目的 对甲状腺功能亢进症（简称“甲亢”）儿童的心率减速力（DC）、心率加速力（AC）、心率变异性（HRV）进行分析，并探讨甲亢儿童的血清甲状腺激素水平与DC、AC及HRV的关系。方法 选取甲亢儿童47例，另选取50例健康儿童为对照组，对所有受试者行24 h动态心电图检查，将甲亢组与对照组的DC、AC、心率（HR）及HRV各指标[RR间期总体标准差（SDNN）、RR间期平均值的标准差（SDANN）、相邻RR间期差值的均方根（RMSSD）、低频功率（LF）、高频功率（HF）]进行比较，并将甲亢儿童的甲状腺激素指标[游离三碘甲状腺原氨酸（FT3）、游离甲状腺素（FT4）]与DC、AC及HRV各指标进行相关性分析。结果 甲亢组的DC、SDNN、SDANN、RMSSD、LF、HF均低于对照组；AC和HR均高于对照组（P < 0.05）。甲亢儿童的血清FT3、FT4与DC、SDNN、SDANN、RMSSD、LF、HF均呈负相关（P < 0.05）；与AC和HR呈正相关（P < 0.05）。结论 甲亢儿童的心脏自主神经功能受损，表现为迷走神经张力降低。血清甲状腺激素水平越高，迷走神经张力越低，提示发生心血管疾病的危险性越大。

Objective To investigate deceleration capacity of heart rate (DC), acceleration capacity of heart rate (AC), and heart rate variability (HRV) in children with hyperthyroidism and the correlations of serum thyroid hormone levels with DC, AC, and HRV. Methods A total of 47 children with hyperthyroidism were enrolled as hyperthyroidism group and 50 healthy children were enrolled as control group. The subjects in the two groups underwent 24-hour ambulatory electrocardiography. The two groups were compared in terms of DC, AC, heart rate (HR), HRV parameters[standard deviation of normal-to-normal RR intervals (SDNN), standard deviation of average normal-to-normal RR intervals (SDANN), root mean square of successive differences between adjacent RR intervals (RMSSD), low-frequency power (LF), and high-frequency power (HF)]. The correlations of thyroid hormone indices[free triiodothyronine (FT3) and free thyroxin (FT4)] with DC, AC, and HRV were analyzed. Results Compared with the control group, the hyperthyroidism group had significantly lower DC, SDNN, SDANN, RMSSD, LF, and HF and significantly higher AC and HR (P < 0.05). In the children with hyperthyroidism, serum FT3 and FT4 levels showed significant negative correlation with DC, SDNN, SDANN, RMSSD, LF, and HF and significant positive correlation with AC and HR (P < 0.05). Conclusions Children with hyperthyroidism have cardiac autonomic nerve dysfunction manifested as reduced vagal tone. Vagal tone decreases with the increasing serum thyroid hormone levels, suggesting an increased risk of cardiovascular disease.