Frontal QRS-T angle in patients with Graves' disease: association with thyroid function and cardiovascular parameters

Thyroid hormone excess may alter ventricular electrophysiology, affecting both depolarization and repolarization. The frontal QRS-T (fQRS-T) angle reflects the directional relationship between these processes and may provide information on ventricular electrical heterogeneity. However, data on the fQRS-T angle in overt hyperthyroidism (OHT) remain limited. We evaluated the fQRS-T angle in patients with Graves' disease presenting with OHT compared with euthyroid controls.

This retrospective single-center study included 55 patients with Graves' disease and biochemically confirmed OHT and 42 euthyroid controls. Frontal QRS and T axes were calculated from ECG measurements in leads I and aVF. Between-group comparisons, multivariable regression adjusted for age, sex, body mass index, and heart rate, sensitivity analyses, ROC analysis, and correlations with thyroid function parameters were performed. Results: The median fQRS-T angle was greater in patients with OHT than in controls (21.89° [12.37-44.09] vs. 17.36° [9.02-27.29], p = 0.006), with a rank-biserial correlation of 0.328 (95% CI 0.106-0.535). An fQRS-T angle >45° occurred in 23.6% of patients with OHT and in none of the controls (p < 0.001), whereas the QRS and T axes did not differ significantly between groups. After adjustment for age, sex, body mass index, and heart rate, OHT remained associated with a greater fQRS-T angle (β = 9.00°, 95% CI 1.77-16.22; p = 0.015), with consistent findings in sensitivity analyses. Discriminatory performance was modest (AUC 0.664, 95% CI 0.552-0.768). No significant associations were observed between fQRS-T angle and FT3, FT4, TSH, or heart rate.

Patients with Graves' disease and OHT exhibited greater discordance between ventricular depolarization and repolarization despite similar individual QRS and T axes. This association persisted after adjustment for heart rate and other potential confounders, suggesting that fQRS-T widening may reflect electrophysiological alterations associated with OHT rather than tachycardia alone.

Overt hyperthyroidism due to Graves' disease is associated with a wider fQRS-T angle independently of age, sex, body mass index, and heart rate. Larger prospective, multicenter studies with longitudinal ECG assessment are needed to determine the reversibility and prognostic significance of these alterations.