POWER SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY IN CHILDREN AND ADOLESCENTS WITH IDDM

OBJECTIVE - To investigate power spectral analysis (PSA) of heart rate variability (HRV) in children and adolescents with IDDM, its relation ship with other measures of HRV and standard cardiovascular responses, and factors associated with reduced HVR. RESEARCH DESIGN AND METHODS - A total of 130 subjects with IDDM aged 12.8 +/- 3.2 years and 108 he althy control subjects were studied. Power spectra were analyzed from supine electrocardiograph (EGG) recordings by processing into consecut ive R-R intervals and analysis using fast Fourier transformation. Stan dard cardiovascular responses to deep breathing and standing were perf ormed. RESULTS - IDDM subjects had a reduction in total power includin g both low-frequency (0.05-0.14 Hz; P = 0.0001) and high-frequency (0. 14-0.40 Hz; P = 0.0002) components. These changes were seen from diagn osis. Other measures of HRV, coefficient of variation (CV) and standar d deviation (SD) of mean resting heart rate, were also significantly l ower in IDDM. All 20 (15%) of the 130 IDDM subjects with total power l ess than the 5th percentile in control subjects also had reduced HRV w hen measured by CV of heart rate. There was an independent relationshi p between age and the high-frequency component in IDDM subjects and co ntrol subjects. Total power correlated with mean heart rate (r = 0.56; P < 0.0001), CV of heart rate (r = 0.90; P < 0.00001), SD of heart ra te (r = 0.91; P < 0.00001), heart rate response to deep breathing (r = 0.45; P < 0.0001), and duration in IDDM subjects. There was no correl ation with short-term or long-term metabolic control. Retesting of 27 subjects showed a variability in total power and its components compar able to other measures of HRV and standard heart rate responses. CONCL USIONS - Changes in HRV are a sensitive and reproducible measure of ea rly autonomic dysfunction in childhood. In this age-group, PSA appears no more sensitive a measure of reduced HRV than other closely correla ted measures of HRV.