Prevalence and influence of hyperthyroidism on the long-term outcome of catheter ablation for drug-refractory atrial fibrillation

Background: Hyperthyroidism is usually regarded as a reversible cause of atrial fibrillation (AF); however, one-third of patients remain in AF despite euthyroid restoration. We hypothesized that a significant number of AF patients with hyperthyroidism (Hyperthyroid-AF) as well as those without (Non-thyroid-AF) would benefit from catheter ablation of AF (AF ablation). This study aimed to clarify the prevalence of hyperthyroidism in candidates for AF ablation and to compare the long-term outcome of AF ablation between the Hyperthyroid-AF and Non-thyroid-AF groups. Methods and Results: This study enrolled 337 consecutive patients with AF who underwent a first AF ablation that mainly involved extensive encircling pulmonary vein isolation. Sixteen (4.7%) patients had hyperthyroidism; the remaining 321 (95.3%) did not. In the Hyperthyroid-AF patients, a euthyroid state had been restored for at least 3 months before the ablation. During a mean follow-up period of 4±1 years after ablation, AF recurred in 7 patients (44%) with Hyperthyroid-AF and in 139 patients (43%) with Non-thyroid-AF (P=0.91 by the log-rank test). In the multivariate Cox regression models, the presence of hyperthyroidism was not associated with a higher risk of AF recurrence (hazard ratio, 0.87; 95% confidence interval, 0.40-1.88; P=0.73). Conclusions: In the AF ablation candidates without structural heart disease, hyperthyroidism was not rare. After euthyroid restoration on pharmacological treatment, hyperthyroidism was not associated with a higher risk of AF recurrence.