Heart Rate Variability Predicts Therapeutic Response to Metoprolol in Children With Postural Tachycardia Syndrome

PURPOSE

To improve the metoprolol therapeutic effectiveness, we aimed to explore whether baseline heart rate variability (HRV) indicators before metoprolol treatment were useful for predicting its efficacy for postural tachycardia syndrome (POTS).

METHODS

We recruited 45 children with POTS who received metoprolol and 17 healthy controls. All children underwent a standing test or basic head-up tilt test and 24-h dynamic electrocardiography before treatment. After 3 months of metoprolol, therapeutic responsiveness was evaluated. The usefulness of baseline HRV parameters in predicting the effectiveness of metoprolol was studied and the long-term cumulative symptom rate was analyzed.

RESULTS

The baseline HRV frequency domain indicators for power, ultra-low frequency, very-low frequency, low frequency (LF), high frequency (HF), and total power (TP) as well as time domain indicators were significantly lower for responders than non-responders to metoprolol; however, low-frequency normalized units and LF/HF ratio were markedly greater for responders than non-responders. On series-parallel analysis, combined baseline triangular (TR) index ≤ 33.7 and standard deviation of all normal-to-normal intervals (SDNN) index ≤ 79.0 ms as cut-off values yielded sensitivity, specificity and accuracy of 85.3, 81.8, and 84.4%, respectively, to predict therapeutic responsiveness to metoprolol. On long-term follow-up, the cumulative symptom rate was significantly higher with TR index > 33.7 and SDNN index ≤ 79.0 ms, TR index ≤ 33.7 and SDNN index > 79.0 ms or TR index > 33.7 and SDNN index > 79.0 ms than TR index ≤ 33.7 and SDNN index ≤ 79.0 ms (P < 0.05).

CONCLUSION

Combined TR index ≤ 33.7 and SDNN index ≤ 79.0 ms were useful preliminary measures to predict therapeutic response to metoprolol in pediatric POTS.

Frequency Domain Indices of Heart Rate Variability are Useful for Differentiating Vasovagal Syncope and Postural Tachycardia Syndrome in Children

OBJECTIVE

To explore the value of frequency domain indices of heart rate variability (HRV) in the differential diagnosis between pediatric vasovagal syncope and postural tachycardia syndrome (POTS).

STUDY DESIGN

Eighty-five patients aged 7-16 years with either vasovagal syncope or POTS were enrolled in the experimental group; 18 healthy children served as controls. Holter electrocardiography was used to detect HRV frequency-domain indices in patients with vasovagal syncope, patients with POTS, and control subjects. The differences in HRV indices were compared between the vasovagal syncope and POTS groups. The receiver operating characteristic (ROC) curve was calculated to analyze the predictive value of HRV for the differential diagnosis between vasovagal syncope and POTS in children. In addition, 37 children aged 7-17 years with either vasovagal syncope or POTS were recruited as an external validation group.

RESULTS

The daytime ultra-low frequency (dULF), nighttime ULF (nULF), daytime very low frequency (dVLF), and nighttime VLF (nVLF) were higher in the vasovagal syncope group compared with the POTS group (P < .01 for dULF, dVLF, and nVLF; P < .05 for nULF). The dULF, nULF, dVLF, and nVLF yielded a sensitivity of 73.3%, 71.1%, 68.9%, and 62.2%, respectively, and a specificity of 72.5%, 62.5%, 60.0%, and 60.0%, respectively, to differentiate vasovagal syncope from POTS. The external validation with clinical diagnostic standard showed that a dULF cutoff value of 36.2 ms² for differentiating POTS from vasovagal syncope yielded a sensitivity of 71.4%, a specificity of 75.0%, and an accuracy of 73.0%.

CONCLUSION

dULF may be a useful measure for the differential diagnosis between vasovagal syncope and POTS in adolescents.

Bioelectrical Impedance Analysis (BIA) of the association of the Japanese Kampo concept "Suidoku" (fluid disturbance) and the body composition of women

Background

In Japanese Kampo medical practice, suidoku (fluid disturbance) is one of the most important concepts for selecting the proper medication. Suidoku is an excessive or uneven distribution of fluid that is indicated by splashing sounds and pitting edema. However, few objective reports about suidoku have been published. Bioelectrical impedance analysis (BIA) uses resistance values obtained from weak electrical currents to estimate body composition, including intracellular and extracellular water and muscle and fat mass. In this study, we used BIA to search for objective factors that can discriminate the various types of suidoku.

Methods

Two hundred twenty-nine patients who visited the Kampo Medicine Clinic of Kyushu University Hospital from June 2010 to August 2015 were divided into non-suidoku (n = 180, 80 male and 100 female), splashing sound (n = 32, 8 male and 24 female) and edema groups (n = 17, 5 male and 12 female). Body composition values were taken from the electronic medical records of InBody730 (a vertical, segmental, multi-frequency analyzer by InBody, Tokyo Japan) testing done at the initial visit. Various parameters of the body composition values of female in the non-suidoku and suidoku groups (splashing sound and edema groups) were compared: there were too few male patients to provide significance.

Results

The age and body weight were significantly lower in the splashing sound group than in the non-suidoku group (p < 0.05). In contrast, the body weight of the edema group was significantly heavier than that of the non-suidoku group (p < 0.05). In ROC analysis, the percent Body Fat ≤ 27.8 %, Muscle Mass Index of the Trunk ≤ 6.5 kg/m², VFA (Visceral fat area) ≤ 5.4 and BMI ≤ 19.2 kg/m² were associated with splashing sound, and Muscle Mass Index of Legs ≥ 4.8 kg/m² and BMI ≥ 21.4 kg/m² were associated with edema.

Conclusion

Our data suggest that the use of this type of BIA to estimate body composition would be a useful tool for the diagnosis of suidoku for women.

Comparable accuracy of micro-electromechanical blood flowmetry-based analysis vs. electrocardiography-based analysis in evaluating heart rate variability

BACKGROUND

Because the conventional evaluation of autonomic nervous system (ANS) function inevitably uses long-lasting uncomfortable electrocardiogram (ECG) recording, a more simplified and comfortable analysis system has been sought for this purpose. The feasibility of using a portable micro-electromechanical system (MEMS) blood flowmeter to analyze heart rate variability (HRV) for evaluating ANS function was thus examined.

METHODS AND RESULTS

Measurements of the R-R interval (TRR) derived from an ECG, simultaneously with the pulse wave interval (TPP) derived from a MEMS blood flowmeter, in 8 healthy subjects was performed and resultant HRV variables in time and frequency domains were compared. The TRR- and TPP-derived variables were strongly correlated (coefficients of regression for low frequency (LF), high frequency (HF), and LF/HF of 1.1, 0.66, and 0.35, respectively; corresponding coefficients of determination of 0.92, 0.63, and 0.91, respectively (P<0.01)). In addition, the values of LF, HF, and LF/HF, as analyzed using TPP, changed significantly from the supine to the standing position in another 6 subjects.

CONCLUSIONS

Miniaturized-MEMS blood flowmetry can be used to perform HRV analysis for the evaluation of ANS function, which is as accurate as analysis based on ECG within comparable tolerances. As MEMS blood flowmetry can more easily and comfortably record physiological variables for longer durations than ECG recording, and can further capture skin blood flow information, this device has great potential to be used in a wider area of physiological analyses.