Patient: Male 53-year-old Final Diagnosis: Thyrotoxicosis-induced cardiomyopathy Symptoms: Dyspnea Medication:— Clinical Procedure: — Specialty: Cardiology • Critical Care Medicine Objective: Unusual clinical course Background: Thyrotoxicosis-induced cardiomyopathy is a rare but potentially life-threatening condition that occurs in less than 1% of thyrotoxic individuals. Severely impaired left ventricular systolic function can lead to an overt cardiogenic shock requiring mechanical circulatory support. Abnormal cardiac structure and function are potentially reversible after achievement of euthyroid state. Case Report: We present a case of a 53-year-old patient with a diagnosis of thyrotoxicosis-induced acute heart failure. Transthoracic echocardiography revealed a mildly dilated left ventricle and severely reduced systolic function with ejection fraction of 20%. Subsequently, the patient developed refractory cardiogenic shock, which was treated with the use of extracorporeal membrane oxygenation (ECMO). After early intensive treatments to achieve euthyroid state, the clinical status significantly improved. Echocardiography prior to discharge showed improvement of left ventricular ejection fraction to 40%. The anti-TSH receptor was positive and Grave’s disease was diagnosed. The patient eventually returned to baseline functional status and could return to basic activities of daily living without limitations. Conclusions: Early diagnosis of cardiac involvement in patients with thyrotoxicosis is critical. Promptly delivered intensive treatment with rapid achievement of euthyroid state can reverse cardiac dysfunction and improve patient outcomes. The use of ECMO can be considered as a “bridge” to recovery of cardiac function after restoration of euthyroid state.