HEART-RATE-VARIABILITY IN DIABETIC CHILDREN - SENSITIVITY OF THE TIME-DOMAIN AND FREQUENCY-DOMAIN METHODS

Heart rate variability (HRV) is a noninvasive index of the neural acti vity of the heart. Although also influenced by the sympathetic activit y of the heart, HRV is essentially determined by the vagal stimulation of the heart. Several HRV abnormalities have been described in adults with diabetes mellitus. However, there are few data on HRV in childre n with diabetes mellitus. In the present study, HRV was assessed in se ven healthy children, 10 diabetic children with good glycemic control and 11 diabetic children with poor glycemic control. All had normal st andard cardiac autonomic function tests, obtained from 24-h Holter tap es. HRV was measured by calculating six time-domain (mean R-R interval (RR), standard deviation of the R-R interval [SDRR], standard deviati on of the mean of 288 R-R intervals [SDANN], the mean of the 288 stand ard deviations computed for each 5-min period [SD], percentage of diff erences of adjacent R-R intervals of >50 msec for the entire 24 h [pNN 50], and the root mean square of successive differences [rMSSD]) and f our frequency-domain (low frequency [LF], high frequency [HF], total h eart rate power spectra, and LF/HF ratio) indexes. SD, pNN50, rMSSD, L F, HF and total heart rate power spectra were markedly and significant ly reduced in diabetic children with poor metabolic control. The 24-h variation of low- and high-frequency components of heart rate power sp ectra of the latter children had a different shape. Thus, diabetic chi ldren with poor metabolic control (elevated HbA1c and B2M levels) have a low HRV compared to those diabetic children with good control and h ealthy children. These results can be interpreted as evidence of cardi ac autonomic neuropathy in diabetic children with asymptomatic diabeti c autonomic neuropathy.