Evaluation of the Tpeak-Tend Interval as an Arrhythmogenicity Index in Graves' Disease

Abstract

Introduction.Graves’ disease is the most common cause of hyperthyroidism. The mortality rate increases by 20% in hyperthyroid patients; cardiac problems are the leading cause of death and arrhythmia is the most common cardiac complication.
 Our study aimed to evaluate the corrected QT interval (QTc), the Tpeak-Tend interval (Tp-e), and the Tp-e/QTc ratio to predict arrhythmia risk in patients with Graves’ disease.
 Methods. The study included 64 patients with Graves’ disease and 57 euthyroid controls. The 12-lead electrocardiograms of the individuals under study were evaluated. The QTc interval, the Tp-e interval, and the Tp-e/QTc ratio of all participants were determined and statistically evaluated with thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) values.
 Results. Tp-e (p < 0.001) and QTc (p < 0.05) were significantly prolonged in the group of patients with Graves’ disease as compared to the control group. Heart rate was higher in patients with Graves’ disease as well (p < 0.05). Correlation analysis in patients with hyperthyroidism demonstrated that Tp-e (r=0.372, p=0.002), QTc (r=0.291, p=0.020), and fT3 levels were significantly and positively correlated. Similarly, Tp-e (r=0.271, p=0.030), QTc (r=0.259, p=0.039), and fT4 levels were significantly and positively correlated.
 Conclusions. We observed a significant prolongation of the Tp-e and QTc intervals with the increase in fT3 and fT4 levels. On the other hand, our study demonstrated that the sensitivity and specificity of Tp-e in the prediction of hyperthyroidism were 70.3% and 70.1%, respectively (AUC=0.724 (CI: 0.629-0.818)), the optimal cut-off value=83.5 ms). The Tp-e interval, which has recently been used as one of the arrhythmogenicity indices, may be an indicator of arrhythmia risk in patients with Graves’ disease.