Heart rate variability in healthy children and in those with congenital heart disease both before and after operation

There are no reports of standard measures of heart rate variability (HRV) in pediatric patients with heart disease. Time domain (standard deviation of all normal RR intervals [SDNN], standard deviation of all 5- minute mean RR intervals, average standard deviation of all 5-minute RR intervals, and frequency domain (total, low- [LF], and high-frequency [HF] power) measures of HRV were (1) obtained in 45 healthy children, (2) compared between 36 children with congenital heart disease and age-matched controls, (3) compared before and after surgery, and (4) compared between age-matched postoperative patients staying <7 days (group I, n = 16) and those staying longer (group II, n = 16). In healthy children, SDNN increased rapidly during infancy and more gradually thereafter, while the LH/HF ratio decreased until preschool age, with a later increase into adolescence. Compared with controls, preoperative patients had decreased total (53 ± 55 vs 84 ± 75 beats/min²/Hz, p = 0.01) and HF (12 ± 14 vs 29 ± 46 beats/min²/Hz, p = 0.03) power despite having similar heart rates. In the immediate postoperative period, all measures of HRV were decreased from preoperative values. Groups I and II did not differ in mean RR interval or HRV preoperatively; however, postoperatively, HRV was decreased in group II when compared with group I (SDNN 53 ± 17 vs 40 ±14 ms, p = 0.01), although the mean RR interval remained comparable (499 ± 81 vs 481 ± 62 ms, p = 0.3). It is concluded that (1) there are significant age-related changes in HRV in healthy children, (2) preoperatively, children with congenital heart disease have reduced total and HF power when compared with healthy controls, (3) HRV is further reduced postoperatively in all patients, and (4) prolonged postoperative hospitalization is associated with a greater reduction in HRV.