Lee Kai Yi

Ministry of Health Holdings,
Singapore

Abstract Title: Magnesium Use in Pre-Excited Atrial Fibrillation

Biography:

Lee Kai Yi graduated from National University of Singapore in 2020 and is currently an emergency medicine senior resident in Singapore. She is not affiliated to any institution and areas of interest include out-of-hospital cardiac arrests and arrhythmias management. She has published in reputable journals including Resuscitation.

Research Interest:

A 65-year-old man with a history of hypertension presented to the Emergency Department with a 2-hour history of acute shortness of breath and palpitations. On arrival, he was tachycardic with a heart rate of 178 beats per minute, blood pressure of 110/75 mmHg, and oxygen saturation of 92% on room air. A 12-lead electrocardiogram (Figure 1) demonstrated a broad complex tachyarrhythmia at 230 beats per minute with varying morphology suggestive of pre-excited atrial fibrillation (AF). Given his tachypnoea, synchronized electrical cardioversion was performed for unstable tachyarrhythmia.

Despite synchronized cardioversion at 100 Joules, the arrhythmia was refractory. As the patients dyspnoea improved, intravenous (IV) magnesium sulfate (10 mL) was administered, slowing the rate of conduction via the accessory rhythm on telemetry. IV procainamide was initiated at 1 gram (14.9 mg/kg) loading dose. Cardiology was consulted and the patient was admitted to a high-dependency unit for close monitoring and procainamide infusion at 1mg/min. Further investigations revealed primary hyperthyroidism, with positive thyroid-stimulating hormone receptor antibodies. A diagnosis of Graves’disease with AF and aberrant conduction was made, and treatment with carbimazole was initiated. His rhythm reverted back to sinus on 2nd day of admission. Hyperthyroidism is a well-recognized precipitant of atrial fibrillation due to increased adrenergic sensitivity and enhanced myocardial automaticity. IV magnesium is a relatively safe adjunctive therapy in atrial fibrillation with rapid ventricular response, acting by prolonging atrial and atrioventricular nodal refractoriness and reducing cellular automaticity.

This case highlights the potential safety and therapeutic role of magnesium in the management of atrial fibrillation associated with hyperthyroidism, even in the presence of pre-excited or aberrantly conducted rhythms.