Overt hyperthyroidism is associated with increased dispersion of ventricular repolarization: a case-control study

Background: Overt hyperthyroidism is associated with increased cardiovascular morbidity, including tachyarrhythmias and heart failure. Although standard electrocardiographic abnormalities are well recognized, data regarding advanced markers of ventricular repolarization heterogeneity remain limited. We aimed to evaluate electrocardiographic dispersion parameters as markers of altered ventricular repolarization in patients with overt hyperthyroidism. Methods: This single-centre retrospective case-control study included 97 adults: 55 patients with overt hyperthyroidism and 42 healthy euthyroid controls. Six ventricular repolarization dispersion parameters were assessed from standard 12-lead ECG recordings: QT dispersion (QTd), Bazett-corrected QT dispersion (QTcBd), Fridericia-corrected QT dispersion (QTcFd), JT dispersion (JTd), Fridericia-corrected JT dispersion (JTcFd), and Tpeak-Tend dispersion (Tp-ed). Group comparisons, correlation analyses, receiver operating characteristic (ROC) analyses, and internally validated multivariable modelling were performed. Results: All six parameters were significantly higher in overt hyperthyroidism than in controls (all p < 0.001). The best discriminatory performance was observed for JTcFd (AUC 0.813) and QTcBd (AUC 0.804). In multivariable analysis, Tp-ed remained independently associated with overt hyperthyroidism. Correlations between thyroid hormone levels and dispersion indices were weak and non-significant. Conclusions: Our findings suggest an association between overt hyperthyroidism and increased ventricular repolarization heterogeneity, as reflected by alterations in ECG-derived repolarization parameters. These results support the presence of electrophysiological changes in overt hyperthyroidism; however, the clinical implications regarding arrhythmic risk remain uncertain, as no clinical arrhythmic outcomes were assessed.