Ventricular extrasystoles and intracellular electrolytes before and after potassium and magnesium infusions in patients on diuretic treatment.

Thirty-four patients suspected of being magnesium deficient were given intravenous infusions of potassium and magnesium. The muscle contents of sodium, potassium, magnesium, and chloride were determined by atomic absorption spectrophotometry on skeletal muscle samples obtained by percutaneous biopsies. The frequency of ventricular etopic beats (VEBs) was assessed from a 3-hour ECG tape recording before the infusions and after the completion of each infusion. The potassium infusions did not result in any changes in the cellular potassium content, nor in the frequency of VEBs. After the magnesium infusions, however, a significant increase was noted in the cellular potassium content and likewise a significant decrease in the frequency of VEBs. This emphasizes the importance of magnesium in potassium metabolism.