Successful Heart Rate Management of Atrial Fibrillation Due to Thyroid Storm Using Intravenous Amiodarone

Abstract

Intravenous amiodarone is commonly used for heart rate control in patients with atrial fibrillation who are at risk of hemodynamic instability; however, its administration in patients with severe thyroid dysfunction is often avoided because of its known thyroid toxicity. Furthermore, the existing literature focusing on this topic is limited. Here, we present a case of thyroid storm, atrial fibrillation, and reduced left ventricular systolic function, whose rapid heart rate was successfully controlled using intravenous amiodarone in conjunction with antithyroid drugs. An 83-year-old man presented to the emergency department with worsening dyspnea for over 1 week and was diagnosed with impending thyroid storm and heart failure with reduced ejection fraction. Treatment with thiamazole, potassium iodine, hydrocortisone, and intravenous landiolol, a short-acting beta-blocker, was initiated. Although the patient initially had a sinus rhythm, he developed atrial fibrillation with a rapid ventricular response associated with low blood pressure. An increased dose of landiolol further lowered blood pressure but failed to control the heart rate. Therefore, intravenous amiodarone was initiated, leading to a reduction in heart rate, without causing further hemodynamic instability, and an eventual return to sinus rhythm. There was no recurrence of atrial fibrillation, and the intravenous amiodarone was discontinued 48 h after administration. The final diagnosis was thyroid storm caused by painless thyroiditis. He was transferred to a long-term care hospital on day 69. Theoretical evidence suggests that amiodarone used in combination with antithyroid drugs may mitigate the potential thyrotoxicity, rendering it a favorable choice for patients with thyroid storm and atrial fibrillation. Hence, intravenous amiodarone may be considered for heart rate control in patients with atrial fibrillation if the initial therapy for thyroid storm with beta-blockers fails. However, further research and clinical studies are required to validate the safety and efficacy of this approach.