[Indices of electrocardiogram dispersion mapping during 5-day exposure in dry immersion]

The article presents the results of ECG dispersion mapping in the investigation of 13 young healthy people during 5-d dry immersion (DI). This was the first study of 24-hour variations in dispersion of ECG microoscillations. For this purpose, 20-30 min fragments were "cut out" of every hour of Holter monitoring records to analyze their means after averaging over every 4 hours. Heart rate (HR) and QRS-amplitude were analyzed simultaneously. Index of metabolic adaptation (HR(max/MiO(max)) was calculated. Based on the results, alterations in ECG signal became distinct on DI day-3. They started with a considerable rise of the main ECG amplitudes, especially at night (10.00 p.m. to 6.00 a.m.). The myocardium index makes a significant rise in the period from 10.00 p.m. till 2.00 a.m. However, this index reached its maximum values on DI day-5 in the time intervals from 3.00 till 6.00 p.m. and from 10 p.m. till 10.00 a.m. On DI day-5, of particular interest was a marked HR growth from 10.00 p.m. till 02.00 a.m., and in the post-sleep hours (07.00-10.00 a.m.). Consequently, all this looks like a series engagement of first electrical and then energy metabolism processes in the myocardium reaction to DI. Finally, the increased pulse rate suggests an integral nature of the cardiovascular reaction. This picture of alterations provides grounds for hypothesizing energy metabolism genesis of these reactions.