Abstract 3283: Overweight Children Lack Heart Rate Complexity at Rest and After Acute Nitroglycerin Administration
Background: Nonlinear tools used to measure heart rate variability (HRV) have been shown to provide additional prognostic information beyond conventional HRV measures (time and frequency domain) for characterization of autonomic dysfunction and cardiovascular disease risk. Previous studies with conventional HRV methods have indicated dysfunctional autonomic modulation of cardiac function in overweight children as compared to normal-weight. However, no studies have characterized differences in these populations utilizing sample entropy as a complexity measure of HRV.
Hypothesis: We hypothesized that as compared to normal-weight children, overweight children would display diminished heart rate complexity at rest and this dysfunction would be further realized by an autonomic provocation test (acute nitroglycerin administration).
Methods: Participants were overweight children (Body Mass Index: BMI > 85 percentile, weight=70.3±3.0 kg, 11 M, 15 F, age=11.5±0.1 yrs, Tanner stage=1.9±0.2, n=26) and normal-weight children (BMI < 85 percentile, weight=41.0±3.2 kg, 7 M, 3 F, age=11.5±0.3 yrs, Tanner stage=1.9±0.3, n=10). Ten minute time intervals of electrocardiograms were recorded at rest and after acute administration of sublingual nitroglycerin (0.3 mg) for detection of non-ectopic R-R intervals. Sample entropy was calculated from the R-R intervals with the fixed input parameters m=2 and r=0.2 standard deviations of the R-R interval data. Differences in sample entropy between groups at rest and the change after nitroglycerin were analyzed with independent t-tests. Results were reported as mean ± SEM.
Results: During resting conditions, a significant difference was found between groups in sample entropy (normal-weight=1.737±0.05 vs. overweight = 1.521±0.05; P= .024). The reduction in sample entropy from rest to after nitroglycerin administration was significantly greater in normal-weight (1.296±0.11, delta= −0.475 ±0.09, n=9) as compared to overweight (1.321±0.05, delta= −0.189±0.07, n=23) (P= .034).
Conclusion: The results of the study indicate that overweight children lack heart rate complexity at rest and have a blunted autonomic response to acute nitroglycerin administration which may increase cardiac disease risk.