study on heart rate variability signals in healthy children and in patients with congenital heart disease

ABSTRACT

During the last decade the interest in the field of pediatric electrophysiology was progressing and attention towards pediatric arrhythmic mortality became of extreme concern. Analyses of heart rate variability [HRV] signals are one of the sensitive tools to study the autonomic control of the heart uming to solve the arrhythmic morbidity and mortality in the pediatric age group. Few studies had reported the normal values of HRV parameters in infants and children. As autonomic disturbances and arrhythmia are common features in patients with congenital heart disease, we tried to establish ranges for HRV parameters in normal individuals and in patients with congenital cardiac defects. One hundred and fifty infants and children were the study population. 50 patients had a cyanotic congenital heart diseases; 29 males and 21 females, with a mean age + SD of 88.75 +/- 139.8 months and 50 patients had cyanotic congenital, heart disease; 18 males and 32 females, with a mean age of 5.62 +/- 3.05 months. 50 subjects with no evidence of structural heart disease were included as controls; 24 males and 26 females, with a mean age of 6.33 +/- 3.65 months. For age matching between the study groups and controls, 50 normal subjects were compared with a cyanotics while only 36 of them were compared with cyanotics patients, The normal limits [mean +/- SD] of frequency domain HRV parameters for all the 50 controls were LF ms[2] [388.7-509.5], LF-n.u [36.8-62.08], HF ms[2] [489.1-709.6] HF-n.u. [44.3-74.3] and LF/HF ratio [0.5-0.9]. The normal limits of HRV parameters for the 36 controls age-matched to the cyanotic group were LF ms[2] [386.5-514.1], LF-n.-u [39.5-61.9], HF ms[2] [515.0-693.4], HF-n.u [50.1-70.9], and LF/HF ratio [0.54-0.86]. There was a significant negative correlation between age and both LF n.u and HF n.u. with insignificant effect on LF/HF ratio. However, there were no gender variations in the studied HRV parameters of the control groups. We observed a significantly lower HF-n.u and higher LF ms[2], LF-n.u, HF ms[2] and LF/HF ratio in both acyanotics and cyanotics when compared to controls. We also noticed that high frequency bands HF m[2] and HF-n.u. were abnormally high in a large number of acyanotics and the LF/HF ratio was relatively higher in cyanotics, although the differences were statistically insignificant. The final results provided a basis for heart rate variability signals in children. Normal ranges for the various parameters were determined. Cyanotics express more sympathetic predominance than a cyanotics which might render them more susceptible to arrhythmias