Effect of the Magnesium Infusion on the Late Potentials in Patients After Acute Myocardial Infarction

Late potential (LP) in patients after myocardial infaretion (Ml) is widely used to identify patients at risk for malign arrhythmia. This study examined the effect of magnesium treatment on LP in patients after acute MI.
METHODS
The study group (SG) consisted of 26 patients who received 1 gr/day MgS04 infusion for the first five days, and the control group (CG) consisted of 15 patients who received placebo infusion after acute MI. Signalaveraged ECG and rhythm analysis were recorded on the 1" (first) and the 6'h (second) days after acute MI.
RESULTS
In the first and the second records, LP was found to be positive in 10 (38%) and 5 (19%) cases (p=0.13), respectively in SG with a relative reduction ratio of 50%, and 5(33%) and 4 (27%) cases (p=0.69) respectively in CG with a relative reduction ratio of 18%. In the first and the second records, QRS interval, Root Mean Square voltage (RMS40) and the duration of low amplitude signals (LAS40) were found to be 107.4±13.9 vs 99.3±14.2 ms; p=0.043, 32.9±19.4 vs 44.7±20.1 ).IV; p=0.035, 36.8±17.9 vs 27.6±12.8 ms; p=0.037 respectively in SG, and 110.4±12.0 vs 105.4±13.2 ms, 31.8±17.9 vs 39.1±18.7 ).IV, 39.2±14.8 VS 33.7±12.1 ms respectively in CG. Comparison of the SG and CG, shortening ratio in QRS interval (7.6±3.2 vs 4.6±4.4% respectively, p=0.03), increas.ing ratio in RMS40 (52.9±37 .8 vs 30.4±22.0% respectively, p=0.002) and reduction ratio in LAS40 (24.2±11.3 vs 12.6±11.7% respectively, p=0.004) were significantly higher in SG compared to CG. In comparison of the first and the second records, the ineidence of ;;::: grade II ventricular arrhythmia was significantly reduced (20 cases 77% vs 4 cases 15% respectively, p0.05).
CONCLUSION
MgS04 infusion provides significantly improvement of the LP parameters and reduces the ineidence of ventricular arrhythmia.