High-Normal Thyroid Function and Risk of Recurrence of Atrial Fibrillation After Catheter Ablation

Abstract

Background: It has been shown that the concentration of serum free thyroxine (FT₄) is independently associated with atrial fibrillation (AF), even in euthyroid persons. This study investigated the effect of a high-normal level of FT₄ on recurrence after catheter ablation of AF. Methods and Results: The 244 consecutive patients with paroxysmal AF and who underwent circumferential pulmonary vein isolation (PVI) were prospectively enrolled. Exclusion criteria included prior or current thyroid dysfunction on admission, amiodarone medication for 3 months before admission. After a mean follow-up of 416±204 (91-856) days, the recurrence rates were 14.8%, 23.0%, 33.3%, 38.7% from the lowest FT₄ quartile to the highest FT₄ quartile, respectively (P=0.016). After adjustment for age, sex, left atrial diameter, and PVI, there was an increased risk of recurrence in the subjects with the highest FT₄ quartile compared with those with the lowest quartile (hazard ratio 3.31, 95% confidence interval 1.45-7.54, P=0.004). As a continuous variable, FT₄ was also an independent predictor of recurrence (hazard ratio 1.10, 95% confidence interval 1.02-1.18, P=0.016). Conclusions: Patients with high-normal thyroid function were at an increased risk of AF recurrence after catheter ablation.  (Circ J 2010; 74: 1316 - 1321)