Obesity is characterized by hemodynamic and metabolic alterations. Autonomic control on cardiac function involvement is controversial. The aim of the study was to assess early sign of cardiac autonomic dysfunction in obesity, using time- and frequency-domain heart rate variability (HRV) analysis in a pediatric population.
Methods: 32 obese children (OB) (17 M, 15 F; 13.9 +/- 1.7 y) were compared with 13 healthy lean subjects (7 M, 6 F; 12.9 +/- 1.6 y). For each participant, the authors performed a clinical examination, laboratory testing, blood pressure (BP) measurements, and 24-hour electrocardiograph/ambulatory BP monitoring. The spectral power was quantified in total power, low-frequency (LF) power, index of sympathetic tone, high-frequency (HF) power, index of vagal tone, and LF/HF ratio. Low frequency and HF were averaged to obtain 3 measures: 24-hour, daytime, and nighttime levels. Total, long-term, and short-term time-domain HRV values were calculated.
Results: The obese children had higher casual and ambulatory BP, and higher fasting glucose, insulin, and triglyceride levels. Overall HRV values were not significantly lower in OB. The obese children had significantly lower 24-hour and nighttime high-frequency normalized units, and time-domain measures of vagal activity. Low-frequency power showed an inverse but not significant pattern. The OB group had significantly greater 24-hour and nighttime LF/HF ratios.
Conclusions: The authors found an increase in heart rate and in BP associated with parasympathetic heart rate control decrease in stabilized obese normotensive children.