Relationship between serum free thyroxine and recurrence of atrial fibrillation after radiofrequency catheter ablation

Objective To explore the correlation between serum free thyroxine(FT4)and recurrence of atrial fibrillation(AF)after radiofrequency catheter ablation(RFCA)and its possible mechanism. Methods A total of 156 patients [97 males, (62.2±9.1)yrs] with AF undergone RFCA were enrolled in the study from September 2013 to December 2015 in the First Affiliated Hospital of Soochow University; in which 135 patients(86.5%)had paroxymal AF, and 21(13.5%)persistent AF. Logistic regression analysis was used to evaluate the effect of FT4 on the recurrence of AF in postoperative follow-up. Results After a mean follow-up of 12 months, 50 patients(32.1%)experienced recurrence, of which 39 cases(28.9%)were in paroxysmal AF group and 11 cases(52.4%)in persistent AF group(χ2=4.605, P=0.032). The recurrence rates were 12.8%, 22.5%, 36.8% and 56.4% in different FT4 quartile groups, from low to the high respectively(P<0.001). After adjustment of age, sex, LAD, persistent AF and electrical cardioversion, there was an increased risk of recurrence in the subjects with the highest FT4 quartile(OR=5.030, 95%CI: 1.450-17.446, P=0.011). FT4 was also an independent risk factor of recurrence(OR=1.328, 95%CI: 1.106-1.594, P=0.002). According to Receiver Operating Characteristic(ROC)curve, FT4 had a sensitivity of 72.0% and a specificity of 61.3%(AUC=0.707)in predicting recurrence of AF after ablation. Conclusions High FT4 level may increase AF recurrence after RFCA. Key words: Atrial fibrillation; Catheter ablation; Thyroxine; Recurrence