Abstract
Atrial fibrillation is a common cardiac arrhythmia worldwide. In patients with hyperthyroidism, atrial fibrillation is the most common comorbid cardiac condition. Here, the authors report a case of a 47-year-old female with no significant medical history who presented with heart failure symptoms. Further analysis confirmed atrial fibrillation with a dilated atria and severe mitral regurgitation. In addition, she was found to be hyperthyroid. Accordingly, electrical cardioversion treatment was initiated, and her hyperthyroidism was managed. This resulted in her normal sinus rhythm being restored and subsequently being maintained. A repeat echocardiography 6 months later showed resolution of mitral regurgitation, improvement of atrial size and normalization of the left ventricular systolic function. Therefore, based on this case report, the authors suggest that atrial remodeling and functional mitral regurgitation secondary to atrial dilatation can be reversed by restoring and maintaining the sinus rhythm.