OBJECTIVETo predict the therapeutic efficacy of oral rehydration salts (ORS) by quantifying changes in heart rate during the head-up test (HUT) in children with postural tachycardia syndrome (POTS).

METHODFifty-four children from Peking University First Hospital during July 2005 to September 2013 were enrolled into POTS group. Twenty healthy children were enrolled in this study as the control group. Children with POTS were treated with ORS and successfully followed up. HUT test was done before and at the end of the treatment. POTS children were further divided into responding group and the non-responding group depending on if the symptom scores were reduced by 50% or greater after the treatment. The heart rate, systolic blood pressure (SBP) and diastolic blood pressure (DBP) changes during the HUT test were analyzed between the control group and the POTS patients. A receiver operating characteristic (ROC) curve was used to analyze the predictive value of the increase in heart rates (from the supine to upright) and the maximum upright heart rate in 10 minutes after ORS treatment.

RESULTPOTS children were 6-17 (11.3 ± 3.0) years old and the control group children were 10-12 (11.0 ± 0.8) years old. The changes of the heart rate during the HUT was different between the POTS patients and the controls ((41 ± 10) vs. (20 ± 7) beats/min, t = -10.441, P = 0.000) . There was no significant difference between the two groups in the maximum upright heart rate in 10 minutes during the HUT ( (117 ± 12) vs. (114 ± 8) beats/min, t = -1.322, P = 0.192) . The symptom scores were reduced compared with those before treatment ((3.2 ± 1.8) vs. (5.7 ± 2.0), t = 10.958, P < 0.001) and the heart rate changes from supine to upright were decreased in 30 patients ((33 ± 11) vs. (41 ± 11) beats/min, t = 2.956, P = 0.006). Compared with the non-responding group (28 cases), the heart rate change during the HUT test was great in the responding group (26 cases) before treatment ((46 ± 10) vs. (37 ± 9) beats/min, t = -3.582, P = 0.001), and the maximum upright heart rate in 10 minutes was also high in the responding group ( (122 ± 12) vs. (113 ± 10) beats/min, t = -2.693, P = 0.010). The ROC curve showed that ORS for children with POTS would be predicted to be effective when the pre-treatment increase of heart rate was 41 beats/min (sensitivity 72% and specificity 70%), or when the maximum upright heart rate in 10 minutes was 123 beats/min before treatment (sensitivity 48% specificity 56%). When the two indices were used together, sensitivity was 84% and specificity was 56%.

CONCLUSIONThe changes in heart rate during the HUT was useful in predicting the response to ORS in children with POTS.