Abstract: Objective　To study the prognostic evaluation value of  QT interval dispersion in children and adolescents with postural tachycardia syndrome（POTS）. Methods　From July 2012 to May 2020，75 children and adolescents who had their first visit or admission to the Pediatric Syncope Clinic of  The Second Xiangya Hospital of Central South University due to syncope or presyncope and were definitely diagnosed with POTS were selected as the POTS group；in the meanwhile 75 children and adolescents who had physical examination in the hospital were selected as the control group. QT interval were measured by 12-lead electrocardiography in a basal state，QT interval dispersion（QTd） was calculated，and the data was processed with SPSS 22.0 statistical software. Results　1. Comparison between the two groups：Compared with the control group，the POTS group had a significantly longer QT interval，including the maximum QT interval（QTmax）， minimum QT interval（QTmin），QTd，corrected  maximum QT interval（QTcmax） ，corrected minimum QT interval（QTcmin） and corrected QT interval dispersion（QTcd）（P＜0.001 or 0.05）.  2. Prognostic evaluation value：During the follow-up of 55（36，114） days after intervention，compared with the non-responsive group，the responsive group had a significantly longer QTd and QTcd（P＜0.001）. QTd has the largest AUC（0.910） and the best cut-off value was 30.00 ms. The sensitivity to predict response to POTS intervention was 82.90%，and the specificity was 81.78%. Conclusion　QTd of electrocardiogram has a good value in the estimation of the prognosis of POTS in children and adolescents.

Key words: postural tachycardia syndrome, head-up tilt test, electrocardiography, Q-T interval, child, adolescent

摘要： 目的　探讨QT间期离散度（QTd）对儿童及青少年体位性心动过速综合征（POTS）的预后估测价值。方法　选取2012年7月至2020年5月因晕厥或晕厥先兆在中南大学湘雅二医院儿童晕厥专科门诊首次就诊或住院，明确诊断为POTS的儿童及青少年75例为POTS组，匹配同期在本院进行健康检查的儿童及青少年75例为对照组。测量两组基础状态下12导联心电图QT间期，计算QT间期离散度（QTd）。采用SPSS ?22.0统计软件进行数据处理。结果　（1）两组比较：POTS组较对照组最大QT间期（QTmax）、最小QT间期（QTmin）、QTd、校正最大QT间期（QTcmax）、校正最小QT间期（QTcmin）、校正QT间期离散度（QTcd）延长（P＜0.001或0.05）。（2）预后估测价值：POTS组干预后随访55（36，114） d，有反应组较无反应组QTd、QTcd延长（P＜0.001）。QTd的AUC最大（0.910），其最佳截断值为30.00 ms时，预测对POTS干预有反应的灵敏度为82.90%，特异度为81.78%。结论　心电图QTd对儿童及青少年POTS的预后有较好的估测价值。

关键词: 体位性心动过速综合征, 直立倾斜试验, 心电描记术, QT间期, 儿童, 青少年