Introduction: Changes in thyroid hormone level can affect the cardiovascular system. The aim of this study was to show how the Tpeak -Tend (Tpe) interval, which is a new marker of ventricular arrythmia, is affected in patients who have become euthyroid following Levothyroxine treatment for hypothyroidism, as this has not been examined previously in literature. Materials and Methods: This, cross-sectional study included a total of 119 females aged 18-45 years, separated into 3 groups as hypothyroid, euthyroid and control groups. For evaluation of the QTc and Tpe intervals, examination on precordial V5 lead was made of all the ECGs taken routinely on presentation of the patients. Results: The Tpe and QTc intervals of the hypothyroid group were determined to be significantly prolonged compared to those of the euthyroid and control groups (p<0.001) and the values of the euthyroid and control groups were similar. A positive correlation was determined between TSH levels and Tpe and QTc intervals. Tpe interval AUC= 0.801,(%95 CI: 0,719 - 0,884) was higher than that of QTc AUC= 0.689, (%95 CI: 0,591 - 0,786) Conclussions: The Tpe duration was evaluated in respect of the risk of arrythmia in hypothyroid patients. In patients who had become euthyroid, the Tpe interval was found to be similar to that of healthy individuals and was more predictive than QTc. In the light of these findings it can be recommended that measurement of the Tpe interval should be preferred to QTc as a marker of the arrythmogenic effect in hypothyroid patients.
1. Sangster, J.K.,. Panciera D.L, Abbott J.A.. Cardiovascular Effects Of Thyroid Disease. Compend Contin Educ Vet; 2013. 35(7): P. E5.
2. Dillmann, W.H., Biochemical Basis Of Thyroid Hormone Action In The Heart. Am J Med, 1990.88(6):626-30.
3. Zaidi, M., Et Al. Dispersion Of Ventricular Repolarisation: A Marker Of Ventricular Arrhythmias In Patients With Previous Myocardial Infarction. Heart, 1997. 78(4): 371-5.
4. Yamaguchi, M., Et Al., T Wave Peak-To-End Interval And Qt Dispersion In Acquired Long Qt Syndrome: A New Index For Arrhythmogenicity. Clin Sci (Lond), 2003. 105(6):671-6.
5. Yan, G.X., Antzelevitch C.. Cellular Basis For The Normal T Wave And The Electrocardiographic Manifestations Of The Long-Qt Syndrome. Circulation, 1998. 98(18): 1928-36.
6. Galetta, F. Et Al., Changes In Heart Rate Variability And Qt Dispersion In Patients With Overt Hypothyroidism. European Journal Of Endocrinology 2008. 158(1):85-90.
7. Altun, A., Et Al., The Relationship Between Ventricular Repolarization And Thyroid Stimulating Hormone. Ann Noninvasive Electrocardiogr, 1998. 3:19.
8. Nathaniel C, C.L., Azrin Ma. Qtc Prolongation In Hypothyroidism. J Am Coll Cardiol, 1994. 23:36a.
9. Sharp, N.A., Neel D.S., Parsons R.L.. Influence Of Thyroid Hormone Levels On The Electrical And Mechanical Properties Of Rabbit Papillary Muscle. J Mol Cell Cardiol, 1985. 17(2): 119-32.
10. Funck-Brentano, C, Jaillon P. Rate-Corrected Qt Interval: Techniques And Limitations. Am J Cardiol, 1993. 72(6):17b-22b.
11. Gurdal, A., Et Al., Evaluation Of Tp-E Interval, Tp-E/Qt Ratio And Tp-E/Qtc Ratio In Patients With Subclinical Hypothyroidism. Ther Adv Endocrinol Metab, 2017. 8(3):25-32.
12. Kweon K.H., Park B.H., Cho C.G. The Effects Of L-Thyroxine Treatment On Qt Dispersion In Primary Hypothyroidism. Journal Of Korean Medical Science, 2007. 22(1): 114-116.
13. Yontar, O.C., Et Al., Assessment Of Ventricular Repolarization Inhomogeneity In Patients With Mitral Valve Prolapse: Value Of T Wave Peak To End Interval. International Journal Of Clinical And Experimental Medicine, 2014. 7(8):2173-2178.
14. Panikkath, R., Et Al., Prolonged Tpeak To Tend Interval On The Resting Electrocardiogram Is Associated With Increased Risk Of Sudden Cardiac Death. Circulation. Arrhythmia And Electrophysiology, 2011. 4(4):441-447.