We report a case of severe amiodarone-induced thyrotoxicosis (AIT) in a medically complex patient at high risk of malignant arrhythmias and discuss her treatment course, which involved plasma exchange (PLEX).
A 39-year-old woman presented to clinic with abnormal thyroid function tests (TFTs), on a background of Emery-Dreifuss Muscular Dystrophy (a rare genetic condition affecting skeletal and cardiac muscle), restrictive lung disease, OSA, atrial fibrillation with previous stroke, ventricular tachycardia (VT) and previous cardiac arrest due to ventricular fibrillation. She has a permanent pacemaker and implantable cardiac defibrillator (ICD) in situ. She was previously on amiodarone for over a year for recurrent ventricular tachy-arrhythmias requiring ICD shocks, which was ceased five months prior due to abnormal TFTs. Upon review, she reported a history of weight loss and deconditioning, and episodes of palpitations (confirmed VT on ICD interrogation). TSH <0.01mIU/L, FT4 68pmol/L and FT3 12.5pmol/L, prior TFTs were unremarkable. TSH receptor antibody and thyroid peroxidase antibody were negative. Thyroid ultrasound showed normal appearing thyroid gland and vascularity, and thyroid uptake scan showed minimal uptake (0.2%). Impression was of type 2 AIT.
She was admitted and multi-disciplinary input was obtained regarding her ongoing management, including from cardiology, endocrine surgery, anaesthetics and intensive care. Given her severe thyrotoxicosis and risk of malignant arrhythmia, the decision was made for total thyroidectomy, with admission for peri-operative optimisation. She was commenced on cholestyramine, dexamethasone, and continued metoprolol. The patient underwent one session of PLEX, with significant improvement in FT4 to 37pmol/L and FT3 to 3.8pmol/L. She successfully underwent total thyroidectomy the next day.
Total thyroidectomy should be considered emergently in those with underlying left ventricular systolic dysfunction, severe underlying cardiac disease or malignant arrhythmias(1). Decision making should be made with a multi-disciplinary approach. Plasma exchange can acutely lower thyroid hormone levels to bridge towards definitive surgical management(2).