Abstract
BACKGROUND: The relationship between thyroid hormone sensitivity and atrial fibrillation (AF) progression remains unclear. OBJECTIVE: This study aimed to investigate the relationship between impaired thyroid hormone sensitivity and the progression of AF in individuals with normal thyroid function. METHODS: This retrospective cross-sectional study included 1,190 consecutive patients with AF, who were classified into paroxysmal AF (n = 623) and persistent AF (n = 567) groups. Data on cardiac ultrasound and serum biochemical parameters were obtained. Thyroid hormone sensitivity was assessed using a parametric thyroid feedback quantile-based index (PTFQI), thyrotropin-thyroxine resistance index (TT4RI), and peripheral free triiodothyronine/free thyroxine (FT3/FT4) ratio. Logistic regression analysis was performed to assess the relationship between thyroid hormone sensitivity indices and AF classification. RESULTS: Compared with the paroxysmal AF group, patients with persistent AF exhibited significantly higher PTFQI and TT4RI values and a lower FT3/FT4 ratio (P for trend <0.001). In the multivariable logistic regression analysis, persistent AF was independently and significantly associated with elevated TT4RI and PTFQI as well as a reduced FT3/FT4 ratio (all P for trend <0.05). In the fully adjusted model, the odds ratios (95% confidence intervals) for TT4RI, PTFQI, and FT3/FT4 ratios were 1.038 (1.010-1.066), 4.063 (1.527-10.809), and 0 (0-0.071), respectively. Quartile-based analysis further revealed a consistent and significant association between higher PTFQI scores and the probability of persistent AF across all upper quartiles (P < 0.01). The FT3/FT4 ratio demonstrated a non-linear association with persistent AF, acting as a risk factor in the third quartile (Q3, P for trend = 0.018) and as a protective factor in the fourth quartile (Q4, P for trend = 0.003). No statistically significant differences were observed between TT4RI quartiles. CONCLUSION: Impaired thyroid hormone sensitivity may contribute to the progression from paroxysmal to persistent AF in euthyroid patients; however, its clinical predictive value requires further validation in large-scale studies.