Heart rate variability and heart rate turbulence in hypothyroidism before and after treatment.
BACKGROUND
Cardiac autonomic dysfunction may develop in patients with clinical or subclinical thyroid hormone deficiency. Heart rate variability (HRV) and heart rate turbulence (HRT) are used for evaluating changes in cardiac autonomic functions and also used to provide risk stratification in cardiac and noncardiac diseases. The aim of this study is to evaluate cardiac autonomic functions before and 6 months after thyroid replacement therapy in patients with thyroid hormone deficiency.


METHODS
Forty hypothyroid patients (mean age 48 ± 13, four male) and 31 healthy controls (mean age 51 ± 12, three male) were included in the study. Twenty-four hour ambulatory electrocardiogram recordings were taken using Pathfinder Software Version V8.255 (Reynolds Medical). The time domain parameters of HRV analysis were performed using the Heart Rate Variability Software (version 4.2.0, Norav Medical Ltd, Israel). HRT parameters, Turbulence Onset (TO), and Turbulence Slope (TS) were calculated with HRT! View Version 0.60-0.1 software.


RESULTS
HRV and HRT parameters were decreased in the patient group (SDNN; P < 0.001, SDANN; P < 0.009, RMSSD; P = 0.049, TO; P = 0.035, TS; P < 0.001). After 6 months of thyroid replacement therapy, there were no significant changes observed in either HRV or HRT.


CONCLUSIONS
Hypothyroidism may cause cardiac autonomic dysfunction. Treating hypothyroidism with L-thyroxine therapy does not effectively restore cardiac autonomic function. HRV and HRT can be used as to help monitor cardiovascular-related risk in this population.
Cardiology Department, Faculty of Medicine, Gaziosmanpasa University, Tokat, Turkey. dretaci@yahoo.com
Atac
A
Celik
Pelin
P
Aytan
Huseyin
H
Dursun
Fatih
F
Koc
Kerem
K
Ozbek
Mustafa
M
Sagcan
Hasan
H
Kadi
Koksal
K
Ceyhan
Orhan
O
Onalan
Ersel
E
Onrat
D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000294:innervation; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D013974:Thyroxine / Q000627:therapeutic use
D013974:Thyroxine