Efficacy of intravenous magnesium sulphate in supraventricular tachyarrhythmias.

This study was conducted to evaluate the clinical efficacy of intravenous (i.v.) magnesium sulphate 2 gm bolus in sustained supraventricular tachycardia (SVT) and atrial flutter-fibrillation with fast ventricular rate of more than 160/min (AF-FVR) and to compare it with i.v. verapamil 5 mg. In this randomised controlled trial, 68 cases of SVT and 86 cases of AF-FVR were studied. Patients with evidence of renal dysfunction and systolic blood pressure less then 90 mm Hg were excluded. Response was considered when the heart rate fell to less than 100/min. In SVT, 33.3% (11 out of 33) responded to magnesium sulphate which was significantly less than verapamil (23 out of 35, 65.7%) p = 0.007. Similarly, in AF-FVR, response was more with verapamil (25 out of 45, 55.6%) than magnesium sulphate (8 out of 41, 19.5%) p < 0.0001. Response to magnesium sulphate was better in patients with IHD. There were no significant side effects, except flushing and sense of warmth with i.v. magnesium sulphate. Serum magnesium rose significantly after i.v. magnesium bolus. Though magnesium sulphate is a weaker antiarrhythmic drug than verapamil, further studies are needed to identify subgroups of supraventricular tachyarrhythmias which would respond to magnesium sulphate.