UDC

612.111

Authors

Irzhak Lev Isakovich, Syktyvkar State University named after Pitirim Sorokin (Syktyvkar, Russia)

Abstract

The paper dwells on the functional significance of time parameters of human ECG elements variability when accelerating and decelerating the heart rate using laboratory tests. It presents the mean values (M ± SD, s) and cardiointervalograms showing the duration of ECG elements in four subjects of both sexes aged 18–23 years before and after the functional tests. Initially, PP intervals of the subjects ranged between 0.73±0.06 and 0.90±0.09 s, PT intervals – between 0.44±0.02 and 0.56±0.02 s, and TP segment – between 0.17±0.05 and 0.40±0.07 s. PT intervals accounted for 56–77 % and TP segments for 23–44 % of the entire PP duration. In experiments with heart rate acceleration, after 5 min of normobaric hypoxia (9 % O2) and 1 min exercise (100 W) PP intervals were reduced by 12 and 24 % and TP segment by 32 and 80 % respectively compared to the initial values. PT interval stayed virtually unchanged (within the limits of error). Under these conditions, PT intervals accounted for 70–90 % and TP segments – for 8–30 % of PP duration. At exercise peak, the share of TP was reduced to zero. In experiments with heart rate deceleration, after 1 min of orthoclinostatic test and 0.75 min of voluntary breath holding (inspiratory apnea) PP was increased by 1/3 and TP – by the factor of 1.5 and 2.3 respectively. PT interval stayed on the initial level. The share of PT in the total duration of PP interval was reduced to 48–59 %, while TP on the average reached up to 50 %. The cardiointervalograms showed that PP interval and TP segment were almost identical in variability, while PT variability was at the minimum level.

Keywords

electrocardiogram, intervals, segment, functional tests.

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