Background It has been shown that serum free thyroxine (FT4) concentration is independently associated with atrial fibrillation (AF) even in euthyroid persons. This study aimed to testify the impact of high-normal level of FT4 on recurrence after catheter ablation of AF.
Methods Two hundred and forty-four consecutive patients with paroxysmal AF underwent circumferential pulmonary vein isolation (PVI) were prospectively enrolled. Exclusion criteria included prior or current thyroid dysfunction on admission, amiodarone medication for three months before admission.
Results 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). Adjustment for age, gender, left atrium diameter, PVI, there was an increased risk of recurrence in the subjects with the highest FT4 quartile compared with those with the lowest quartile (HR 3.31, 95% CI 1.45 to 7.54, p=0.004). As a continuous variable, FT4 was also an independent predictor of recurrence (HR 1.10, 95% CI 1.02 to 1.18, p=0.016).
Conclusions Patients with high-normal thyroid function were at an increased risk of AF recurrence after catheter ablation.