Atrial Fibrillation Secondary to Levothyroxine Overdose with Underlying Secondary Infection

This case report presents the clinical course and management of a 62-year-old female patient with atrial fibrillation (AF) secondary to levothyroxine overdose along with an underlying secondary infection. The patient was admitted with sudden onset dyspnea, altered sensorium, and neurological deficits. Upon examination, she exhibited tachycardia, irregular heart sounds, and extensive crepitations in the respiratory system. Her electrocardiogram (ECG) showed an absent P wave with a varying RR interval. Laboratory investigations revealed abnormal thyroid function tests (TFTs) and raised polymorphonuclear cells, in addition to hyperglycemia. The patient was managed in the intensive care unit (ICU) with bilevel positive airway pressure (BiPAP) and supplemental oxygen, treated for AF with intravenous (IV) amiodarone, and her blood sugar was controlled with insulin infusion. Discontinuation of levothyroxine therapy was advised. Subsequently, her AF was terminated, and sinus rhythm was restored. Her neurological examination showed right-sided hemiplegia with aphasia. After 1 week of treatment, her TFTs normalized, and she was discharged on appropriate medication.