dFisher’s exact test.