Thyroid Storm Presenting With Refractory Atrial Arrhythmia and Tachycardia-Induced Dilated Cardiomyopathy: A Case Report.

Thyroid storm is a life-threatening endocrine emergency characterised by extreme hypermetabolic derangement. Cardiovascular complications, including supraventricular arrhythmias and high-output cardiac failure, are well-recognised; however, the combination of refractory atrial flutter, tachycardia-induced dilated cardiomyopathy and severe biventricular dysfunction represents an uncommon and particularly challenging presentation. We report a 59-year-old woman with no prior cardiac history who presented with progressive malaise, exertional dyspnoea, palpitations and systemic symptoms. She was found to be in haemodynamically significant narrow complex tachycardia exceeding 200 beats per minute with a calculated Burch-Wartofsky score of 95, consistent with thyroid storm. Transthoracic echocardiography demonstrated severely impaired left ventricular systolic function with an ejection fraction of 15-20%, severe biatrial dilatation and echocardiographic evidence of pulmonary hypertension, consistent with tachycardia-induced dilated cardiomyopathy. Multiple rhythm-control and rate-control strategies were required, including direct-current cardioversion, adenosine, magnesium, digoxin, beta-blockers and escalating infusions. Amiodarone was discontinued following multidisciplinary review due to concerns regarding iodine-induced exacerbation of thyrotoxicosis. Thyroid storm was treated with propylthiouracil, Lugol's iodine, hydrocortisone, propranolol and cholestyramine. Serial echocardiography demonstrated interval improvement in left ventricular systolic function, supporting a reversible tachycardia-mediated mechanism. This case highlights the diagnostic and therapeutic complexity of thyroid storm with refractory arrhythmia and underscores the importance of early recognition, multidisciplinary management and careful selection of antiarrhythmic therapy.