Evaluation of heart rate variability in pediatric patients with beta thalassemia major: Cross-sectional study

Table 2 Comparison between the two studied groups regarding heart rate and heart rate variability parameters, mean ± SD/median (25^th-75^th percentiles)

Parameter	β-thalassemia (n = 40)	Controls (n = 40)	P value
Minimum HR (bpm)	63.35 ± 13.06	58.50 ± 4.44	0.031
Maximum HR (bpm)	161.4 ± 16.98	147.5 ± 5.31	< 0.001
Average HR (bpm)	100.6 ± 13.03	103.3 ± 3.49	0.216
SDNN (ms)	79.18 ± 32.08	137.2 ± 17.53	< 0.001
SDANN5 (ms)	74.43 ± 23.75	122.5 ± 19.89	< 0.001
SDNN index (ms)	41.70 ± 14.85	101.0 ± 20.14	< 0.001
RMSSD (ms)	28.43 ± 13.81	54.13 ± 14.80	< 0.001
pNN50 (%)	8.93 ± 8.12	32.65 ± 11.48	< 0.001
HF power (ms2)	323.4 (239.9-404.1)	537.0 (269.3-872.3)	0.002
LF power (ms2)	670.8 (537.3-814.2)	614.0 (335.0-733.1)	0.125
VLF power (ms2)	1283.3 (1005.2-1441.2)	1240.0 (864.4-2050.5)	1.000
LF/HF ratio	2.11 (1.64-2.68)	1.16 (0.89-1.50)	< 0.001

No significant sex-based or age-dependent differences were observed in heart rate variability parameters among the patient group, suggesting that autonomic dysfunction in β-thalassemia may not be influenced by these demographic factors. HR: Heart rate; SDNN: Standard deviation of all normal-to-normal intervals; SDANN: Standard deviation of the 5-minute average normal-to-normal intervals; RMSSD: Root mean square of successive differences; pNN50: Percentage of successive normal-to-normal intervals differing by > 50 ms; LF: Low frequency; HF: High frequency; VLF: Very low frequency.