There was a non - significant difference between the serum magnesium levels in patients with arrhythmias and without arrhythmias: admission to the hospital (0.82 ± 0.12 vs 0.85 ± 0.07 mmol / L, p = 0.147), within the first 24 hours (0.83 ± 0.13 vs 0.83 ± 0.09 mmol / L, p = 0.911), after 3 - 5 days (0.94 ± 0.1 vs 0.88 ± 0.13 mmol / L, p = 0.138).