Effect of intravenous magnesium on ventricular tachyarrhythmias associatedwith acute myocardial infarction

Ventricular ectopy and left ventricular dysfunction are important predictiv e factors for an unfavourable outcome following an acute myocardial infarct ion (MI). Tachyarrhythmias are a major cause of death subsequent to Evil. M agnesium was postulated to have an antiarrhythmic effect after MI. Therefor e we have investigated the influence of intravenous and oral magnesium (Mg) therapy on ventricular tachyarrhythmias. 67 patients with myocardial infarction (MI) diagnosed according to the WHO criteria of anamnesis, infarct-specific electrocardiogram (ECG), and enzyma tic status were included in a prospective study. 23 patients (group I) rece ived 2 g Mg per day (= 82 mmol Mg/24 h) intravenously for the first 3 days followed by oral magnesium adipate administration of 3 x 2 coated tablets o f magnesium 50 Apogepha (= 300 mg Mg/24 h or 12.34 mmol Mg/24 h, respective ly) for the full duration of the study. 26 patients (group 2) received only i.v. magnesium for the first 3 days after admission (2 g Mg/24 hi. The res ults of this treatment were compared to those of a control group of 18 MI p atients without magnesium administration. All groups were identical with re gard to other forms of treatment. The magnesium levels in serum and erythro cytes of all patients were measured at the following time points: days 0 (a dmission time), 1, 2, the day of discharge (about day 20) and after 12 week s. The tachyarrhythmias were monitored by 24-h-continous-electrocardiograph y on days 0, 1 and on the day before discharge (about day 20). The serum ma gnesium levels rose significantly during i.v. Mg-administration (1 and 2 da y) but decreased in group 2 subsequently until the time of discharge from h ospital. In contrast group 1 patients receiving oral as well as intravenous magnesium did not show this drop. The uptake of magnesium into the erythro cytes was less obvious. The erythrocyte magnesium concentration of the cont rol group remained significantly low in serum and red blood cells. Signific antly less ventricular premature beats and runs (< 5 ventricular premature beats and > 5 ventricular premature beats) compared to admission day were o bserved in both treated groups. These data suggest that the frequency of ve ntricular tachyarrhythmias is reduced by administration of intravenous magn esium and support an early high dose administration of intravenous magnesiu m in the wake of myocardial infarction.