Hyperthyroidism Linked to Higher ECG Repolarization Dispersion

Key Takeaways

• Adults with overt hyperthyroidism had higher values across all six 12-lead ECG ventricular repolarization dispersion parameters than healthy euthyroid controls, with all between-group comparisons reported at p < 0.001 and the largest elevations approaching about 50% to 60%.
• In a 97-adult retrospective case-control cohort, including 55 adults with overt hyperthyroidism and 42 healthy euthyroid controls, JTcFd and QTcBd showed the strongest individual discrimination, with AUCs of 0.813 and 0.804, respectively.
• Correlations between thyroid markers and dispersion indices were weak overall, Tp-ed remained independently associated in weighted multivariable analysis, and no clinical arrhythmic outcomes were evaluated, leaving risk implications uncertain.

Ventricular repolarization dispersion was consistently higher in overt hyperthyroidism on routine 12-lead ECG, with JTcFd measuring 41.05 vs 25.76 ms, approximately 59% higher than in euthyroid controls. In 97 adults overall, including 55 with overt hyperthyroidism and 42 healthy euthyroid controls, that pattern extended across QT-, JT-, and Tp-e-derived indices rather than a single marker alone. The case-control study of ventricular repolarization dispersion in overt hyperthyroidism did not assess clinical arrhythmic outcomes.

This single-center retrospective cross-sectional analysis screened 953 hospital records and enrolled 100 adults, with 97 included after 3 incomplete cases were excluded. Participants were hospitalized between June 2022 and June 2025, and when more than one ECG was available, investigators selected the tracing closest to thyroid hormone measurement. The six assessed parameters were QTd, QTcBd, QTcFd, JTd, JTcFd, and Tp-ed. Standard 12-lead ECGs were measured digitally with ImageJ, with some manual measurement steps and no formal reproducibility assessment, and weighted analyses after entropy balancing were consistent with the unadjusted between-group pattern.

Across the ECG profile, dispersion was higher in the overt hyperthyroidism group for QT-, JT-, and Tp-e-derived measures, including QTcBd at 45.85 vs 30.66 ms, about 50% higher than in controls. JTcFd and QTcBd provided the strongest individual discrimination, with AUCs of 0.813 (95% CI 0.721–0.904) and 0.804 (95% CI 0.714–0.895); exploratory thresholds of JTcFd at 32.7 ms or higher yielded 71% sensitivity, 81% specificity, and 75% accuracy, while QTcBd at 37.9 ms or higher yielded 73% sensitivity and 76% specificity. Within the overt hyperthyroidism subgroup, correlations between FT3, FT4, or TSH and dispersion measures were weak overall and non-significant, with FT3 × JTcFd reported as the strongest example at ρ = 0.258, 95% CI −0.004 to 0.480, p = .057. In weighted multivariable analysis, Tp-ed remained independently associated with overt hyperthyroidism, and the internally validated penalized model showed a C-index of 0.851 with a calibration slope of 1.04; the authors framed those findings within a retrospective single-center study, a small cohort, exploratory thresholds and modeling without external validation, one ECG per participant, possible measurement variability, and residual confounding from higher resting heart rate.

Clinician Questions

Which ECG repolarization dispersion markers were higher in overt hyperthyroidism than in euthyroid controls?

In adults with overt hyperthyroidism, all six assessed ventricular repolarization dispersion parameters were higher than in healthy euthyroid controls: QTd, QTcBd, QTcFd, JTd, JTcFd, and Tp-ed, with every between-group comparison reported at p < 0.001.

Which ECG markers best distinguished overt hyperthyroidism from healthy controls in this cohort?

Among adults with overt hyperthyroidism versus healthy controls, JTcFd and QTcBd showed the strongest individual discrimination, with AUCs of 0.813 and 0.804, respectively. The reported exploratory thresholds were JTcFd 32.7 ms or higher, with 71% sensitivity, 81% specificity, and 75% accuracy, and QTcBd 37.9 ms or higher, with 73% sensitivity and 76% specificity; the authors presented these as cohort-level exploratory cutoffs rather than established standalone diagnostic thresholds.

Did thyroid hormone levels correlate with ventricular repolarization dispersion in overt hyperthyroidism?

Within the overt hyperthyroidism subgroup, correlations between FT3, FT4, and TSH and the six ventricular repolarization dispersion parameters were weak overall and non-significant. The strongest reported example was FT3 × JTcFd at ρ = 0.258 with p = .057, and no correlation clearly excluded zero.

Did the analysis evaluate arrhythmia outcomes in adults with overt hyperthyroidism and abnormal ECG dispersion?

The analysis did not assess clinical arrhythmic outcomes or longitudinal follow-up in adults with overt hyperthyroidism, so the reported ECG dispersion differences describe electrophysiologic variation rather than observed arrhythmia events or proven risk.