Atrial fibrillation as the initial presentation of hyperthyroidism: Two cases: Graves' thyroid storm and toxic adenoma.

Atrial fibrillation (AF) is a recognised but potentially reversible manifestation of hyperthyroidism and may occasionally precede classic thyrotoxic symptoms. We report two cases in which AF was the initial presentation of hyperthyroidism with distinct aetiology and clinical severity. The first had rapid AF from Graves' disease, and the second had new-onset AF due to a solitary toxic adenoma. These cases emphasise the importance of routine thyroid evaluation in patients presenting with new-onset AF.