We have located links that may give you full text access.
COMPARATIVE STUDY
JOURNAL ARTICLE
RANDOMIZED CONTROLLED TRIAL
Heart rate variability and QT dispersion in patients with subclinical hypothyroidism.
Biomedicine & Pharmacotherapy 2006 September
UNLABELLED: The effect of subclinical hypothyroidism (SH) on cardiovascular autonomic function and ventricular repolarization has not been yet elucidated. The aim of the present study was to evaluate the dispersion of QT interval, i.e. an index of inhomogeneity of repolarization, and heart rate variability (HRV), i.e. a measure of cardiac autonomic modulation, in SH patients.
METHODS: The study included 42 patients (29 women and 13 men; mean age 53.2+/-14.2 years; body surface area 1.76+/-0.14 m2) with SH, as judged by elevated serum TSH levels (>3.6 mIU/l; range, 3.8-12.0) and normal free thyroid hormones (FT4 and FT3) and 30 euthyroid volunteer. Subjects with cardiac, metabolic, neurological disease or any other systemic disease that could affect autonomic activity were excluded from the study. Patients with SH and control subjects underwent a full history, physical examination, standard 12-lead ECG, and 24-h ambulatory ECG monitoring. To evaluate the effect of treatment with L-thyroxine on QT dispersion and HRV, 15 patients with SH were randomly assigned to receive therapy with L-thyroxine. All the subjects were evaluated at enrolment and after 6 months.
RESULTS: Patients with SH showed higher QT dispersion and lower HRV measures than healthy controls (P<0.01 for all). In SH patients, the standard deviation of N-Ns (SDNN) was negatively related to TSH (r=-0.42, P=0.006), while low frequency (LF)/high frequency (HF) ratio was positively related to TSH (r=0.42, P=0.006). Moreover, in SH patients both QT dispersion and QTc dispersion were positively related to TSH (r=0.64 and r=0.63, P<0.001 for both). After 6 months, the patients treated with L-tiroxine exhibited a reduction of QT dispersion and an increase of HRV parameters.
CONCLUSION: The results of the present study demonstrated that SH can alter autonomic modulation of heart rate and cause increased inhomogeneity of ventricular recovery times. Accordingly, early L-thyroxine treatment may be advised not only to prevent progression to overt hypothyroidism but also to improve abnormal cardiac autonomic function and ventricular repolarization inhomogeneity.
METHODS: The study included 42 patients (29 women and 13 men; mean age 53.2+/-14.2 years; body surface area 1.76+/-0.14 m2) with SH, as judged by elevated serum TSH levels (>3.6 mIU/l; range, 3.8-12.0) and normal free thyroid hormones (FT4 and FT3) and 30 euthyroid volunteer. Subjects with cardiac, metabolic, neurological disease or any other systemic disease that could affect autonomic activity were excluded from the study. Patients with SH and control subjects underwent a full history, physical examination, standard 12-lead ECG, and 24-h ambulatory ECG monitoring. To evaluate the effect of treatment with L-thyroxine on QT dispersion and HRV, 15 patients with SH were randomly assigned to receive therapy with L-thyroxine. All the subjects were evaluated at enrolment and after 6 months.
RESULTS: Patients with SH showed higher QT dispersion and lower HRV measures than healthy controls (P<0.01 for all). In SH patients, the standard deviation of N-Ns (SDNN) was negatively related to TSH (r=-0.42, P=0.006), while low frequency (LF)/high frequency (HF) ratio was positively related to TSH (r=0.42, P=0.006). Moreover, in SH patients both QT dispersion and QTc dispersion were positively related to TSH (r=0.64 and r=0.63, P<0.001 for both). After 6 months, the patients treated with L-tiroxine exhibited a reduction of QT dispersion and an increase of HRV parameters.
CONCLUSION: The results of the present study demonstrated that SH can alter autonomic modulation of heart rate and cause increased inhomogeneity of ventricular recovery times. Accordingly, early L-thyroxine treatment may be advised not only to prevent progression to overt hypothyroidism but also to improve abnormal cardiac autonomic function and ventricular repolarization inhomogeneity.
Full text links
Related Resources
Trending Papers
Challenges in Septic Shock: From New Hemodynamics to Blood Purification Therapies.Journal of Personalized Medicine 2024 Februrary 4
Molecular Targets of Novel Therapeutics for Diabetic Kidney Disease: A New Era of Nephroprotection.International Journal of Molecular Sciences 2024 April 4
Perioperative echocardiographic strain analysis: what anesthesiologists should know.Canadian Journal of Anaesthesia 2024 April 11
The 'Ten Commandments' for the 2023 European Society of Cardiology guidelines for the management of endocarditis.European Heart Journal 2024 April 18
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app