OBJECTIVE: To examine the effect of levothyroxine treatment in patients with subclinical hypothyroidism on electrocardiographic variables, especially on ventricular repolarization-related factors. METHODS: Sixteen women (mean age, 48.2 years) with subclinical hypothyroidism were treated with levothyroxine for 16 weeks. All standard 12-lead electrocardiographic recordings were scanned and transferred to a computer, and the QT intervals were measured on 300 times magnified recordings. QT dispersion, which reflects the heterogeneity of the ventricular repolarization, was calculated by the difference between the QT maximum and the QT minimum. RESULTS: We found that, after 16 weeks of levothyroxine treatment, the QT interval decreased from 387.2 +/- 10.8 ms to 345.6 +/- 13.0 ms (P<0.0001). The study patients exhibited a significant reduction of QT dispersion from 46.5 +/- 5.3 ms to 30.7 +/- 5.8 ms (P<0.0001). On linear regression analysis, a positive relationship was found between QT dispersion and logarithmic serum TSH levels (r = 0.492; P<0.0001). CONCLUSION: We conclude that serum TSH concentration has a role in ventricular inhomogeneity and, therefore, that subclinical hypothyroidism may predispose to ventricular arrhythmias. A large-scale, multicenter, randomized trial should be undertaken to address the benefit-to-risk ratio of levothyroxine treatment on cardiac inhomogeneity in patients with subclinical hypothyroidism.
OBJECTIVE: To examine the effect of levothyroxine treatment in patients with subclinical hypothyroidism on electrocardiographic variables, especially on ventricular repolarization-related factors. METHODS: Sixteen women (mean age, 48.2 years) with subclinical hypothyroidism were treated with levothyroxine for 16 weeks. All standard 12-lead electrocardiographic recordings were scanned and transferred to a computer, and the QT intervals were measured on 300 times magnified recordings. QT dispersion, which reflects the heterogeneity of the ventricular repolarization, was calculated by the difference between the QT maximum and the QT minimum. RESULTS: We found that, after 16 weeks of levothyroxine treatment, the QT interval decreased from 387.2 +/- 10.8 ms to 345.6 +/- 13.0 ms (P<0.0001). The study patients exhibited a significant reduction of QT dispersion from 46.5 +/- 5.3 ms to 30.7 +/- 5.8 ms (P<0.0001). On linear regression analysis, a positive relationship was found between QT dispersion and logarithmic serum TSH levels (r = 0.492; P<0.0001). CONCLUSION: We conclude that serum TSH concentration has a role in ventricular inhomogeneity and, therefore, that subclinical hypothyroidism may predispose to ventricular arrhythmias. A large-scale, multicenter, randomized trial should be undertaken to address the benefit-to-risk ratio of levothyroxine treatment on cardiac inhomogeneity in patients with subclinical hypothyroidism.
Authors: Connie M Rhee; Gregory A Brent; Csaba P Kovesdy; Offie P Soldin; Danh Nguyen; Matthew J Budoff; Steven M Brunelli; Kamyar Kalantar-Zadeh Journal: Nephrol Dial Transplant Date: 2014-02-25 Impact factor: 5.992
Authors: Julieta Fernandez-Ruocco; Monica Gallego; Ainhoa Rodriguez-de-Yurre; Julian Zayas-Arrabal; Leyre Echeazarra; Amaia Alquiza; Victor Fernández-López; Juan M Rodriguez-Robledo; Oscar Brito; Ygor Schleier; Marisa Sepulveda; Natalia F Oshiyama; Martin Vila-Petroff; Rosana A Bassani; Emiliano H Medei; Oscar Casis Journal: Thyroid Date: 2019-06-13 Impact factor: 6.568