Heart rate variability and QT dispersion in patients with subclinical hypothyroidism

摘要: The effect of subclinical hypothyroidism (SH) on cardiovascular autonomic function and ventricular repolarization has not been yet elucidated. aim the present study was to evaluate dispersion QT interval, i.e. an index inhomogeneity repolarization, heart rate variability (HRV), a measure cardiac modulation, in SH patients. Methods: included 42 patients (29 women 13 men; mean age 53.2 ± 14.2 years; body surface area 1.76 0.14 m 2 ) with SH, as judged by elevated serum TSH levels (> 3.6 mIU/l; range, 3.8–12.0) normal free thyroid hormones (FT4 FT3) 30 euthyroid volunteer. Subjects cardiac, metabolic, neurological disease or any other systemic that could affect activity were excluded from study. Patients control subjects underwent full history, physical examination, standard 12-lead ECG, 24-h ambulatory ECG monitoring. To treatment L-thyroxine HRV, 15 randomly assigned receive therapy L-thyroxine. All evaluated at enrolment after 6 months. Results: showed higher lower HRV measures than healthy controls (P < 0.01 for all). In patients, deviation N–Ns (SDNN) negatively related (r = –0.42, P 0.006), while low frequency (LF)/high (HF) ratio positively 0.42, 0.006). Moreover, both QTc 0.64 r 0.63, 0.001 both). After months, treated L-tiroxine exhibited reduction increase parameters. Conclusion: results demonstrated can alter modulation cause increased recovery times. Accordingly, early may be advised only prevent progression overt but also improve abnormal inhomogeneity.