Thyroid dysfunction and risk of atrial fibrillation in patients with hypertrophic obstructive cardiomyopathy: a multicenter cohort study

Background: Atrial fibrillation (AF) is a common and clinically important arrhythmia in patients with hypertrophic obstructive cardiomyopathy (HOCM). Thyroid dysfunction influences atrial electrophysiology and remodeling; however, its association with AF in HOCM remains poorly defined. Methods: We retrospectively analyzed 755 consecutive patients with HOCM (mean age 48.65 ± 14.12 years; 60.0% male) from three tertiary centers (2019-2024). Patients were categorized by thyroid-stimulating hormone (TSH) levels as <0.55, 0.55-2.49 (reference), 2.50-9.99, and ≥10.00 mIU/L. Multivariable logistic regression and restricted cubic spline analyses were performed. Supplementary Cox proportional hazards regression was performed as a sensitivity analysis using exact event timing. Results: During 12-month follow-up, 107 patients developed incident AF (cumulative incidence, 14.2%). After multivariable adjustment, elevated TSH was independently associated with AF (TSH 2.50-9.99 mIU/L: OR 1.981, 95% CI 1.126-3.512; TSH ≥10.00 mIU/L: OR 4.306, 95% CI 1.061-17.485). Supplementary Cox regression yielded consistent results (TSH 2.50-9.99 mIU/L: HR 1.824, 95% CI 1.087-3.061; TSH ≥10.00 mIU/L: HR 3.685, 95% CI 1.018-13.337). Restricted cubic spline analysis demonstrated a U-shaped association between TSH and AF risk. Conclusions: In this multicenter retrospective cohort of patients with HOCM, both subclinical and overt hypothyroidism were associated with a higher risk of incident AF. Our findings indicate that thyroid function status may be associated with AF risk and could potentially contribute to risk stratification; prospective interventional studies are warranted to determine whether thyroid optimization can reduce AF risk.