Association of Hypothyroidism With Atrial Substrate Burden and Recurrence Following Catheter Ablation of Atrial Fibrillation

BACKGROUND AND OBJECTIVES: Hypothyroidism has been linked to increased atrial fibrillation (AF) susceptibility. We aimed to identify factors associated with AF recurrence after catheter ablation and to compare arrhythmogenic substrates and recurrence rates between euthyroid and hypothyroid patients. METHODS: We retrospectively reviewed patients who underwent AF ablation from 2015 to 2019. Baseline clinical, echocardiographic, and electrophysiologic parameters were compared between hypothyroid and euthyroid groups. Pulmonary vein (PV) and non-PV (NPV) triggers, as well as AF drivers, were analyzed. Multivariate Cox regression identified predictors of AF recurrence. RESULTS: Among 591 patients (mean age 57.2±11.1 years; 450 male), 65 (10.9%) had hypothyroidism. These patients had more hypertension (49.2% vs. 34.0%, p=0.016), larger left atrial diameter (LAD, 41.1±6.3 mm vs. 39.1 ± 6.3 mm, p=0.015), more NPV triggers (41.5% vs. 26.4%, p=0.01), and more AF drivers (26.2% vs. 12.5%, p=0.003). AF recurrence was higher in the hypothyroid group (44.6% vs. 18.1%, p<0.001). Independent predictors of recurrence included AF drivers, NPV triggers, LAD, Peak E velocity, and E/e' ratio. Hypothyroidism was not an independent predictor, but mediation analysis showed that its effect on recurrence was predominantly indirect. Kaplan-Meier analysis showed higher recurrence in hypothyroid patients (log-rank p<0.0001). CONCLUSIONS: Hypothyroidism was associated with a higher burden of atrial triggers, drivers, and AF recurrence. Its impact on recurrence was likely an indirect effect of structural and arrhythmogenic remodeling. Comprehensive driver mapping may improve ablation outcomes in this population, warranting further prospective validation.