EN
The aim of this work was to prove if diagnostic, transe- sophagal pacing of the left atrium of the heart resulted in changes of the serum Mg concentrations and if there was a dependance between changes of serum Mg level and electrophysiological parameters. The patients with transesophagal pacing induced arrhythmias were characterized by lower input serum Mg level in comparison to those in which the arrhythmias didn't occur. Mg concentration increased after the pacing in their case.