Portella Renata Boschi, Pedrosa Roberto Coury, Coeli Claudia Medina, Buescu Alexandru, Vaisman Mario
Endocrine Service and Cardiology Service of the Federal University of Rio de Janeiro, Av. Oswaldo Cruz 73/2201 Flamengo, Rio de Janeiro, Brazil.
Clin Endocrinol (Oxf). 2007 Aug;67(2):290-4. doi: 10.1111/j.1365-2265.2007.02879.x. Epub 2007 May 24.
Subclinical hyperthyroidism (SH) has been associated with exercise intolerance, changes in cardiac morphology, atrial arrhythmias and sympathovagal imbalance. The aim of this study was to evaluate the vagal reserve and modulation by a sympathetic stimulus in nonelderly patients with SH without cardiovascular problems.
We carried out a cross-sectional study, comparing data of the heart rate variability (HRV) of SH patients and healthy controls at rest and after vagal and sympathetic stimulation.
We studied 16 female patients with at least 6 months of SH and 16 healthy female controls with the same median age (40 vs. 34.5 years).
We used the tilt test, with electrocardiographic record at rest, during the respiratory sinus arrhythmia (RSA) manoeuvre and after tilting, in order to analyse HRV in the frequency domain (%high frequency (HF) and low/high frequency ratio (LF/HF) using Biopotentials Captation System software.
The median TSH level was 0.03 mU/l in patients and 1.37 mUI/l in controls. The median free T4 was 1.37 ng/dl in patients and 1.20 ng/dl in controls. Patients demonstrated a significantly smaller difference between %HF during the RSA and %HF at rest than controls (median -7.5 vs. 36.6, P < 0.001). There was a lower difference between LF/HF ratio after tilting and LF/HF ratio at rest in patients than in controls (1.5 vs. 5.3, P = 0.005).
Subclinical hyperthyroidism affects cardiovascular autonomic balance in otherwise apparently healthy nonelderly females by blunting vagal responses.
亚临床甲状腺功能亢进（SH）与运动不耐受、心脏形态改变、房性心律失常及交感迷走神经失衡有关。本研究旨在评估无心血管问题的非老年SH患者的迷走神经储备以及交感神经刺激对其的调节作用。
我们进行了一项横断面研究，比较SH患者和健康对照者在静息状态下以及迷走神经和交感神经刺激后的心率变异性（HRV）数据。
我们研究了16名患有至少6个月SH的女性患者和16名年龄中位数相同（分别为40岁和34.5岁）的健康女性对照者。
我们采用倾斜试验，在静息状态、呼吸性窦性心律不齐（RSA）操作期间以及倾斜后进行心电图记录，以便使用生物电位采集系统软件在频域分析HRV（高频百分比（HF）和低频/高频比值（LF/HF））。
患者的促甲状腺激素（TSH）水平中位数为0.03 mU/l，对照者为1.37 mU/l。患者的游离T4中位数为1.37 ng/dl，对照者为1.20 ng/dl。与对照者相比，患者在RSA期间的HF百分比与静息时的HF百分比之间的差异明显更小（中位数分别为-7.5和36.6，P < 0.001）。与对照者相比，患者倾斜后的LF/HF比值与静息时的LF/HF比值之间的差异更低（分别为1.5和5.3，P = 0.005）。
亚临床甲状腺功能亢进通过减弱迷走神经反应，影响了其他方面看似健康的非老年女性的心血管自主平衡。
