Risk Factors for Orthostatic Hypertension in Children.

OBJECTIVE: To investigate the risk factors for orthostatic hypertension in children. STUDY DESIGN: Eighty children with orthostatic hypertension were enrolled in the group with orthostatic hypertension, and 51 healthy children served as the control group. Demographic characteristics, clinical history, daily water intake, nightly sleep duration, the results of the standing test, and complete blood count were recorded and compared between the 2 groups. The risk factors for pediatric orthostatic hypertension were determined by logistic regression analysis. RESULTS: Body mass index and red blood cell distribution width were higher in the group with orthostatic hypertension than in healthy children, whereas daily water intake and sleep duration were lower. Logistic regression analyses showed that, if a child suffered from overweight, suffered from obesity, had a daily water intake of less than 800 mL, or had a red blood cell distribution width that was increased by 1%, the risk of orthostatic hypertension would be increased by 6.069 times (95% CI, 1.375-26.783; P < .05), 7.482 times (95% CI, 1.835-30.515; P < .01), 4.027 times (95% CI, 1.443-11.241; P < .01), or 4.008 times (95% CI, 1.698-9.461; P < .01), respectively. However, if the sleep duration was increased by 1 hour, the risk of developing orthostatic hypertension would be decreased by 74.3% (95% CI, 54.6%-85.4%, P < .01). CONCLUSIONS: Increased body mass index, inadequate water intake and sleep duration, and elevated red blood cell distribution width were identified as risk factors for pediatric orthostatic hypertension.

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.

Acceleration Index Predicts Efficacy of Orthostatic Training on Vasovagal Syncope in Children.

OBJECTIVE: To explore the value of the acceleration index as a predictor of therapeutic response to orthostatic training in children with vasovagal syncope (VVS). STUDY DESIGN: Thirty-three children with VVS were recruited and treated with orthostatic training. The therapeutic response of each patient was evaluated after 3 months of treatment. A Pearson correlation was calculated between the acceleration index and the severity of VVS. The value of the acceleration index in predicting the therapeutic response to orthostatic training was assessed by analysis of the receiver operating characteristic curve. RESULTS: Among the 33 children with VVS, 20 were found to be responders and the remaining were nonresponders. The mean acceleration index was significantly lower in responders compared with nonresponders (21.10 ± 6.61 vs 31.36 ± 9.00; P = .001) and it was negatively correlated with positive response time in the head-up tilt test, with systolic blood pressure and with diastolic blood pressure at positive response time in the head-up tilt test (P < .05). The receiver operating characteristic curve for the predictive value of the acceleration index showed that the area under the curve was 0.827 (95% CI, 0.676-0.978; P = .002), and a cutoff value of the acceleration index of 26.77 yielded a sensitivity of 85.0% and a specificity of 69.2%. CONCLUSIONS: The acceleration index may be useful for predicting the efficacy of orthostatic training on VVS in children.

Hemocytometric Measures Predict the Efficacy of Oral Rehydration for Children with Postural Tachycardia Syndrome.

OBJECTIVE: To explore whether hemocytometric measures could be qualified predictors for the effect of oral rehydration salts (ORS) in children with postural tachycardia syndrome (POTS). STUDY DESIGN: Thirty-five children with POTS and 29 healthy children were enrolled. General information, hemodynamic status, and baseline hemocytometric variables were collected. Children with POTS received ORS therapy and were followed up for 3 months. The independent risk factors of developing POTS were explored. A receiver-operating characteristic curve was used to evaluate predictive value of hemocytometric variables for therapeutic effectiveness of ORS therapy. RESULTS: Children with POTS had larger mean corpuscular volume (MCV) and lower mean corpuscular hemoglobin concentration (MCHC) values than controls (P < .05). The baseline MCV values positively correlated with heart rate elevation from supine to upright (r = 0.294, P < .05). Both larger MCV and lower MCHC values were independent risk factors of developing POTS (for MCV, P < .05, OR 1.222; for MCHC, P < .05, OR 0.936). In children with POTS, responders to ORS had baseline lower MCV and higher MCHC than nonresponders (P < .05). The receiver-operating characteristic curve for the predictive value of MCHC showed that area under the curve was 0.73. CONCLUSIONS: MCHC values could be used to predict the effectiveness of ORS for treating POTS in children.

Electrocardiography-Derived Predictors for Therapeutic Response to Treatment in Children with Postural Tachycardia Syndrome.

OBJECTIVE: To explore whether electrocardiography (ECG) variables could be used to predict responses to physical treatment in children with postural tachycardia syndrome (POTS). STUDY DESIGN: Forty children with POTS and 32 healthy controls were enrolled in this study. General information and hemodynamic and supine ECG variables, including QT interval dispersion (QTd), were collected. The children with POTS received physical treatment and 3 months of follow-up. A receiver-operating characteristic curve was used to evaluate the value of ECG variables for predicting the effectiveness of physical treatment. RESULTS: Compared with the healthy children, the children with POTS had longer baseline QTd and heart rate (HR)-corrected QTd (QTcd), but shorter minimum QT intervals (QTmin) and minimum HR-corrected QT intervals (P < .05). In children with POTS, responders to physical treatment had a longer baseline time between QRS complexes (RR) interval of minimum QT interval and a longer QTcd compared with nonresponders. A longer QTcd was a significant risk factor for the presence of POTS (OR, 1.022; P = .02) and for undesirable responses to physical treatment in children with POTS (OR, 1.044; P = .03). Baseline QTcd was positively correlated with the HR elevation from supine to upright seen in children with POTS (r = 0.348; P = .003). Receiver operating characteristic curve analysis demonstrated an area under the curve of 0.73, and using 43.0 msec as a cutoff of QTcd yielded a sensitivity of 90% and a specificity of 60%. CONCLUSION: QTcd might be useful for predicting the effectiveness of physical treatment for POTS in children.

Total peripheral vascular resistance, cardiac output, and plasma C-type natriuretic Peptide level in children with postural tachycardia syndrome.

OBJECTIVE: To investigate the total peripheral vascular resistance (TPVR), cardiac output (CO), and plasma C-type natriuretic peptide (CNP) levels in children with postural tachycardia syndrome (POTS) during supine, upright, and return to supine. STUDY DESIGN: Twenty-nine children with POTS, aged 12 ± 3 years, were recruited, and 32 healthy children, aged 11 ± 2 years, served as controls. Heart rate (HR), blood pressure, TPVR, and CO were continuously monitored with Finapres Medical System, and plasma CNP levels were detected with Sandwich immunoluminescence assay. RESULTS: In children with POTS, upright TPVR and CO were significantly lower than those in supine position, and they rose again when they returned to supine position. However, in healthy control patients, both TPVR and CO did not change during supine, upright, and supine again positions. Also, in the supine position, there was no significant difference in TPVR and CO between POTS children and control subjects (P > .05). When upright, however, TPVR and CO in children with POTS were significantly lower than those of controls. Plasma CNP levels were significantly greater in children with POTS than that of controls (32.8 ± 9.7 vs 24.2 ± 8.4 [pg/mL], P < .01), and symptom scores and ΔHR positively correlated with plasma CNP levels in children with POTS (symptom scores: r = 0.490, P < .01; ΔHR: r = 0.508, P < .001), but CO negatively correlated with plasma CNP levels (r = -0.446, P < .01). CONCLUSION: Reduced TPVR and CO associated with the elevated plasma CNP might be involved in the pathogenesis of POTS.

Erythrocytic hydrogen sulfide production is increased in children with vasovagal syncope.

OBJECTIVES: To explore the differences in erythrocyte hydrogen sulfide (H2S) production in children with vasovagal syncope (VVS). STUDY DESIGN: A total of 54 children including 27 with VVS, aged 6-16 years (mean age 11.3 ± 3.3 years), and 27 healthy children, aged 3-17 years (mean age 10.4 ± 1.8 years) were included in the study. Children with VVS had symptoms of dizziness, pallor, blurred vision, nausea, and some had syncope. Erythrocyte H2S production was measured by a sulphur-sensitive electrode. Flow-mediated dilation (FMD) of brachial artery was measured for each patient by vascular ultrasound. RESULTS: H2S production from erythrocytes was significantly increased in the children with VVS compared with controls (P < .01). The erythrocytic H2S production in the VVS-vasoinhibitory subgroup was obviously higher than that in VVS-cardioinhibitory (P < .05) and VVS-mixed inhibitory subgroups (P < .05). FMD in the VVS-vasoinhibitory subgroup was greater than that in the VVS-cardioinhibitory (P < .05) and the VVS-mixed subgroups (P < .05). The erythrocytic H2S production had a positive linear correlation with FMD in children with VVS (P < .05). CONCLUSIONS: Increased erythrocyte H2S production may be involved in the pathogenesis of VVS in children.

Plasma copeptin and therapeutic effectiveness of midodrine hydrochloride on postural tachycardia syndrome in children.

OBJECTIVES: Midodrine hydrochloride is used clinically to treat children with postural tachycardia syndrome (POTS), but it is not effective in all patients. This study was designed to explore the changes in plasma copeptin and its predictive value in assessing the therapeutic efficacy of midodrine hydrochloride in children with POTS. STUDY DESIGN: The study included 33 children with POTS and 26 healthy children. The group with POTS received midodrine hydrochloride treatment for 1.5-3 months. The plasma copeptin was measured using a sandwich immunoluminometric assay. A receiver operating characteristic curve was used to explore the predictive value of plasma copeptin. RESULTS: The plasma copeptin in the group with POTS was significantly higher than that of the control group (10.827±2.459 pmol/L vs 8.845±1.471 pmol/L, P<.001). The plasma copeptin in responders to midodrine hydrochloride was significantly higher than that of nonresponders (12.082±1.998 pmol/L vs 9.646±2.301 pmol/L, P=.003). Receiver operating characteristic analysis on the predictive value of plasma copeptin showed that the area under the curve was 0.800 with a 95% CI of 0.640-0.959. Using a plasma copeptin level of 10.482 pmol/L as the cutoff point produced both favorite sensitivity (81.3%) and specificity (76.5%) in predicting the efficacy of midodrine hydrochloride therapy in children with POTS. CONCLUSIONS: Plasma copeptin may be considered as a predictive biomarker for the likelihood of successful treatment of children with POTS with midodrine hydrochloride.

Postural orthostatic tachycardia syndrome with increased erythrocytic hydrogen sulfide and response to midodrine hydrochloride.

OBJECTIVES: To evaluate the use of erythrocytic hydrogen sulfide (H2S) in predicting the therapeutic efficacy of midodrine hydrochloride for children with postural orthostatic tachycardia syndrome (POTS). STUDY DESIGN: Fifty-five children were included in this study, involving 28 children with POTS (POTS group) and 27 healthy children (control group). Children in the POTS group received midodrine hydrochloride treatment. Erythrocytic H2S production was measured; a receiver operating characteristic curve was used to assess if erythrocytic H2S could predict the therapeutic response to midodrine hydrochloride treatment. RESULTS: H2S production from erythrocytes was significantly higher in the POTS group than in the control group (P < .01). H2S production was also significantly higher in responders to midodrine hydrochloride than in non-responders (P < .05). The change in symptom score and baseline erythrocytic H2S production had a positive linear relationship (P < .01). There was also a positive correlation with the change in heart rate (P < .05). The receiver operating characteristic curve showed an area under curve value of 0.813. Erythrocytic H2S production yielded a sensitivity of 78.9% and a specificity of 77.8% in predicting the efficacy of midodrine hydrochloride therapy for children with POTS. CONCLUSION: Erythrocytic H2S could serve as a useful predictor of therapeutic response to midodrine hydrochloride in children with POTS.

Twenty-four-hour urinary sodium excretion and postural orthostatic tachycardia syndrome.

OBJECTIVE: To investigate whether 24-hour urinary sodium excretion could be an indicator of the effectiveness of salt supplementation in children with postural orthostatic tachycardia syndrome (POTS). STUDY DESIGN: The patient group comprised 30 children with POTS, and the control group comprised 10 healthy children. Serum sodium and 24-hour urinary sodium excretion were measured in all children, and the relationship between 24-hour urinary sodium and symptom severity was analyzed in the 30 patients. At 1 month after initiation of salt supplementation, the receiver operating characteristic curve was used to explore the probability of correctly discriminating responders to salt supplementation from nonresponders using 24-hour urinary sodium excretion as an indicator. RESULTS: Patients with POTS had lower 24-hour urinary sodium excretion than controls (P = .022). Symptom severity was negatively correlated with 24-hour urinary sodium excretion (OR, -0.754; P = .000). The receiver operating characteristic curve demonstrated a sensitivity of 76.9% and specificity of 93% for correct prediction of responders and nonresponders to salt supplementation when a 24-hour urinary sodium excretion of 124 mmol/24 hours was used as the cutoff value. CONCLUSION: Our results indicate that 24-hour sodium excretion of <124 mmol/24 hours is an indicator of the effectiveness of salt supplementation in children and adolescents with POTS.

Plasma hydrogen sulfide in differential diagnosis between vasovagal syncope and postural orthostatic tachycardia syndrome in children.

OBJECTIVE: To explore the predictive value of plasma hydrogen sulfide (H(2)S) in differentiating between vasovagal syncope (VVS) and postural orthostatic tachycardia syndrome (POTS) in children. STUDY DESIGN: Patients were divided between the POTS group (n=60) and VVS group (n=17) by using either the head-up test or head-up tilt test. Twenty-eight healthy children were selected for the control group. Plasma concentrations of H(2)S were determined for children in all groups (POTS, VVS, and control). RESULTS: Plasma levels of H(2)S were significantly higher in children with VVS (95.3±3.8 µmol/L) and POTS (100.9±2.1 µmol/L) than in children in the control group (82.6±6.5 µmol/L). Compared with the VVS group, the POTS group had plasma levels of H(2)S that were significantly increased. The receiver operating characteristic curve for the predictive value of H(2)S differentiation of VVS from POTS showed a H(2)S plasma level of 98 µmol/L as the cutoff value for high probability of distinction. Such a level produced both high sensitivity (90%) and specificity (80%) rates of correctly discriminating between patients with VVS and patients with POTS. CONCLUSION: H(2)S plasma level has both high sensitivity and specificity rates to predict the probability of correctly differentiating between patients with VVS and patients with POTS.