Risk Factors for Persistent Atrial Fibrillation Following Successful Hyperthyroidism Treatment with Radioiodine Therapy

OBJECTIVE: To investigate the predicting factors for persistent atrial fibrillation (AF) following radioiodine therapy for hyperthyroidism. METHODS: Standard 12-lead ECG and 24-h Holter monitoring were performed in 94 patients (38 males, mean age 46.1±8.2 years) with persistent AF following radioiodine therapy for hyperthyroidism. Left ventricular (LV) function was assessed with two-dimensional echocardiography. RESULTS: Euthyroidism or hypothyroidism was achieved in 81% and 19% of the patients, respectively, after radioiodine therapy. At the end of follow-up (1.6±1.3 years), LV ejection fraction in the 52 patients with LV dysfunction was increased from 39.3±3.3% to 59.0±5.5% (p<0.01). In the 38 patients with pre-treatment paroxysmal AF, no AF was documented during the follow-up. In the 45 patients with pre-treatment persistent AF, AF was found in 27 (60%) during the follow-up. Multivariate logistic regression analysis showed that more than 55 years old in age (RR 2.76, 95% CI: 1.16-8.79, p<0.01), duration of hyperthyroidism (RR 3.08, 95% CI: 1.22-11.41, p<0.01) and duration of pre-treatment atrial fibrillation (RR 2.96, 95% CI: 1.31-7.68, p<0.01) were independent predictors for persistent AF following radioiodine therapy. CONCLUSION: Older age, duration of hyperthyroidism and pre-treatment duration of AF are risk factors for persistent AF following radioiodine therapy.