Sudden cardiac death complicating newly diagnosed atrial fibrillation in the setting of subclinical hyperthyroidism.

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and a predictor of all-cause mortality. Subclinical hyperthyroidism is an independent risk factor for developing AF but its clinical significance in younger patients has not been established. We describe a clinical case of a 44-year-old female with newly diagnosed AF, degenerating to ventricular fibrillation in the setting of subclinical hyperthyroidism.