Heart rate variability and its response to thyroxine replacement therapy in patients with hypothyroidism

目的　测定甲状腺功能减退 (甲减 )患者心率变异 (HRV)及观察甲状腺素替代治疗后的变化。方法　记录 38例甲减患者与 2 1例正常者 2 4小时动态心电图 ,并进行HRV分析。 18例甲减患者治疗 3月后重复HRV测定。结果　甲减时 ,HRV的时阈指标较对照组明显降低 ;频阈指标中 ,高频功率 (HF)较对照组明显增高 ,而低频 (LF)与HF比值较对照组显著减低。甲减患者经甲状腺素替代治疗后 ,HRV时阈指标和频阈指标均明显改善 ,且与FT3和FT4 的恢复程度相一致。结论　甲减时 ,自主神经活动明显改变 ,且以迷走神经兴奋性增加占优势。这种自主神经异常在甲状腺素替代治疗后可部分改善。

Heart rate variability and its response to thyroxine replacement therapy in patients with hypothyroidism

Objective To analyze heart rate variability (HRV)and its changes with thyroxine treatment in patients with hypothyroidism. Methods HRV was analyzed using 24-hour electrocardiographic recording in 38 patients with hypothyroidism and 21 normal controls. The changes in HRV were evaluated for the 18 hypothyroid patients after 3 months of thyroxine therapy. Results The time domain measurements of HRV in hypothyroid patients were much lower than those in the control group. As to HRV frequency domain, the high frequency power was significantly higher, but the ratio of low frequency power to frequency power for hypothyroid patients was lower than in the controls. These abnormal changes of HRV measurements in hypothyroid patients were improved after treatment with thyroxine and were associated with recovery of serum concentrations of FT(3)and FT(4).Conclusions Patients with hypothyroidism often have autonomic neuropathies with a higher level of vagal tone. These abnormalities could be partly improved by thyoxine therapy.