SERUM MAGNESIUM AND CARDIAC ARRHYTHMIAS WITH SPECIAL REFERENCE TO DIGITALIS INTOXICATION

Serum Mg++, Ca++ and K+ values were determined on 45 patients with various types of cardiac arrhythmias. The mean serum magnesium of 1.43 ± 0.19 mEq, per L. was not significantly different from the mean of 1.6 ± 0.20 mEq. per L. found in normals. There was no relationship between the serum magnesium level and the type of arrhythmia.Digitalis intoxication was present in 21 patients. Serum magesium levels were significantly higher after correction of the intoxication syndrome, even though magnesium intake was not supplemented beyond that ordinarily found in the diet. The low serum magnesium was probably secondary to decreased food intaken and thus to low Mg++ intake during the period of cogestive failure, and to diuresis induced during the therapy of the congestive failure. The possibility of an intra-extracellular shift or change in the “bound” fraction of serum Mg++ cannot be evaluated from this data.