U-shaped association between serum free triiodothyronine and recurrence of atrial fibrillation after catheter ablation

Abstract

Thyroid dysfunction affects the outcomes of atrial fibrillation (AF) catheter ablation. However, it remains unclear if the variations in thyroid function, especially in the triiodothyronine levels, are associated with AF recurrence in euthyroid subjects. This study investigated the associations of thyroid hormone levels with arrhythmia recurrence after AF catheter ablation in euthyroid patients. A total of 1115 consecutive AF patients who underwent catheter ablation were prospectively enrolled and had their thyroid function measured prior to the procedure. The serum free triiodothyronine (FT3), free tetraiodothyronine (FT4), and thyroid-stimulating hormone (TSH) levels were assessed as predictors of recurrence and were adjusted for potential confounders. The subjects were divided into five quintile groups according to the FT3, FT4, and TSH levels, respectively. After a median follow-up of 723days (interquartile range, 180-1070), 47.2% of patients experienced recurrence. After multivariate adjustment, subject in the lowest and highest FT3 quintiles showed increased risk of recurrence (hazard ratio [HR] 1.60, 95% confidence interval [CI] 1.26-2.03, P < 0.01, and HR 1.47, 95% CI 1.16-1.87, P < 0.01, respectively), compared to the median quintile of FT3 levels. Regarding the FT4 level, the highest quintile group showed a higher risk of recurrence (HR 1.27, 95% CI 1.01-1.60, P = 0.04). The TSH levels were not associated with AF recurrence. Both high and low FT3 levels were associated with AF recurrence after catheter ablation. High-normal FT4 levels were also related to AF recurrence; however, no association was found between normal TSH levels and AF recurrence.