Clinical Research Directory

Inclusion Criteria: Each participant must meet all of the following inclusion criteria to participate in this study: 1. Admitted to a participating hospital ICU 2. A newly documented episode of fast Atrial Fibrillation with heart rate \>120/min confirmed by a 12-lead ECG assessment regardless of baseline rhythm (note- The AF can be acute or chronic diagnosis) 3. Undergoing, or able to commence continuous electrocardiographic monitoring ("telemetry") as part of their routine clinical care 4. Treating physician determines the patient has clinically significant AF that requires medical treatment Exclusion Criteria: 1. Age \<18 years 2. Palliative goals of care or expected to die in the next 12 hours 3. Fast Atrial Fibrillation (\>120/min) present for \> 48 hours 4. Treatment with digoxin or a class I or III anti-arrhythmic medication within the preceding 24 hours 5. MgSO4 dose of \> 3g IV in the last 2 hours. 6. History of high grade Atrio-Ventricular conduction block or bradyarrhythmia without pacemaker 7. Non-cardiac indication or contraindication to one of the study treatments (hypertensive disorders of pregnancy, pre-term labour, neuromuscular junction disorders i.e. known Myasthenia gravis; documented prior history of amiodarone toxicity or relative contraindication such as thyroid disease, cirrhosis, pulmonary fibrosis, etc.) 8. Recent cardiac surgery during index hospital admission 9. Known pregnancy 10. Sustained (more than 10 continuous seconds documented on a rhythm strip) ventricular arrhythmia within the past 24 hours 11. Known or suspected pre-excitation syndrome 12. Persistent hyperkalemia \> 6mmol/l despite treatment 13. Previously enrolled in the MAGNAM trial 14. Recent lung transplantation (during this admission)