Magnesium sulphate with the cell membrane threshold potential stabilizing effect has been reported as an effective drug for rate and rhythm control for post-operative atrial fibrillation and the atrial fibrillation presented in the hospital emergency unit. However, there was inadequate data about the efficacy of Magnesium sulphate for treatment of new onset atrial fibrillation in the hemodynamically unstable patients admitted in the medical intensive care unit.