Magnesium in Acute Myocardial Infarction (The Mami Study): Effect of Early Versus Late Magnesium Administration on CK-Levels
Introduction: Two major studies have evaluated intravenous magnesium in patients with acute myocardial infarction. LIMIT-2 found a 24% reduction of mortality (day 28) in the magnesium treated group. However, ISIS-4 demonstrated no such benefit on mortality (day 35). In LIMIT-2, patients were started on intravenous magnesium immediately after admission, in contrast to ISIS-4, where magnesium was administered later.
Hypothesis: The beneficial effect of magnesium in acute myocardial infarction (AMI) depends upon early administration of the drug.
Methods: 102 patients undergoing thrombolysis (rt-PA) for acute myocardial infarction were randomised to receive magnesium at two different times. In group 1 the magnesium infusion was started concurrent with thrombolysis, group 2 received magnesium 3 hours later. Total dose of magnesium was 72 mmol (bolus of 8 mmol, followed by a continous infusion for 22.5 hours at a rate of 3.2 mmol/h).
Results: Maximum Ck levels (Ck max.) in group 1 were higher than in group 2 (1126 vs. 911 U/l) and reached the peak earlier (9.6 vs. 10.5 hours). In patients with anterior wall infarction these trends are more destinct: in group 1 (n=23) and 2 (n=21) Ck max. was 1598 U/l and 1241 U/l respectively. Group 1 reached these levels after 8.3 hours as opposed to 9 hours for group 2. A subgroup analysis was performed on patients with documented reperfusion (ECG: 70% reduction of initial ST-elevation after 3 hours). These patients had a Ck max. of 1694 U/l if magnesium had been started early (group 1) and 1209 U/l in group 2. These differences did not reach statistical significance.
Conclusion: Early administration of magnesium in AMI leads to higher and earlier maximum Ck levels which might indicate earlier and more pronounced reperfusion. The results of the MAMI study presented above might elucidate the divergent results of LIMIT-2 and ISIS-4.
KeywordsAcute Myocardial Infarction Acute Myocardial Infarction Magnesium Sulfate Magnesium Sulphate Intravenous Magnesium
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