目的：心率变异性作为评价患儿心率变异程度的量化指标,临床上应用越来越广泛。该研究的目的是探讨不明原因心悸患儿心率变异性(HRV)的特点,为心悸患儿的临床诊断提供参考。方法：对34例不明原因心悸患儿,27例正常儿童进行动态心电图检查,分析动态心电图的STT变化及心率的昼夜节律变化,心率变异性时域指标两两比较。结果：心悸患儿时域指标相邻正常RR间期均数的标准差(SDNN)、相邻正常RR间期差值的均方根(RMSSD)、相邻正常RR间期差值大于50ms的个数占总心博数的百分比(PNN50)降低,与对照组相比差异有显著性(P<0.05)。其中15例患儿STT改变的特点符合β受体功能亢进症的诊断标准。结论：不明原因心悸患儿的心率变异性时域指标SDNN,RMSSD,PNN50均有下降,结合STT改变的特点,心率变异性分析可为临床诊断β受体功能亢进症和心脏神经官能症提供参考。

OBJECTIVE: Measurements of heart rate variability (HRV) are increasingly used as markers of cardiac autonomic activity. The aim of this study was to investigate the characteristics of HRV in children with palpitations of unknown causes so as to provide a basis for the etiologic diagnosis of palpitations. METHODS: Thirty-four children with palpitations of unknowns causes (Study group) and 27 aged-matched healthy children (Control group) were enrolled in this study. Three time domain indexes of HRV from 24-hr Holter monitoring (SDNN, RMSSD and PNN50) were analyzed. The changes of ST-T segment and the circadian variation of heart rate were examined. RESULTS: Three time domain indexes of HRV significantly decreased in the Study group compared with those of the Control group (P <0.05). Fifteen patients in the Study group showed ST-T segment changes, characterized by a descended ST segment and a low-flat T wave during daytime but the changes disappeared during sleep. The circadian changes of heart rate were also observed in the 15 patients. The change characteristics were consistent with the diagnostic criteria of beta-receptor hypersensitivity. CONCLUSIONS: Three time domain indexes of HRV decrease in children with palpitations of unknown causes. HRV analysis along with ST-T segment change characteristics appears to be helpful for the etiologic diagnosis of this disease.