Thyroid storm and arrhythmic storm: a potentially fatal combination.

Thyroid storm is a rare clinical emergency with a mortality rate between 20% and 30%. Cardiac arrhythmias associated with thyrotoxicosis are usually supraventricular. Ventricular arrhythmias are rarely associated with this entity and tend to occur in patients with intrinsic cardiac disease. We present a 35-year-old woman with Graves disease and a thyroid storm manifested with multiple malignant dysrhythmic episodes, without underlying cardiac disease. The mechanism for ventricular arrhythmia is not clear but seems to be due to the increased myocardial excitability directly caused by the thyroid hormones. The presence of myocarditis lesions may constitute an arrhythmogenic substratum and contribute further to this manifestation. This case emphasizes the importance of cardiac monitoring in patients with thyroid storm.