Short-term outcome of early electrical cardioversion for atrial fibrillation in hyperthyroid versus euthyroid patients

Background: Atrial fibrillation (AF) is the most common cardiac complication of hyperthyroidism. The influence of the time of cardioversion on hyperthyroidism-induced AF remains unclear. The aim of this study was to compare short-term outcomes of early electrical cardioversion for AF in hyperthyroid and euthyroid patients. Methods and Results: Sixty-seven subjects with persistent AF (duration, 10 days-12 months) were divided into two groups according to thyroid function: Euthyroid (Group 1, n = 36, female/male: 23/13, mean age: 61.77 ± 10.45 years) and hyperthyroid (Group 2, n = 31, female/male: 10/21, mean age: 65.43 ± 6.40 years). Two patients were excluded for unsuccessful cardioversion (one in each group). In Group 2, 19 patients had clinical and 11 had subclinical hyperthyroidism. Following transthoracic and transesophageal echocardiography, cardioversion was performed until the highest energy was reached (270 J) or until sinus rhythm was achieved. AF recurrence was detected in 13 of 35 patients (37.1%) in Group 1 and in 11 of 30 patients (36.9%) in Group 2 (p = 0.96) at one month. Recurrence rate was higher in the clinical hyperthyroid patients than in the subclinical hyperthyroid patients (52.6% vs 9.1%, p = 0.021), but neither the clinical nor the subclinical hyperthyroid subgroups were significantly different from Group 1 in terms of recurrence rate (p = 0.27 and p = 0.13, respectively). Conclusions: Electrical cardioversion should be performed for patients with persistent AF and hyperthyroidism as soon as possible.