Assessment of Cardiac Autonomic Modulation during Adolescent Obesity

Abstract

RABBIA, FRANCO, BERNARD SILKE, ANDREA CONTERNO, TIZIANA GROSSO, BARBARA DE VITO, IVANA RABBONE, LIVIO CHIANDUSSI, AND FRANCO VEGLIO. Assessment of cardiac autonomic modulation during adolescent obesity. Obes Res. 2003; 11:541-548. Objective: To investigate the cardiovascular autonomic function in pediatric obesity of different duration by using standard time domain, spectral heart rate variability (HRV), and nonlinear methods. Research Methods and Procedures: Fifty obese children (13.9 Ϯ 1.7 years) were compared with 12 lean subjects (12.9 Ϯ 1.6 years). Obese children were classified as recent obese (ROB) (Ͻ4 years), intermediate obese (IOB) (4 to 7 years), and long-term obese (OB) (Ͼ7 years). In all participants, we performed blood pressure (BP) measurements, laboratory tests, and 24-hour electrocardiogram/ambulatory BP monitoring. The spectral power was quantified in total power, very low-frequency (LF) power, high-frequency (HF) power, and LF to HF ratio. Total, long-term, and short-term time domain HRV were calculated. Poincaré plot and quadrant methods were used as nonlinear techniques. Results: All obese groups had higher casual and ambulatory BP and higher glucose, homeostasis model assessment, and triglyceride levels. All parameters reflecting parasympathetic tone (HF band, root mean square successive difference, proportion of successive normal-to-normal intervals, and scatterplot width) were significantly and persistently reduced in all obese groups in comparison with lean controls. LF normalized units, LF/HF, and cardiac acceleration (reflecting sympathetic activation) were significantly increased in the ROB group. In IOB and OB groups, LF, but not nonlinear, measures were similar to lean controls, suggesting biphasic behavior of sympathetic tone, whereas nonlinear analysis showed a decreasing trend with the duration of obesity. Long-term HRV measures were significantly reduced in ROB and IOB. Discussion: Autonomic nervous system changes in adolescent obesity seem to be related to its duration. Nonlinear methods of scatterplot and quadrant analysis permit assessment of autonomic balance, despite measuring different aspects of HRV.

The use of short-term analysis of heart rate variability to assess autonomic function in obese children and its relationship with metabolic syndrome

“…Rabbia et al [15] studied 50 obese children; 11--15 years of age to detect CV autonomic functional changes in obese children. The mean heart rate, TP, LF, HF and LF/HF were estimated using the HRV method with a 24 h recording period.…”

Limiar de variabilidade da freqüência cardíaca em adolecentes obesos e não-obesos

“…Com exceção da intensidade relativa de 20% do VO 2pico , o índice SD1 apresentou um comportamento semelhante nos adolescentes obesos e não-obesos. A atividade parassimpática diminuída no início do exercício físico nos adolescentes obesos reflete, possivelmente, a disfunção simpato-vagal que estes adolescentes apresentam em repouso (9)(10)(11)17) . Em um estudo prévio conduzido em nosso laboratório, com amostra semelhante à do presente estudo, foi observado que os adolescentes obesos apresentaram modulação autonômica cardíaca alterada em repouso (11) .…”

“…Esta intensidade do esforço físico, correspondente ao término da expressiva retirada da atividade vagal, vem sendo denominada na literatura científica de limiar de variabilidade da freqüência cardíaca (LiVFC) (2) . Em adolescentes obesos, o estudo da VFC em repouso tem mostrado que estes indivíduos apresentam uma disfunção simpato-vagal cardíaca, caracterizada por redução da atividade parassimpática e possivelmente aumento da atividade simpática (9,10) , associados, aparentemente, à disfunção dos mecanismos de controle baroreflexo da freqüência cardíaca (11) . No entanto, pelo melhor do nosso conhecimento, nenhum estudo até o momento investigou o impacto da obesidade na adolescência sobre a resposta autonômica durante a realização de esforços físicos, assim como, sobre a relação entre a resposta autonômica e as respostas metabólicas.…”

The obese child in the Intensive Care Unit. Update

“…70 Obesity is an independent risk factor for arterial hypertension in pediatrics. [71][72][73][74] Obese patients have endothelial and vascular smooth muscle dysfunction, 73 as well as a reduced parasympathetic nervous activity. 75,76 Arterial hypertension has been associated with a larger left ventricular mass in obese children.…”

“…75,76 Arterial hypertension has been associated with a larger left ventricular mass in obese children. 74 Severe uncontrolled hypertension may lead to early organ damage. 77,78 …”