Faysal Şaylık1, Tufan Çınar2, Murat Selçuk2, Tayyar Akbulut1

1Clinic of Cardiology, Van Regional Training and Research Hospital, Van, Turkey
2Clinic of Cardiology, Sultan II. Abdulhamid Han Educational and Research Hospital, İstanbul, Turkey

Keywords: Hypothyroidism; cardiac electrophysiology; cardiac arrhythmia


Introduction: Subclinical hypothyroidism (SH) is defined by slightly elevated thyroid-stimulating hormone (TSH) levels with normal free triiodothyronine (fT3) and thyroxine (fT4) levels. SH is related to cardiovascular events, including malignant arrhythmias. Cardiac electrophysiological balance (iCEB) and its corrected form with heart rate (iCEBc) are useful electrocardiographic (ECG) parameters for the prediction of malign arrhythmias. In this study, we aimed to evaluate iCEB and iCEBc in SH patients.

Patients and Methods: A total of 164 patients (n= 82 patients with SH and n= 82 controls) were enrolled in this study. iCEB was calculated by dividing QT by QRS, and iCEBc was calculated by dividing corrected QT (QTc) by QRS. The groups were compared based on ECG parameters. Correlation and multiple linear regression analyses were used to assess the association of ECG parameters with TSH levels.

Results: There were no differences between the groups regarding clinical and laboratory findings. Tp-e, QT, QTc, Tp-e/QT, Tp-e/QTc, iCEB, and iCEBc were significantly prolonged in SH patients compared to controls. In correlation analyses, all of the abovementioned ECG parameters were significantly correlated with serum TSH levels. Multiple linear regression analysis indicated that Tp-e, iCEB, and iCEBc were independently associated with serum TSH levels in SH patients.

Conclusion: To our knowledge, this was the first study to demonstrate that iCEB and iCEBc were both prolonged in SH patients compared to controls, and both of them were independently correlated with TSH levels in such patients.

Ethics Committee Approval

The approval for this study obtained from Van Training and Research Hospital, Clinical Research Ethics Committee (Decision No: 2021/18, Date: 06.10.2021).

Peer Review

Externally peer-reviewed.

Author Contributions

Concept/Design - All of authors; Analysis/Interpretation - FŞ; Data Collection - TA, MS; Writing - FŞ; Critical Revision - FŞ, TÇ; Final Approval - TÇ, MS, TA; Statistical Analysis - FŞ.

Conflict of Interest

The authors declared that there was no conflict of interest during the preparation and publication of this article.

Financial Disclosure

The authors declared that this study has received no financial support.