High-Normal Thyroid Function and Recurrence of Atrial Fibrillation after Catheter Ablation: A Study Related to Dietary Structure and Iodine Intake

Abstract

Background: Thyroid function is increasingly recognized as an important modifiable factor for atrial fibrillation (AF); however, it is unclear if the changes in thyroid hormones, even within the normal range, are associated with AF recurrence after catheter ablation. Thus, we investigated the relationship between thyroid hormones and AF recurrence. Methods: A total of 388 consecutive AF patients (mean [standard deviation] age, 59*9 [9*7] years; 240 males [61.9%]) who underwent catheter ablation were enrolled and had thyroid functions measured before the procedure. Patients were followed for 12 months or until they presented with the first AF episode after a blanking period. Findings: After a 1-year follow-up, 104 (26*8%) patients experienced AF recurrences after an ablation procedure. Kaplan-Meier analysis revealed that patients with high-normal free tetraiodothyronine (FT4) or free triiodothyronine (FT3) levels had a lower recurrence-free survival compared to the low-normal groups (P = 0*037 and P = 0*035, respectively), and those trends were more prominent in younger patients (P = 0*028 and P = 0*031, respectively). Although higher tetraiodothyronine (T4) levels were not associated with higher AF recurrence rates in the general population, there was a significant difference in AF recurrences between higher and lower T4 levels in younger and male populations (P = 0*004 and P = 0*003, respectively). After multivariate adjustment, patients in both the high-normal FT4 and FT3 groups had an increased risk of recurrence (hazard ratio 1*70; 95% confidence interval, 1*14-2*53, P < 0*01). Interpretation: Both high-normal FT3 and FT4 levels are associated with AF recurrence, especially in younger populations, which suggests a low daily intake of iodine, especially in some iodine-abundant areas. Trial Registration: This study was registered at chictr.org.cn (identifier ChiCTR1800017465). Funding Statement: National Key R&D Program of China (Grant no.2016YFC1301003), the National Science Foundation of China (Grant no. 81873484), National Key R&D Program of China (Grant no. 2016YFC1301003), the National Science Foundation of China (Grant nos. 30900612, 81800231 and 81873484), the Clinical Research Fund of Zhejiang Provincial Medical Association (Grant nos.2015ZYC-A16 and 2018ZYC-A11), the Nature Science Foundation of Zhejiang Province (Grant no. LZ16H020001), Medical Science Research Foundation of Zhejiang Province (Grant no. 2018ZD017), the Zhejiang Provincial Natural Science Foundation (Grant no. LY15H020002 and Y17H020020), the Department of Science and Technology, Zhejiang Province (Grant no. LGF19H020011), People's Republic of China. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study was approved by our hospital Institutional Review Board and all of the patients gave informed consent.