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

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). 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. 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. Erythrocytic H2S could serve as a useful predictor of therapeutic response to midodrine hydrochloride in children with POTS.

Yang J ，Zhao J ，Du S ，Liu D ，Fu C ，Li X ，Chen S ，Tang C ，Du J ，Jin H ... -  《-》

Midregional pro-adrenomedullin as a predictor for therapeutic response to midodrine hydrochloride in children with postural orthostatic tachycardia syndrome.

This study was designed to explore the predictive value of the midregional fragment of pro-adrenomedullin (MR-proADM) in assessing the therapeutic efficacy of midodrine hydrochloride for children with postural orthostatic tachycardia syndrome (POTS). Midodrine hydrochloride is an important therapeutic option for children with POTS. However, there has not been any method to predict response to the drug. The MR-proADM is produced in equimolar amounts to adrenomedullin (ADM), and directly reflects levels of the rapidly degraded active peptide, ADM. Fifty-seven children with POTS were designated as the POTS group. Twenty healthy children served as the control group. The children in the POTS group received midodrine hydrochloride treatment. The plasma concentration of MR-proADM was measured, using a sandwich immunoluminometric assay. A receiver-operating characteristic curve was used to explore the predictive value of MR-proADM. Plasma levels of MR-proADM were significantly higher in children with POTS (75.0 [62.5 to 96.0] pg/ml) than in the control group (58.5 [50.3 to 69.0] pg/ml). Plasma levels of MR-proADM in responders to midodrine hydrochloride was significantly higher than that of nonresponders (76.0 [66.0 to 91.0] pg/ml vs. 59.0 [54.0 to 65.5] pg/ml, p < 0.01]. A receiver-operating characteristic curve on the predictive value of MR-proADM showed that the area under the curve was 0.879 with a 95% confidence interval of 0.761 to 0.997. Using a cutoff value for MR-proADM of 61.5 pg/ml produced both high sensitivity (100%) and specificity (71.6%) in predicting the efficacy of midodrine hydrochloride therapy for treating POTS. MR-proADM can help guide midodrine hydrochloride therapy in the management of POTS in children.

Zhang F ，Li X ，Ochs T ，Chen L ，Liao Y ，Tang C ，Jin H ，Du J ... -  《-》

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

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. 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. 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. Plasma copeptin may be considered as a predictive biomarker for the likelihood of successful treatment of children with POTS with midodrine hydrochloride.

Zhao J ，Tang C ，Jin H ，Du J ... -  《-》

Flow-mediated vasodilation as a predictor of therapeutic response to midodrine hydrochloride in children with postural orthostatic tachycardia syndrome.

This study was designed to explore the value of flow-mediated vasodilation (FMD) as a predictor of therapeutic response to midodrine hydrochloride (MD) in children with postural orthostatic tachycardia syndrome (POTS). One hundred and eight children diagnosed with POTS and 20 healthy control children were enrolled. All children with POTS received MD and were followed up for 3 months. FMD of brachial artery for each participant was measured by vascular ultrasound. Symptom scores, FMD values, and head-up test (HUT)/head-up tilt test (HUTT) outcomes were investigated before and after treatment. A receiver operating characteristic curve was used to explore the value of FMD as a predictor. Baseline FMD (%) and increased heart rate (beats per minute) during HUT/HUTT were significantly greater in children with POTS compared with control children (FMD: 11 ± 3% vs 6 ± 2%, p <0.001; increased heart rate: 38 ± 9 vs 7 ± 7 beats/min, p <0.001, respectively). Before treatment, MD responders had greater FMD values than MD nonresponders (p <0.05). Symptom scores, excessive increases in heart rate during HUT, and increased FMD values were all reduced significantly after treatment (all p <0.05). The receiver operating characteristic curve for the predictive value of FMD showed the area under the curve to be 0.790 (95% confidence interval: 0.679 to 0.902; p <0.001) at 1-month and 0.803 (95% confidence interval: 0.669 to 0.936; p <0.01) at 3-month therapy. FMD of 9.85% had a high sensitivity (1-month therapy: 71.6%; 3-month therapy: 74.4%) and specificity (1-month therapy 77.8%; 3-month therapy: 80%). In conclusion, FMD is a predictor of the efficacy of MD for treating children with POTS.

Liao Y ，Yang J ，Zhang F ，Chen S ，Liu X ，Zhang Q ，Ai Y ，Wang Y ，Tang C ，Du J ，Jin H ... -  《-》

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

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. 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). 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. 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.

Zhang F ，Li X ，Stella C ，Chen L ，Liao Y ，Tang C ，Jin H ，Du J ... -  《-》