Serum, lymphocyte, and erythrocyte potassium, magnesium, and calcium concentrations and their relation to tachyarrhythmias in patients with acute myocardial infarction☆

Abstract 

Serum, lymphocyte, and erythrocyte potassium, magnesium, and calcium levels were measured in 215 patients during the five days following acute myocardial infarction. Serum potassium fell from 4.25 ± 0.05 to 4.08 ± 0.06 mmol/liter (p <0.001), magnesium from 0.93 ± 0.01 to 0.85 ± 0.01 mmol/liter (p <0.001), and calcium from 2.4 ± 0.02 to 2.2 ± 0.08 mmol/liter (p <0.001). Lymphocyte potassium increased from 18.1 ± 1.5 to 51.6 ± 4.3 pmol/100 cells (p <0.001) and magnesium from 2.0 ± 0.1 to 8.2 ± 0.8 pmol/100 cells (p <0.001), whereas calcium decreased from 2.9 ± 0.27 to 1.4 ± 0.25 pmol/100 cells (p <0.001). Erythrocyte cations remained constant. There was a larger increase in lymphocyte potassium in patients with tachyarrhythmias than in patients without (70.4 and 46.9 pmol/100 cells, respectively, p <0.001), whereas the presence of a high lymphocyte magnesium level was associated with a significant decrease in the development of tachyarrhythmias, despite high potassium concentrations. It is suggested that lymphocyte cation concentrations mirror myocardial interstitial concentrations and that a high interstitial magnesium level has a protective effect on the increased cell excitability due to, and despite, a high interstitial potassium level.

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