A total of 109 consecutive patients were included in a double blind, randomized trial of the effect of intravenous magnesium sulfate in acute myocardial infarction. Of these 63% received intravenous fibrinolytic therapy. Twenty four-hour Holter monitoring of heart rhythm was performed during the initial hospital stay. A significant reduction in total cardiac mortality in hospital and during the 9 months follow-up was found in the magnesium treated non-thrombolytic group (P < 0.05). Within this subgroup development of heart failure was decreased (P < 0.01). No effect of magnesium infusion on ventricular arrhythmias was demonstrated, instead we found a greater proportion of patients with short runs of ventricular tachycardias in the magnesium treated non-thrombolytic group (P < 0.05), which may represent an increase in spontaneous reperfusion.
Conclusion: these results indicates that magnesium infusion may have a beneficial effect on mortality in patients with acute myocardial infarction not receiving thrombolytic therapy, but opposes the view that the benefit is related to an antiarrhythmic effect. No additional effect of magnesium to ongoing fibrinolytic therapy could be demonstrated regarding mortality, reinfarction and heart failure.