Life-threatening arrhythmias after intravenous lidocaine alone or with magnesium in myocardial infarction complicated by ventricular fibrillation.

To compare the effects of Lidocaine (LID) alone or with Magnesium Sulfate (M) on life-threatening ventricular arrhythmias which followed cardioverted prolonged ventricular fibrillation (VF) during an acute myocardial infarction (AMI), we studied 34 (24.63%) out of 138 patients aged from 52 to 83 years (mean: 66.92 + 8.82) with an anterior AMI, who had cardioverted prolonged VF. Twenty patients (58.8%)--Group A--received LID 2 mg/min at constant-rate infusion through a subclavian catheter following a bolus of LID 100 mg, whereas 14 patients (14.2%)--Group B--received LID at the same dose + M 2.5 mg/min. All the patients had continuous monitoring and LID serum level was measured daily by means of immunofluorescent method (TDX Abbot; range 1.5-5 micrograms/ml). Group A had the following mean serum levels of LID; 250 + 0.9; 1.52; 245 +/- 0.9; 3.20 + 1.1. Group B showed: 2.65 + 1.2; 2.80 + 1.8; 3.10 + 1.2; 3.25 + 1.1. Continuous monitoring displayed the following arrhythmias respectively for Group A and Group B: VT 37 times vs 16(P less than 0.05, significant), transiently cardioverted VF during therapy 17 times vs 6(p less than 0.01, significant), 8 deaths from VF vs 6 - 3 from VF and 3 from asystole - (p = NS). LID + M treatment seemed to be more effective than LID alone to reduce life-threatening arrhythmias following cardioverted prolonged VF of AMI but not the deaths. In addition, M would raise moderately LID serum level and this fact, not yet well known, needs further investigation.