[Dilated thyrotoxic cardiomyopathy].

We report a case of reversible, dilated cardiomyopathy due to thyrotoxicosis, which occurred in a young male without any underlying heart disease. The patient presented a clinical picture of cardiogenic shock related to severe left ventricular dilation and dysfunction and with new-onset atrial fibrillation and very high ventricular rate. In spite of vigorous medical therapy, there was only a mild improvement of clinical and hemodynamic status and ventricular rate persisted inappropriately elevated. Subsequently, laboratory test results allowed for recognition of thyrotoxicosis (secondary to Graves's disease) and then specific thyrostatic treatment was added. There was a prompt clinical improvement and parallel, progressive reversal of left ventricular dysfunction. The patient could be converted to normal sinus rhythm and one week later was discharged in good condition. We discuss the pathophysiological mechanism for the induction of this rare form of thyrotoxic cardiomyopathy and emphasize that awareness of this possible presentation of hyperthyroidism is essential to identify patients with potentially reversible dilated cardiomyopathy.